Need Help!- Setting inches per minute

[revricky]

Hi everyone- I am having trouble getting any speed out of my X & Y axis on my cnc router that I built. I am runing MACH 3 software, 1/2-13 threaded rod lead screw, 282 oz/in motors in Unipolar mode. The best I can get is btween 7.5 and 9 in/min without it starting to chatter and stop. I have tried just about every compination of speed and acceleration with no luck. I am using 2600 pulses on both axis.

[ger21]

What kind of drives are you using? What voltage are you running at? Sounds like full step? Also, threaded rod is very inefficient, so about 70% of your torque is wasted right there.

[Rick7702]

Keling Hybrid Motors, 282 oz/in, K173 driver boards, 200 steps per revolution,3.5 vdc

[Crevice Reamer]

Hi Rick! Do you have a link for that driver? What is Power supply Voltage and Amperage? What is max Voltage & Amps for drivers? What size router are we talking about?

CR.

[Rick7702]

HI-
Thanks for the reply. The power supply is 9vdc-17amps,the K179 stepper driver board can be found at a lot of different place but here is one:http://www.electronics123.com/. The K179 supply current is 0.1A max, motors 6a max per winding. The Keling 23H276-30-8B stepper motors in unipolar mode is rated at 3.0a max/phase, 2.76 volts/phase. I hope these are the answers you are looking for..........Rick

[ger21]

Those drives are not going to get much speed. Increasing the power supply voltage to 30 Volts should get you close to triple your speed. Not sure if that drive needs current limiting resistors to do that, but I suspect it does.

Going to a HobbyCNC drive and 36V should be even faster. If you change drives, I'd also switch to multiple start acme.

[Rick7702]

Thanks for the information. I don't understand how I can increase the voltage to 30 volts when the spec's for this motor lists it at 2.76/phase at 3.0amps/phase?? I am using a resistor pack now.. I am looking at going to a larger motor on the X & Y axis which will require a different power supply, I think! I have a pretty heavy table on the X axis(28" wide x 36" long) and it is running on linear bearings and rails. The router is a Porter Cable 1.5 hp 1/2".

[Crevice Reamer]

Stepper Voltage is explained in this CNC Basic Primer:

http://cnczone.com/forums/showthread...709#post572709

CR.

[Rick7702]

Thanks a million. I read ALL of it and I do understand. Back to the drawing board!!

[revricky]

HI All- Back again and the problem has not changed! I changed the power supplies to 27vdc@6 amps per drive( one for each motor) I have a 10 ohm limiting resister in series with the lead to each motor. I have changed one of the motors to a Keling 1200 oz/in because of the size and weight of the table. The end result is the same. I can get as high as 150 ipm with the motors disconnected and it drops back to an average of 11ipm under load. All axis' roll with very little resistance and can be moved via turning by hand quite easily. I am about to junk the whole project!! Any help WILL BE GREATLY APPRECIATED.

[ger21]

Get a HobbyCNC drive, run at 36V, go back to the smaller motors, and switch to acme screws, preferably 1/2-8 2 start or similar, and you may get 150-200ipm. Hard to say without seeing the machine. You're probably getting resonance from full step drives. Microstepping will help minimize it and give you more speed. Also, on larger motors, torque drops off very rapidly as rpm's increase. It's very possible that at ~300rpm, that the 282oz motor would have more torque than the 1200 motor.

[lmlamb]

I've been using the Rockcliff 4 axis controller with 2 NEMA 17 motors driving a two axis quilting machine using a cable drive. I've noticed that the Mach3 software appears to not control speed or ipm as well as it should. I have tried several different variations of algorithms to adjust the speed closer to an acceptable rate (12 ipm), but then I find that when I do a speed calibration check of 1 in, the x axis and the y axis both go all the way to the plus stops. This appears to be a mistranslation of the distance setting in Mach3. Otherwise all tests have shown that a favorable speed setting is 4000 steps per min. in full step mode. This allows for no skipped steps on these motors. I find that, yes, each axis can be set to half-step, however there is about a 20% loss of torque. I find that this is not acceptable in the
use project that I am working on now. My question is this, is there is formula that can be used with Mach3 to cut the distance travelled down to an acceptable level?

Any help would be greatly appreciated.

Larry