Curious about moldmaking

[High Seas]

Background - I'm getting into the smal cnc application 'cause everyone I spoke with wanted an arm and a leg to build me some molds for low pessure IM. Figured I'd build the machine and the molds for the price they wanted for the molds.

My original pieces are a bit larger, more like the size of a hockey puck or a pack of cards - but a bit more intricate. Thought I'd do the molds of delrin and hand cast resin ('glass fiber renforced - carbon won't work in this app)

BUT - a home made injection molding machine - who'd-a-figured?!

So, for HOME CNC - have you started building it? Look any easier/harder than putting a home built cnc together? Is the book informative useful - would you recommend a purchase of the book? Estimate on costs? Source of materials for molding listed too? SIZES - are they scaleable? What size are you making?

For NeoMiller -- could you do a master "plug" and build several molds from silicone, then finish as needed - drill the hole for example? Silicone is easy (especilly the 1:1 stuff but won't get the life so build a few molds. Or do 'ya need a reason to use the mill? [I know once mine gets builit I GOTTA! -- or I'll be sleeping outside!]

Appreciate your thoughts - y'all can do it thru the forum or direct via the email side.
Jim

[NeoMiller]

I agree that drilling a hole in a plastic rod is much easier but it is no fun. I want to make this mold (my first one) as a hands on experience.

Can anyone please post some pictures and/or drawings of simple molds.

HighSeas, can you please point to some more info on "silicones". It does seem interesting.

[High Seas]

No worries!
The nice thing they are easy - if not messy a bit - but hey let the chips fall.
RTV - room temp vulcasning (cure)and casting resinss are a great boon to modelers and there are heaps of sites out there that give more specifics. You can cast just about anything as you'll see from the following pages:
First, a good text intro - but no pics -are at this long thread from somewhere:
http://www.ravensforgeminiatures.com/faq20413.html

These are 2 well thought of outfits:
http://www.smooth-on.com/moldmaking.htm

and:
http://www.alumilite.com/

Some of the companies have trial kits you can order that might be a good size for your project. But then after that the sizes get a bit bigger but they seem to be ok size-wize. I haven't yet ordered from these 2 - but while I'm here in the 'states I will - I use folks overseas when there (ATI and Nuplex).

I bumped across the "materials" web site the other day haven't spent much time looking at it yet:
http://www.matls.com/index.asp?ckck=1

Basically, you need a mold [cnc built], PVA (release agent and wax), the RTV, and something to cast with [resin, foam, whatever]. BTW, there is a site that shows how to use LEGOs as the mold box and even has a calculation for how much molding material you need to fill it.

If you need some more I'm sure other modelers will chime in too - I bet balsaman has some links from the rc pages too.
Jim

[HomeCNC]

So, for HOME CNC - have you started building it? Look any easier/harder than putting a home built cnc together? Is the book informative useful - would you recommend a purchase of the book? Estimate on costs? Source of materials for molding listed too? SIZES - are they scaleable? What size are you making?

No I have not started building yet. I did order two of the heating elements called out in the book.

The book looks very informative. It is basic enough for a novice in this area. It shows the machine, and how to build it. It sources the heating element. The book uses one element but I wanted a larger volume shot so I am going to use two elements in the heating block.

One of the projects of this book is to make the crank knob for the machine. The mold is held against the injection nozzle by a screw jack. This screw jack needs a knob for your hand to tighten with. Your first mold will be to make this knob.

The book says you can use many different types of material, like milk jugs, plastic bottles or even a place to get REAL material like the big boys use.

I would get the book if you are not too good at designing from scratch. The machine is simple. It's a frame that will hold the mold against the injection nozzle (screw jack) and the nozzle sticks out of a block of steel that has the chamber for melting the plastic. There is a piston rod that is attached to a long handle at the top.

Operation: You place the mold on the screw jack platform and raise the mold up to the injection nozzle. Apply pressure to hold the mold together and keep the nozzle from leaking plastic.

You turn on the heating element to heat the melting chamber and the mold. Raise the handle to lift the piston rod and fill the chamber with plastic chunks. Let it melt. When ready, pull the handle with enough force to fill the mold with plastic.

[ullbergm]

Originally posted by HomeCNC No I have not started building yet. I did order two of the heating elements called out in the book.

is there a estimated cost in the book or do you have any ideas based on the parts list?

[HomeCNC]

They don't place a cost in the book. That would not be smart because the book ages and costs change.

The material for the frame is standard angle iron I think it's 1 x 1. It's bolted together so you don't have to know welding. The rest is just steel material that can be had from a scrap yard.

The heating elements and oven thermometor are two thing that need to be purchased. I can't remember how much the heating plug was but I think they are around $25.00 each.

[DLMACHINE]

How about you guys showing off some of your mold work. Post some pics of your favorite pieces.

[peter]

hi neomiller
in this country we call them manumoulds
there good for getting a few hundred components
you can make it out of aluminuim
then i would make a sleeve ejection to get it off
ejection pin to create hole then sleeve to eject it off
best regards
peter

[cadcam]

How about you guys showing off some of your mold work. Post some pics of your favorite pieces.

Here is one http://www.ppcadcam.com/html/tounge_scraper.html

[eintnl]

For a single cavity, molding a cylindrical shape will be quite interesting for you in terms of gating.

Cheers.