Resin printing with wax supports?

[Rob de Bie]

A couple of months ago, I spent a lot of time making 3D CAD models of some model parts that I wanted. But the outsourced resin printing was a bit of a disappointment: the great number of supports left a lot of 'nubs'. Take for example this M116 napalm tank in 1/48 scale, that had more than 50 nubs:

 

 

The work removing the nubs and repairing the detail lost made it a useless exercise. Most of my parts were pretty much unusable.

 

I let the experience sink in, and then remembered that I had a model printed many years ago, in PMMA resin, with *wax* supports. Here's the model, and all the whitish areas are formerly supported by wax, that was subsequently removed by the manufacturer before delivery:

 

 

If I remember correctly, the Shapeways 'FUD' (Frosted Ultra Detail) looked similar (but not blue), so maybe they were done the same way.

 

Is this printing technique still commercially available? I would gladly spend some more money and get parts without those annoying supports / nubs.

 

Rob

[ICMF]

Yes, it's still available via Shapeways.

[Iceman 29]

This known phenomenon is not due to the supports but to the stagnation of the resin on the side of the plate.

In the case of your tank, you should have printed it vertically, reducing the surface in front of the tray, and hollowing out with the slicer to limit the tension on the supports.

 

Like this float:

 

 

[Rob de Bie]

23 hours ago, ICMF said:

Yes, it's still available via Shapeways.

 

I don't see it listed.. Unless 'Fine Detail Plastic' is the same?

Rob

[Rob de Bie]

8 hours ago, Iceman 29 said:

This known phenomenon is not due to the supports but to the stagnation of the resin on the side of the plate.

In the case of your tank, you should have printed it vertically, reducing the surface in front of the tray, and hollowing out with the slicer to limit the tension on the supports.

 

Like this float:

 

 

Thanks for the suggestions! Your picture shows an interesting alternative solution: put a 'tower' of supports next to the print object, and support the print object with a few horizontal bars (the float supports in your picture). It's almost like a sprue attachment on a normal injection moulded part.

 

You write 'reducing the surface in front of the tray', can you explain that? Do you want to minimise the area when viewed vertically down on the printing tray?

 

How does the hollowing out help? Is it because it reduces the printing area, therefore it reduces the forces on the print object, and therefore less support is required?

 

Rob

 

 

 

[Iceman 29]

The recess reduces suscitions when the hardened resin is pulled out of the film on the bottom of the tray.

 

It is also necessary to make a hole at the bottom of the piece to let the air in.

 

Otherwise the surface of the part may suffer until a design hole appears higher up.

 

It took me a while to understand this effect, but it is obvious.

 

Clearly the part is a suction cup, and this tends to delaminate the successive layers until a hole appears to let the air in.  

 

So you need a hole for each compartment like here when you print directly on the plate.

 

With the base supports it's the same. Chitubox has a "puncture" function because of this phenomenon. 

 

On the other hand, the more hollow the part, the less important the surface to be peeled off, the less damage to the film, and the less risk of breaking the supports if the tensile force in relation to the surface to be peeled off is less important.

 

Print without holes in the base, print directly on the tray.

You can see the delamination stopping at the first windows.
At different heights as the hull compartments are watertight.

 

 

 

The solution, two holes.

 

 

For the hollow float, you can see the two small holes that serve as vents.

 

 

 

[Rob de Bie]

On 11/6/2021 at 9:05 PM, Iceman 29 said:

The recess reduces suscitions when the hardened resin is pulled out of the film on the bottom of the tray.

[snip]

For the hollow float, you can see the two small holes that serve as vents.

 

Many thanks for your extensive explanation! I learned new things that I will try to use for my parts.

 

Rob