Stepper motors stall

[ricks]

I have an issue with my X axis stepper motors stopping above 8 ips for jog speed.

I have swiveled the motors away from the rack. Using the K command and arrow keys the motors run up to speed for 2 or 3 seconds, then the shaft stops, but as long as I hold the arrow key down it sounds as though the motors are turning, but the shaft is not. As it powers down from releasing the arrow key, the shaft will turn again.
Repeats same every time.
Happened only once on the Y axis.

Set my move speed to 10 ips, does not stall.

Is this the stepper motors loosening steps?
If not, anyone have some ideas?

My machine:
Just upgraded my prt to the 4G board.
SB ver 3.4.30
2 X motors
2 Y motors
1 Z motor
All motors are PK296A1A- SG3.6

Computer:
1.8GHZ Pentium 4
1 GB Ram
Win XP Pro
Erased the hard drive.
Loaded only Windows and SB
ATEN USB to Serial converter

ShopBot.ini:
'ShopBot Configuration Version 3.4.30 --- 01-12-2007 09:24:14
' Copyright 1997-2006 ShopBot Tools, Inc. All Rights Reserved.
VK,
VD, 1, 3, 0, 0, 2, 1, 0, .1, 0, 1, 1, -642, -7500, 8800, 4600
VU, 2546.4790, 2546.4790, 2291.831, 2546.4790, .05, , , .25, 13.8889, 1, 1, 1, 1, 1
VA, 39.9151, -26.5449, 3.9999, .0000, .0000, 554.3493, 25.7913, .6645, .0000, .0000, .0000
SA
SO, 4,-1
VS, 5.00, 2, 1, 720, 10.00, 4, 3, 1440
VR, .4, .4, .4, .4, .4, .4, .4, .4, .2, .2, 100, .10, 65
SW, 2
VL, -.5, 96.5, -.5, 48.5, -2, 8.0, -3.0, 8.0, 0, -500, 500, 5
VP, 6, 96, 48, 6, 0, 1, 0, 1, 1, 0
VC, .5000, , , 1.00, 0, 10, 1.00
VB, .1, 4.0, 1.0, .50, , 0,
VI, 4, 0, 0, 0, X, Y, Z, Y, 4, B
VN, 1, 1, 0
FS, C:\SBPARTS, *.sbp, c:\SbParts\Custom
UN, SbEdit.exe
SM


Rick Samish

[Brady Watson]

Rick,
You are hitting the communication wall with the 4G board and your specific computer. The communication speed depends upon your individual computer & the length of your USB cable.

If you want to increase com speed (and tool speed) you can install a USB 2.0 PCI card in your machine. Then go into the Device manager & 'View by connection', look for the 2.0 card & the entry that is labelled 'enhanced'. This is the root that you want your tool connecting to. If your computer already has a USB 2.0 compliant port on it, make sure the tool is connecting to the enhanced port.

Hope that helps/makes sense
-B

PS- Your ramps look a little long. Try changing all of the ".4" values to ".2".

[ricks]

Thanks Brady,
I will try all your recommendations.

Rick

[ricks]

Update
Looked a little deeper into my computer settings, the USB is on a 2.0 enhanced port. The USB cable is the one that came from Shopbot, about 10 feet.
I'm actually fine with the 8 ips jog, and the cut speed is plenty fast for my work. The increased resolution is what I am really after.

I was also thinking since my X & Y motors have 18 tooth gears that that is probably limiting my top speed?

Also, I like the .2 ramp settings much better.

Thanks,
Rick

[richards]

Everything else being equal, you will get higher speeds by using gears with more teeth. A 20 tooth gear will give you 1.11X the speed; a 25 tooth gear will give you 1.388X the speed; a 30 tooth gear will give you 1.66X the speed. However, you will also lose resolution by the same factor. (What one hand giveth, the other hand taketh away.)

A greater number of teeth will also give you more contact area, which is good, but require more power from the motor, which might be bad.

On my Alpha, I've reduced my jog speed to 12-ips, down from the 30-ips that I used for the first 1-1/2 years. What I lose in speed, I regain in peace of mind. Seeing the gantry hit the mechanical stops at high speed isn't good for my old heart.

[Brady Watson]

Rick,
I'll add to what Mike said...You definately will want to increase pinion size. While on paper a 18T gear would provide more torque & resolution, it doesn't have as many teeth engaged in the rack as say a 25T gear. I think that you would be happy with a 25T setup, with great resolution (actually better than a 1:1 Alpha...by a large margin) and you will see increased pinion life & a smoother ride...plus your jog speeds will be up around 11-14 IPS.

-B

[ricks]

Thanks Mike & Brady,
I'll order some new gears.
Rick