How to print a simple bi-convex lens shape - not for optics?

[nzo 16]

Hi all,

I'd like to experiment with printing a simple bi-convex lens shape, something like an old-style magnifying glass or loupe on my UM2+. Transparency and optical qualities are not required. So it will be thick in the middle, tapering to thin on the outer edge.

[media=71309][/media]

I want use PLA to print the finish as smooth as possible, but will probably have to do some post-print sanding and polishing. Diameter will be about 4 to 5cm, max thickness about 1 to 1.5 cm.

My question is: would such a model be best printed flat on the build plate and on top of a raft.? I'm thinking of making it solid PLA. I haven't messed with rafts before.

Any suggestions appreciated. Thank you!

Edited October 14, 2017 by Guest

[ahoeben 1,884]

Split it down the middle and glue two parts together?

[nzo 16]

Hadn't thought of that ahoeben.

I don't know if glueing the two halves might create a thin layer of glue 'color' (different to the print's color) that will become visible when I cut into the lens post-processing.

Only one way to find out

[geert_2 557]

I think by far the simplest method is like ahoeben says, but then you are going to have quite visible layer-steps, like stairs, especially in the center.

If you want less visible steps, maybe printing it vertical might be an option? But then you would need to design a sort of support beam structure around it, for good adhesion to the glass and for stability. If your printer has no Z-axis issues, this should give a smoother surface and require less post processing, I think. Of course the support needs to be cut off afterwards.

Would be interesting to compare both methods.

Edited October 16, 2017 by Guest

[ahoeben 1,884]

I did not specify which axis to split the lens on. If you split the lens so you have a circle as the ground plane, then you are going to get fresnel-lens-like steps on the lens. But it you split the lens along the other orthogonal axis, you get a fairly smooth result (and a smaller contact area to smooth out after gluing)

[eldrick 65]

Print it with Slic3r's Adaptive Layer Height to get a much smoother surface with greatly reduced stair-stepping.

[nzo 16]

Thank you all! I lost this post and only just found it again. Very useful info.