Reply with QuoteAre your acceleration values too high? What is your max rapid set up in motor tuning? The value you lose isnt constant is it? You mention a 10mm difference.
Loss of Position on Sherline CNC milling machine
hi all,
I am very new to my CNC machine as I have recently acquired it. I managed to connect it up and get it working, cutting scrap wood. My setup is sherline 2010 milling machine with xyz, using the sherline supplied controller. I use UC100 adapter to my computer running Mach3.
The issue I am experiencing is a serious position loss. When I jog the machine say 50mm in either of x, y or z direction, and then jog it back 50mm, I am losing something like 10mm.
I can't figure out how to solve this issue, things that I've already done:
- tighten up the various bolts
- tighten backlash
- tighten gib
The loss of position is so significant it doesn't cut back into a previously made slot, so it's just ruining all my work pieces so far. I've wasted quite a number of MDFs already trying to troubleshoot this issue...
Regards,
Aloysius
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Re: Loss of Position on Sherline CNC milling machine
Are your acceleration values too high? What is your max rapid set up in motor tuning? The value you lose isnt constant is it? You mention a 10mm difference.
A lazy man does it twice.
Re: Loss of Position on Sherline CNC milling machine
I used the figures that came in the sherline (metric) XML file that I got off MACH support ftp:Originally Posted by Fastest1
Meanwhile I have disassembled the whole thing and reassembled my machine, checking all the backlash features and making sure I've done them right. I've done a test cut again and this was what I got:
The whole thing is just badly mangled up from the loss of position...
I need help
Re: Loss of Position on Sherline CNC milling machine
It's not backlash; problems like this are caused by lost steps. That usually is due to trying to go too hard, too fast, with too much acceleration. Tightening the gibs will make things worse, not better. Lubrication can help. You may be trying to cut too deeply, or with incorrect feed, speed or RPM values. Are you jogging while the tool is engaged in the material? Try jogging in air first, so you can separate the problems of the machine itself from the problems involved in cutting something; they're different. Adjust your velocity and acceleration values downward until it can execute simple moves reliably, and then work on your feeds and speeds for actually cutting things.
[FONT=Verdana]Andrew Werby[/FONT]
[URL="http://www.computersculpture.com/"]Website[/URL]
Re: Loss of Position on Sherline CNC milling machine
I have done cuts with much slower speeds too, it's just as bad. And I am absolutely clueless already on how to solve the problem. I've dismantled and reassembled the machine a couple of times, reconnected the cables, changed my computers, uninstalled stray software etc. But I am getting no where...
Re: Loss of Position on Sherline CNC milling machine
Velocity and acceleration are two different things. Velocity is the top speed that the machine achieves in the course of a move, like the 65 mph you cruise down the highway at in your car. Acceleration is the initial burst of speed that gets you there. If you floor it from a standing start, you burn rubber; with too much acceleration on a CNC machine you lose steps. Try turning the acceleration of each axis down to about 10% of the (reasonable) velocity, and try that. If you're still losing position, cut it in half and try again. Lubrication helps too.
[FONT=Verdana]Andrew Werby[/FONT]
[URL="http://www.computersculpture.com/"]Website[/URL]
Re: Loss of Position on Sherline CNC milling machine
I have had PC's that cant generate a stable stream as far as I can tell. There can be many factors. Can you tell when in the code it is losing position? Usually a squeal of some kind.
A lazy man does it twice.
Re: Loss of Position on Sherline CNC milling machine
Hi I can only paste the code here as I can't upload it...
G21
G90
G1 Z3.810 F228.6
G0 X57.150 Y63.500
G1 Z-0.711 F100.0
G1 X6.350 Y63.500 F100.0
G1 X6.350 Y12.700 F100.0
G1 X57.150 Y12.700 F100.0
G1 X57.150 Y63.500 F100.0
G1 Z-1.422 F100.0
G1 X6.350 Y63.500 F100.0
G1 X6.350 Y12.700 F100.0
G1 X57.150 Y12.700 F100.0
G1 X57.150 Y63.500 F100.0
G1 Z-2.134 F100.0
G1 X6.350 Y63.500 F100.0
G1 X6.350 Y12.700 F100.0
G1 X57.150 Y12.700 F100.0
G1 X57.150 Y63.500 F100.0
G1 Z-2.845 F100.0
G1 X6.350 Y63.500 F100.0
G1 X6.350 Y12.700 F100.0
G1 X57.150 Y12.700 F100.0
G1 X57.150 Y63.500 F100.0
G1 Z-3.556 F100.0
G1 X6.350 Y63.500 F100.0
G1 X6.350 Y12.700 F100.0
G1 X57.150 Y12.700 F100.0
G1 X57.150 Y63.500 F100.0
G1 Z-3.971 F100.0
G1 X6.350 Y63.500 F100.0
G1 X6.350 Y12.700 F100.0
G1 X57.150 Y12.700 F100.0
G1 X57.150 Y63.500 F100.0
G21
G90
G1 Z3.810 F100.0
G0 X0.000 Y0.000
G4 P0.1
For my machine I've set the velocity max at 100mm/minute and acceleration as awerby suggested to 10% of that, 10mm/minute. It's still losing position, something like 1mm per cycle around the square. I'll snap some pictures.
This is the finished result...
Re: Loss of Position on Sherline CNC milling machine
Try another PC. Are you using a parallel port?
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A lazy man does it twice.
Re: Loss of Position on Sherline CNC milling machine
Are you sure that's mm/minute and not mm/second?
[FONT=Verdana]Andrew Werby[/FONT]
[URL="http://www.computersculpture.com/"]Website[/URL]
Re: Loss of Position on Sherline CNC milling machine
I'm also new to cnc and not sure if I can help and this maybe a stupid question, I use uccnc and not familiar with mach 3. Have you calibrated the steps in mach 3?
