Plastic molding?

[JimRayden]

Not nevessarily stompbox related, but aswell might be. I'm looking into DIY plastic molding.

More particular, I'd like to know about the materials used. Is the stuff poured into the molds anyhow different than the hardened stuff? To rephrase, can a random plastic object be simply melt and reshaped? I'm assuming the process isn't that simple but it's a nice way to make my point.

I'm talking about knobs, pickup rings, truss rod covers and other stuff for my guitar (and perhaps stompboxes).

If it turns out to be too much of a hassle, I can always go with wood though.

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Jimbo

[JimRayden]

Furthermore, I've read that epoxy is a nice thing to mold stuff out of. True?

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Jimbo

[markm]

I think most plastics are molded using a process that they term Injection Molding where the molten plastic is literally injected into
the mold via some type of pressure system.

[John Lyons]

I'm sure it's way beyond doing it in my basement but I really like the feel/color
and texture of a polished ABS plastic box.

These are made from 4" ABS pipe caps. Lotsa work but they are fun.
It would be really cool to make square and or Wedge shapped ones!!!!!!!

It would be great if we could come up with a mold process. More so the components of the material of the plastic.
Think about it. different colors and swirled colors, two tone, multiple color in layers etc etc etc!!

[R.G.]

There are two kinds of plastics, thermoplastics and thermoset plastics.

Thermoplastics like PVC melt to liquid with heat, then re-harden like wax. If the heat is not so high as to be chemically destructive, this can be done repeatedly, and is the foundation of the recycled plastics industry. Thermoplastic injection molding typically involves a one- to many-ton machine which keeps several liters of plastic molten and then forces it into the mold at pressures measured in the units to hundreds of tons.

Thermoset plastics are liquids that are mixed together and either heated in an oven or self-heat and cure into the final form. Heating these plastics may soften them but it also damages them in the process so they do not re-set with their former properties. Some thermosets never melt, they simply burn. Examples are phenolic resins, catalyzed urethanes, and polyesters and epoxies.

Thermosets are easier to deal with as an amateur plastics hacker, because you don't have to heat them to a very viscous liquid and then force them into molds while they're still hot. With thermosets, you mix up the chemicals, pour the liquid into the mold at room temperature, and then either leave them alone for a while or put them into an oven and bake them.

Thermosets are more expensive, but much cheaper to work with. Thermoplastics are cheaper materials, but have very expensive tooling required.

I highly recommend you go to an arts and crafts store and buy a few blocks of "Fima" or "Sculpy" polymer clay. These are colored "clays" that are actually uncured thermoset plastics mixed with filler particles and color. You mold them to the shape you like, then bake them to hard plastic in a 270F oven. Polymer clay "jewelry" is a big craftsy deal. Do the google.

If you want to make many of whatever, get yourself some rubber molding compound, some sculpting wax, and some epoxy, urethane, or polyester casting resins. Sculpt what you want out of the wax. Brush/dip/etc. the rubber molding compound over it and let the rubber cure. Remove the wax. Pour catalyzed stuff into the rubber mold. Remove that one. Pour it full again.

There are epoxy clays, filled two part epoxys, that set up super hard. Some are insulators, some are conductors depending on the filling. Plumbing places have this stuff for fixing plumbing leaks and car parts store have it as "JB Weld" or similar.

There is an almost infinite amount of preexisting information on how to do stuff like this. I can point you if I know more of what you want to do.

[JimRayden]

My initial though was to see if I can mold a pickup ring for my Marilyn (yes, you read right, she's got a name ). Then playing with that though, I realised I could make use of many other plastic dinghies also. What about a self-molded pick holder? Or even a beercan holder.


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Jimbo

[ISC]

Not exactly plastic,  this was discussed at 18Watt.com and maybe of interest to you 

http://www.alumilite.com/

Trevor

[John Lyons]

Thanks for that Alumilite link. Pretty cool stuff.

[MetalGod]

I'm sure it's way beyond doing it in my basement but I really like the feel/color
and texture of a polished ABS plastic box.

These are made from 4" ABS pipe caps. Lotsa work but they are fun.
It would be really cool to make square and or Wedge shapped ones!!!!!!!

It would be great if we could come up with a mold process. More so the components of the material of the plastic.
Think about it. different colors and swirled colors, two tone, multiple color in layers etc etc etc!!

where did you get the knobs for the pedal on the right - they look really cool and I want some 

[billings]

http://www.smallbearelec.com/Detail.bok?no=472

[BlueToad]

Here's one option:
http://lindsaybks.com/dgjp/djgbk/inject/index.html
But knobs are about the limit of what you can make with it; You could of course scale it up, but then you might need more than a lever to get the plastic into the mold.

[sfr]

I have fixed gaps in plastic (binding on guitars that I've built) using pieces of the plastic melted down in an appropriate solvent (Acetone or MEK in my case) The solvent melts the plastic to a liquid or "goopy" state depending on the mix ratio, and eventually evaporates away leaving the plastic behind. The evaporation takes a while to complete (at least, if you want to work the finished product at all) and completly disolving the plastic in the solvent can also take a while, depending on how small you cut up the plastic.   

I doubted the possibility for making an actual shape with this method, but recently I've run across some car modder's groups online, where they hack MP3 players and computers and stuff into their autos, and apparently many of them use a similar method to reconstruct their hacked-apart center consoles around the newly installed units. 

I'm unsure how far this approach could be taken, but it's interesting to experiment with.  I actually "painted" some scuffed-up-aluminum with leftover goop when I was fixing the gaps in that binding; it adhered rather well in a fairly thick coat, that so far seems to be fairly resistant to wear, and I've been meaning to experiment with using it as a more durable coating over a stompbox.  While I think the other methods mentioned here are more feasible, this is just another interesting thing to experiment with. 

[rfoust]

If you check out the Musical Intrument Makers Forum (www.mimf.com) you can find a tutorial on casting plastic. I don't remember who posted it, but it was recently placed into the archives and demonstrates how to cast pickup covers and knobs.

Note -- you'll have to register to view the tutorial. Once registered, click on the library link and go to the bottom to where the recently added discussions are.

[gez]

Furthermore, I've read that epoxy is a nice thing to mold stuff out of. True?

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Jimbo

As has been mentioned, you can buy epoxy putty, though it's expensive and I have no idea how easy it is to use.  As for Epoxy resin, it's usually used in conjunction with carbon fibre.  Not something for the amateur.  I've had some experience of working with glass fibre; if you ever go down that route you need to do some reading (procedure, safety etc).  Not easy to work with, even when 'green' (still curing).  Not something I'd use for small things either.

[R.G.]

It is very hard to beat the simplicity of polymer clay. You can make rubber molds and press the stuff into it for replication (they sell molds for doll's faces in the A&C stores). You can roll it out into a thin sheet, then form the sheet. You can cookie-cutter holes in the sheet, then form. You can roll or extrude "noodles" of the stuff for bosses, ledges, decoration, etc. Anything you can do with simple modelling clay can be done - and then it bakes to a solid filled plastic, which can be cut, sawed, drilled, and threaded. There is no chemical mixing to do, it's non-toxic, and has a long shelf life.

By the way, if you are going to do any dinking with any chemicals, go to someplace that sells vinyl, latex, or nitrile gloves. I buy them at our local Harbor Freight in boxes of 100 when they are on sale. A box of 100 latex goes for about $4 and a box of 100 nitrile goes for about $6. I use the nitriles as a better "barrier cream" for working on the cars, tractor and Bobcat. It keeps the oil and grease out of the crevices in my hands and nails and makes cleanup a breeze. If you're going to be mixing things like urethane, epoxy, or polyester, get a pair of safety glasses. One drop of methyl ethyl ketone hardener in  your eye will cause you to reflect on your childlike naivete for a long time.

[Plectrum]

Some thermosets never melt, they simply burn. Examples are phenolic resins, catalyzed urethanes, and polyesters and epoxies.

That's interesting...
I went to a plastics shop and enquired about the possibilty of making my own picks (amongst other things, and of course - I like a non-standard pick shape ), and the guy just said "na mate - resin's too brittle and weak, forget it".
He didn't mention other resins. Which type do you think would be best for thin-ish (.60mm) picks? they would heve to be slightly flexible and durable.
...I'm aware that there still may be no real solution to this using the thermosets and the molding itself would have to be very well implemented.
Grant

[John Lyons]

For Picks you should look for the correct thickness of Nylon. I bet you can get it at Mcmaster Carr  (spelling?) they have flat, square, tubular,  shaped everything pretty much. Give it a shot.

The knobs on my Black ABS boxes are Dakaware knobs, NOS and found here and there. I'm not sure of any current makers of this style unfortunatley. And the smallbear link above are not even close to that shape and size. These are about 1.25 inches across.

John

[JimRayden]

It is very hard to beat the simplicity of polymer clay. You can make rubber molds and press the stuff into it for replication (they sell molds for doll's faces in the A&C stores). You can roll it out into a thin sheet, then form the sheet. You can cookie-cutter holes in the sheet, then form. You can roll or extrude "noodles" of the stuff for bosses, ledges, decoration, etc. Anything you can do with simple modelling clay can be done - and then it bakes to a solid filled plastic, which can be cut, sawed, drilled, and threaded. There is no chemical mixing to do, it's non-toxic, and has a long shelf life.

I did a little research and it looks like the thing I'm looking for.

Hmm, everyone seem to be making figures and jewelry out of it, I can't seem to find anything practical made out of it. What kind of plastic does it exactly set into? Close to the stuff used for pickguards, pickup rings and similiar?

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Jimbo

[Mark Hammer]

From what I've seen in stores, it cures/dries fairly firm, rather than soft or floppy.  Whether it has the structural rigidity of pickguard material is another thing.  In its favour, though, you can often get preformed sheets with interesting patterns (remember, this IS sold primarily to people who want to make jewellery), including tortoise-shell, and pearloid patterns.  How well these patterns hold up after exposure to heat for melting/shaping purposes I could not say.

[Frodoro]

I think most plastics are molded using a process that they term Injection Molding where the molten plastic is literally injected into
the mold via some type of pressure system.

Exactly markm, the process is definitely called plastic injection molding. I think it is better if you used plastic instead of wood. You can easily make a form of shape through plastic rather than wood.