Friday, July 1, 2016

A very Accurate Way to Set Your Gap

UPDATE:  I am now testing Mylar at a thickness of 10 mil (.254mm) and 15 mil (,305mm).  I have a feeling that I need to find 12 mil (.305mm) to test, which may be the 'sweet spot' for the gap.   10 mil and 15 mil sheets can be found in art stores.  15 mil holds the build plate; but, the bottom layer shows signs of delamination.  
UPDATE #2:  May 2017 - I recently found 11 mil plastic material that works very well with the original tip in the Micro.  The secret is to just let the tip kiss the surface of the plastic.  The tip should not grip the plastic against the print table because the print table is flexible.  
As I continued to run my stringing tests using Tough 3D Ink (Utility Grey) it was apparent that this material REALLY likes to stick to the print table with large footprint objects.  Because one of the M3D Micros is destined to go to my grandchildren it is imperative for me to find the EXACT gap setting that finds that perfect balance between sticking while printing and not taking extraordinary measures to remove once it has printed.

To me too much adhesion becomes a safety issue because the only items I know that can remove stubborn items from a print plate have sharp edges and children don't always point sharp edges in the right direction no matter how many times they have been told.

It is not enough for me to find the right item around the house, like a card or some thickness of paper, because if others are going to use the printer the method of setting the gap that i come up with must be able to be easily replicated.

Fortunately, we have an old tool that can help solve this very new problem... the Tappet Gauge, also known as a Feeler Gauge.  This tool typically is used to set the clearance between the valve stems and valve tappets of gasoline engines.  It is very inexpensive and readily found in automotive stores.  Or, if you prefer, it's easily found on eBay or Amazon.

Tappet Gauges include a number of metal leaves.  Each leaf has a precise thickness.  All that I've ever purchased mark the thickness of the leaves both in SAE (American Standard) and Metric.  For our purposes Metric is my choice.  Here is an image of the style I prefer.

Tappet or "Feeler" Gauge


This version has angled ends; but, you may prefer blades that are perfectly straight.  In either case, blades can be used singly or combined together to measure very precise gaps.

Since it is metal, it is important that we don't try to force a leaf blade under the print jet.  These need to used gently and with care.  But, as you get used to using one, you will find, with some experimentation, it not only helps you to set the proper gap; but, also helps you to obtain a perfectly leveled print table.

I wish I could pass on a precisely arrived at gap.  But, I'm still chasing that one down for the Tough 3D Ink.  Looking at the print now running, it appears that my latest setting may be just a hair to wide,  I say that because the filament doesn't appear to be as smoothly laid down as in previous prints.  However, I'll let it run to see the final result.  

To me, chasing the perfect print is all part of the challenge and fun of 3D printing.  If we do not let ourselves become frustrated by what we deem as failures; but, use those failures to learn, then each attempt becomes a tiny move forward to consistently great results.  Learning our tools and how THEY want to work is key to having fun with 3D printing. 

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