Backplot

Watch the Backplot Movie 

An issue came up this week that reminded of something I read recently.  I was doing some light reading in a CNC reference book and the author was making the case that any user of a CNC machine should be able to manually create their own output file without relying entirely on a CAM program.  He felt that by being able to do it manually, the user would have a better understanding of what the CAM software is doing, and would be better able to make small changes in the output file without having to re-create it when something wasn't quite right.

This week a customer had a problem cutting out a job, which raised a question about the cause of the problem.  Was there a problem with the design?  Was there a problem with the driver translating the design into the output file?  Was there a configuration problem on their machine, or was there a mechanical problem on the machine?  The machine guys usually point their fingers at the software, and the software guys are always sure that it is a machine problem.  So how do you solve the problem?

When the question gets to me, the first thing I want to do is check the design file to make sure the geometry is doing the right thing, and that the toolpaths have been created as the user intended.  Then I check the output file to make sure that it is correct.  If you aren't familiar wth G and M Codes or HPGL, looking at the output file can be a problem. To the untrained eye the output files look like a jumble of letters and numbers.

We have created a small utility called Backplot that lets you review a plot of an output file so you see essentially what the CNC machine is seeing in terms of instructions.  In Backplot you can step forward and backward through the file as a way of looking at specific locations.  This can make it much easier to home in on a problem area.  It won't necessarily tell you what to do to resolve the issue but it can sure help you visualize the problem.  By looking at an output file before you send it to your machine, it can also help you spot a problem before it goes to the machine.  Maybe you forgot to include the proper lead in, or maybe you defined one pass instead of the intended three passes.  These can become obvious in a hurry by looking at the output file in Backplot.

Backplot is distributed freely to our EnRoute users.  In version 4.1 it installs automatically in the EnRoute folder.  If you have a version of EnRoute prior to 4.1 the EnRoute Team will be happy to send you the latest version of Backplot.  I have created a short introductory Backplot Movie that is a good way to get started with it. 

As far as the customer's issue, we were able to confirm that EnRoute was creating the output file correctly.  The hardware guys still think it's a software issue, but in this case I was able to demonstrate (maybe only to myself) that EnRoute was creating the output file correctly.