Author Topic: Homemade plastic injection molding? (Read 10987 times)

darkcape · « **on:** May 17, 2004, 12:41:03 pm »

I am currently building a cabinet and thought it would be cool to have a 3d effect on the marqee or side panel. however I have no idea how to do this. I can mold in clay and have done some metal work with molds but I have no idea where to get plastic to melt down? or aquire it in some kind of raw form? Does anyone know how to do this? I was thinking of making my own trigger joystick also but don't think that I can work in high desnity plastics. Just looking for some side art possibly in the same plastic ice cube trays are in. (doesn't melt well and I'm sure the fumes are toxic)

any ideas?

Stingray · « **Reply #1 on:** May 17, 2004, 01:18:31 pm »

Injection molding is way expensive. You might try resin instead. Check some scale modeling sites for more info on resin molding.

-S

Lilwolf · « **Reply #2 on:** May 17, 2004, 04:59:30 pm »

slightly off topic here..

but..

is there a solution for recreating in small demand parts?

for instance... I have two t2 controllers... and the fire button is worn down. I adjusted them to get them to work... but they don't click back smoothly (but still work).

Is there an easy way to create them?

I could see some buisness around here for refurb smaller items like that..

jcoleman · « **Reply #3 on:** May 17, 2004, 05:05:23 pm »

Look into vacuum-molding. It might actually be called "vacuform" or something along those lines. One way or the other, it's pretty easy to do at home from off-the-shelf parts. I remember some article on Slashdot where someone used this method to create a homemade Stormtrooper costume.

Coleman

SirPoonga · « **Reply #4 on:** May 17, 2004, 06:26:37 pm »

yeah, vacuum forming is probably the best. There is a book out there on how to make your own manual plastic injection molding machine. But making molds is expensive.

darkcape · « **Reply #5 on:** May 17, 2004, 06:31:20 pm »

I also looked at vacuum molding. but the big issue here was having something solid enough to bump into (A lot of drunk people wandering around an arcade machine leaning up against the site could be disastrous) would be great to use vacuum molding to create a mold but then what to fill it with that would be Strong enough to take minor abuse. Looking at the resin idea looks like the right path. I actually thought of using glue slicks melted down but could see people with fingernails scratching it. Resin idea looks great just having hard time finding a distributor. (will post one when I find one)

Mooters · « **Reply #6 on:** May 17, 2004, 07:01:17 pm »

Found the link to the article if anyone was interested

http://slashdot.org/article.pl?sid=01/02/17/226237&mode=thread&tid=101

Spyder

Stormy151 · « **Reply #7 on:** May 17, 2004, 09:12:19 pm »

Vacuform. The "bumpy" parts on the Star Wars cabinets were probably vacuformed. In the case of vacuforming, it's not the molds- but the machine that's "relatively" expensive- in terms of money, or time if you build one. You can build a home vacuformer fairly cheap, but the bigger you get- the harder it is to heat the plastic, unless you build one with large heating elements, which costs $$$. Small ones can use the oven as a heat source.

For those that don't know about vacuforming, basically, a sheet of plastic (most often styrene) is suspended in a frame. You heat the plastic until it becomes soft. You have your mold placed on a table full of holes (kind of like an air hockey table but bigger and more holes). You drape the heated soft plastic over the mold, and activate the vacuum, which sucks air through the holes in the table and the plastic forms around the part.

Here's an example. Make your own Stormtrooper armor:

http://www.studiocreations.com/howto/vacuumforming/index.html

Generic Eric · « **Reply #8 on:** May 17, 2004, 10:18:09 pm »

How durable is this stuff? Is it good for buttons and such? how about gun holsters?

Stormy151 · « **Reply #9 on:** May 18, 2004, 02:41:01 am »

Depends on the plastic/thickness. Styrene not so much, but ABS would probably work for a gun holster, so would Kydex.

Buttons, probably not. You could probably make a cover that fit over an existing button though.

Generic Eric · « **Reply #10 on:** May 18, 2004, 02:55:41 am »

Quote from: Stormy151 on May 18, 2004, 02:41:01 am

Depends on the plastic/thickness. Styrene not so much, but ABS would probably work for a gun holster, so would Kydex.

Buttons, probably not. You could probably make a cover that fit over an existing button though.

Right...about the buttons, I was thinking about what Lilwolf was asking about the T2 grenade button

dag2000 · « **Reply #11 on:** May 18, 2004, 03:22:32 am »

See : /http://www.studiocreations.com/howto/vacuumforming/index.html

depressd · « **Reply #12 on:** May 18, 2004, 02:52:52 pm »

What about protoplast pellets or sheets for the molding. You can cast your clay molds in this stuff to make a positive mold. It's very rigid after it sits for a while. I use it for custom halloween fangs. It works really well. There are tons of free info on using this stuff on various halloween sites.

http://www.wfr-aquaplast.com/tmppcc_default.htm

Psychosylph · « **Reply #13 on:** May 18, 2004, 04:00:40 pm »

A way to make smaller pieces...

http://www.gruntville.com/howtos/customgrills/index.php

darkcape · « **Reply #14 on:** May 18, 2004, 07:05:10 pm »

Psychosylph. I think that is exactly what I've been looking for. you all are amazing I will be posting picts of the cabinet when finished. thanks to everyone posting. vacuum forming was more versitile then I though maybe a halloween costume in the future. thanks a tone I hope this discussion continues with more ideas.

lookos like i'll be getting Resin from http://www.alumilite.com/ hope it doesn't cost too much I'll tell what I pay and see if i've been ripped off or got a great deal.

mp2526 · « **Reply #15 on:** May 18, 2004, 08:11:04 pm »

Quote from: darkcape on May 18, 2004, 07:05:10 pm

Psychosylph. I think that is exactly what I've been looking for. you all are amazing I will be posting picts of the cabinet when finished. thanks to everyone posting. vacuum forming was more versitile then I though maybe a halloween costume in the future. thanks a tone I hope this discussion continues with more ideas.

lookos like i'll be getting Resin from http://www.alumilite.com/ hope it doesn't cost too much I'll tell what I pay and see if i've been ripped off or got a great deal.

You might compare Alumilite with http://www.smooth-on.com on pricing. Haven't checked myself, so not sure which is better.

Stormy151 · « **Reply #16 on:** May 18, 2004, 08:46:13 pm »

Also check out www.polytek.com. I use their Easyflo 60 resin and TinSil 70-25 mold rubber.

darkcape · « **Reply #17 on:** May 20, 2004, 11:45:42 am »

looked at the other resins and they looked good but went with the alumilite. since it was at a hobby shop right next to my house. for $30 for the 28 ounce kit initial tests were awesome. stuff is really hard (not sure if hard enough for buttons) and pours realy smooth. wasn't quite ready for the massive exothermic reaction not hot enough to burn but definatly gives off some heat. pictures to come soon (well soon in my book is about 2 weeks)

said7 · « **Reply #18 on:** May 20, 2004, 02:01:19 pm »

cant wait to see! Id love to take a shot at some mold making.

Psychosylph · « **Reply #19 on:** May 20, 2004, 05:51:20 pm »

Quote from: darkcape on May 18, 2004, 07:05:10 pm

Psychosylph. I think that is exactly what I've been looking for. you all are amazing I will be posting picts of the cabinet when finished. thanks to everyone posting. vacuum forming was more versitile then I though maybe a halloween costume in the future. thanks a tone I hope this discussion continues with more ideas.

lookos like i'll be getting Resin from http://www.alumilite.com/ hope it doesn't cost too much I'll tell what I pay and see if i've been ripped off or got a great deal.

Glad it worked out. I just got lucky and had read that article the day before I saw your post.

darkcape · « **Reply #20 on:** June 19, 2004, 05:33:53 pm »

Ok got most of what I was looking for with this. except of course experiance and talent. the first step I went thgouh was to make the clay master. I can not stress enough how the better you make this the better the finished product will look.

darkcape · « **Reply #21 on:** June 19, 2004, 05:38:03 pm »

Next step was really fun. put the clay in some kind of container and pour in the latex. (sticking with alumilite i used the high strength mold making rubber base 2 most expensive part of the whole project.) I used a sandwich sized plastic bowl to pour latex around the clay. the clay is in there trust me.

darkcape · « **Reply #22 on:** June 19, 2004, 05:42:26 pm »

Then after waiting for 48 hours (it still wasn't completely cured maybe should have waited 36 hours) I pulled out the latex but came out pretty well and removed the clay. giving me the cast to make penguin (in case you couldn't tell what it was "told you the most important step was creating a good mater")

darkcape · « **Reply #23 on:** June 19, 2004, 05:43:41 pm »

Then poured in the alumilite and waited 5 minutes. (easiest part)

darkcape · « **Reply #24 on:** June 19, 2004, 05:47:14 pm »

Then removed the set platic and viola plastic 3d piece. i need to do a lot of sanding and painting to get this fixed up. hope this helps anyone out there. not sure if i'll be able to make a pacman guy with my talents but hopefully this will help someone out there with some ideas.

Xiaou2 · « **Reply #25 on:** June 19, 2004, 10:24:19 pm »

Heya,

Just wanted to pass on some notes about aluminite.

It may appear hard - but at any less than 1/2" and its pretty brittle. Drop it to the floor and it will break in many places. This means that any fine details are very much in danger of cracking off at the slightest pressure.

The stuff isnt too expensive - but - the rubber needed to make the molds is! And since you need a lot of it... it adds up fast, especially if you make mistakes... or have to make several molds.

The plastic itself has to be just the right tempature as well as pre-heating the mold to ensure it will develop correctly. Sometimes my parts would come out sticky because of this - and wouldnt cure properly.

Thinking about this now... the water meltable plastic is actually much harder and durable than alluminite. The only drawback is that its kinda tricky to work with... as well as the fear of it changing form in a 'heated' situation.

I suppose if you coat alluminte creations in some sorta hard epoxy... you might have better durrability. Id recomend other stronger and more professional plastics.

Btw - if you want to experience aluminite without buying it - its sorta the same as 'JB Weld'.

Ohh - and about your mold there... you might try making a 2part mold next time. Took me a little bit to get the hang of it...

by submerging only half the object into the rubber, and half into clay. When the rubber cures... then you remove the clay, clean it up, and wipe it with release agent... then fill the rest of the mold to completely cover the part. When that is cured... you should be able to pry the 2 halves appart. Dig a 'fill' channel to the main empty body. You can use rubber bands to keep the parts together when you fill it.

If done this way.. there is very little problems with having to sand and clean up the parts. However... if you have too many odd caverns and details... air bubbles will get caught when you try to cast the plastic. Supposedly, if you have a Vaccume chamber, you can illiminate this problem... but, they are major expensive.

ErikRuud · « **Reply #26 on:** June 21, 2004, 10:17:25 am »

Alumilite, Smooth-on and many others are polyurethane resin. JB Weld is an epoxy, not really the same.

Sticky castings are usually caused by inaccurate measuring of the two parts. Part A in poarticular canabsorb moisture from the air. This added moisture can also cause the stickiness.

Polyurethane resins come in moany varieties. If the standard resins are not strong enough use some of the others. Smooth-On's "Task" series of resins are designed for high strength.

I use the smooth-on resins to create HO Scale slot car bodies. I have had bodies come out brittle. I have also had them come out with the consistency of a fruit roll. You HAVE to get the mixture just right.

You can recycle some of the silicone mold material from your old molds and mistakes by cutting them in small chunks and using them as filler in ne molds. Just keep the filler chunks away object that you are molding.

http://erikruud.freeservers.com/maelstrom/resin.htm

http://erikruud.freeservers.com/maelstrom/Resin/index.html

http://erikruud.freeservers.com/maelstrom/Resin/pictures.html

darkcape · « **Reply #27 on:** June 21, 2004, 11:18:39 am »

ERIK genius idea useing old latex to fill in the voids. I would not have thought of that in a million years. glad I havn't trashed my old mold yet.

and I have to agree JB weld and alumilite are extreamly different only similarities are that you mix 2 halfs to make a whole. will look into smooth-on but i'm very happy with alumilite. and i can pick it up at the store next to my house.

does anyone have any idea where to get larger quanties of latex for the mold? for 10 - 20 pieces the 20 oz jar is going to take forever with a lot of wasted conatiners.

back to the clay mines. never would have thought I had lost so much technique from high school art class.but i guess if you don't use it you lose it.

ErikRuud · « **Reply #28 on:** June 21, 2004, 12:08:12 pm »

Yes, it is nice to pick it up at the hobbyshop, but they tend to just carry the basic varieties. If you need something else(high strength, clear, etc), you will have to order it from somewhere.

Most of the resin suppliers have silicone (not latex) in larger (Gallon) sizes.

You could use latex, but it has a tendency to shrink.

I cannot take credit for the recycling idea, it has been around for a while.

I like to use Legos for making mold boxes on smaller items.

Xiaou2 · « **Reply #29 on:** June 21, 2004, 05:29:20 pm »

Guess I should have been a bit more specific. I meant that in terms of brittle-ness...jb weld is simular.

When its dry - jb weld has a simular texture, feel, strength, and cracking property. While it is a paste - its still a plastic like substance made from a 2 part mixture.

darkcape, if you use sculpy - you can bake your model hard... and that will give you the ability to do the 2 part molds - (using clay to temp. cover one side).

Aluminite carries the gallon jugs of the rubber. Its like
100$ a gallon i think. Which is how things add up quickly : ( I dropped like 500$ easily trying to make tron spinners.. but failed cause the encoder wheel spokes were too brittle, missing, bubbled...ect.

mp2526 · « **Reply #30 on:** June 21, 2004, 06:59:45 pm »

as mentioned before vacuuming helps tremendously, and if you look around you can find a lab desiccator on eBay and a A/C vacuum pump will work fine. Here is an example of what a desiccator looks like. They come in various sizes and are made either in glass or synthetic compound.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=26406&item=3822836150&rd=1

If a vacuum is too much, then the next best thing is an air compressor (especially if you already own one) and a paint pressure pot (ie http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=37515).

The concept is similar, but rather than sucking all the air bubbles out, you compress the air bubbles out.

darkcape · « **Reply #31 on:** June 22, 2004, 12:07:45 pm »

I love this group. awesome responses from everyone.
someday i'll have to setup a vaccuum press but cost and space is my major problems here. (yeah the full cabinet is taking up a lot of space right now but I can kind of pacify the wife with it now.)

where does one get silicon to make molds with? I've seen the stuff on mythbusters allong with ballistic jelly (don't even want to think about the cost of that) but where do you get it? anyone have a favorite outlet? and is it that much cheaper then the latex. or as often seen does someone have another option.

and I love the lego mold box idea might have to go raid my brothers kids stash. great idea again Erik.

I've played around with the sculpty stuff a bit to make hard forms but didn't really like it wierd shrinkage and non uniform hardening. but that could also be do to the toaster over I was using.

ErikRuud · « **Reply #32 on:** June 22, 2004, 01:18:56 pm »

Silicone rubber is available from Smooth-On, Alumilite, Eager Plastics, PolyTek, Micro-Mark and just about every other place that sells two part resins.

I am pretty sure that the stuff in your Alumilite kit is silicone and not latex. As far as I know, Alumilite does not sell latex.

darkcape · « **Reply #33 on:** June 22, 2004, 11:17:27 pm »

Yep you are right. Read the label "rtv mold making rubber base" main ingredients siloxane silica.from dow corning. but hey not for human injection dang now i need to make new plans for my weekend.

smooth-on looks less expensive. just need to shop around and find someone that carries it in the gallon size.


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