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Old 05-13-2015, 07:05 PM   #101
Len-Tikular
 
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Originally Posted by cfellows View Post
A couple of things come to mind, and please pardon me if I'm stating the obvious. Just trying to cover all the bases.

First, of course, would be to check if the downfeed clamp is loosened. I know, it sounds silly, but I frequently tighten my clamp to make the spindle assembly more rigid during level cutting then forget to loosen it when the Z-axis needs to move.

The second would be the speed setting on the rapid movement of the Z-axis. If you are using Mach3, you can set the maximum rate of speed in the config/motor tuning menu option. I have 425oz in nema 23 steppers with an inductance of 24 milli-henrys so, while they have a lot of low end torque, they won't spin very fast. The gearing on my Z-Axis is such that it takes 48000 steps per inch of travel. It seems to run consistently in both directions without skipping steps at about 15 inches per minute but I have it set to 10 with acceleration set to 1 in per sec per sec. I keep it set really low since Z-Axis speed isn't really important to me.

I don't know how familiar you are with Mach3, but you can hold down the shift key while you press FN and Down Arrow or Up Arrow to do a rapid movement of the Z-Axis. I set my speed by setting the speed at about 50 inches per minute and run the Z-Axis up and down several times using the computer keyboard. If it skips steps, I drop the speed down another 5 in per minute and try again. I repeat this until it moves smoothly without ever skipping. Then I usually drop it down a few steps until I get the best sound from the stepper.

Hope this helps.

Chuck
Thanks Chuck,
Yep, I'm using Mach3
My steps per are set to 1910 (after tuning) that's very strange as that is no where near the 48,000 that you have set on yours. I copied your setup with a 15 Tooth Pulley and a 36 Tooth Pulley. 2.4:1 I also confirmed that it takes 10 turns of the crank for 1" movement on the quill.
I use Mach 3 with Micro-stepping drives. The drives are set for 2000 steps/revolution and is also set for 10 micro-steps per full step.
My velocity was set rather high at 600mm/minute so I'll bring that down a good deal.
So I'm a little confused with your 48,000 steps/per. Hmmmm
The drives I am using are MSD542 from Motion control products.
What did I do wrong ?
George


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Old 05-14-2015, 03:38 PM   #102
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If you have Mach3 set up to use millimeters, then 1910 steps per mm is about right. I have mine set up in inches, so it takes 48000 steps to go an inch.

48,000 / 25.4 = 1890

600mm per minute is too high. That's about 23in per minute and mine won't run that fast. I think dropping your velocity down to around 300mm per minute would fix your issue.

Sounds like your driver is working OK. What do you have your current limited to? Also the voltage on your power supply?

Chuck


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Old 05-14-2015, 06:19 PM   #103
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If you have Mach3 set up to use millimeters, then 1910 steps per mm is about right. I have mine set up in inches, so it takes 48000 steps to go an inch.

48,000 / 25.4 = 1890

600mm per minute is too high. That's about 23in per minute and mine won't run that fast. I think dropping your velocity down to around 300mm per minute would fix your issue.

Sounds like your driver is working OK. What do you have your current limited to? Also the voltage on your power supply?

Chuck
Ok, that explains the steps/per nicely, thanks Chuck. Peak current is set to 4.2Amps. I am using a 48v 7.3 Amp Switched mode Power supply into 3 M60TH100-400s 4Nm Steppers, rated at 2.8v per phase at 4 amps. 3Mh.
I'll drop the velocity down to 200-300mm/min and see if that does the trick.
Many thanks
George
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Old 06-02-2015, 09:32 AM   #104
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That did the trick Chuck.
I bought some nice new 2 flute hi-helix cutters.
I managed to pocket a 52mm Dia hole 15mm deep at 400mm(15 inches) per minute at 1mm pass depth with no issues at all. I used parafin misting as a coolant.
Thanks for your help.
George
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Old 06-06-2016, 03:17 AM   #105
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Chuck,

Given the benefit of hindsight, when converting your RF30, would you still go with the Nema 23 425oz, 48v DC, 3 to 1 geared combination

I'm converting a RF30 and am following your thread intently.
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Old 06-06-2016, 01:33 PM   #106
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Chuck,

Given the benefit of hindsight, when converting your RF30, would you still go with the Nema 23 425oz, 48v DC, 3 to 1 geared combination

I'm converting a RF30 and am following your thread intently.
I did change the gearing to 2:1 which gives me more speed. I can get up to about 16" per minute fast travel but I rarely run it at more than 4 inches per minute when cutting since I'm usually using 1/4" or smaller end mills. I'm happy with the setup and wouldn't change anything else. I sometimes wish I had a higher spindle speed, maybe 5000rpm, but I think the spindle bearings would overheat. They already get pretty warm at 2500rpm.

Chuck


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