Saturday, June 2, 2012

Begining to tune the printrbot...

Last weekend I got the printrbot built and working, and while it was a busy week and I didn't have much time, I started working on getting better prints.  Once I had passable replacements printed for the parts I thought I would break doing adjustments I started playing with the extrusion and bed temps, the printing speeds, the percentage of fill and most of the settings in slic3r... One at a time of course.  I highly suggest that you do this because the understanding of exactly what each setting does, where it gives valid/perfect/bad results and the tradeoff between printing time and final quality is invaluable (not the same thing to read about these things as it is to see the results in your hands). 

During the process I also found that one of the z-axis smooth rods was a little loose.  I did a short term fix by adding a polypropylene film wrap around the rod before inserting it into the base.  I also tightened the x and y axis belts (I was a afraid to push it as far as I usually tighten belts without replacements).

While printing on blue tape works, printing on kapton tape (poly imide) is a completely different world...  There is no need to check the z-axis height each time - set once and so far it has held over 20 prints without adjustment.  Kapton also makes a much more uniform surface height than blue tape.  But the nicest thing is that it doesn't release during the print (no edge lifting) and as the bed cools down it's very easy to get the parts off.  While most people seem to like really wide tape, I like the relatively thin 1 inch wide tape.  I got mine (the high temp/low static type) from digikey because I was putting in an order for something else anyway.
The print here is a simple calibration piece and while I had the settings dialed in reasonably well, I found that the x and y axes were 103% of what they should have been and the z-axis was 105%... not so good.

What I should have done was to check the calibration after tightening the belts, but it didn't occur to me... I calculated the new numbers and added them to the g-code in slic3r and bingo, the sizes were right.

Now the prints come out the right size, I like the internal fill pattern and percentages, the temps are good.  There are still things to work on and fine tune, but I can get reliable of good quality, so it's time to print a set of good replacement parts...

My new filament isn't here yet so I just made the gears, the bed clamps. the belt clips, the x axis carriage and the extruder parts.  Now it's time to start working on the remaining little problems to see how good the build quality can get... 

One important note is that now that I'm looking at the quality I have been printing so many multiple copies of objects -> and multiple copies means that I am beginning to get a good idea of how reproducible the defects/anomalies are and which parts/structures are the sources of errors.  By far the most accurate and reproducible part is the extruder... whoever was involved with the design deserves a nod of thanks and pat on the back - once I got it dialed in it's been very reliable.

While I suspect there are differences in everyone's specific build, a very very good place for information in understanding how slic3r works is here.

Probably not a lot of time this week to work on it, but I am finally beginning to understand google sketchup and design my own things.