I’ll probably be using an SLA printer to make the parts. I noticed the only mention of material is PLA.
Would a resin serve as an acceptable material for the CNC machine?
I’m not an engineer and I don’t have have an SLA printer, so my answer is theoretical. The most important aspect of the plastic parts used in the MPCNC is stiffness. PLA is the stiffest, commonly used, 3D printed filament. According to datasheets, carbon fiber filled PETG and ABS are a bit stiffer, but at a significantly higher price and require hardened nozzles.
The measure of stiffness I’ve seen on this forum is Young’s Modulus. In a quick search, I found a datasheet for a particular PLA indicating it had a modulus of 2300 MPa (higher numbers are better), so I’m using this as a ballpark figure. I then found this site which lists the properties of different resins. The Young’s Modulus is only listed for a minority of the resins, but according to the table, there are three resins with a comparable modulus to the PLA I found:
- Resione at 2880
- 3D Materials at 2400
- Elegoo at 2100
So in theory, with the right resin, it should work. Do you have an SLA printer big enough to print the MPCNC parts? The core is pretty big.
I have both types of printers. I printed a universal mount on my Anycubic Mono X using Sirayatech resin… I looked great, hole lined up perfectly, tool mount slid into it perfectly… When I mounted it and went to tight up the screws that clamp the tool holder to the universal mount, I heard cracking. Now I’m not a heavy handed person by any stretch. I’ve been a field service tech for over 30 years, and have an excellent ‘feel’ for how tight to tighten screws down in plastic! 
Bottom line it, I believe that most resins are just too brittle for use on the MPCNC. I’ve not tried the more exotic (Read: Expensive) resins, but things are changing all the time with new resins being introduced all the time. I’d be surprised if someone doesn’t come out with a fantastic resin with all the properties we’d like to see in the next 5 years or so, but right now, I don’t think there’s a solid choice.
Ron
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Here’s some specs from one of the resin types I’ve been investigating (Polyjuice water washable resin). Are we talking about the flexural modulus? I’ve also used the Elegoo water washable resin.
- Viscosity: 100-350MPa·s（25℃，m.pa.s）(NDJ-8S Rotary viscometer（25℃）
- Wavelength: 385nm - 410nm
- Density: 1.05 - 1.25g/cm3 (Densitometer 25℃)
- Flexural modulus: 1.882 - 2.385Mpa
- Flexural strength: 40 - 70MPa
- Deformation temp.: 80℃
- Thermal expansion: 95*E-6
- Volume shrinkage: 3.72-4.24%
- Linear shrinkage: 1.05-1.35%
- Tensile strength: 1.779-2.385MPa
- Tensile modulus: 36 - 52MPa
- Elongation at break: 11%-20%
- Hardness(Shore D): 80-85D
- Glass transition temp.: 100℃
- Notched impact strength: 41-48 j/m
It’ll fit on a Saturn.
Not sure how you’d cure it though. The geometry makes spots you can’t drain unless you put a bunch of holes on the sides. Even if you slice it solid, I don’t think it will cure more than a few millimeters into the sides. This’ll cause cracking after a while.
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I wouldn’t use resin as it is quite brittle, it will be likely to crack and break.
I wish would fit on my Photon S or the Crealty LD002H
I’ve been mixing Siraya Tech Tenacious 50/50 with great results. Makes it not so brittle and much less likely to crack or break even when you drop the part.