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J.T.'s 8" f/10.6 Ed Jones Chiefspiegler build

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#101 Jon_Brumbaugh

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Posted 31 January 2020 - 01:16 PM

JT,
Rustoleum makes a product called "filler primer" it comes in a rattle can and is very popular with the 3d printing community. I have never used the product personally but I hear it works well, I guess it is some sort of primer bondo mix, it's supposed to fill the layers. If the printer has a heated bed a try layer of hair spray on the glass sticks really well with PLA, and leaves a very smooth finish, however it will be glossy. It sticks really well when its warm, and the print pops right off when it's cooled!

#102 jtsenghas

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Posted 31 January 2020 - 06:38 PM

JT,
Rustoleum makes a product called "filler primer" it comes in a rattle can and is very popular with the 3d printing community. I have never used the product personally but I hear it works well, I guess it is some sort of primer bondo mix, it's supposed to fill the layers....

Very interesting,  Jon, and great to hear from you again! That sounds very interesting and useful. I've noticed on playing with these lens cell parts that it takes only a little sanding to take off the high spots and produce relatively smooth surfaces,  but a lot of sanding to take the surfaces all the way down to the low spots. I suspect that sanding, priming, and then sanding again may do well for getting smooth surfaces with minimal dimensional change. 

 

These lens cells must have very good dimensional integrity inside the lens seats, and I don't want to either build up or sand down these locating surfaces much. I'm mostly trying to get a nice dull black finish to minimize reflected light,  and to experiment with materials and methods for future projects. 

 

The primer I'm using did an excellent job of adhering very well to the PLA, and though it laid down with a bit of orange peel (pebbly surface) it sanded smooth after drying very easily with 340 grit paper. I noticed that it leveled my printed surfaces well,  but those had been sanded nearly level anyway. I can imagine a filler primer could be even more accommodating.

 

I discovered,  unfortunately,  that the acrylic Black 3.0 paint didn't adhere to it noticeably any better to it than it had to the PLA.  Though it lays well and sticks very well to porous surfaces like cardboard and wood,  it takes several thin coats to cover this primer and scratches fairly easily when dry. 

 

I'm going to sand off what Black 3.0 I've applied to Ed's lens cell,  reapply primer,  lightly sand that,  and then paint with the Ultra Flat Black spray paint I usually use. The improved adhesion would be preferred for keeping the optics clean,  and the primer and topcoat should go well together. 

 

I am very pleased with Black 3.0 on raw wood,  however and plan to use it inside my UTA of my 12.5" dob which has thin birch plywood there. 


Edited by jtsenghas, 31 January 2020 - 06:57 PM.


#103 jtsenghas

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Posted 01 February 2020 - 09:57 PM

Yes,  the primer shown a few posts ago and the flat black paint I usually use worked well. Even this primer fills a lot,  so I loosened the lens seat with a 2" Forstner bit by hand after both primer and top coat. This should be a lot less reflective than the printed plastic. Since these lens cells will be buried in a tube or narrow box about midway between the round 3" secondary and the focuser,  they are certainly black enough.  It was fun to experiment with sanding and painting 3d printed PLA. I think taking down the high spots with sandpaper before priming,  and priming twice with sanding between primer coats is the way to go if one wants to hide the printing artifacts.

 

This cell will be off to Ed perhaps Monday. 

 

20200201_213945_compress88.jpg


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