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View Full Version : Epilog Summit servo vibration problem with low speed vectors, below 11%



Jeff Bromagem
03-19-2015, 7:35 PM
Hello,
I am having an odd problem with my "new to me" Epilog Summit (1996) 25 watt laser.
It seems to be doing good on vector cutting if I have the speed set above 10-11%, the curves may seem a little choppy/stepped, but I don't know what it did when "new" for comparison.
Speed set below 11% and I get a loud vibration/humming type sound (not all the time) and the cutting gets sporadic. For example: If I cut a small 1" oval, the the small arcs on the left and right ends are burning deep while the top and bottom barely get marked, this is with power set at 1%! I tried many different power settings, no change.
Most speed settings less than 10 will create this "vibration/chatter", there may be a few that didn't, but it seems sporadic. Circles seem worse than squares.
I have checked the bearings and carriages and the head moves smoothly left to right and back and forth with no play or tight areas. Belts are not loose. Pulleys spin freely.
I took a video on my iphone, but it's a .mov file that probably won't attach here.
It seems to do raster engraving fine, though I haven't tried to slow that down below 11%, so I'll have to try that.
Any ideas to test motors, driver, etc?
Thanks in advance for any help!
Jeff

Jeff Bromagem
03-23-2015, 11:52 PM
Hello,
Thanks to Al Ursich who sent me some Epilog technical notes, I think I have found the problem with my laser vibration at low speeds, below 11%, raster or vector.
To make a long story short, instead of the Epilog fix of tightening the Y axis motor's belt (which did not work) I resorted to loosening it a little. That has resolved the problem so far.
Many thanks to AL. Glad the fix was simple and cheap!
Jeff

Bill George
03-24-2015, 7:42 AM
Hello,
Thanks to Al Ursich who sent me some Epilog technical notes, I think I have found the problem with my laser vibration at low speeds, below 11%, raster or vector.
To make a long story short, instead of the Epilog fix of tightening the Y axis motor's belt (which did not work) I resorted to loosening it a little. That has resolved the problem so far.
Many thanks to AL. Glad the fix was simple and cheap!
Jeff

Are you sure you don't have a bad bearing or belt?

Jeff Bromagem
04-13-2015, 2:04 PM
Hi Bill,
Thanks for the reply.
I have checked the belts and bearings and everything looks good.
The vibration problem was reduced somewhat by loosening the belt, but is still very much present.
More in-depth details to the problem and what I have looked into are below.
I posted the following info on an electronics forum in case someone there could help:


I hope someone can shed some light on a problem I am having with a DC brushed Servo motor in a factory made laser engraver.
The machine is no longer supported by the US manufacturer because it is 19 years old. Talking to them is useless. Same problem with the motor manufacturer, even though they appear to make the same motors for OEM configurations.
I am not an electronics technician, but i have a very good understanding of general electronics, electric and repairs. What I try to describe may not be the correct terminology, but hopefully I'll get the idea across! Here is the problem:
The laser engraver uses (2) 48 volt brushed DC servo motors for the X and Y axis control. The motors do not have any gear reduction or reduction in the way of different sized pulleys on the belts that drive the carriage. The Y axis is generally rotating fairly slow as it moves. Probably in the range of 30-100 rpm for moving to the start/home positions, etc. When the laser is in "vector cutting" mode, as in a CNC type use, it rotates very slowly when the speed is set to the minimum ranges of the driver (in the PC or machine control panel). The machine is supposed to be able to be controlled in speed setting from 1-100% for various engraving/cutting and applications.
When the speed is set to most settings below 10% the Y axis motor will set up a severe vibration that affects the speed and causes "jerky/stalling/erratic" movement. It seems to be fine above that speed. It does not always start vibrating instantly at a given low speed but can start after 4-6 rpms.
One old bulletin from the manufacturer states that "the Y motor is set to low gain on start-up and will not vibrate, but when it is engraving the gain is set high, and the machine will vibrate if the short belt is loose".
They are referring to the timing belt from the motor to the axle shaft that drives the Y axis. I have tightened to their recommendations , and tried a variety of different belt settings, tighter and more loose , but no joy. I have removed the motor from the mount and held it in my hand with no load and get the same vibration, so I don't think it is "machine" related bearings, loading, etc.
Since the motor manufacturer does not offer any parts or motors, I have disassembled the motor to check it over. I thought the ball bearings were too loose, so replaced those with new R4A-ZZ-C3 ball bearings, I removed any end play on the shaft, checked the encoder for dirt, dust, etc. (none), checked the brushes for wear, brushes looked almost new, maybe not quite seated in to the armature/rotor yet, as they were worn only on half of the rectangle surface, they may a have been replaced shortly before I bought the unit. The bars on the armature/rotor are clean, smooth, not worn, the gaps between are void of build-up, and in general look very good.
At this point I'm considering all options.
I probably can't change the frequency or pulses sent by the proprietary controller board.
I can't find a replacement motor yet on e-bay, but don't necessarily think it's the motor at this time.
Could it be the pwm frequency that is being sent to the motor is setting up a resonant frequency within the motor?
If I could set the "gain" to the motor to a little less, that might resolve the problem, but how could I do that?
Should I remove the motor and run it with a dc power supply to seat the brushes better (for full contact)?
Would a resistor in series to the motor or capacitor across the motor do any good? I don't want to blow the control board.
I only see two larger electrolytic capacitors on the control board, near the heat sinks, neither "look" bad, no swelling, leaking, etc. but I could check them if that could be the problem.
I have considered changing the ratio on the motor drive to a 2:1 ratio and changing the encoder wheel from 512 cpr to 256 cpr so the motor will rotate at twice the speed and maybe avoid the problem.
Any ideas or comments are appreciated.
Sorry so long!
Thanks,
Jeff

Bill George
04-13-2015, 3:37 PM
Have you found this website yet? http://www.geckodrive.com/products-order.html

Lots of info on both stepper and servo motors and controls. I have used the stepper motor drives in a couple of projects and they are great!

And capacitors do age out and become "bad", so your suspicion that one could be bad is valid.