CNC - JGRO Router
This category will contain articles relating to the JGRO CNC Router project and upgrades.
About the JGRO CNC Router
When I started looking for a CNC Router design I found plenty. The problem I had was I was strapped for cash. Seems like I am always strapped for cash now that I think of it! Oh well. Then I stumbled upon a free design from a CNC Zone member named JGRO on the CNC Zone website. I looked at the drawings and thought the design looked pretty good and went with it. You can download the plans by clicking the icons below. Please keep in mind that these plans cannot be sold, they are ONLY for your personal use. Also, I am posting these plans without the explicit permission of the author. If the owner of this plan contacts me, I may have to pull them down and let you find them elsewhere. But for convenience sake, get them here.
Click the icon to the left to download the JGRO Router plans in PDF format. You will need adobe reader to view these plans. You can download and install Adobe Reader for free from www.adobe.com. If you already have Adobe Reader installed, clicking the icon to the left will most likely open the plans up in a new tab or window in your web browser. If you would rather directly download the file then right click the icon and select either "save target as" or "save link as" from the context menu.
Rebuilding The Bed
The vast majority of water damage to the machine was to the bed assembly.· For those of you who have the JGRO drawings, I am referring to CNC_DTL01 (Support Motor Side), CNC_DTL02 (Support Bearing Side), CNC_DTL05 (Base Support Structure)and CNC_DTL06 (Bed Support).· The Base support and the end support had absorbed enough moisture to cause a lot of swelling in the MDF.· The Bed support didn't really swell but did sag about 3/8 of an inch.· Needless to say, these would need to be remade.
I kind of struggled with accurate cuts when making the first bed supports.· I was not much of a wood worker then and probably and only marginally better now. Particularly with the little short pieces that went between the long ribs of the bed.· So this iteration I decided that I wanted to do a much better job of making these two assemblies.· After noodling the situation for a bit, I decided to remake these parts in 3/4 inch MDF instead of half inch and instead of making short braces to go between the long ribs, I decided I would do half lap dadoes.· The end result will be a heavier bed but much more rigid bed than what I had made during the initial build.
Rebuilding the Base Support Structure (CNC_DTL05)
I kept all the outside measurements to the original plan. 40.500 inches long by 24.000 inches wide and 3.000 inches tall.· I made the pieces that make up the ribs and cross pieces to half lap with close fitting dadoes.· You can get a better idea by looking at the DXF file for the new part.· You can get it by clicking the DXF Icon to the left of this paragraph.· ·What follows is a pictorial process of these pieces going together.
In this image I have all the parts cut, dadoed and ready to assemble.· The six blocks you see at the bottom of the photo are dadoed at right angles to each other.· I made these to hold the parts together at right angles while the glue set up.· You will get a better idea in the following pictures.
Now the gluing begins.· Here the first cross piece is attached to the three longitudinals with glue.· Here you see the blocks I was talking about in the paragraph above.· They assure the parts are connected at right angles and that the edges are flush with each other.
Finally, the short side pieces are glued in to complete the frame.· I have to stop at this point on the frame because I need to get some dowel rod.· I want to add these through the outside joints to help strengthen them.· Also, I want to bolt the top to the frame using barrel nuts.· All said and done, this should be a lot more rigid than the original version of the base support structure.
The image on the left is the completed base support frame.· The image on the right is the original base support frame.· You can see how I used heavier members, 3/4 inch on the new versus 1/2 inch on the original.· Now don't get me wrong, I honestly think that is the machine didn't get wet, I would be using it as I originally made it today.· However, if I have to rebuild I may as well try to improve the original design.· I will show a couple of pictures of the dowels and barrel nuts as soon as I complete them.
It has been a couple of days since my last post.· Anyway, If you look at this picture you will see that I am adding dowels to all the outside joints.· Although there should be no flexing from side to side or from front to back, I wanted to add these as additional strength to the joint.· I used 1/4 inch diameter by 1-1/4 inch long dowels.· They are drilled about 1/16 deeper than the dowel and the dowels are coated with glue, and a little glue run in the hole and spread with a toothpick.· Then the dowels are driven in to just below the surface of the material.· This way they do not interfere with bolting the front and back uprights to the machine.· The only flex in the assembly now is the ability for it to rack or twist.· That will be resolved when the top is glued down to the framework.· When the top has been glued down, I will install dowels in it as well to give a better joint.
With the dowel rods all glued in and dry, I glued to the top to the bottom frame support.· I really wish I had about a dozen or so more of these clamps.· I used all I had.· I have done that a few time.· It just seems like you never have enough of them.· Anyway, I am a little off topic.· When the Base Support Structure is dry, it will be complete and ready for installation when I finish the bed support and end pieces.· When I get to the end pieces, I will discuss the attachments and how to determine the hole spacing for the pipes.
Rebuilding the Bed Support (CNC_DTL06)
Just like the Base Support Structure, I kept the same outside measurements. 40.500 Inches long x 20.000 inches wide x 1.750 inches tall.· I also made this out of 3/4 inch MDF instead of the called for 1/2 inch material.· I scaled the members accordingly.· You can get a DXF drawing of this modification by clicking the DXF Icon to the left of this paragraph.· Again, I made this with half lap dadoes like the Base Support Structure.· What follows is a pictorial of the process.
The next step was to cut all the pieces to their proper length.· Here I have attached a fence to my miter saw.· When building anything, I found that it is best to take plenty of time for setup.· The nice thing with using this fence is that every cut of a given length is exactly the same as the last.· It sure is an improvement over my freehand cutting skills.
Here I am cutting the dadoes in the frame pieces.· What you see on my table saw is a dado sled.· These are incredibly easy to make and make cutting crosscut dadoes a breeze.· Here you see I have a fence attached with stop blocks.· This way all the pieces that I push through will have the dado cut in the same place as the last.· This is a must if you want the pieces to come together nice and square.· The photo is from the back of the saw by the way.
Well now comes the glue up.· I will not bore you with so many pictures of the process this time.· I realized after this dried, I added the middle two longitudinal pieces that I could not clamp three then two, that on the next cross piece I had to glue to all five longitudinals.· So I glued them all and weighted it all down.
I told you that I was not going to drive you crazy with a bunch of photos of the same operations on the bed support frame like I done on the Base Support stuff.· At any rate the frame is all glued together and the dowels rods have been installed.· Next is to glue the top to it.· I will do that when the base support is dry.
Finally the top is being glued down to the bed support frame.· Now that we are near done with this portion of the rebuild I want to admit that my dadoes were not perfect.· Like I said earlier, I am not much of a wood worker.· As a result, the tops of the base support and the bed support are not perfectly fitted to the frame.· There is a little bit of overhang here and there.· Not loads of overhang.· something less than 1/16 of an inch.· Now overhang on the long sides is of no real concern.· But on the short end, well that may or may not matter but I want a good fit for the ends.· I will show you how I plan to correct that when I start assembling the components back together.
Rebuilding the side supports (CNC_DTL01 and CNC_DTL02)
Next on the list are the side supports.· I am rebuilding these with no changes in dimensions to the plans.· I may alter some holes because of the new bottom support and the Bed support but I will cover that when I start the assembly.
Nothing real remarkable here.· I am gluing up the first side support.· Sometimes you just never really have enough clamps.· These were slippery little devils.· Getting things aligned was a pain and I am glad I had William and Zachary, my two oldest sons there to help hold everything in position.
Rebuilding the Gantry Bottom (CNC_DTL18) and the Gantry Front (CNC_DTL20)
Although the Gantry Bottom and Gantry Front are not part of the bed, I put it here because it needed replacing because of the water damage.· Now I need to point out that the Gantry front was in good shape, but when Zachary and I went to remove it, it had stuck to the front of the gantry.· It had stuck so bad that a good amount of the front was left behind stuck to the gantry front when we went to drive it off.
The gantry bottom was made to the original specifications outlined in the JGRO router plans.· Zachary and I got busy working on it and cut it out, drilled and tapped and installed it before we thought to take a picture.· At any rate, it isn't anything special.· If you have built the JGRO router then you have made this part.
Here the gantry front has been cut and laid out.· I have finished center punching the holes and it is ready to drill.· I did not drill the holes for the anti-backlash assembly because mine is at a different hole pattern.· I will drill these hole when I do the assembly.
Here the Gantry front is fitted to the gantry.· The outside bolts are snug, but the center bolt is left loose.· I need to super glue the wooden threads before I actually attach this permanently.· Well, I need to drill the holes for the anti backlash nut as well.
Putting it back together.
After taking all the time to cut the dadoes in the bed pieces for a close fit and gluing them together, I made a mistake.· The bed support had a bow in it after the glue dried when I attached the top.· I had an idea that I thought would fix the problem for me.· I took a piece of 3/4 inch plywood and a piece of two inch angle iron and clamped it all together.· Then put several bolts through it thinking that it would hold the bed straight.· Well it was better, but still had a slight bow to it.· Well, a friend of mine stopped by and we jawed about it a while and came up with another idea to straighten it up.· As you will see in the next paragraph, it worked pretty good.
The bow in the table was downward.· We took a couple of small blocks and set a piece of angle iron on top then used a C-Clamp to pull the bow out of the table.· We used a straight edge and a light to check that the bed was flat.· Once we had the the bed flat we drilled some 1 inch by 1/8 inch strap and bolted it to the side with six bolts.· If you click on the picture you will get a better idea of what I am trying to say.· You can see the angle clamped to the other side of the table and the closer side with the strap iron bolted on.· You can also see that the table is pretty flat.· Small gaps exist because of irregularities in the plywood.
Here the bed support is bolted back onto the machine. You can see the strap Iron will not interfere with the gantry of the machine. Now I was left with the decision as to use the plywood as my sacrificial bed, or replace it with something a bit more smooth. Well, I decided that since I put all those bolts in there I may as well use it as part of the bed structure. I know this loses more cutting depth, but at least for now that is not a concern for me. A close look at the picture will show you several of the 20 bolts that are countersunk into the top.
Here is a video of the first cutting after the bed was built but before any real adjustments and before the strap iron was added. It was cutting this little plaque that showed just how bad the bow was in the bed.
That concludes the bed rebuild. Now, I will look at replacing the stepper motors with better motors and new electronics to run them. Watch that upgrade in another menu link.
JGRO CNC Router - Updates, Upgrades, Fixes and other stuff
A lot of time has passed since I built my JGRO Router.· My wife and I were busy remodelling and heavily involved in the Band Booster organization. The Router got stuffed into the basement of my out building and sat there unattended and neglected for a long time. · We developed a leak and water ran on the machine soaking the MDF base.· Even though it was painted it still warped.· Well all I can say is that was a lesson learned.
Then September 3rd, something horrible happened. Cotton, our dog passed away. She was 15 years old and only about a month from 16. Well, we buried the old girl in a homemade box under the shade tree in the back yard. I told my wife we could use the CNC Router to make a plaque for her and cast it in aluminum for a grave marker. Well, when I retrieved the machine and seen the damage, I knew I would have to rebuild.
Assessing the damage
Most of the machine was intact and in good shape except for the bed and the bottom board of the gantry. I knew that there were some other modifications I wanted to make to the machine as well. For example, I never put the electronics to bed in its own enclosure, never got around to making more cast pipe clamps and never made a decent router clamp. So the pages that are listed below the JGRO Updates menu item are the upgrades and fixes that I have done to the machine.
JGRO CNC Router Build Log
I have been looking at a bunch of web sites about CNC and its related functions. When I joined CNCZone I found some plans for a CNC wood router that I think will meet my needs. You can find the same plans and follow along with my build progress by going to CNC Zone and downloading them from the downloads section. The plans are in PDF format so you will also need a copy of Adobe Acrobat reader to view them. If you need Acrobat Reader you can get it free from Adobe's Website. You can also get the plans as zipped DXF files from there as well.
The image you see to the left was obtained from Thunterman's website and shows what the finished machine should look like. I would encourage you to take a look at Thunterman's website, you can see pictures of his machine and video of it's first cut. You can get there by going to http://cnc.hobby-site.com/cnc.htm. If you have downloaded and opened the plans you will see this is the first page.
When I looked over the plans, I thought I would start with the router table (the Y axis) and work my way up, but after some reading on CNC Zone I decided it would be better to start with the Z Axis (the part that will hold the router) and work my way out. I decided to take this approach so that if there are any differences in measuring, I can adjust new parts to fit the ones I have already made.
To start out, I took some graph paper and went through the plans and laid out all the pieces I would need to build the router. This project will require a full sheet of 1/2" MDF and a full sheet of 3/4" MDF. I went to Lowes to purchase the MDF, when I got there I found they carried 3/4" but not 1/2". I went ahead and got a sheet of 3/4" MDF and had them cut it into two 4 x 4 panels so I could haul it in the back of my van. If you are uncomfortable with this process, It has been done for you in a post on CNC Zone along with a piece of software that will help you with the process. You can read about it by going to this thread on CNC Zone.
Getting past First Cut Fever - When I bought plans to build a boat from Stevenson's Projects, I also decided to buy the video to help me decide if I was up to the task. One thing they talk about is First Cut Fever. That is the feeling you experience right before you start the project, not wanting to mess it up you get a little apprehensive about making the first cut. Well, I didn't suffer too bad, I figured at only $20 a sheet, I could absorb the financial cost if I messed up. (And I expected to.)
I have all the dimensional pieces cut from the sheet of 3/4" MDF. I have never used MDF before but I have to admit, it is really easy stuff to work and that is saying something with my limited wood working ability. One thing I feel I should point out is that when you cut MDF the resulting dust is very fine and gets on everything. I would cut outside if weather permits and make sure you use safety glasses and a dust mask. It is always better to be a little over safe than sorry! I think I will start with some simple pieces that will not affect other dimensions first.
I decided I would start with the Y axis pipe rail supports first. These little blocks will support and align the pipe rails that the gantry, (Y AXIS) will roll on. I cut these with a 1-1/2" spade bit. Surprisingly they come out pretty good. The first one I done I messed up by running the bit all the way through the piece of MDF. This left me with a nasty ragged edge on the bottom of the block. The next one I ran the bit through just enough so the tip of the bit would poke through the other side, then flipped it over and finished up. I did not have the correct drill size for the 1/4-20 tap so used a 13/64" bit instead. It is over sized by .002" but I figured it was probably close enough for government work. After drilling a tapping the four outer holes I soaked the threads down with Super Glue to help strengthen them. (Another little tip I got from CNC Zone) There are eight more block like these required for the X-AXIS and Z-AXIS. The only difference is that they are a little smaller. Instead of being 2.5" x 2.5" with a 1.5" hole bored in the middle they are 2.0" x 2.0" with a 1" hole. I will do these next just to have them done.
I finished up the X and Z axis pipe rail support blocks. These were made just like the Y axis blocks above. I was surprised how long these took to complete, well at least until I thought about it a bit. 8 block with 9 holes each (72 Holes) 4 of which need to be tapped (32 holes) and then those 32 holes have to be soaked down with super glue. So I guess it should have taken a little while. I do want to mention something about the super glue. Super glue is a respiratory and eye irritant. Breathing the fumes can be rough on you. I find it best to follow the recommendations someone made on cnczone, take them all outside, sit with a breeze to your side and glue them up. I done these blocks in my kitchen and by the time I was half done my eyes were starting to burn pretty good. Just something I wanted to pass along. Well I can think of nothing else to waste space by this picture so I will move on.
Here is a picture of the back of the Z axis. Notice that I do not have the anti-backlash nut installed or the roller blade bearings. I still have to get these parts. You will also notice that I used 1-1/4" angle iron rather than the aluminum angle that is mentioned in the plans. I only went this route because I could not readily find aluminum angle in 1-1/4". I found it in 1" and 1-1/2" but no 1-1/4"
Finally here is a shot of the side of the Z axis assembly just for completeness. I will most likely be starting on the X axis parts tonight if I have time. I am starting to get the bug to get this project rolling along a little faster than what it is. After looking at so many homemade machines across the Internet and at cnczone, I am itching to make my first cut. Thanks again Bob (from Bob's Metal Casting)for giving me some direction and some courage to start a project of this magnitude. Be sure to stop by once in a while to see where I am at on the project! Have fun.
I did manage to find some skate bearings and attach them to the Z Axis bearing supports. I thought I would include a picture so you can see them attached. I had to file the impressions below the mounting bolts a little more before the 1/2" pipe would slide without interference. I was surprised to discover just how smooth this arrangement slides.
Getting the bearings has spurred me to do more tonight. I started on the X-Axis. I have the X axis platform and the X axis top plate finished. I am hoping that I can get a little more done tomorrow night. I think as long as I stick to my theory that a little work on the machine frequently will get more done than a lot of work infrequently will get me done with it sooner holds out I will be fine. You know how it can go sometimes, You get engrossed in a project and then near the end life has a way of jumping in front of you and making you attend to it. I will try to post a picture as soon as I finish the X axis bottom plate.
All of the X Axis parts have been cut out and any holes that needed threading have been threaded. I still need to super glue the threads and make the bearing slides for the X axis before this part will be done. In all truthfulness, I probably should have been finished with this assembly by now but I got side tracked. My controller board I ordered from HobbyCNC arrived and I wanted to see some motors run. More on that in a bit. For those of you following along with the plans in hand, you will notice that the bearing hole for the lead screw has been piloted and nothing else. The reason is because I still need to get some 3/8" ID flanged bearings for the lead screw. I have decided to go with 3/8-16 all thread for lead screws for a couple of reasons. 1) They are a little more rigid than the 1/4-20 thread that the plans call for. 2) All thread was chosen to help keep the cost down. If I make another machine I will go for better hardware for lead screws at that time.
Stepping Off The Main Path - ;-) (pun intended)
A lot of research time and energy went into deciding what to do about controlling stepper motors. I played with a bunch of circuits ideas and even built a couple. But the more I learned about controlling steppers and the circuits that do that job, the more I moved away from building them myself. (I need to confess a little too, Bob from Bob's Metal Casting told me right up front to just buy a controller and be done with it. I should have listened as it would have allowed me to be further along on the project than what I am now. Next time Bob, I will try to listen a little better! ;-) ) There are several ways you can run a stepper motor, you can drive them at full step or half step with simple circuits, but the faster they go the more torque they lose, so then you have to up the voltage, but doing that requires you to use BIG power resistors to limit the current through the coils and that wastes power and generates lots of extra heat. The next best thing to do is drive them with a circuit that senses current and will turn the voltage to the coils on and off to maintain a predefined current level through the coils (known as a chopper circuit). Then if you need more resolution you can microstep but that requires more circuitry. Well to make a long story short, I think you can buy a kit and build it cheaper than you can fetch the components and make the circuit board for yourself. (Not to mention, de-bugging is simpler.) There are quite a few kits available through the web to drive stepper motors. Some are better than others, some are capable of driving larger motors. I chose HobbyCNC's 4 axis controller board because it was affordable and met the requirements of the motors I had on hand to use. I am not advocating them as the best controller available. I urge you to check around and get what suits your needs for your project. That aside, I soldered the board up Saturday. The instructions are clear and concise. Here is a picture of the completed board in it's temporary mounting.
Now that the controller board was complete I needed a power supply that would be big enough to drive a couple of fans and 3 or 4 stepper motors. I had a couple of options as far as power supplies go. I could have used some computer power supplies and put three of them in series fro 36 Volts to poer everything and it would have been able to supply about 20 Amps. Or my second choice would have to been to build my own. Most people who build a power supply from scratch generally make a simple filtered DC supply. The supply is not regulated and may not be pure DC. There could be small amounts of ripple seen on it if you scope it out. The controller board I bought has an onboard regulator for the IC's to run from and since I had a couple of large transformers and caps I took this route. (One caveat I may run into here is that I do not know what the current capacity of my transformer is. The primary has a 2 Amp fuse on it and it steps it down to 37.5 Volts on the secondary. The Voltage ratio is 110:37.5 or about 3:1. Using this I can assume the current capacity of the secondary is 2*3=6 Amps. If this is the case I will need to look at getting a different transformer or winding my own. I will use it though for testing until I can get another one. My basis for power requirement is calculated as follows: 4 Motors all of which are rated at 2 Amp per phase. Two coils could be energised at the same time. This would give me a total of 4*2*2=16 Amps of current required. You can see the transformer I have is more than a light weight for the job. If you are wanting more details about the power supply just drop me an email and I will be happy to discuss them with you.
Here is a picture of the completed stepper motor controller assembly. You will notice that there are two fans. The controller boards offer 24 VDC out for a cooling fan. Since I did not have a 24 V fan I wired 2 12Vdc fans in series. I figure one to cool the power supply and one to help cool the controller board. Just some FYI: The capacitor I used was a 40,000 uF 50Vdc and the rectifier is attached to the metal plate you see between the power supply and controller board. You cannot see the bridge but you can see the bolt that holds it to its heat sink. Also I have added a heat sink to the stepper motor controller chips. It is important to keep these things cool to insure proper operation. And finally the controller board is mounted with 1.5" standoffs to the same metal plate that the rectifier is. I chose to do this to make sure that plenty of air would pass under the controller board as well.
These three stepper motors were salvaged from some Genicom Wide Carriage printers. These are PJT80A2 steppers. I could not find specs for these motors and the only thing listed is 1.68 Ω/Θ (Ohm/Phase) Now I don't know for sure but one stepper type you can find in a Genicom is a PJ80A1. These two steppers have the same ohm/phase rating and are the same physical size. I have elected at my own risk to use the specifications for the PJ80A1 steppers on my PJT80A2 steppers because I suspect they are equivalent. I could find out I am WRONG. I should not you should do things like this at your own risk. The stepper motors run at 2 Amps per Phase, so to run these I had to set the current limiting pots on the controller board to 0.36 vdc. The motors were hooked up and run with TurboCNC software. All three run in both directions. I feel like it was a success and that I can now turn my attention back to building the machine. Once the steppers are hooked up to the machine, I can then determine through cutting and some experimentation how fast and hard they can be driven.
Well except for a couple of bolts the X Axis is finished. Sort of anyway. I still need to get bearings for the lead screw and that stuff, but the main construction is finished. Here is a view of the front with the Z Axis assembly attached. Now if your like me, you would call the Z Axis Assembly the router assembly and then call the X Axis assembly the Z Axis. But the plans call them the prior so I will stick with that.
Here is a side view of the assembly. If you pay attention the image I have have here is upside down. One thing I have noticed is that the grooves that hold the angle iron in place are a little too deep. A mistake I made and not the fault of the plans. As a result, my pipes are very nearly all the way to the inside of the pipe adjusting blocks. They adjusted out but if I were to have problems I would have to figure out a way to shim these tracks up or make new piece to hold the angles.
Finally, here is a shot of the back of the assembly. Notice the center bolts are not in and the dowels are missing. I bought some 1/4" CRS rod to make dowels with only because I feel a little more comfortable with it. I would imagine that 1/4" hardwood dowel would do nearly the same thing. I just think that steel dowels will make it a little more rigid. The truth is, I think it will only be as strong as the MDF is. I am also curious what the weight difference between 3/4" MDF and the same size cast Aluminum. I also wonder if it would be just as strong cast as one piece in say 1/2" thickness. I am getting ahead of myself. I like to cast metal and this machine will help me produce patterns for another machine. Now to get back on the project.
Finally, here is a shot of the Gantry Bottom. There is not much to say about this part other than there 7 holes to tap and threads to super glue. I am hoping that I can find a little time this weekend to finish up the Gantry. On a good note, the 1/2" sheet of MDF that I ordered showed up this evening so I will be able to continue with the Base / Y Axis assembly. This project has been a wonderful so far. I cannot say enough about how well the JGRO plans are written (drawn). John has done a wonderful Job with them. I hope he does the same someday for his second machine.
Although I am not done with it, I felt like I have enough of the Gantry completed to post a few pictures of it's progress. In this picture you are looking at what would be the front of the gantry. Looking at the rectangular hole at the back of the gantry, I deviated a bit here. The corners are radiused at 1" and I marked them as such. My problem was the largest bit I had was 1 1/2" so the rectangular space is actually 1/4" smaller than what the plans called for. I am guessing that this space was put in the back to help reduce the weight of the gantry.
This is a view of the right side of the gantry. I suppose I should rotate this image so it sits as you would look at it. Anyway, here you see the adjusting blocks for the X axis pipes. These blocks, people inform me, will strip their threads easily if one is not careful. I am hoping they last long enough for me to make some patterns to cast some from Aluminum. If not I suppose I will deal with it then. Notice the hole for the lead screw bearing has not yet been drilled. I have not got around to ordering them yet so don't really know what size they will end up being. Instead I placed a pilot hole.
Finally, here is a top view of the gantry. If you look closely, you can see that the bearing blocks are not attached to the left side of the gantry (right side in the image). I need to get some more hardware.
There are a few things left to do before the gantry is complete. I have to make the pieces that hold the slide assemblies as well as the slide assemblies themselves. The gantry has only been put together with the bolts only being finger tight. Aside from the gantry bottom all screw threads need to be super glued and re-tapped. I hope to finish the gantry by the end of the week. Well, that is it for now. I am getting closer to having my very own cnc foam mill. I am starting to get really excited and the ideas for its use just keep popping up everywhere I go. Till next time ... Happy building.
I thought I would put together the parts that I have made so far. I just wanted to see what they looked like together. Now keep in mind that the machine is not adjusted and there are no pipe supports on one side of the gantry so it may look a little helter skelter.
This is a side shot of the gantry. You will notice the profile of the Z axis on the left side.
Finally, here is a shot of the top of the Gantry Assembly. Again you will notice that the stepper motors and lead screw assemblies are not installed. I am planing on trying to get some more of that stuff this weekend. I have to admit, the plans by JGRO (John) are very well done and easy to follow. So far the whole process has been very enjoyable.
Well, I spent Friday shopping with my wife. Fortunately for me, my wife isn't one of those women who like to shop till you drop, touch EVERY item in the store, buy twice as much as you need and take the rest back tomorrow. She likes to get in, get what she wants, and get out. I could enjoy shopping with her! HEHEHE Anyway, I think I have bought enough hardware to finish the machine, and while I was out ordered lovejoy couplers from a local bearing place and got the flanged lead screw bearings. I have decided to go with 3/8" threaded rod for the lead screws for now. And lastly, I bought a router for the machine. I got a Hitachi 2.25 hp router that comes with both 1/4" and 1/2" collets. And since I was in the area, I got a vee bit and a 1/4" upcut bit. I figure that would get me started. The only thing that I am missing now is spacers for the Y Axis bearings and some plastic to make the Anti-backlash nuts from.
Enough play, back to building. I have started on the last leg of the project so to speak. Here you see the base end that will hold the lead screw bearing and the Y Axis pipe guides. I still need to super glue the threads. As a matter of fact, I still have threads to glue up on the gantry assembly. (So maybe there is one part of the project that isn't too fun.)
Last but not least, here is a picture of the base support from the bottom. Here you can see all the little blocks put in place for bracing. I want to point out something about my experience with this. I used small finishing nails and glue to put this part together. When nailing into the 1/2" MDF it _WILL_ split without a pilot hole. I use a 1/16" bit to pilot all the holds for the entire length of the nail. This helped a lot but still managed to split a few of the block. (FWIW) Stay tuned ... I am nearing a month in the build and I think I see the end in site. As long as life keeps giving me 45 minute and hour breaks, I just may have this machine moving in a couple of weeks. (I hope!) Till next time, happy casting, mold making, machine building, (insert your favorite thing here).
In my last update I told you that I still had some work to do on the Gantry. Well, I have all the holes super glued and re-tapped and the Gantry put back together. Also you seen the base support structure and the base ends that hold the lead screw bearing and the motor. This base assembly has been put together and as you see here it forms the Y axis of the machine. I did run into some difficulty when assembling this part. It seemed that the holes that I cut for the Y axis pipes were a little too close together and I could not get the pipes in. To fix this, I took some of the surface off the bearing support blocks and off the gantry sides. I took a little from each side then done another test fit. Here you see the whole thing put together. Just as a note, I am really surprised how easy the gantry slides along the Y Axis. I thought with all the weight of the gantry, X Axis and Y Axis assembled that it would be a workout for the motor. I have not used the motor yet but based on pulling or pushing it by hand I do not see any problems with it.
At this point I am only lacking the cutting table support and table top. I have most of that cut out and will start assembling them when I get some time, but for now I thought I would work on the lead screw assemblies. Here you see the Y Axis lead screw, Lovejoy coupler and anti-backlash nut. This has not been put together. I done this to get an idea of what it would look like. I was itching to make something move, so I decided I would go ahead and get the X axis setup and running.
In this image we are looking through the back cutout of the gantry at the anti-backlash nut assembly. The plans called for Delrin and not sure where to order fro to get the best price, I settled on using some cutting board material that you would get at your local superstore (read Walmart). Of the couple of places that I read about Delrin, I seen that some of it being sold was approved by the FDA for use in a food setting. I figured the cutting board plastic may be similar enough to Delrin that I could get away with using it. The plastic was cut on my table saw with a carbide blade. This stuff cuts wonderfully, just like butter. All the holes were drilled using a wood template. The plastic is nearly impossible to mark. When drilling I used a low speed typical of what you would set up to drill steel. The bits cut the plastic in long curly strings. I was pleased with how well it drills. Also, the plans called for 1/2" stock. The cutting board I used was 7/16". I figured it would be close enough. Tapping the plastic is a little interesting. The tap cuts the plastic just fine. The interesting part was that you can't really get it to chip like you can wood or metal. At some point the tap is difficult to back out. I ended up running the tap all the way through, pulling the plastic away from the tap then backing it out. Also, the threads cut into it has very little backlash. I think if you want to be super simple, you could get by with only the 1/2 of the nut. I decided though that their would probably be wear so I made the second half as well so I could adjust it later if need be.
Here is another place I deviated from the plans. Originally, John specified 1/4-20 threaded rod for the lead screw, I used 3/8-16 mostly because I hope it will have a little less whip at high speed. Also, John used set screw couplers to attach the motor shaft and lead screw. Instead, I decided on Lovejoy couplers. These can be bought for less than $10.00 each. The Lovejoy coupler consists of three parts. The two outer parts are steel with a bore of whatever size you need. In my case 1/4" for the motor and 3/8" for the screw. And in the middle is a hard rubber / plastic like insert. The nice thing about this setup is that you can have some mis-alignment in your lead screw and the motor can still turn it without binding. Some people have used reinforced rubber hose for the same reason. I should point out that depending on how tight the insert is, it is possible to introduce some amount of backlash back into the system. I believe I have seen on one instance on CNCzone where one person cut new inserts with their cnc from Delrin. I could be wrong but I think it was joeche2000 or something like that.
Lastly, here is picture of the stepper motor that drives the X Axis attached. This motor like the others was 'rescued' from an old Genicom printer. This motor is a PJT80xxx and I could not find any specifications for it. But I did find specs for a PJ80xxx. Normally I would not have used another motors specs but in this case both motors had the same dimensions and same 1.68Ω/Θ rating and both motor were used in Genicom Printers. I am going out on a limb and assuming that one is a replacement for the other. I could be wrong and burn stuff up but at least for now they are spinning with my HobbyCNC controller.
The moment of truth had finally arrived. I had the X Axis completely assembled and I wanted to see it move. What can I say, I am impatient! I hooked the motor up to my controller and fired up the computer. I am using TurboCNC as my control software for reasons I will get into later in another part of the website. I went into the config part of TurboCNC and told it I had 1 Axis. Next I went to the configuration for that one axis and set the step and direction pins, set the active logic levels to low, started the calculator and told it that I had 400 steps per revolution (half stepping a 200 step / rev motor), set the lead screw to 16 threads per inch and set the max step frequency to 1000Hz. Next I went to the setup menu and started the Jog screen. I set the distance to .5" and pressed the right arrow key, well it moved left toward the negative side of the axis. No problem, I have the motor leads reversed, I will fix that after I shutdown and let the system discharge. I held a ruler in place and sure enough, it looks like it is moving as close to a half inch as I can see. I set it to one inch and jogged it, sure enough, it moved an inch, then to five inches and jogged, again it moved five inches. At this point (as I think I told Bob) I felt like a kid at Christmas. I was happy with what it was doing. Next I started to play with the max pulse rate setting in the configure | Axis screen. I kept bumping it up 1000 Hz and trying it out to see if I would lose steps. I stopped when I got to 5000 Hz. Not that I was missing steps but because it seemed to be running great there and it would provide me with some sort of base line to work with when I go to tweak it out later. So, what were my Rapids? I figured I would try to calculate them. If I have this wrong, please someone email me and let me know how to calculate it correctly.
First note that I had the maximum pulse frequency set to 5000 Hz. That means in one second that the computer will send 5000 pulses to the controller with each pulse telling the motor to step one position. Also recall that the motor I am using is rated at 200 steps per revolution and that I am half stepping it giving it a total of 400 steps per revolution. Since I know the frequency of the steps and the number of steps per revolution I can calculate the number of revolutions the motor makes in one second by the following calculation.
5000 Hz / 400 Steps = 12.5 Revolutions per second.
Next, rapids are expressed in inches per minutes and we have a value that is in seconds. Since there are 60 seconds in a minute we can multiply our result above by 60 to get the motors revolutions per minute (RPM).
12.5 Revolutions per second x 60 seconds = 750 RPM
Now that we know how fast the motor will turn in one minute lets work on getting that into linear motion. We are turning a screw that has 16 threads per inch. What that means is that if we turn the screw one time, we will move the nut attached to it 1/16" or 0.0625". Or if we look at it another way, if the screw has 16 threads in one inch if we turn the screw 16 times we would have moved the nut one inch. So if we divide our result above by 16 we will have a distance per minute. This is what we are looking for.
750 RPM / 16 Threads per inch = 46.875 Inches per Minute
Hmmm ... I initially thought I would only get about 30 IPM from these little motors. Maybe they can give me more. If I can use them where they are without adjusting the step pulse frequency, then I am doing 150% better than my planned outcome. But I will refrain from getting too excited yet. I want to see how it all does when the router is hanging on the mix.
With a little luck I will have some time this weekend to make the Y Axis move. It has quite a bit more weight to pull around than the X Axis does so probably will be my benchmark axis. Stay tuned ... till next time. Happy Building!
The boys (BJ, Zachary and Michael) and I turned a good deal of attention to our project this weekend. We managed to get the Y Axis running from the computer and the cutting table finished. Here is the machine as it stands so far. As a test we attempted to draw circles with it, but because there is 5 inches between the Z axis mounting plate and the cutting table the Pens and pencils we tried just flexed too much to know how well the circle was being drawn.
I also played with the pulse rate frequencies to see where I would miss steps with the Y Axis. I pushed it up to 7000Hz before I started losing them. At the 6000 Hz range it done OK, but being on the safe side I went ahead and set the rate at 5000Hz. Now for just moving the thing at a rapid I am pretty happy with the 40+ inches. Now to be truthful, I don't know if I can keep it there or not. I still have a router to attach to the Z axis which will add a few more pounds of weight to the gantry, so in the end I may have to drop it. Worse case scenario is I will have to replace some motors with larger ones. I think the next 'BIG' test will be to see how the 110 oz-in motors deal with the weight of the router. I expect that it will have to move pretty slow to keep from losing steps. I also thought about adding some springs to the Z axis to help with the lift. Time will tell. Keep checking back, I should have this running by June 1st.
I T ' S···A L I V E ! ! !
I think the above line really sums it up very well. I finally got to the point I am cutting material, but first let me discuss how I got there.
When I left you last, I had both the X axis and Y axis running from the computer and tried to draw a few circles and squares, but the pen flexed so bad that I could not tell what was working right and what was not. So next I started on the Z axis, I installed the Z axis lead screw the same way as the others. Two bearings, lovejoy coupler and 3/8-16 all thread for the screw. Now if you remember, I used cutting board material for the anti-backlash nut and it is less than the 1/2" Delrin material called for in the plans. The cutting board I used was something like 7/16" thick. This poses no problems at all for the X and Y axis since the nuts are screwed to the parts that drive these axis. The problem comes from the Z axis, this nut should sit in a slot that was cut to hold it. When I cut that slot I cut it assuming I would be using 1/2" material for the nut. So now I faced the dilemma of how to fix it. Naturally, the best fix would be to make a nut from the required size material or remake the parts that hold the nut. Well, I decided to shim the space left by the nut. The shims I installed were made from steel sheet metal. This seems to be working for now. Once I start cutting I want to remake some of the less than perfect parts and replace them with either better cut wood parts or cast aluminum parts. I will get into that later.
With the Z axis lead screw installed I observed that the motor had to work a bit harder to pull the load up. When I tried to run it at the same speed as the X and Y axis it would lose steps. Currently the Z axis is running at 3000Hz which is 60% of the other axis on the machine. But the thing to note here is that once the motor was slowed down it seemed to drive the axis just fine. Next I built a bracket to hold the router to the Z axis plate. In this image it is hard to tell what it looks like since I have a couple of hose clamps wrapped around it. (More on that later.) After mounting the router I attempted to drive it with the stepper motor. Success, there was no obvious difference between driving the Z axis with the router as there was without it. Now, I just had to cut something.
Here is a line of curved text that I made with DeskEngrave. For those of you who do not know, DeskEngrave is free software available from DesKAM. The software will create either a DXF or G-Code file from your entered line of text. When using a V cutter you can route the line of text into whatever. In my case a piece of MDF. Here is what I learned. The table is not parallel with the X axis, this can be seen from the line that you see routed from the bottom center to the left and between some of the letters. Also, I set the cut depth to 0.200" deep, a value that to me does not look so good for this project and font. OK, the problem with the X axis not being parallel to the cutting table is really a non issue. I did not take the time to line things up so what else could I expect. I just was not thinking. To fix this problem I made a gauge that sit from the table to the bottom pipe of the X axis. I used this gauge and adjusted the Y axis guide pipes until the gauge just touched the bottom X axis guide pipe. This would get me reasonably close and I could mill the table top to get it exact. But for me this is probably close enough, less than 1/64" difference over the whole run of the X axis. Now if you need something very precise, you may want to mill your table top. But for me, this is intermediary, I plan on taking the machine apart and painting it and replacing some parts and adding a couple of modifications. I will go over them as I go along.
After the adjustments were made here is my second attempt. This line of text was created with the same software as above, DeskEngrave. This time though, I only set the cut depth to 0.050" deep. Notice that difference. This piece turned out very well for what it is, I am starting to get really excited about the potential of this piece of home built equipment. I am thinking I should have taken this project on a lot sooner than I did!
Now I am beginning to tell myself that I can use this machine to start making patterns for my Gingery lathe. I load up the code I wrote to cut the lathe cross slide ways support, lay a piece of wood on the table and start cutting, each pass puts a bit of a bigger smile on my face, I am thinking that this is just too good to be true, and wouldn't you know it. Half way through the project the wood clamp I made for the router broke where the screws that clamp it go together. That's OK though, I knew this would be a really weak link and had planned on making two of them to hold the router to the Base support. I also knew that running it with one clamp was folly, but you know how us mad scientists can get caught up in the excitement of things.
OK, after having broke the router clamp, I knew it was time to turn my attention back to the machine. What needed to happen to make it a little better than what it was? Here I sat down and decided that I would want new router clamps cast from aluminum rather than made of wood, so that would be the first thing to take care of. Second, the pipe supports being made of wood are not really durable enough for the job they were put to. Most people replace these with ones made from Delrin and that is probably a great choice, but since I have no Delrin, I will cast these from aluminum as well, besides, I think the cast pieces will be far better than the plastic ones. This is the next thing I do after the new clamps. Now I am also seeing a few things I need to do. This includes, making some sort of dust covers for the Y axis guide pipes, they collect a LOT. I don't know if it will impact the system or not, but I would rather try to keep them a little cleaner than what they are. I need to set up some sort of vacuum system. If you have never cut or routed MDF, it must be the messiest think man has ever invented. It cuts and works like butter, but the dust is super fine, floats in the air and settles on everything. I have to find some dust collection system to keep it down. Additionally, the machine needs painted, I live in Tennessee and the humidity here is unbearable. I can just imagine that the machine is sucking up moisture like a camel after a long haul in the desert! And finally, I need to find a suitable housing for the electronics and some neat way of handling the wiring not to mention some limit switches. I am sure if I keep thinking about it I can come up with another half dozen things, but for now I need to concentrate on the router and pipe supports.
After a while of playing with IMSI TurboCAD Learning edition, I came up with a drawing of the router clamp. I made sure that the drawing only contained the outline of the clamp and not concentric circles with rectangles on the end. I will talk more about this in the G Code section when I have time. Once the drawing was done, I used ACE converter to convert the DXF file to a G Code file. ACE Converter is available from DAK Engineering (the home of TurboCNC) and is a free download. You can get it by clicking the link above. Once I had the file converted to G Code I only had to copy and paste the block of code for the number of passes I needed to cut through the material. I am using 3/4" MDF for the pattern so I decided on 6 passes each taking 0.125" cut. The picture you see here is the pattern with a couple coats of primer. Guess what, A new problem. The resulting pattern is not the same size as the drawing I made to cut it. I am going to guess that this can be from a couple of things. 1) Either I am losing steps (I cut it at 20 inches per minute). 2) My router is flexing around because it isn't clamped well. 3) I have some backlash in the system. But this is OK for this particular pattern. I will chuck the casting in the lathe and bore the inside to near the diameter needed for the router. I will also attach the casting to a angle plate so that the bottom can be cut perpendicular to the clamp side.
Well that is it for now. I will show you more as I get some time and try to catch up some of the other parts of this project. Stay tuned and check back once in a while. Happy building!
When I last left you I had cut out a pattern for a new router support ad given it a few coats of primer and a clear coat or two. The pattern as you recall did not cut quite right to size but since there was material left to remove it was not such a problem. The problem I did run into though was that there was not enough draft in the pattern to allow me to remove it from the sand without breaking the edges of the mold. Frustrated after a half dozen tried to mold it, I decided to use a rasp and file some more draft into the pattern. This at first seemed like a good idea, but I soon discovered that it would not leave enough stock to cut with the lathe. I abandoned the pattern in a (cough) fit of rage and decided I would start with the pipe supports instead.
I knew this time I had to be a little more diligent in my design and set out to create the support. The problem was I did not know how to cut the taper. Very fortunately for me, Bob was kind enough to help me by generating the G-Code for me, while I took to reading material to try to learn how to do it.
This is the finished pattern made on the machine. Before cutting this I checked all my anti-backlash nuts to make sure they were adjusted. I found no real problems so I thought if the pattern does not cut to the right size I will have to look for lost steps or somewhere else for my problems. But when all was said and done the pattern had come out perfect. What you see here is mostly how it came off the machine with the exception of cutting the tabs off and very little sanding. I have decided that I will cut another pattern out with the same code and cast two of these at the same time. If life ever gives me a break to do some fun stuff rather than work, I will post the results here.
Well a lot of things have happened since I last commented on this page. I thought I would list a few of them before they slipped my mind totally.
I have taken the mill apart, to paint and do some upgrades. So far I have the base painted and the four Y-Pipe supports cast. I hope to assemble this part back together this week. Also, I have decided that it needs to have some sort of a structure of its own to sit on. I think I will make a frame from 2x4 material with some casters to that it can be moved around easy. Once I have the base back together I will snap a picture of it to post so you can see the progress. I have to admit, the aluminum pipe supports screwed down to the gray machine looks kinda nice. But then again, my wife would argue that I have no color perception anyway. Take a look for yourself when I get them posted. Also, as a side note, for those of you who occasionally check on this page. Progress will be slow, as I have started building on the new workshop and have some serious remodelling to do in the house. Keep the faith, updates will show up occasionally. :-)
I have not done much since my last post. I thought I would post a picture of the new Y-Pipe support for you to look at, and the gray color paint I selected for the router. Anyway, time is not on my side to get much work done on it because I have so much other building and remodelling projects to finish first. But those few minutes that I can steal here and there to work on thing will add up over time I hope.
Some of the stuff for my machine I had on hand and other stuff, I done little dumpster diving. But I thought I would try to keep track of my costs as I purchased things so that I would have some clue as to what I had in the project. Maybe this will be a help to someone trying to figure out how much this would cost them. I suppose your milage may vary.
|3/4" MDF||$21.00||Most of the machine is made from this with the exception of the base and bed supports. I bought this at Lowes.|
|Misc. Hardware||$18.00||I decided that I would but hardware as I needed it. This was the hardware for the Z and X Axis. (Bolts, Nuts and that sort of stuff)|
|HobbyCNC Controller||$106.00||This is a 4 Axis chopper circuit controller. I ordered it from HobbyCNC.|
|1/2" MDF||$23.00||I had to order this. No company that I called carried this stuff on the shelf. I got this from Lowes.|
|Misc. Hardware||$23.00||Again, I have been buying hardware as I need it. This was for the Gantry and the rest of the X Axis.|
|Gas Pipe||$24.00||I had a small piece of 1/2" gas pipe layng around that would work for the Z Axis. I bought enough 1/2" and 1" pipe to do the X Axis and Y Axis.|
TOTAL PROJECT COST - $215.00
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