That looks fantastic, Michael! I'm still stalled on my build for the moment, so it's always great to see others making good progress. Keeps my hopes for the future alive.
I know I owe some more build pictures, but I just had to post.
No cable management, no limit switches, no real motor tuning. Just barely have the electronics working. I still have some adjustment and tuning of the mechanical parts to do as well.
http://www.youtube.com/watch?v=g7ldl-1aGyo]Michael's Momus CNC first motion - YouTube
That looks fantastic, Michael! I'm still stalled on my build for the moment, so it's always great to see others making good progress. Keeps my hopes for the future alive.
I still need to post the metal part of the build, but the electronics are easier, so we will do that first.
Again, I have to be different and I have to be cheap.
Steppers: LIN ENGINEERING 5718M 2A Unipolar motors for all axes. Small compared to some, but they only cost $10 each. NEMA 23 sized, so they fit just fine. The ones I ordered from E-Bay were 8 wire, thus they could be wired unipolar, bi-polar parallel or bi-polar serial. One reason I picked them (Price being primary) was that I could use any stepper controller I wanted. They are listed at 130 in-oz unipolar, 294 in-oz bipolar.
5718 High Torque Stepper Motor |NEMA 23
I bought them from e-bay seller “cncjunkie”. Note that he sells them with and without the attached gear. Get them without as it’s hard to remove and it’s not the right size. I bought them with the gears hoping they were correct. It took two hours to remove three gears. They were Loctited to the shaft.
Electronics suite: Probably not one you have seen before. SOC Robotics MK4 Break-out-board and 4 MK160 bi-polar drivers. The drivers are 3.5 amp maximum. Why? Again, cost (as usual) and perceived quality). The drivers are the usual TB6560 chips, but these are a completely different design. I e-mailed the company in Canada and he convinced me that he know what he is doing. Time will tell, huh? $65 bucks.
SOC Robotics Smart Embedded Products
I bought them from E-bay seller “modularcnc” who is actually SOC-robotics themselves. Current price looks to be $75.
Power supply(s): Again, cheap as I can be, I needed 24 volt power supplies and about 10 amps or so. I didn’t find exactly that, but I did find 6.5 amp supplies for $15, so I bought two. I used one for the X-axis and one for the Y and Z. Why so cheap? They used a proprietary power connector. No problem, just soldered on some pigtails.
I got my stepper motor wire and pulleys from Hubbard CNC just like most folks do.
So, what does it look like? The power supply board will fit in the forward right bay and the CNC controller will fit in the aft right bay next to the X-axis stepper. For now, I just put both boards on a larger board to keep them off the floor. I’m not happy with the mounting hole layout on either board, so I’m thinking I’ll wait until I can CNC some better ones.
The metal part of the build: This kicked my butt far more than it should have. Mostly my fault though and Iíll tell you what I did wrong along the way. Also, there are not many in-process pictures as I somehow managed to not store them someplace I could find them. Sorry about that. That also means Bob wonít get to see too much more blue tape.
To recap, this is not a standard build as I made the left and right sides of the machine the same height and width with the possibility of using the new left hand bays for more entertaining guts. I also made a few enhancements and will note so when they come up.
Letís start with a little safety info. Iím using a common woodworking sliding compound miter saw and itís not supposed to be used for metal working. So, I took off some of the plastic parts and then put down ľĒ hardboard on the fence and table. I knew Iíd probably kill the blade, but it was due for replacement anyway. Iíd suggest buying a cheap blade if you go this route. I cut the aluminum on the miter saw just fine. I also cut a few steel parts. I do not recommend it. The blade is missing a few teeth and is completely dull now. Remove any dust bag on the miter saw and clean up all saw dust before proceeding. I also did a few cuts on the table saw. I completely vacuumed all woodworking dust up before using it. When youíre done with all the parts, you will have this metal mess to clean up.
Part layout: Always measure starting from the same place on the part. Donít measure some holes from one end, some from the other. If the part length is not dead-on, you will have errors you may need to fix later. I believe Bob is going to be more consistent when he does the next revision of the drawings. Also, its generally better to mark each hole using the end of the part than to lay out from hole-to-hole. Tiny errors on each measurement add up and the last hole can be off a lot. So, do the math and re-mark the drawing before laying out the part.
Organization: At the drill press (or portable drill if thatís all you got), you will be switching bits frequently. I took a scrap of wood and laid out my bits and their use so Iíd not lose them.
I chose to cut each part or pair of parts individually instead of doing all one operation and then going on to the next one. I did this for a few reasons. Firstly, I wanted to get one or two finished to make sure I had the process down before ruining a lot of metal. Secondly, I have a bit of carpel tunnel syndrome and tendonitis and tennis elbow and the repetitive operations start to hurt after a while. Thirdly, I wanted to build up the machine as I went. To the third reason, I chose to start with the x-axis parts first, then the y-axis and then the z-axis. I left the drive components and various bracketry to the end as they werenít needed to see the cool parts move.
X rail plates. Since the left and right hand x-rail plates are now mirror image, they both look like part 37 except one doesnít get the motor holes. I also left out the front pulley attach holes and will explain why later. These parts are taped together and laid out at one time and processed as much as possible before separating and doing the motor holes. If your stepper motor has a raised face that needs to fit in the 1.5Ē hole, make sure it fits by filing and sanding the hole prior to laying out the 4 attachment bolt holes. Also, you might consider match drilling those 4 holes using the stepper motor itself for accurate alignment. Measuring 0.928 ainít easy. I have a set of transfer punches so it was an easy matter to put the motor in place, center punch the 4 holes and then go back to the drill press and drill them.
For the x rail angles, again, I made two part 34 and just didnít cut the motor holes.
Ditto the X rails themselves. Same on both sides using part 33. This is my first real screw-up. I drilled these to a .3125 clearance hole instead of a tapped ľ-20. No problem, right. Iíll just get some ľĒ all thread, cut it into lots of little buttons, plug the holes, loctiting in the plugs then redrill. It didnít work all that well. I had an extra length of steel, so the right hand rail got re-made. Iím still using the plugged left hand rail and since its working fine, it will probably stay that way. But, it was a hassle not worth doing. When I went to tap the plugs, they would spin in the holes even though they were loctited in.
Here is a pic of the repaired holes.
And the finished left rail.
Y-axis gantry: Invest in a step drill that electricians use for drilling into metal boxes and use that to cut the big holes in the gantry tube. I chose to cut the notches on my table saw with the work piece held vertical once the holes were drilled. Not everyoneís cup of tea, but it works for me.
For all the 0.75 x 0.75 parts, the process is pretty much the same. Mark -drill-mark-drill-mark-drill until your head hurts. I use a fence on the drill press table set to a 3/8 center line and only mark for the length on the part. At some point, you will screw up and drill an off-set hole on center line. And you will yell at yourself. Oh well! You will also drill set-screw holes on the wrong side. No worries, just drill completely through and tap the side you like. Heck, tap all the way through if you like. No harm done. I elected to not make the counter bores except for parts larger than 0.75 thick. It works fine. For the thicker parts, you need the counter bore because your tap is likely not long enough.
Y motor mounts. You can skip cutting the notch. It adds nothing but making the part look pretty. Just make both 10-32 holes the same. If your motors have a raised face on them, you need to add some relief in the top face of the mounts or space your motor up on some washers.
Here is where you need those fasteners with the heads ground down. I just bolted them through a scrap of wood and sanded them down with my drum sander. The fence you see in the pic was just bumped a bit closer to the drum with each pass. Quick and consistent.
Not much else to say, the axis goes together fairly quickly once all the parts are done. Iíll talk about the belt attachment later. There is one issue you might want to fix on part 8. Go ahead and assemble and adjust. The x-axis can be attached later. You donít need to slide it on from the end.
More of the same. I screwed up and drilled a through hole instead of a #10 tapped holes for one of the set screws in a bearing block (part 15). Fortunately, only once. I was able to Loctite in a piece of all-thread and redrill successfully here. Plenty of surface area for the Loctite unlike the x-rails.
The only thing difficult here is the z motor mounts. For these, you need to cut the 0.625 radius and it seems difficult. But its not with a little trick. Again, skip cutting the diagonal on these parts. Itís unnecessary. Go ahead and drill the 0.3125 holes in part 20 and the mating ľ-20 holes in part 21.
Create a sandwich with some scrap plywood or mdf as a spacer. The spacer needs to be 0.75Ē. Plywood is a bit undersized, so some masking tape can be used as a shim to get the thickness right. Bolt your part 20, your spacer, and then part 21 together making sure your motor mount holes are outboard if you already drilled them. Use a c-clamp opposite the bolt holes or the parts will want to spread apart. Then, with the center marked and pre-drilled, use a bi-metal hole saw to cut all the way through. You can use a bit larger hole saw and itís not critical. I happen to have a 1.5Ē hole saw, so my radius was 0.75. Also, take the plastic pads off your c-clamp. They melt and stick.
Assembly of the carriage is straightforward. Put it all together on the bench first. Then, remove the lower part 16 with whatever happens to be attached to it. Place the carriage on the gantry and re-install part 16. No need to remove the gantry.
The Z-axis is straight forward. If using one of the available Bosch mounts, account for the different lower two hole spacing before assembly or you going to be taking it apart again. But itís not difficult if you do.
Odds and ends:
Y-axis. You can use a 250 tooth (50 inch) continuous belt for the y-axis without any modifications. Itís a perfect fit. No need to worry about installing a spliced belt. The continuous belts at McMaster-Carr can be had in kevlar belting which is a bit less stretchy than the suggested glass belted.
X-axis. You can use a 210 tooth (42 inch) continuous belt for the X-axis with a little modification. It works nice and Iím real happy with this deviation from the plans. This is why I didnít drill the forward pulley holes in the x-axis motor plate. Iíll have to detail the exact part dimensions for this in another post, but basically, you create a sliding pulley mount. You install the belt with the plate in its most aft position and then use the jack screw to tension the belt. It works real slick. Just donít over tighten the belt.
Timing belt clamps.
Firstly, for part 8, the x-belt plate, the two lower holes are better off being tapped ľ-20. Not 0.3125 thru as defined in the drawing. Its too hard to get the nuts on the bolts as designed. It would be a very easy change.
If you have a table saw and donít mind scaring yourself a bit, you can cut the grooves using a thin kerf carbide blade. You start at one edge of the part and then just move the fence right exactly 0.2Ē and make another pass until you get all the grooves cut. I clamped a digital caliper to the tablesaw fence to guarantee correct placement. Use a good push block and a second hold down, eye protection and you should probably wear a cup too.
I used ĺ x ĺ hardwood. Much quicker and easier. If you counter bore the ends with a ĹĒ forstner bit, you can eliminate the custom washers. I'll deal with the wiring and limit switches in a separate post.
Wow, fantastic post! All of the modifications you've made are really well thought out and implemented. I particularly like that jack screw tensioner on the X belt. But I do think I'll skip the method you used to cut the grooves in the belt clamp. I'm pretty comfortable around my table saw, but that would be pushing the boundary a bit too much for me.
Thanks for figuring out how long of a continuous belt will work on the X and Y. I've been meaning to do that for a while now. I'm really kicking myself now that you point out that both sizes are nice round figures. I'll have to include this info in the next plan revision. But why couldn't you have posted this a couple of weeks ago? I just got an order from McMaster Carr a few days ago and this definitely would have been included, had I known. I've been wanting to test out some different belt/cord materials for a while now.
I do see a little bit of blue painter's tape in a few of those photos. Although you make up for any shortage of tape in photos by showing us your nice baby blue limit switches.
One last thing- those black button head screws and flange nuts look sweet.
Thanks for the kind words. You will have to do some math on the exact position of the tensioner. I just laid it out and center punched the loose end of the slottted holes. The nice thing is it can be done post-assembly and you don't really need to know the location. Eyeball works fine.
The limit switches are lime green. You need a new monitor (or new eyes)
Yes, I like the black oxide fasteners. Not too much more money but the 5/16 locknuts I thought were ridiculously expensive, so I passed. I really should take it apart and polish the aluminum and paint the steel black.
And somewhere, somehow, I'll find more uses for blue tape.
Do you have any drawing of your router clamp ? or can you take better picture ?
I do not think I have a drawing. I just scratched this out on engineering paper and laid it out directly on the metal. The dimensions are partly based on what scrap metal I had around the house and not optimum.
The basic hole locations are derived from this mount you can find in the sketchup 3D library.
Bosch Colt - Fireballv90 by daveand5 - Google 3D Warehouse
I kept the vertical spacing the same, and used 1/4" material for the mount. You also cannot use just the forward pinch bolt as you cannot lift the router straight up. You need to use a two piece upper clamp as shown in the pics above.
After I built the mount, I found that you need to space the router outboard about another 1/8" to give some more clearance for the mounting bolt heads and the side of the router body.
My current version of this mount uses the existing Z-azis holes. No new holes are drilled, but I consider this design sub-optimal and my next revision will use a different mounting hole position.
I used 1/4" thick aluminum as I found a scrap in my storage shed. It was riddled with screw holes from whatever equipment I salvaged it from. 1/4" material, butted together so you are using the edge of the material to hole screw threads necessitates the use of #6 fasteners as a maximum and even then, hole placement is critical and your violating recommended edge distances for fasteners. Its not the right material for this application.
My next revision will be from 1/2" phenolic and I hope to start cutting that this weekend. When I'm sucessful, I will share dimensions with the group. If you don't have or know how to use SketchUp, I can probably scratch out some basic dimensions this weekend.
Lots of info on the build!
What do you really think about your MK4 and MM160's?
I am in the process of getting some parts for a machine of my own, and snagged up the same eBay lot from the same seller you did... only I scored mine for $32ish
Do you have any suggestions for matching steppers / P/S to go with this? I want to start small with an engraver / PCB mill type setup and was thinking about going the 70oz in to play with, or going around the 270oz in range to allow for future upgrading to a medium sized machine.
I'm currently waiting for my nuts and bolts and timing belt to come in. Hopefully this week. I finished up the metal work except for 4 pieces which is simple drill holes. The only thing I wished I waited was the stepper motors. I got 3x 425 oz and it came with 8mm shafts. Can't seem to find any 10 tooth pulley with a bore size of 8mm.
Anyone knows if going to a 16 or 24 tooth going to be a problem?