Second Momus Build (Pro Version)

[bjesson]

What drives are you using, and what voltage are you running at?

I'd try as Louie suggests, but I'd try 1/8 stepping first. COuld be that your PC is having trouble with the high pulse rate. You might also try increasing the pulse width.

louie/ger

using tb6560 drives. I played around with the microstepping all they way back to full step. the only way I can get any decent torque is if I set the velocity very low. At that point the machine seems to just crawl. When I set to 50ipm (reading the torque chart i should get most at 500rpm or so) the motors just whine and dont move the gantry, torque seems completely gone. Im using 24 volts but being on 4 steppers now instead of 3 I will try cranking it up a bit to see if any better results. I did try swapping the motors (270 oz in on 5 start and 495 on 1 start and as ger pointed out a few months ago the performance was terrible. the 495 on the 5 start is a nice strong combo but i can only run it at 40 ipm velocity. Anything higher and it wont move the carriage. Im also going to try to up the kernel speed, right now it is set at 35Khz, not sure if this will help in any way.

Thanks guys...

billj

[louieatienza]

louie/ger

using tb6560 drives. I played around with the microstepping all they way back to full step. the only way I can get any decent torque is if I set the velocity very low. At that point the machine seems to just crawl. When I set to 50ipm (reading the torque chart i should get most at 500rpm or so) the motors just whine and dont move the gantry, torque seems completely gone. Im using 24 volts but being on 4 steppers now instead of 3 I will try cranking it up a bit to see if any better results. I did try swapping the motors (270 oz in on 5 start and 495 on 1 start and as ger pointed out a few months ago the performance was terrible. the 495 on the 5 start is a nice strong combo but i can only run it at 40 ipm velocity. Anything higher and it wont move the carriage. Im also going to try to up the kernel speed, right now it is set at 35Khz, not sure if this will help in any way.

Thanks guys...

billj

Hmmm, could be a PSU/drive issue like you mention. I believe the Sherline CNC mill uses only 150in-oz steppers (unipolar) with 10TPI leadscrew, but is capable of milling steel.

I would also check that all your connections are secure/tight. I
just had an incident where my X (gantry) axis looked like it was stalling, until I saw some arcing in the molex connector at the motor. After crimping the female connectors slightly, I go t a good connection, and taped the connectors together. No more problem...

[bjesson]

played around with it for a few more hours. Could only bleed 2 more volts out of the PSU so not much help there. I was able to get better performance out of the 495 oz in on the 10 single start lead screw which tells me my biggest issue no matter what motor i use is the 1/2-10 single start lead screws. I had the bigger motors at 60 ipm and seemed to run smooth with slight stalling. Changing to the 5 start will technically get me 300 ipm which is a bit fast for me but can be dialed to the 150 ipm range and give me more torque in return and hopefully more reliability on the Y axis. I'm also going to dump the 270 oz in stepper and just use 495s on X/Y with the 5 start lead screws. Also going to get a better PSU, the current one was good for the original setup I had but may be a huge factor in the issue i am having since it is only a max 26v/8amp. the 4 steppers alone chew up 8 amps based on specs. 36v/15amp should be plenty. got to order them tomorrow so wont be any updates til end of next week when everything comes in and I mount them.

Thanks for the suggestions so far...
billj

[ger21]

Keep in mind that the 495oz motors are a bad match for a good drive. And you have what's probably the worst drive you can have. Even with a G540, you'd get less than half the performance those motors are capable of. My guess is that you're probably getting less than 1/4 of what the torque curve you have says.

[bjesson]

Got it all figured out. ordered more 1/2-10 5 start lead screws/ABL nut/coupler and mounted them last thursday. Used 1/8th stepping and problem solved. Running it at 150 IPM without any whipping or reliability issues. Very smooth operation and feels like plenty of torque. Now gonna do a full re-alignment to make sure its all squared up and try to cut a test Les Paul archtop out of it.

Is anyone using lubricant on their leadscrew/delrin ABL nut? any recommendations?

Billj

[bjesson]

Finally!! All bugs have been fixed. Had to go with the 495 oz in steppers for all axis just to simplify the headaches, overkill yes, but didnt require anymore troubleshooting. Upped the PS to adjustable 28V/15A to meet what the formulas said I needed. Z was changed from the 3/8-10 1 start to a 3/8-8 4start to match same pulses per rev as X/Y. Currently running at 1/8th microstep on all axis.

Billj

[bjesson]

Table area is 36"x42" with a working area of 21"x25". Total footprint is 44"x44".

[bjesson]

And my first test cut to make sure the machine wouldnt bind, miss steps, or any other issue that could ruin the machine or part. This is an archtop les paul body I modeled in Autocad, imported to Rhino, created gcode in RhinoCAM. 1st 2nd and 3rd pic are the rough cutting with a 3/4" ball end and 4th pic is after the final using a 1/4" ball end mill.

[louieatienza]

And my first test cut to make sure the machine wouldnt bind, miss steps, or any other issue that could ruin the machine or part. This is an archtop les paul body I modeled in Autocad, imported to Rhino, created gcode in RhinoCAM. 1st 2nd and 3rd pic are the rough cutting with a 3/4" ball end and 4th pic is after the final using a 1/4" ball end mill.

Nice...

[jdavidspencer]

Fantastic work!

It would be great to see pictures of finished work done with the Momus machine. I can't seem to find many pictures of what people are using their machines for.

[bjesson]

Fantastic work!

It would be great to see pictures of finished work done with the Momus machine. I can't seem to find many pictures of what people are using their machines for.

I will be running a final version of the archtop from maple tomorrow. will post some pics. I also have pics in older threads of the aluminum parts I made using my original momus cnc. Some of the parts on this new cnc were cut with the old ones. You can see some examples of cutting 3/4 to 1" plate aluminum so all-in-all this design is a great little work horse.

billj

[jdavidspencer]

How does this new machine compare to the old one and are you still looking for better? I love the way you have simplified things, it looks "right".