Injection Molding

[ReWind]

Does anyone here have direct experience doing their own injection molding? Not outsourcing, but either benchtop or commercial machine work in-house or through a pro facility where you have employee/alumni access, etc. and did the molding yourself?

How about die making? I'm interested in hearing about experiences with EDM rams, especially.

Any Solidworks users here?

[ReWind]

I was going to just quietly bump this, as in know things turn slowly but steadily in this forum, but 90 views in a day, huh? That says something.

Well, if none of you have direct experience, what would you like to see being done? Has anyone else at least done some solid reaearch on in-house molding or die making? ...or if someone is hesitent to discuss this, in relation to pickups, openly on the public web, I'd love to chat on the phone about it. My phone number is on my web site and I'm available most all day anyday. Email is good too. This is something
I'm immediately serious about. I've done my homework, just have mimimal personal experience.

[David King]

What's an EDM machine going to cost you in capital, in consumables, in maintenance and in electricity? How many molds are you going to make? Clearly EMG decided it was worthwhile but when you can have a custom mold and a 1000 bobbins cast in China for under $1000 it's going to be a tough call for most of us.

[Jazz P Bass]

Pattern & Diemaking used to be a lucrative craft.
Used to.

[ReWind]

What's an EDM machine going to cost you in capital, in consumables, in maintenance and in electricity? How many molds are you going to make? Clearly EMG decided it was worthwhile but when you can have a custom mold and a 1000 bobbins cast in China for under $1000 it's going to be a tough call for most of us.

Cost me? Nothing. The conversation is free, right?

I've been studying various machinist techniques and tools, lately. Ya, I know I can apply some of what I'm learning about to what I do, absolutely, but you may be assuming I'm WAY further into some mental commitment to a system than I am. There's lots I want to learn. Doesn't mean I'm looking at pumping $20k into a tool and accessories like that without doing the math and having a reasonable likelihood of coming out on top. I've no intention of outsourcing any of my work to China, however.

I would like to better learn Solidworks and some other aspects of CAD/CAM and then have some tools to actually apply my ideas with.

One thing that I'm finding is that with these sorts of machines, there's isn't much middle ground. You have the hobbiest low power/low volume/low longevity stuff, then there are the original big commercial versions. For instance, I'm not seeing much in the way of CNC mills that could work on hardened tool steel for years to come. There's a 3,000lb Southbend J-Head not far from me, actually. $2k. Helluva deal. …of course it's not CNC so using a CAD or G-code file null. Doing elaborate one-offs of big parts isn't something I have much use for.

[Joe Gwinn]

For instance, I'm not seeing much in the way of CNC mills that could work on hardened tool steel for years to come.

True enough, but not required for moldmaking.

A standard approach is to machine A2 steel before hardening. A2 is air hardening, to reduce warpage. Then one grinds and polishes the hardened steel to finish. This step was done manually for many decades, and still is.

https://en.wikipedia.org/wiki/Tool_steel

[Joe Gwinn]

For instance, I'm not seeing much in the way of CNC mills that could work on hardened tool steel for years to come.

True enough, but not required for moldmaking.

A standard approach is to machine A2 steel before hardening. A2 is air hardening, to reduce warpage. Then one grinds and polishes the hardened steel to finish. This step was done manually for many decades, and still is.

https://en.wikipedia.org/wiki/Tool_steel

[Jazz P Bass]

So what are you going to mold?
Injection molding is typically used for plastic. (though not exclusively)
If you are talking metal, the lost wax method may be better suited.

[David King]

As a kid I had a friend who had a little "toy" injection molder that you could make plastic army soldiers with. I'd love to have that thing now. It had a big lever that pumped the molten plastic into the molds. The thing worked really well but it was very easy to burn the crap out of your fingers. No kid would ever get to see such a thing in this age of lawsuits and idiots.

You can make just about anything you want with any size machine tool. The bigger tools will just do it faster and a bit more accurately. The longevity has a more to do with maintenance schedules than with the tool's quality. You are much more likely to take care of a $22000 Bridgeport Mill than you are of a Birmingham knockoff that only costs $2500.

[StarryNight]

Seeing as your in the thought experiment stage with no money invested yet can I ask what potentially you would produce better than what is currently available on the market, and would it be competitively priced?

I've worked front line in polyurethane for a couple of years in my youth. I've worked with two types of injection machines, one low flow and one high pressure. I'm more than willing to share what little I know from two years of pumping parts. It was a pretty competitive business from what I remember. Huge upfront investment. To be seriously competitive you're probably looking at a lot more than $20k for a startup.

[David Schwab]

As a kid I had a friend who had a little "toy" injection molder that you could make plastic army soldiers with. I'd love to have that thing now. It had a big lever that pumped the molten plastic into the molds. The thing worked really well but it was very easy to burn the crap out of your fingers. No kid would ever get to see such a thing in this age of lawsuits and idiots.

You can make just about anything you want with any size machine tool. The bigger tools will just do it faster and a bit more accurately. The longevity has a more to do with maintenance schedules than with the tool's quality. You are much more likely to take care of a $22000 Bridgeport Mill than you are of a Birmingham knockoff that only costs $2500.

I had a toy that let you mold rubber bugs and such. Same kind of deal, except the mold was flat and you poured the compound in it and let it cook. Once again you could burn the crap out of your hand, but who did? I never did.

I remember that injection molder toy.

[David King]

Apparently there's a Gingery book on making your own injection molding rig that attaches to your drill press.
Plastic Injection Molding Attachment for Drill Press Gingery Book 1878087312 | eBay

I watched a fun video of the molding of a fishing lure using cut up 2 Ltr soda bottles. https://www.youtube.com/watch?v=hvJil9lilE0 (kill the sound.)

[Hugh Evans]

Sure, I worked with injection molding in engineering school. The Mechanical Engineering lab had everything we needed, although the shift towards rapid prototyping was going into high gear around the same time. The department was actually making decent money adding material to existing molds because they had one of the first direct metal deposition machines ever (as in prototypes that hadn't accounted for metals being reflective to the 10kW CO2 laser and that oversight leading to a wall clock being cut in half.)

Aside from building a CNC router last year, I've been planning to use the same gantry as part of a ram EDM machine.

As for CAD, I use SolidWorks 2010. It's overkill for just about everything I do, but I never feel limited by it. Plus it's great to verify entire guitar assemblies during the design process before making a single cut with the CNC router.

I take it you're being vague because you have a project in mind? Feel free to send me a PM. I have plenty of experience with a wide variety of processes and have consulted for many large multinational manufacturers in my professional life. So it's easy enough for me to tell you what you're going to be dealing with, and can tell you if there's a better way to reach the same objective... Unless you want to become an injection molder and fabricate dies in house. If you're handy at tinkering, small ram EDM machines can be built for a few grand. The cheapest way to get into injection molding requires purchasing equipment from an industrial surplus warehouse.

[ReWind]

Apparently there's a Gingery book on making your own injection molding rig…

Ya, I've seen the Gingery one, but I don't think it has the capacity to do anything needing real pressure or precise timing. I really only glazed over it though, to be honest. I've read much of his material. I always knew him as the "magneto guy" but he's got a nice selection of guides out there. Check out his "backyard furnace" material.

[ReWind]

Sure, I worked with injection molding in engineering school..…

Yes, I'm definitely interested in die making. I don't know if it's something I'm going to decide to actually pursue doing myself yet or not, but I'm certainly looking into it. I have a number of uses for a mill here already, for making steel tools, parts, dies, and jigs, etc. If I'm already getting a mill that comfortably machines tool steel though - and I also use plastic parts in my pickups ….well, that's sort of how I got to posting this thread.

I really like the concept of taking things from the raw material state to a finished product all the way through, too. I think the ability of SolidWorks is just awesome. The cost of having, I dunno… 10 or 30 dies made at a conservative count, for a variety of small parts over a lifetime, seems to add up to more than the cost of machinery, upkeep, and the learning curve. I've been getting quotes around $4k - 6k for dies of small parts like bobbins and little plastic assemblies. Simple stuff. I see used mills and lathes of far more than sufficient capacity going for less than many guitars and amps cost. Not CNC though, and that would be critical to me if I were to attempt milling molds. I realize that some extremely skilled machinists did the molds without CNC for many many years, but I'm not an extremely skilled machinist.

I hadn't thought about a DIY sinker. I was just turned on to the fact that rams even exist! …then found out they can go for less than the mills. I have lots to look into still. Can you take a block of steel to a mold with just a ram though? I've been getting the impression that rams are more often used for the final details, after the bulk of the material has been hogged out. Like I said though, I'm at the early stages of looking into this. I may well be very wrong.