Need Help!- Joe's 2006...problem with 200oz steppers

[trimbandit]

So after 4 years we finally got the cnc together...what can I say I got distracted by other things.

Anyway, we are running tests in mach using the hobbycnc pro board and the 200oz steppers. We have tried 1/2 step and 1/8 step and 60ipm works fine, but it stalls at 80ipm on all axis. This is not cutting, but just jogging around to test.

Wondering if we might have mach set up wrong or if this is just a limitation of the 200oz motors. I was thinking we would be able to move around at 120 and cut at 80. Is that unreasonable?

Any help appreciated.

Thanks!
Craig

[AJ Negvesky]

Just a couple of questions

1.) What controller software are you using?
2.) What lead screw are you using? 1 2 or 5 start

[Crevice Reamer]

Hi Craig. Nice first post--finally! Welcome to the Zone!

You are actually getting pretty good speed for a unipolar driver. If you are not using a 36V PSU, then going to that may help some. How long and thick are your screws? Screw whip can lessen speeds. Using multi-start screws may help. You could make and install hocky puck anti-resonance dampners.

If screw whip is not a problem, and if you ARE using a 36V PSU, then this should at least double your speeds:

1. Bite the bullet, spend the $249 and upgrade to G540.
2. Wire those motors bipolar parallel, and use 3.48K resistors. They are 4.2A motors and will detune to 237oz--Still more than what you have now.


With G540 and your present motors, you could also upgrade to $60 Keling 7.3A, 48V PSU for even more speed. For max performance with G540, you could replace the 200oz motors with $50 each Keling 381s.

CR.

[ger21]

I can get 190ipm on a larger machine than the 2006 with a Xylotex and 250oz steppers with 1/2-8 2 start acme screws.

Give us a little more info on your screws and power supply.

[trimbandit]

I appreciate the responses.

1. I am using Mach3
2. Screws are 1/2"-10 Acme leadscrew(enco #408-0220). There is whip on the longest screw which is probably 5 feet. I was not sure how much to tighten it. It feels pretty floppy even at rest. However, I have the same stall outs on the short Z screw which does not seem to whip.I believe the screws are single start
3. I am using this driver board package. It runs at 34VDC

It doesn't feel like anything is binding. I can turn the screws with minimal finger pressure.

Cheers,
Craig

[ger21]

So, at 80 ipm, you're getting 800rpm. At 190ipm, I'm spinning my screws at 760rpm.
So, it sounds like your screws are the limiting factor, even though your motors are on the small side.

There are plenty of people getting much faster speeds with a HobbyCNC motor, but they're using different screws and usually bigger motors.

A cheaper option than getting a G540 and different motors would be to get 1/2-8 2 start screws. You may still want larger motors, but the screws alone will give you more speed.

As for the Z axis, does it sound rough? If so, you might be getting resonance. If so, you can make dampers that can possibly help. But you'll need dual shaft steppers to mount them. They made a tremendous difference on my machine.
http://www.cnczone.com/forums/showpo...&postcount=180

[ianober]

I think the lead screws being the issue sound about right Craig. All axis' stall out at the same rate no matter how long or short they are, but we definitely are getting some whip on the Y axis that is causing vibration. We may want to think about different lead screws if you want the higher speeds.

[trimbandit]

Thanks guys. I will try the 2 start screws as a first step.

[trimbandit]

Thanks guys. I will try the 2 start screws as a first step.

Edit: Holy crap $233 shipped for 12 feet of screw and all the nuts. Maybe I will stick to slow speeds.

[ger21]

How about $7.31/ft and $19.50 per nut?
http://www.roton.com/Mating_Componen...family=7060404
http://www.dumpstercnc.com/

When I bought mine 7 years ago, they were $26 for 6 ft.

[trimbandit]

Originally Posted by ger21 How about $7.31/ft and $19.50 per nut? http://www.roton.com/Mating_Componen...family=7060404 http://www.dumpstercnc.com/ When I bought mine 7 years ago, they were $26 for 6 ft.

Thank you! I am going to go ahead and order the 2 start.

[ianober]

Yeah baby!!!!!