[double0jimb0]

Expert here.

When very precision molds are made, what Noctua talks about in "multiple tuning iterations are required until the geometry, cooling, gating, and moulding parameters are perfectly stabilised" is the standard process for this type of stuff. (Gears, bottle caps, or any molds than make 8, 16, 32, 64, or 128x of the same part in one shot, require that you start with "steel safe" geometry, meaning you mold the first test parts, measure them, and then modify the mold (by cutting material AWAY, it's very hard, usually bad idea, to add steel back to a mold)).

You can do your best to determine what geometry is "steel safe", and all of this is baked upon having very good engineering understanding of what material you are molding (and using very expensive software like MoldFlow to simulate this).

Legos are made from ABS, there are decades of research and data on how ABS behaves in mold, it's relatively safe to use results from Moldflow and be pretty confident in it. Noctua is using LCP. LCP is very niche, and it sounds like they themselves are doing the research on moldability/warp/process effects. And while also being a company that produces things on timelines, the friction/side effect is that sometimes best guesses will fail and they have to start over with new molds (that's a 2 month hit usually) and months of testing. That is what they were trying so say.

I design glass-filled nylon and polycarbonate parts/assemblies with tolerances 1-5x higher than theirs. The 6-month delay they described is something I've lived through many times when we had to "cut new molds" because we couldn't salvage the first mold. (Advanced molds like these are $50k - $200k+). As a company/designer gets more experience with new materials and colorants (like their stuff with LCP), they will probably be able to hit end-goals on first try more often as they collect learnings from their failures.

[CableNinja]

Noob here. If you dont mind ive got some questions for you!

Ive recently started messing with the idea of making my own model car kits as a hobby. I understand a lot of the basics, but have never done anything like this before.

Im obviously not going to make kits in mass, but, i plan on doing injection molding using polystyrene. I do not currently have a cnc, but have been eyeing a SainSmart, though they say "can do metal under certain circumstances", but doesnt cover any of those circumstances. I also was looking at various injection machines and the price for entry is insane to me - $1000 for something that would probably burn your house down.

Anyway, to my questions..

1. Suggestions for a hobby cnc that can work aluminum? Id be willing to go as far as $2kUSD, unless theres something more that you think would serve me significantly better 2. Suggestions for a hobby injection machine that can do ~60-100g shots, that wont try to burn my house down, and doesnt cost a ton? 3. Any tips or thoughts for someone diving in to this? 4. Things i should purchase for QoL with cnc or injection molding? 5. Where does one buy materials (in hobby quantity) like aluminum block stock and polystyrene pellets?

[double0jimb0]

Those are all things I've spend some time in, I'm not sure what to say. Learning curves for each one of those things are pretty dang steep. With AI you can probably speed up learning curves, but I think you will still go on many dead ends.

On the small CNC that will work with aluminum... There is a whole tradespace around how small of a feature you are trying to mill vs spindle speed vs machine stiffness & spindle runout. If you were to get something like a HASS you can sorta do it all, but when you get into the hobby stuff, you need to be very certain about what smaller set of machining limitations you will be dealing with and if they will still get you where you need to go. You need to work backwards from what actual tolerances you need to hold for the downstream thing to be able to work. (For instance, if you are making an aluminum mold, when you machine it, you will most likely be repositioning the work piece... if your machine isn't square enough so that when you flip the part on it's side or upside down, then do your next op, the part may not have been square to begin with, so now you have something that won't match the other thing you are trying to mate to.)

I build a 2'x5' 3 axis with ATC, starting from a CNCdepot concept and did my own control. I probably spend as much money on precision straight edges, levels, 90deg blocks, lapping tools, etc that were required to build a machine that could hold tolerances to 0.001", which is probably where you need to be landing to have molds that work.

I guess I am just trying to say it's a very big and ugly can of worms you are opening up.

Before buying anything, you might just want to try using firstcut/protolabs. They will machine the aluminum molds and mold the parts for you. Price per part is not going to be pretty, but it's going to be way less than spending thousands on machines that will never get you to where you want to go.

As for "desktop" molding, there is some startup now pushing their kludged together machine, maybe that is the one you are referencing. I'd stay far away from that thing. I think they were charging a couple $k for it, I feel like you need to be at 5x-10x that for anything reasonable. But at that point, the amount of power and infrastructure you need is well outside anything you'd want to put in your house or even garage. Don't really have a good answer for you here.

One thing to look at, if you are doing those model kits where like 20 parts are all in one flat sheet and you twist them to remove them, people are starting to make these on FDM 3D printers, which might be worth looking at. Now you can prototype and do production on the same machine, which at your stage, is the right place to be.

[buran77]

Thanks for the expert point of view. It was between "difficult polymer" and "marketing blurb". Glad it's the first and I hope anyone from Noctua reads HN and adds this small clarification.

I knew the technology itself can have tight enough tolerances that are not a concern from an engineering perspective when talking about a 0.5-0.7mm clearance, but no details about the challenges of this LCP.