The Purple Rose of Seddon

A weekend of ups and downs.  A good up but some deep, frustrating downs.

BIG UP!  I got Hazel's purple robot finished.  I was so excited I packed it ready for mailing before I took any photos.  Sorry 'bout that.  Smaller related up.  I printed a pink and a purple rose, one each for the girls.

Sorta biggie.  I went out for coffee in the sunshine.  Late afternoon, top down drive.  Seddon was closed so I went to Yarraville for a look.  PEOPLE!  COFFEE SHOPS OPEN!!

Practical biggie.  I printed a circular plate to replace the external flaps on the kitchen exhaust fan.  There were three flaps that were coated in grease, brittle as chalk from UV exposure and one already snapped in half and dangling.  The southerlies skipped and frolicked through the vanes and kept my kitchen/lounge/workshop delightfully chilled.  So I measured twice, designed once and printed once,  I created a thin circular plate with top and bottom trimmed flat.  I printed a 3mm rod to super glue to the top flat end.  Leave to bake over night and in the morning I bent the flap and pushed the rod into the holes in the fan shroud.  Voila!!  My flap is magnifico!!  I could show off but the photo will be meaningless to mere mortals.

The Downs!

I have printed a number of the roses previously and they always worked.  What I did notice every time was an inconsistent 'Click!'.  In my ignorance I thought it was an extruder problem.  The wise ones on the interweb have described a problem with extruders, they click when not pushing through enough plastic.  I thought it was something peculiar to the rose  model because everything else works fine, no clicking.

This weekend I worked out what it is.  It was the hot end, the print head, clipping the top of a petal occassionally.  How was this possible?  Ahha! When these wonderful printers extrude the plastic, it is hot.  It is expanded like all hot things.  When the fine lines of plastic lay down on top of each other they cool, contract, CHANGE SHAPE!  In the worst case the layers can lift off the plate and distort the model, warping the design.  I reported a problem I had with this in a previous post.  I think that warping, twisting, is happening to the delicate petals of the rose.  As the curved surfaces of the petals are cooling they are contracting, the inner and outer shells at a different rate and causing them to straighten.  In affect, causing them to stand taller, just a fraction.  But that is enough.  The gap between the head and the print surface is paper thin, it doesn't take much of a shift to lose that gap.

I tried everything I knew to address the problem and basically just made it worse.  The clicking stopped but the print head lost contact at some point and started laying down hot plastic spider webs.  Remember each attempt to print can take over an hour before it fails.  AAARRRRGGGHH!!  I have decided discretion is the better part of valour.  I stopped wasting PLA.  Maybe it is just a purple plastic problem.  I will address the problem again next week with a different colour.

Yarraville opens
10 minutes wasted
Birds Nest Soup. Two fails.
Foreground, 1hour fail. Background 1h20m fail.
in the red background. The Print Head of Doom.

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