Plastic: mill versus mold....

[leppya]

Hi, so, yeah I'm new... and have some basic (maybe odd) questions. Thank-you in advance for any responses.

Basically I have a small plastic part I want to reverse engineer because it is no longer in production and I'm trying to figure out how to do it best. I'd like to make only 500 of the pieces. They are small plastic things maybe 2" x 3", imagine something like a plastic remote control case. The outside is mostly smooth/rounded, but the inside is fairly complex with some rails, notches, and bumps in the plastic.

Is there a way to know if a plastic part 'can' be milled i.e. it IS possible to mill a certain design vs. no, this is a part that must be created from a mold?

Is there ever a distinction - can all parts be made via either method?

Is it true that a good mold is very expensive.

What about milling plastic in general:
Is this done frequently?
Is there special plastic for milling?
Are there advantages to milling vs molding?

Leppya

[Pres]

Hi Leppya,
Welcome to the forum.
You have asked a lot of (variable) questions but it would help if you could provide a picture (or drawing) of about what you have in mind.
It saves everybody time, including yourself, since you might get less accurate advise without providing the necessary details.

Fwiw, I've machined many injection molds (from billet) that produced hundreds of reject parts before we "got it right".
Shrinkage, vents, gating, etc. each required changing the mold.
Sometimes we had to up the melt temp of the material by 50f to get a good fill. Problem with that is then the whole mold becomes too small (by a few thou) because of material shrinkage.

Bottom line: unless its very difficult to machine, your only reasonable choice is machining.

Fwiw: rigid pvc (eg plumbing pipe) machines well and is relatively inexpensive but it is just one of hundreds of material types available.

Post a pic and what you want it to do. Will it be exposed to sunlight? If so, can it be painted? Oils or other chemical exposure affect the material selection.

hth,
Pres