Can a driver card be your speed issue

[tjfdownsouth]

I have the easy-cnc driver card that I bought for a foam cutting machine and have since retasked it to run a jrgo router. The thing i don't like is that i cannot get it to go over 28ipm before the motors stall. I have a 24V power supply and a 3/8-16 screw so i thought i should be able to get up to 50ipm or so.
I had these motors on it VEXTA PK266-02A from mpja and thought they weren't strong enough so i upgraded to these 57BYGH405A. I tested all travels to make sure they run free and tested the motor without being connected. Everytime i try to go over 28ipm the motor stalls. I have tried changing all of the settings but it continues to stall at about this speed whether the motor is connected to the screw or not. It seems that once the motor gets to whatever rpm this is that is it.

I am thinking it may be the driverboard but before i go buy a G540 or something I would like some other suggestions. This is connected to a dedicated desktop pc that only runs mach3 so it shouldn't be a software issue.

Tim

[ger21]

The drives, motors, power supply, and leadscrew all need to work together as a matched system to optimize performance. With those screws you're using, no matter what you do, 50ipm is unlikely, or about the absolute maximum you'd ever see.

[irving2008]

Originally Posted by tjfdownsouth I have the easy-cnc driver card that I bought for a foam cutting machine and have since retasked it to run a jrgo router. The thing i don't like is that i cannot get it to go over 28ipm before the motors stall. I have a 24V power supply and a 3/8-16 screw so i thought i should be able to get up to 50ipm or so. I had these motors on it VEXTA PK266-02A from mpja and thought they weren't strong enough so i upgraded to these 57BYGH405A. I tested all travels to make sure they run free and tested the motor without being connected. Everytime i try to go over 28ipm the motor stalls. I have tried changing all of the settings but it continues to stall at about this speed whether the motor is connected to the screw or not. It seems that once the motor gets to whatever rpm this is that is it. I am thinking it may be the driverboard but before i go buy a G540 or something I would like some other suggestions. This is connected to a dedicated desktop pc that only runs mach3 so it shouldn't be a software issue. Tim

The reason a motor stalls is simply because the voltage you are driving at isnt sufficient to push enough current through the coils in the time available (1/200 of the rotational speed at full step) to overcome the detent torque of the motor plus any other load. These are 2.4mH motors so the optimal voltage would be 50v. on a 3/8-16 leadscrew 28ipm = 448rpm = 1500 steps/sec. thats about the limit you're going to get on anything below 30v...

If you upped the power supply to 35v you might just hit 2000 steps/sec = 37ipm but you'd be in danger of loosing steps at that speed as you have no margin. warning, dont do this on easycnc, 28v max if you dont want to kill the driver

Your motors are Unipolar and I beleive G450 is a bipolar driver so while you could run these motors on a G450 with a 45v powersupply in bipolar serial mode it will be suboptimal and you might not get much better performance

[tjfdownsouth]

New lead screws will be my next upgrade then. I was just concerned that the mechatronics board my have been limiting my motors rpm's because of mid band resonance or something. I see everyone getting 150-200ipm out of 1/2-10 screws so i had it in my head that i should at least be able get 50ipm out or mine.

Thanks,
Tim

[tjfdownsouth]

Thanks irving, sounds like i need to be happy with what i have for now and save up for some better steppers and driver that will handle more voltage.

Thanks,
Tim

[irving2008]

Originally Posted by tjfdownsouth Thanks irving, sounds like i need to be happy with what i have for now and save up for some better steppers and driver that will handle more voltage. Thanks, Tim

Tim, have a look at the tutorial I wrote here

Trust me, no one is getting 150-200ipm out of a 1/2-10, there's a lot of wishful thinking out there.... maybe just with a reasonable motor and a 5mm or 10mm pitch leadscrew

[ger21]

Maybe with 1/2-10 2 start, more likely with 1/2-10 5 start. I get 55ipm out of my 1/2-10 Z axis, and 155ipm out of my 1/2-8 2 start X axis.

I'm using a Xylotex and 24V, but also have dampers installed to get rid of resonance.

[tjfdownsouth]

i guess what got me hopefull i could go a lot faster is this thread http://www.cnczone.com/forums/showth...highlight=jrgo where he said he was getting 40ipm with 1/4-20 rod.

Tim

[LaserImage]

I'm getting 120 out of 1/2-10, single start. Since they aren't too terribly long, I could get more if I tried, but I don't need any more speed than that.

As for the driver being an issue, YES, absolutely. I had a piece of @#$% mechatronics that I could barely get 30ips without stalling, I upgraded to a G540 and I get 120 on all 3 axes without any other changes - same power supply, screws, everything. I think those two are at the complete opposite ends of the quality spectrum so my results may be better than someone who had a better drive, but you would still see more reliable results with a different drive.

Gary

[tjfdownsouth]

Laser that is encouraging. That board worked fine on the foam cutter since it never needed to go faster than 12ipm but on the router is has seemed lacking. I just thought that i should be able to get better than 25ipm rapids without stalling.

Have you had any issues with the G540, I may start saving for one and just dedicate the other board back to the foam cutter. I am just not sure whether to upgrade the lead screw or the electronics first.

Thanks,
Tim

[irving2008]

Originally Posted by LaserImage I'm getting 120 out of 1/2-10, single start. Since they aren't too terribly long, I could get more if I tried, but I don't need any more speed than that.

I think the key point there is "Since they aren't too terribly long"...

How long are they?


Going back to tjfdownsouth's issue... with a bit more detail to qualify what I said before...

Most JRGO designs are 36" table so with 3/8-16 whip will be a problem above 57ipm anyway (assuming simple bearing support, no fancy angular contact stuff) , so that would be the upper limit even if the motors and driver were optimal.

On those screws the theoretical limit with those motors is about 75ipm, fully driven at 50v/3A... the reality will be less than that...

Going to 1/2-10, the limit for whip is 110ipm on a 36" length (assuming simple bearing support, no fancy angular contact stuff) but the theoretical limit with those motors is about 70ipm, fully driven at 50v/3A... the reality will be less than that...

For the same acceleration rate, on a 1/2-10 screw, the increase in motor power to go from 70ipm to 120ipm is from 10W to 28W... i.e. a three times bigger motor is needed to almost double the speed... the alternative is to significantly reduce the acceleration by a factor of 10 or more... which is fine for rapids but not for cuts...

Reducing the acceleration... so that the motor can 'creep up on the speed' without stalling... is always worth trying as part of the fettling of a new machine, assuming the software allows different rates for G0 and G1 moves. In this instance, of course, the stepper are marginal at 120ipm, the slightest stiffness over the run will stall them but at least they'll start moving... so maybe there's a compromise to be found...

This is why the design of leadscrew/motor/driver combination, and validation of that at the margins, is critical. You can't just throw together any combination and expect it to work efficiently.

[tjfdownsouth]

Thanks guys it looks like i need to get a new board and then upgrade my motors, power, and leads. If i could get 50ipm that would be great for what i do but i don't want to risk a stall and having to scrap something.

I guess i had proceeded knowing that i would not get 100ipm or close but I just thought even with smaller parts I could get 30-40ipm.

Tim