Fun with bee vision colour spaces

I recently spent some time collaborating with Dr Lucas Wilkins, a researcher at the University of Sussex, helping him to visualise the bee vision colour spaces he has been working on. He wanted to be able to show the three dimensional models as a plysical object and 3D printing them is the obvious choice. 

As a 3D printing problem the shapes are interesting because they have no straight lines or flat surfaces, all edges and curves, the "bottom" and "top" are sharp points. After considering printing them with support we tried a simpler option first - slice them in half and then glue them back together with acetone vapor post processing.

A bee vision colour space picture by Dr Wilkins, University of Sussex

After successfully printing the colour spaces we used OpenSCAD to create frames ( in purple PLA in the photo above) by subtracting the colour space shape from the frame for a secure fit.

The details are here in his blog which also gives the links to information about colour spaces and what they are.

All the printing was done on our new Lasercut Mendel90, which will be available from our webstore shortly.

Plastic Primer and ABS adhesion to glass bed

(Summary for the busy - plastic primer does not help ABS adhesion to glass heatbeds!, for those interested in more detail -read on)

I have been using "ABS juice" applied to glass sheets on top of a heated bed for a long time now as the only reliable method I have found to get parts to stick well. The one thing that continues to annoy me is having to reapply the coating between prints. The issue is that the film of ABS does not stay stuck to the glass when it's cool, rather it stays stuck to the part printed on it (which makes perfect sense). What I have been looking for is something that will stick really well to the glass and ABS when hot but only to glass when cold.

This is a quick report on Plastic Primer, designed to get "Plastic" style paints to stick to anything, including glass.

It's the best thing I have found so far but it still does not work that well! The problem is the primer sticks really well at low temperatures <50C but becomes tackier the warmer it gets and by the time it's up to ABS bed temperature it does not stick to the glass very well.

The best results I got were after repeated applications of a thin coat of primer, followed by a wipe with ABS juice. The acetone dissolves the primer, making an ABS and primer mixture. This mixture sticks to the bed better than pure ABS Juice and sticks to the object better than pure primer.

Setting the heated bed to the right temperature is also key: too hot and the primer/juice mixture lifts off with the part, too cold and the abs warps and lifts off the bed. In the picture below the marks towards the centre are from when the bed was too hot (100C) - almost clean glass left. The marks towards the front are with the bed too cold (60C).

The parts I was printing are not normally a problem for warping: the Y bearing mounts for a Mendel90. They have rounded corners which helps to reduce warping as well. An example of the warped parts:

Setting the bed to 80C, no fan and first layer 200% extrusion, I managed to get non-warped prints that stuck to the bed:

That said, this method was far from ideal, and appears to only work with parts that are not very prone to warping.

So..... if anyone knows of an adhesive/primer/something else that sticks really well to glass at 20C to >100C, sticks really well to ABS at >100C but does not stick to ABS at room temperature then let me know!

ABS and Acetone - Look no support marks!

I recently tried printing the sticks bowl, one of Dizingof's great math-art creations. The first time I printed it in PLA with Slic3r's default support settings - this worked well as a print job but the support material was a rather long task to remove neatly

The last picture shows a close up of the bottom of the bowl which is still rough even after all support is removed.

This got me thinking about the acetone vapour treatment that Austin Wilson and Neil Underwood wrote about on the reprap blog. The next version of the bowl I printed in ABS at 125% scale, removed the support material and used the acetone vapour technique to smooth it, the result:

This time the whole model is silky smooth.

Inspired by the success of the surface finish I decided to revisit a print of Binary Roots by virtox. This design is possibly my favourite piece of art on thingiverse, I like the combination of geeky, useful and aesthetic. I had previously printed it in PLA:

 but this suffered from the same support material roughness as the stick bowl.

I had to test a number of abs colours a few weekends ago and combined the testing with a 0.75 scale print of Binary Roots, here it is prior to the vapour treatment with the support marks obvious on the bottom.

And following the acetone vapour bath, smooth and watertight ready to be a miniature plant pot:

Further info on the acetone vapour bath process is well covered in a number of blog posts by Austin Wilson. I wonder if my next Mendel90 will be made with smoothed parts....