[M][T][A] R1 needs to be redesigned.

A project log for Coaxial8or [gd0144]

Full-colour FFF? Multi-materials with unparalleled interlayer bond strength? Abrasives without abrasion?

kelvinakelvinA 04/11/2024 at 10:120 Comments

I've cancelled the PCBWay order for the Coaxial8or R1.

It started small. Small as in a small missing fillet. That was easy to correct.

Then the engineer came back because they had concerns about the M6 threads:

I looked at how Heinz did their threads and one thing I noticed was the taper before the flat wasn't a basic chamfer. I presume this is so that imperfections from the printed thread does not affect the important face that seals against the nozzle.

Thus I went in and did some modifications:

Then I was validating the model and found an extreme minimum wall violation that I unfortunately missed:

The hole is the grub-screw hole and so I had to rethink quite a bit of the design (and this is when I requested the order be cancelled since it could take a while).

Fast forwarding a bit, I moved the grub screws, reduced the clamp block thickness because it no longer had to fit the grub screws, and trimed the body of the heatblock so that I could simultaneously get under 20,000mm3 and $40 autoquote, and I got this:

Side tangent: Trimming around channel 7 / 8

I first tried doing the trim with an extrude and draft angle but it just looked... wrong... so I instead created a cone surface and extruded to that, which actually trimmed off even more material.

Tangent over. Back to the main story of events.

So I was dancing about how my design is now 193cm3 and the autoquote was $38.80, and I was on Discord asking Heinz a few questions to get the latest insights in the technology tree. The response:

-- lots of colors are nice, but biggest improvement is in the coating meachanism itself imho.

-- making it as small as possible for less purge and quick color change

-- similiar to the cetus2 brass insert...

I was going to reply that I felt like colour gamut vs colour change speed would be one of those engineering challenges where one is forced to pick a side. I still feel that way, but that it's not as black and white as I originally thought.

Remember that print of a clip that was supposed to be white but only got to a medium-light grey at best?

Well I looked into the model cross section and determined that I needed to reduce the contact zone between differing materials whilst still being manufacturable. 

Ideally, colour changes inside the melt chamber would be like a Pallete filament splicer, but with molten filament. Another way to think of it is like a 1-dimensional version of offset printing where each colour is separated by some finite distance and the change in colour is a single point on the length of the pipeline:

The final colour output created by merging the combined-effort of previous work with a single colour.

I started sketching a solution that could potentially be geometrically viable yesterday:

Today, I've looked into "Crosshead Extrusion", which is a method to coat wires with insulation:


I'm continuing to experiment with what I can do with the design whilst keeping it compact, ensuring a minimum wall thickness and keeping the pressure as axissymmetric as possible:

The idea is to make the geometry more like a revolved version of the Cetus2 nozzle for each channel. This is also to hopefully make push/pull vtools more effective.

Cetus2 nozzle. If you changed the angles so that the two inputs are perpendicular and then revolve it around the left or right edge of the image, the result is similar to what I've started to come up with.