/diy/ - Do It Yourself

What do you want to make, what plastic do you want to use ?

injection molding is usually for hollow items. the reason injection is needed is so that you can quickly make a light product. if you're doing small runs of items, make your prototype. cast the mold then fill the mold so that you have a solid object. you could use a cheap thermoplastic like nylon beads and just pack them in there and use a hot air gun to melt them. or pour two part epoxy.

voids arn't necessary for small runs so you dont need injection molding. screw holes or whatever can just be machined with a drill.

>>609263
A plastic model kit.
>>609264
Thank you for the info.
So I should just:
1. Make mold. Probably not a silicone, right? Aluminum for start will be good? But how to make metal mold? By using CNC machines?
2. Get some cheap "plastic"
3. Melt it
4. Sandwich plastic between those 2 metal mold parts
5. ????
6. Profit!!!!

>>609282
>A plastic model kit.
Of what ?
>By using CNC machines?
That's the only way it's done normally.
>Get some cheap "plastic"
The point of metal mold injection molding is making a product with high precision and for big production. If you are going for a low run (how much is it?) then you can as well use silicone molds (or any cheap molds). For a model kit you don't need a high precision in micrometers.

>>609298
1.Plastic model kit like those 80's Bandai Gunpla kits.
2. Ok
3. For first run around 20 sets, then if I would get possitive feedback then probably 20 sets each week. Depending of how I organize all the parts in sprue then it could be up to 3 sprues per set. But using Silicone molds will left a lot of excess "flash", maybe not a problem right now.

But is there a way to just pour a liquid plastic into the mold?

And:
- Booklet with instructions
- Box for sprues
What type of company can make them. Something with Paper/Carboard?

>>609307
>But is there a way to just pour a liquid plastic into the mold?
yes
>But using Silicone molds will left a lot of excess "flash", maybe not a problem right now.
depending how you'll sell it, if you sell it to people who know you are doing it by yourself then they can just remove the excess without complains
>Plastic model kit like those 80's Bandai Gunpla kits.
any pictures ?
>- Booklet with instructions
printing/advertising company (that prints flyers, newspapers), you can probably find one online like Artcows
>- Box for sprues
companies that make cardboard boxes, some printing companies can make it too
Just google about stuff in you local area or online companies.

>>609308
Picture of kit from MSV line (early 80's).

>>609312
Will you just copy the old kits or make your own ?

>>609316
I will make new design, not a copy/bootleg.

>>609260
>Is there any possible way to cheap injection molding?

Yes. Gingery has a book on this. You can make manual lever operated desktop injection moulding machines cheaply.

My moulder uses two cartridge heaters and a 1000 watt dimmer switch to control temperature.

>Any way to reduce cost of metal mold?

You can use Aluminium Epoxy to make moulds.

http://www.injectionmolder.net/epoxy%20molds-step_%20by_%20step.htm

Or use any High Temperature Epoxy. Lots of different Resins work fine, as long as they are rated at 180°C they'll do HDPE, LDPE, Polypropylene. A lot of Car body fillers work fine, and some people have made moulds from Bondo.Plastic Padding Chemical Metal works fine in the UK.

Moulds made from seasoned concrete sealed with paving seal also work for things without small details. And Plasters work fine for one shot moulds.

You can also look into Resin casting using Silicone moulds. It's much more forgiving than Injection moulding because Resin is low viscosity and the moulds are flexible.

>>609312
You won't be able to make sprues this large using a machine like this>>609260.
The shot size is just way too small. Doing all those components would require lots of moulds and take a while.

>>609364

Thank you Sir, thank you. ;___;

>>609260

>>610973

>>610974

does DIY let you post PDFs?

I've got one relevant to this thread and I'm having trouble uploading it for some reason.

>>611357
Below a certain size it does. Can you upload it to scribd and link it here?

Here is a link to a PDF about making plastic injection molds out of concrete.


>>611367

thank you.

>>609260
Here is a link to a PDF about making plastic injection molds out of concrete.

http://e-ntrasites.univpm.it/Ingegneria/Engine/RAServeFile.php/f/Giuseppe_Di_Giovine.pdf

>>611367

thank you.

>>609264
No, that's "blow molding". Injection molding is usually for solid items, because it's damn difficult to get a hollow space inside a mold when plastic is being forced into it at several hundred pounds of pressure. . . .

>>611434

how does blow molding work?

I'm guessing its a lot harder to set up a DIY rig for it.

>>609260
why not 3dprint?

>>611558
Not OP but 3d print are expensive and "cheap" 3d print quality are worse than any kid toys you get for free.

>>611449
Blow moulding is the process of creating hollow plastic castings, sort of like rotational moulding - but based on traditional glass blowing methods.

Basically a small blob of Plastic is melted then air is blown through it (like a balloon) inflating it until it sticks to the inside of the mould. It's then demoulded to reveal a hollow casting.

http://www.core77.com/blog/object_culture/george_feredays_personal_blow_molding_gun__16846.asp

This sort of shows the process. But he uses Polymorph that he heats prior to blow moulding - which you couldn't do with standard Thermoplastics.

If you want hollow plastic stuff it's probably easier to rotational mould Resin. Gotta love Silicone moulds.

http://www.instructables.com/id/Make-A-Rotational-Casting-Machine--For-Under-150/

This is what I'm going to do. To make large stuff. Except I'm going to add a motor - so I don't have to sit there turning the handle for hours like a pleb.

I might have a go at Ghetto blow moulding though - should be straight forward. Same sort of gun but with heating elements and temperature control, maybe have a male threaded extruder - cast the corresponding female nut into moulds, so you can screw the gun to your mould. Connect gun to air compressor (read fridge compressor) with tank.

>Screw gun to mould
>heat plastic to melting point
>turn on compressor - to fill tank
>open valve on tank to blow air through gun
>???????????????
>Profit???????????

>>611367
No it doesn't.

>>611667
>>611558
For small production runs 3d printing is the way to go. It's a lot cheaper than making molds.

You can make an injection mold system for REALLY SMALL parts, but not stuff much bigger.

Now if you don't like the cost of 3d printing, or want to do a large production run, you can print a positive of what you want to make and do urethane casting.

>>612081
> print a positive of what you want to make and do urethane casting

I think this is a good use of 3d printing technology - basically just using it to create masters for other moulding processes.

>>609260
Pressure casting is the easiest way to produce plastic parts. You can even diy it on the cheap. All talk about it being expensive is firepower of the highest fagnitude. You only need

>a fridge compressor - for pressure and a vacuum
>a paint pressure pot. Or a pressure cooker - if you're desperate, or willing to fuck around a lot.
> a PSI gauge
> either a large mason jar or a length of pvc pipe and two Polycarbonate ends - for the vacuum chamber
> two valves, one for the pressure pot, one for the vacuum chamber - to release/equalize pressure after you're done.

Casting resin can be as cheap as you want. You can even make cheap moulds out of Silicone sealant (with a few additives).

>>612129
>Casting resin can be as cheap as you want. You can even make cheap moulds out of Silicone sealant (with a few additives).

tell us more.


>>612129
>Pressure casting is the easiest way to produce plastic parts. You can even diy it on the cheap. All talk about it being expensive is firepower of the highest fagnitude. You only need

>list o' stuff


can you show us how to combine all that stuff together.

>>611793

I got one of these.

will it do the job?

Why not resin kits? They are quite easy to be made and as long as you don't fuck up the thickness of the parts or have any bubbles modelers won't be disappointed for a low volume production.

dakkadakka.com wiki/en/Simple_Two-Piece_Mold_for_Casting_with_Resin
smooth-on com Model-Making/c1290/index html
cast-a-walker blogspot it/

Not the previous poster but with sealant the main difference is in the waiting time for the silicone to dry, number of pulls from a single mold and detail, there are many guides around the net with additives to add to achieve faster drying times or higher number of details but the hobby stuff to make molds is not that expensive. I use a rubber 2k pink something that goes for 90€ for an 25 liter can, only problem with large quantities of the stuff is that it expires after a couple of months and you have to keep it in the dark at a 20 or something degrees

>>612764
>Silicone sealant (with a few additives).

I wrote about this before. Its in the guide, which is in this link:

https://archive.foolz.us/diy/thread/573327/#q573875

>Casting resin can be as cheap as you want

Yes you have to pay for Resin whereas you don't have to pay for waste Plastic. But the cost of mould making materials for Injection Moulds is still comparable to the combined cost of cheap Resin and Silicone.

Silicone moulds are also very easy on undercuts, so they're much more forgiving to make - as you can always flex or stretch them to release the casting.

>combine all that stuff together

Its pretty straight forward really. The compressor connects to the pressure pot via a hose. The Pressure pot needs a PSI gauge connected to it (so you can measure the pressure). It also needs a Valve stuck on top of it (just any simple ball valve), so you have a means of releasing pressure. Its just a tank with a means of receiving air, a means of measuring it, and a means of releasing it - it needs nothing else.

The Vacuum chamber is even simpler. Its either a large mason jar with a valve attached to its lid, connected to your vacuum pump via a hose. Or a length of PVC pipe with silicone sealant around the top and bottom with two Polycarbonate sheets forming the ends, with a valve attached to the top sheet.

Vacuum chambers are significantly less complex because as the air is sucked out the lid is pulled tight forming a seal. So it needs to be a sturdy cylinder with a flexible rubber seal. Other than that it should be transparent - so you can view the degassing process.

>>612767
I should imagine that would be fine - I was just thinking aloud in that post - I'm not keen to enter into the Blow Moulded Flamingo production race just yet.

>>609364
I built the Gingery injection molder maybe 12 years ago. The linkage binds up so look at redesigning that. The shot size is poor, not what you are after. Think a knob on you car radio, about that big tops.

There are cheap injection molders that attach to a drill press for the same injection style for a few hundred bucks. Time is money and all that.

I would like to get a surplus injection molder of industrial size someday but I think until we strike it rich it is probably more economical to find somebody with a high production machine and pay for a production run. Until you get there you can do the small shots using the verticle press style machines

>>609264

>injection molding is usually for hollow items

Stopped reading right there.

>>612816
>>Silicone sealant (with a few additives).
>I wrote about this before. Its in the guide, which is in this link:
>https://archive.foolz.us/diy/thread/573327/#q573875


Kickass. Thanks anon. :)

>>612948
I like the design in >>609260 better. You could lost foam cast most of those bits out of strong Aluminium.

Even the heating block could be cast out of one block of foam - couldn't you just heat a steel bar with a blowtorch - then use it to burn out the cavity. Then use the same bar for the plunger. Burn out two more holes for the heating elements. Cast it - tap a hole in the bottom, screw on brass extruder.

I'd move the clamp to the bottom, so you're clamping moulds vertically to the Injector. You don't need to horizontally clamp mould halves together - you can drill holes in the moulds for bolts. It's more important that the mould is clamped tight to the machine to stop plastic pissing out the top when it should be forced into the mould cavity. A vertical clamp will still exert enough force to close the moulds whilst at the same time securing the mould to the injector.