Solving the Riddle

As a proud 2 year owner of a Phlatprinter MK1 modified into an MK1.5 belt driven CNC foam cutting machine, I was ready to move up to something that could handle a little more than just foam and something that had an overhead gantry instead of cutting from the bottom up.

I had been a member and moderator on the Phlatforum and a strong supporter for some time and enjoyed watching it grow.

So in late November (2010), I placed my order for the Phlatprinter \\\ and waited patently for it to arrive, and sold my MK1.5 when it finally made its way to my home.

It is now January 10th, 2011 and my Phlatprinter \\\, the third to be shipped, is still not cutting as well as my trusty MK1.5 which is now gone.

Having spent countless hours going every detail in my building of the machine, I was left with the conclusion that a design flaw existed in the new machine as was evidenced by others reporting the same problem.

I published detailed reports of my findings, including videos and alternate methods of calibration on the Phlatforum.

I sent emails to Mark and Trish detailing my results and asking for them to call me.  After the forth email and no phone call, I was becoming uneasy.  I felt like the problem was being swept under the rug with hopes it would go away if no body complained too loudly.

I continued to post results of my tests, looking for answers, hoping others would join in with their opinions.  

The problem stems from the fact that two drive rollers, made from conveyor rollers which are driven by a stepper motor to move material between them and two spring loaded pressure rollers, are skewing the material causing the material not to return to the exact location from which it started. 

When cutting circles, the cuts had straight edges in two sides which indicated backlash in the drive train.

I just want to define the problem so that it is well understood by even the most non-technical among us.

Have you ever used a belt sander?

If you have, you know that it contains two rollers in which the sandpaper travels over via a driven roller and an adjustable roller.  Adjusting the front roller such that it moves unparallel to the rear roller causes the sandpaper to shift left or right in the same manner as the skew occurs in the Phlatprinter \\\.

In my next post, I will discuss how the skew is introduced in the Phlatprinter \\\ and what I am doing to fix it on my machine until such time as Mark and Trish develop their own solution which I am sure will incorporate some of what I have already documented.