More speed!

#1
Hi Jerome,

I have 1.8 degree per step motors (200 steps/revolution), and I am running them in half-step mode - so effectively 400 steps/mm or 0.0025mm/step for Jedicut.

With 1 millisecond delays per step (the smallest integer I can put in the configuration) I am limited to 2.5mm/second wire speed which is fine for cutting, but painful for positioning. I have run this machine at 5mm/second with no problems in the past, however Jedicut doesn't seem to be able to support this.

I can make the motors run at 3.75mm/second by running the timer at 6KHz while the software is configured for 4KHz, but I'm not sure if this is a good idea from the software's perspective. (it makes the maths difficult, and probably dynamic heat control will be out by 1.5X as well)

Do you have any ideas for solutions? (apart from running the motors in full step mode which is not as smooth)

Simeon.

Re: More speed!

#3
Hi Jerome,

I have entered 1 as the speed.

I use one of the older Hobby CNC boards (with ballast resistors rather than chopper current limiting).

It seems that to make the cut faster I either need to lie to Jedicut about the speed of the timer, or wait less than 1 millisecond between steps (which is not possible because speed is an integer).

I have overcome this frustration to some degree by manually positioning the wire to the starting angle of the swept wing which removes all of the positioning travel, however it still takes around 12 minutes to cut one core (large chord flying tailless wing).

Simeon.

Re: More speed!

#5
Hi,

Yes, I have used an older version of GMFC in the past and was running at 5mm/s with no problem. I could go faster than that with GMFC, but started to lose steps(I have re-built my slides since).

TurboCNC has no problem running faster provided the steppers ramp up to speed first.

Simeon.

Re: More speed!

#6
Small hint to cheat on this one (:P):
If you reprogram the PIC, you can allow more than one step per command from the parallel port. For example, on my custom card (golemdev card), I set it to 0.25mm per step, so each time the parallel sent one step command, the motor can do 50 step (or as much as you wich). I was doing 30mm per second on mine (200 steps per turn and using 1/4''x20 driver rod). Sorry, I know only how to program my PIC (PIC16F684), not yet the one coming on the MM2001 (but should be easy if you can get the code file and using MLAB software).
Guillaume T. Ing. M.Sc.
Table: GolemDev 4 axes transformée en découpe de foam. Electronique Custom.

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