Sunday, July 3, 2016

M3D Micro: Polyester Film/Plastic Sheet vs. Metal

Sorry for the rapid fire posts that seem to contradict each other; but. I'm on a very tight schedule to learn the M3D Micro inside and out.  And, just as it happens when we are working on a new, complex design each iteration gets better and better.

I am not just learning for me.  I have more than enough 3D printers to accomplish what I want to print.  But, I need to come up with the most straightforward answers to M3D Micro questions because (1) I believe that this is, ultimately, going to become the most important printer for our cadets and teachers and (2) I want my granddaughters to have the best user experience possible with the M3D Micro I just bought for them.

The names of the game when it comes to setting the gap for a 3D printer are Precision and Repeatability.  Saying "Use a piece of paper" or "Use 3 pieces of paper" just doesn't do it for me.  Paper thickness is all over the place.

Without question, using a metal tappet gauge gives us precision and repeatability.  But, while I know how to use a metal Tappet Gauge without damaging the print jet that might not be true of a child.

Fortunately, there is another way to be precise without resorting to a metal tool.  The reason I know about this particular method is because every single 3rd Generation Cube from 3D Systems included one.  It's simply a polyester film / plastic sheet strip, of a precise gauge, and it works beautifully with the 3rd Gen Cube.  There is a VERY different feel when using plastic, rather than paper or metal, to set the gap.  It is MUCH easier to repeat the same setting over and over.  It really is nice.

I would get more of the 3rd Gen Cube gap strips.  But, the optimal gap for the 3rd Gen Cube is NOT the same as that for the M3D Micro.  The 'gap tool' for the 3rd Gen Cube does not work well with the Micro.

Fortunately, we have a well-stocked art supply store nearby that carries a variety of polyester film / plastic sheets.  So, I stopped by to see what they had.

By now, I knew, from the tests with the Tappet Gauge that the 'sweet spot' for the Micro gap is somewhere between .254mm and .381mm.  Since polyester film / plastic sheets are calibrated in "Mils", this put me in the range of 10-15 Mils... with 12 Mils, the likely best candidate.  Here's how Mils break down when converted to millimeters.
  • 10 Mil = .254mm
  • 12 Mil = .305mm
  • 15 Mil = .381mm
All I could find was 10 Mil and 15 Mil.  So, if 10 Mil was too small a gap, then I would have to use Bed Height Offset to make a slight gap increase adjustment.  Perhaps the best measure of the effectiveness of a gap is the appearance of the first layer and how well the first layer adheres to the second layer.

I ran 3 test prints and here is an image comparing the bottom layers.

Bottom Layer Comparison
The 10 Mil print definitely has the best look to the first layer.  The 15 Mil test had some 1st and 2nd layer adhesion issues.  To simulate a larger Mil, I simply entered an Bed Level Offset to +.01 after setting the Z=0 gap with the 10 Mil plastic strip.

Bed Height Offset to Simulate 12 Mil
 
While the first layer is not as smooth as the 10 Mil print, the integrity between layers was excellent.  It also was slightly easier to remove.

Using the Offset works for me; but, I would like to get it down so that simply using a single polyester film / plastic sheet strip would definitively set the gap and the bed leveling.  So, I will continue to hunt for 11 Mil and 12 Mil.

But, if I can't find them, the cadets and my granddaughters can get by with the 10 Mil strip. 

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