[mlk1950]

I am running the HobbyCNC pro 4 -axis pro board, with 305oz-unipolar rating, 4.2v, 3A, 200 S/R, 3.2mH, Size #23, Dual Shaft, stepper motors. My screws are dual 1/2”, 8 /2-start on the X, single 3/8”, 8/2-start on the Y and 3/8” , 10 single start on the Z. I was running dual steppers on the X, and decided to go with a single stepper with 2 belts. Every so often when I hit the forward or reverse keys on the X, the stepper stalls. When it stalls, say in the forward movement, if I hit the reverse, it will move. Then when I hit the forward after going in reverse, it works. I let Mach calculate the steps per on the X and Y and it set it at 3200. I have the accel set at 40 inches per and the velocity set at 35. I am running the Dumpster Anti-backlash nuts and they seem to run free. I have checked for any mechanical binding, and found none. Why is the X stepper stalling.
Any help will appreciated.
Mike

[ger21]

Your acceleration is too high. Acceleration is typically 10-20% of the velocity. I have smaller motors on my machine, with a Xylotex, with the same screws. I use an accel of 10, with a velocity of 150.

Try lowering your accel to 20.

[Devastator]

I have almost the exact same setup as you. Hobbycnc EZ driver, 291 oz. in motors, one motor with two belts on the X. I have mine set @3200 steps per unit as well. Biggest difference in our machines is that I use 5 start screws.

My velocity is 125 and accel is 15. Rock solid at that setting.

[mlk1950]

Thanks Gerry, did not know that. So the velocity is what dictates how fast your axis moves? I thought it was the other way around. I learned something new again.So what could I run the velocity at ? This is a home built 24" x 48" Solsylva machine.

[ger21]

All machines are different, and a lot of factors come into play. You should be able to get to somewhere between 100-150ipm.

[Devastator]

This is a home built 24" x 48" Solsylva machine.

Same as mine...Solsylva 24X48....http://www.cnczone.com/forums/cnc-wo...lva-build.html I can jog @400 IPM, but I don't dare run it that fast. If I ever get around to hooking up my G540, I imagine I could get close to double that. Like Gerry said, each machine is different. I just kept bumping up the velocity setting until I got it to fail to see where my red line was, then set the accel at roughly 33% of that for reliability.

[mlk1950]

Went out last night and changed the Accel. The stepper did seem to run alot smoother and longer without stalling. But just when I was starting to feel good about it , it started to stall on me again. Not as often, but still stalled. I might take the stepper I was using as the slave to the X and switch it with the one that's on there now and see what that does. The reason I went to one stepper and two belts on X was when I was running two steppers on the X, one would loose steps every so often.

[mlk1950]

All machines are different, and a lot of factors come into play. You should be able to get to somewhere between 100-150ipm.

Man, I wouldn't know how to act with speeds like that. I've always carved at 35 ipm or slower

Same as mine...Solsylva 24X48....http://www.cnczone.com/forums/cnc-wo...lva-build.html I can jog @400 IPM, but I don't dare run it that fast. If I ever get around to hooking up my G540, I imagine I could get close to double that. Like Gerry said, each machine is different. I just kept bumping up the velocity setting until I got it to fail to see where my red line was, then set the accel at roughly 33% of that for reliability.

I'd like to see some pics of your machine. Maybe I could get some ideas from you on what upgrades I could do. I just upgraded the screws on the X and Y from Acme 10 single start to 8-2 start.

[Devastator]

I'd like to see some pics of your machine. Maybe I could get some ideas from you on what upgrades I could do. I just upgraded the screws on the X and Y from Acme 10 single start to 8-2 start.

The acme five start screws were the best investment I made. Since you slowed down your accel and are still getting stalling, you either have binding or resonance. I found when I set mine up that it doesn't take much binding to cause skipped steps. I spent many hours adjusting to get everything to move like silk. I haven't had to touch it since. Some people have a big problem with resonance with the Solsylva/hobbycnc driver combo. I never have, although I did build a damper for my Z while I was trying to track down the cause of another issue. I suspect that my choice of leadscrews helps that by not requiring the steppers to turn at high RPM's.

When yours stalls, is it during accel, or at full rpms? That can help narrow it down.

The biggest upgrades I done to my machine were in the rigidity components added. Like steel angle, laminated ply beams, larger fasteners and threaded rod than the plans call for, etc. Even the bed of mine is a torsion box that weighs 300 pounds. It is a very heavy machine. The heavier I make it the better it performs.

On my bearing mounts I didn't make them built in to the uprights like the plans show, I made them out of rectangular steel and bolted them on. They are fully adjustable to line them up properly. There are still a lot of things I would have done differently, but as the machine was already built I had to come up with ways to add on my modified components. It is a really good basic platform to cut your teeth on and can be a great machine if you have the time to fix the problems inherent in the design.

Let me know if you'd like photos of specific component upgrades and I'll post them to my build log.

[ger21]

Went out last night and changed the Accel. The stepper did seem to run alot smoother and longer without stalling. But just when I was starting to feel good about it , it started to stall on me again. Not as often, but still stalled. I might take the stepper I was using as the slave to the X and switch it with the one that's on there now and see what that does. The reason I went to one stepper and two belts on X was when I was running two steppers on the X, one would loose steps every so often.

Lower your accel even more than. Try 10

[mlk1950]

The acme five start screws were the best investment I made. Since you slowed down your accel and are still getting stalling, you either have binding or resonance. I found when I set mine up that it doesn't take much binding to cause skipped steps. I spent many hours adjusting to get everything to move like silk. I haven't had to touch it since. Some people have a big problem with resonance with the Solsylva/hobbycnc driver combo. I never have, although I did build a damper for my Z while I was trying to track down the cause of another issue. I suspect that my choice of leadscrews helps that by not requiring the steppers to turn at high RPM's.

When yours stalls, is it during accel, or at full rpms? That can help narrow it down.

The biggest upgrades I done to my machine were in the rigidity components added. Like steel angle, laminated ply beams, larger fasteners and threaded rod than the plans call for, etc. Even the bed of mine is a torsion box that weighs 300 pounds. It is a very heavy machine. The heavier I make it the better it performs.

On my bearing mounts I didn't make them built in to the uprights like the plans show, I made them out of rectangular steel and bolted them on. They are fully adjustable to line them up properly. There are still a lot of things I would have done differently, but as the machine was already built I had to come up with ways to add on my modified components. It is a really good basic platform to cut your teeth on and can be a great machine if you have the time to fix the problems inherent in the design.

Let me know if you'd like photos of specific component upgrades and I'll post them to my build log.

Yes, I built mine to specs. The one thing I did was to use 6/4 poplar for the gantry. I jointed it, thickness planed it and cut the groove in the center with a dado. I never have been real comfortable with the bearing mounts. I would like to see how you did your bearing mounts and supports. Also, I am running 1/4 steps and was wondering if I should be running 1/2 steps instead. My computer is a 1 gig dell with 2 gig of memory. I was thinking of a binding issue, because I know it only takes a few thousandths to mess things up. I have been carving with mine for about 4 years now and have never had hardly any problems up until recently. My stalling problem is getting better but shows it's ugly head every so often.

[Devastator]

Also, I am running 1/4 steps and was wondering if I should be running 1/2 steps instead.

1/4 steps sounds right for the leadscrews you are using. I use 1/8 steps but I have faster lead screws. You might try 1/8 steps just to see how it behaves. Most of what mine is set at was determined by trying every setting I could. I put hand knobs on the ends of all of my leadscrews so that I can turn all of the axes by hand to feel for binding. These knobs do double duty to set the bearing preload. I also use thrust bearings on all axes so I can set the preload without loading the radial bearings.

Agreed on the bearing mounts on that design. That was the first thing I changed. Aluminum flat bar bent at an angle is too weak to hold the gantry to the rail. I use aluminum rectangle bar stock cut at an angle. I'll try and get some photos on my build thread for you.

[mlk1950]

Thanks to you and Gerry, I think I'm on the right track now. You know when this thing was working right, I just kind took it for granted. When it started messing up I said a few things I can't repeat here. Guess after 4 years of carving things have to start loosening up a little. Of course having having my accel and velocity backwards didn't help either. BTW Gerry, I set that to 10 and that seemed to smooth it up even more.
Thank you for your help.
Mike

[ger21]

I'd use 1/8 microstepping. It should make your motors run smoother. And it really has nothing to do with the screws you're using, unless your PC can't output steps fast enough.

[mlk1950]

I tried the 1/8 microstepping, and it didn't seem to like it. So, I have it back to 1/4 with 65 on the Velocity and 10 on the Acceleration and seems to like that the best. So far no stalling when I jog it. Maybe I just don't have enough computer to support the 1/8th. I set the Velocity at 100 when I had it at 1/8 just to see what it would do, and it stalled.

[ger21]

What voltage are you running at?

Sounds like you may be seeing resonance.

I can run my machine, which is probably heavier than yours, at 150ipm on the dual driven X, and 190ipm on the Y axis. Using a Xylotex set to 1/8 stepping, 24V, and 250oz motors, with a 1Ghz PIII with 512MB of RAM.

I have dampers on my motors. Without them, the machine is almost unusable.

[mlk1950]

Well I've got more than enough computer. Do you mean the voltage on each axis? Or the voltage at the main terminal? If so I'll have to check. The transformer I believe is 24 volts. I won't be able to check till tomorrow morning, so I get back then. It's been 4 years since I built the control box and I just don't remember.

[Devastator]

And it really has nothing to do with the screws you're using, unless your PC can't output steps fast enough.

I mentioned it because of resolution and also with higher microstepping I've noticed that mach limits the max velocity. If you have slower screws, you can use lower microstepping and still have good resolution.

[Devastator]

Guess after 4 years of carving things have to start loosening up a little.

I'd suspect binding over resonance since you've already been running for four years. Something has changed, tightened, or worn. Could just be dust build up on the rails, bearings, leadscrews too. If I were you I would clean everything, lube it up, adjust bearing clearances/preload then check for binding by hand. If you really take some time to fine tune it, you might find that it actually performs better than when first built.

[mlk1950]

What voltage are you running at?

Sounds like you may be seeing resonance.

I can run my machine, which is probably heavier than yours, at 150ipm on the dual driven X, and 190ipm on the Y axis. Using a Xylotex set to 1/8 stepping, 24V, and 250oz motors, with a 1Ghz PIII with 512MB of RAM.

I have dampers on my motors. Without them, the machine is almost unusable.

I checked the voltage on my HobbyCNC board this morning and it was 30 DCV. This was measured at the TB6 terminal. I installed a damper on the X and got her running 100 ipm nice and smooth. As far as the binding, I think it's good as I have checked all this during the screw upgrade and the stepper reconfiguration process.
Thanks to you, Gerry and Devastor I think I'm in the ballpark now. At least it's narrowed down and I know what to focus on for improvement. Thanks much for your help.