Messages

11

General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 24, 2009, 08:15:04 PM »

I have different Backlash settings for each axis. I'm not using any for Z but I have tested and set X and Y correctly to get a perfect Circle. I tried the setting for the Shuttle Accel but got wierd results. With the setting at 5 and moving in one direction and then changing directions it changes directions quickly, slows down over about a 5 inch distance and eventually comes to a complete stop then slowly accelerates over the next 5 inches of travel until it's back up to full speed. I found this strange becasue I would have thougth it would have stopped at the point of switching directions then accelerated back to speed not change a full speed, slow down to a stop then accelerate back to speed. Does this seem right?

12

General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 24, 2009, 01:58:31 PM »

OK. I'm playing around with the setting but it's really frustrating. Each time I think I have it set properly it screws up again. I can get it set to complete a Job correctly (after having to cut test pieces), then I move to a new Job and the X axis is messing up, test again, works fine with compensation turned off, change the settings and now it's working again, then 30 minutes cutting later the Z axis screws up, test again now I've fixed that problem... Now I have to rerun the entire job to make sure it isn't screwing up somewhere else. I'm testing 90% and cutting 10%. I can't seem to find a setting that will make it work correctly all the time. Each time I can change the settings to fix the current problem but then it screws up somewhere else. It's messing up on really easy code that I don't understand. Below is the latest example.

N59767 G02 X15.5063 Y9.8769 I-.5063 J-.8769
N59768 G01 X15.5688 Y9.9851
N59769 G02 X15.5688 Y9.9851 I-.5688 J-.9851
N59770 G00 Z.1
N59771 M05
N59772 G53 Z0.
N59773 G53 X0. Y0.
N59774 M01

All it has to do is finish the pocket, move to Z +.1 turn off the spindle and move to X0 and Y0. Instead it moves to Z +.1 then moves right back down to -.1875 where it finished pocketing and moves across the part (cutting where it shouldn't) and stops at some random 8. 9.? postion and stops. The funny thing is that the code is fine and the probem is repeatable. Only thing that makes it work correctly is turing off compensation. I Still don't understand what these settings actually do. What does Shuttle Accell have to do with Backlash compensation and what does the speed % have to do with why it would work correctly or not. It didn't work at all when set at 100%, worked but messed up occasionally at the default setting of 20% and now it is messing up at 50%. Do I just try 75% and see what happens? I know it can't be anything else like noise or grounding issues since when it does mess up It's always repeatable in exactly the same place in the G code and it always goes away when Backlash compensation is turned off. Very Strange. I'm also only running at 20-30ipm with a 1/4" 2 flute cutter so I'm not pushing alot of speed for wood routing.

13

General Mach Discussion / Re: Strange cutting.... Circles for line segments...

« on: October 10, 2009, 11:35:52 PM »

I was only cutting air and using a 1/16" bit so it was really hard to tell the shape of the circle. The line segments/arcs were really small. I was able to get what I needed cut by just eliminating the offset. I really didn't need it with a 1/16" bit on artwork. But I will need to look into this further this week. I haven't had any issues with offsets in the past but this was by far the smallest thing I have cut on the machine and as I mentioned the DXF artwork had very small segments also.

14

General Mach Discussion / Re: Strange cutting.... Circles for line segments...

« on: October 10, 2009, 06:28:09 PM »

It's not in the original DXF. In BobCad I'm selecting the mouth of the pumpkin and creating a parallel offset for the toolpath (instead of using tool offset) and that is when the arcs are being added. Strictly a BobCAD issue....

15

General Mach Discussion / Re: Strange cutting.... Circles for line segments...

« on: October 10, 2009, 01:52:28 PM »

After looking at this further, BobCAD is definetly doing the Arc's. It does G02 the G01 then G02 then G01 throughout the line cut. I don't know why it is putting the Arcs in their since they don't appear on the CAD screen but I'll keep looking at it and see if I can figure it out. It's obviously not a Mach issue as I originally thought. It's almost as if the line segments are so short its having trouble generating the G code.

16

General Mach Discussion / Strange cutting.... Circles for line segments...

« on: October 10, 2009, 11:40:26 AM »

I'm cutting a pumpkin out of wood on my CNC router. I didn't do the DXF file on my CAD, I got it from someone else. When it cuts the teeth of the pumpkin the machine moves in tiny circles as it cuts each line segment in the teeth. If I look at the DXF file the teeth look like straight lines but they are made up of tiny line segments. It appears that when it is being cut the router cuts a tiny line segment, circles around and cuts the next line segment, circles around again to cut the next segment and so on until it completes the line instead of continuously cutting the individual line segments. I've seen something similar to this before but only when I had line segments with directional arrows pointing opposite directions when I generated my G Code for the chain causing the machine to cut one line segment in the opposite direction while cutting a chain. I don't have this issue this time. I'm using BobCAD 21 to generate the G code. When I simulate it in BobCAD it cuts as I would expect it to. It doesn't cut that way when Mach controls the machine. Anyone know what might be wrong? I had been playing around over the last week with Backlash compensation and thougth that might be causing some issues but I have the same issue when it's turned off. Any help woud be appreciated.

17

General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 04, 2009, 05:23:51 PM »

Gerry, Thanks for the reply. My Speed % is set to the default of 20 and the Shuttle is set to .005..... I did what I should have done in the first place and upgraded to the latest stable release of Mach3 after my last post and I ran the same G code and it worked fine, so something changed between the releases. Anyway, it's fixed now. Do you think I need to mess with the Speed % or Shuttle if I have it working now? I'm not exactly sure what they do, but it cuts very nice with it set to the way I have it now.

18

General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 04, 2009, 04:27:11 PM »

Ok. I have it working but I found a big issue... I tested the Backlash settings and got it working perfectly. Then I went today to cut out parts from a 4'x8' piece of 3/4 ply and the first part cut perfect. I have to do multiple passes at 1/4 depth to cut the parts and on the second part, it cut 1/4 depth all the way around, then went around the last 90 deg corner where the G code tells the Z axis to move to +.2" then back down to .5" depth to cut the next pass. The Z axis starts to move up and then the stepper motor makes some strange noise (similar to binding), then moves down .5. At this point it's actually cutting about .70 depth and on the final pass makes a nice deep cut in my table. I spent hours looking at the CAM and the G Code and checking for binding in my table. Nothing is wrong. I  tested the same code maybe 12 times, each time it has the same issue in the same spot of the G code, the Z axis gets off when it try's to move up .2" after rounding the final corner. Mach thinks it moved up but the stepper never made it. Finally I turned off Backlash compensation and it works fine. For some reason the backlash compensation is conflicting with my Z axis movement. It appears that Mach is trying to do the X axis compensation at the same time my Z axis command is telling it to change height and it doesn't like it. Anyone know if this is a known but? I didn't catch it until the bit had already cut thru my spoilboard and into my table!

19

General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 02, 2009, 08:36:01 PM »

Ok. Figured it out. If I set "Backlash Speed % of Max" at 100 as suggested by HossMachine on Youtube, backlash doesn't work for me at all, it does nothing as if it was turned off. If I set it back to the default of 20 then backlash compensation works great! I have about .015 backlash in the X and Y axis and I'll play around with it further but I've got a very nice circle now.

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General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 02, 2009, 07:24:19 PM »

OK. Tested a 2" square... The square looks square but when measured, the width is 2.005 measured top and bottom and the heigth is 2.025 on the right and left sides. The corners appear to be perfectly square, It's just slightly taller than wide but that could also be a Backlash issue.