Mach or Code Problem?

Problems and questions
1

Hi All,
Can anyone help? I have a drawing drawn in Autocad lt 98. The G Code is from Sheetcam and I am using Mach 3. My problem is that the drawing is a flat side panel for a model hovercraft which contains four window panels. When it cuts It does a +15mm rapid movement from start to window 1 and the same to window 2 when it gets to window 3 instead of starting the cut a X-1 it rises to X+15 and therefore misses the cut.
I have replaced the drawing and the G Code looks ok (to me). Can anyone help with a solution??

Regards
Roy

2

When it does the cut at +15, what does the Z axis DRO in Mach say? It could be that you are losing steps.

3

Hi Les,
Many thanks for your reply. The DRO gives the correct reading at Z-1. This is why I believe that the G code and Sheetcam are correct. I am thinking it is a Mach 3 problem? I have done another test run and I find that when it cuts the outer edge of the part the Z Axis then returns to normal and cuts correctly.
Any further thoughts?

Regards
Roy

4

It sounds like lost steps to me. Try reducing the Z axis acceleration or maximum speed.

5

Hi Les,
I have tried reducing the Z axis acceleration and the maximum speed as you suggested but it makes no difference. I have changed the drawing again and it runs ok in the simulation and the dro’s are giving a correct reading all the way through the program.
The Z axis lifts ok 15mm for its fast travel but the motor makes a grinding noise and will not move down to cut.
This is getting very frustrating, any other ideas???

Regards

Roy

6

That grinding noise means that the stepper is losing steps. Check the Z axis ins’t binding. It is also possible that your Z motor is too small. Normally reducing the acceleration and top speed helps with this sort of problem.

7

Hi Les,
I seem to have controlled the noise problem now, but when the gcode calls for a - movement it now goes +.

Any ideas?

Regards
Roy

8

You need to reverse the motor direction. You can do this in Config->ports and pins->motor outputs. Reverse the ‘dir LowAcive’ check box.

9

Hi Les,
Many thanks for all your help, I have now found the problem and fixed it. The problem was lost signals on the Z axis. During transit to me the machine was damaged slightly which I repaired. What I did not find was a small nick in the wire to the Z axis motor. When the Y Axis moved and rolled up the cable carrier it opened the break in the wire and then lost signals. It was only found when my son noticed that when working the Z axis motor became unlocked as the y axis moved plus when moving minus it locked again.
I wonder how many times people hav had that problem.

Once again many thanks for your help and assistance.

Best Regards
Roy