Injection Molding

[ReWind]

I don't speak Turkish, but this looks like a bass pickup cover in SolidWorks, to me.

[kayakerca]

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.

Even a little $1,500 (pre DRO & Power Feed) import from China can be pretty useful for certain types of work.

[David King]

Nice little mill Jim. I'm not sure I could a stand a gear head's noise or lack of speed but I would have loved the square column over the round column R-30 I had for 15 years. My 49 year old bridgeport is holding up nicely despite many decades of abuse by others. I couldn't live without it. I have 3 DROs but haven't had time to install any of them yet. I seem to get by just fine on the dials and a calculator. I paid just over $2K for the BP and have sunk at least that much into tooling. I probably spend 3-4 hours a day on it.

ReWind, Very few injection molding shops will make their molds in-house these days. You can get a mold made in China for under $1000 so that's where all the business has moved to. Shops might not tell you where the mold is going to come from even if that are charging you 2-3 times more for it. If you aren't fussy about surface finish you can save a lot of time but if you do care then that's where the hours pile up.

[kayakerca]

Nice little mill Jim. I'm not sure I could a stand a gear head's noise or lack of speed but I would have loved the square column over the round column R-30 I had for 15 years. My 49 year old bridgeport is holding up nicely despite many decades of abuse by others. I couldn't live without it. I have 3 DROs but haven't had time to install any of them yet. I seem to get by just fine on the dials and a calculator. I paid just over $2K for the BP and have sunk at least that much into tooling. I probably spend 3-4 hours a day on it.

It's surprisingly quiet David, but your are right on about the speed. Tops out at ~ 1,750 rpm and you certainly wouldn't want to be hogging off material in any serious way. But, for a consumer grade product it does quite nicely for a non-machinist guy in "learner" mode. Definitely no BP though. The 3-axis DRO took close to a week to mount but for me as a beginner, I found it like night and day. Everything became a ton easier. Things like bolt hoe circle function for making bobbin mounting plates that mount to winder shaft mounting plates, centre finding on X and Y axis, and circles and accuracy to 2/10,000 of an inch. Flipping between metric and Imperial. Makes a beginners life much easier. I definitely could not have build all the hardware for my new CNC winder without this little mill. Like you were saying, I also quickly found out quickly that tooling costs more than the mill itself!

[Hugh Evans]

I have nothing against learning about technologies and seeing if you can make use of them... But I would feel guilty if I did not caution you about how much you are biting off. Even if you become a skilled machinist (typical learning curve of many years) and can design and fabricate your own molds, it would need to be for your own satisfaction. You will absolutely spend piles of money, not just to buy or lease an injection molding machine, but also in raw materials and cost of operation. Can it be done, sure. Considering you're talking about simple plastic parts, some of which might already be available to purchase, I would only recommend pursuing this idea if you are okay with having a very expensive hobby that will not make money... Unless you are planning to sell tens to hundreds of thousands of parts. My advice is to explore some other options. Since it sounds like you are interested in plastic, perhaps vacuum and/or pressure molding might be of interest to you.

Ram EDM can do many things. I've seen a quarter used to create it's negative in a block of steel. More importantly, it can create sharp inside corners in parts that would otherwise be difficult or impossible using other processes.

I'm not surprised that you've received quotes for $4k to $6k. I'm also practically certain that less expensive methods can be devised aside from injection molding. If you aren't sure what process to use for a specific part, I'm probably not the only person around here who can give you some ideas about how to make them.

[David King]

Injection molding is the bottom rung of mass manufacturing methods. It's there to make something affordable to everyone. More and more I find we are dealing with ever fewer but wealthier customers who want something that's exclusive, distinctive and "artisanal". The mass market has long since decided that cheapest is best. They would much rather have 6 cheap import guitars than one nice one. You could invest in a nice little CNC router and mill out dozens of very nice plastic or wood covers an hour for a tiny fraction of the cost of you are likely to incur going with injection molded plastic and have something that's unique and much more agile.

On the other hand you could probably have picked up all the tooling and equipment you would need for injection molding and mold making 5 years ago had you know what you were looking for. Ebay has since dried up and prices have come way up since the industrial crash but there are probably still deals out there if you know the market and can take your time.

[Hugh Evans]

Building my CNC router last year has proven to be one of best tool investments I have ever made. I can make any of the guitar parts I could ever need with it. Once a proper spindle replaces the router, it will be fully capable of machining any metal (it can currently machine aluminum and other "soft" metals.) That's why I encouraged looking into other machining and molding techniques.

[David King]

Hugh, do you happen to have a build blog for your CNC? I'd like to get started on one for myself and have no clue where to start. I think I'd have figured it out but there is actually too much info and no way to filter. Cost up front is the main factor followed by loss of accuracy. I see lots of great looking used parts on ebay but no clue which would be adequate.
Maybe we should start a new thread too...

[Hugh Evans]

Unfortunately, very little of the process was recorded. It was based on plans from fine line automation before the site went commercial, but I had the foresight to download all of the CAD assemblies while they were available. This is a rendering from their site of a design that is very similar, but scaled down compared to, the router in my shop:



My machine has a 2' x 4' cutting bed and 6" of Z-axis travel. The router is a Porter Cable 75182 (a special part number for the spindle without base,) which provides 3.25 HP, variable speed, and thanks to some upgraded collets from precisebits.com total indicated runout of 0.0002". The end result has proven itself to have repeatable precision of better than 0.001", and has consistently produced parts that are within ±0.0005". My business partner and I cut, drilled, tapped, and assembled the main gantry in a day from 80/20 t-slot aluminum extrusions.

If you have a chop saw, drill press, tap and die set, and some patience you can absolutely have a similar machine up and running for less than $2,000. A big part of the trick is ordering parts from the right suppliers. For example: automation4less.com sells the aluminum extrusions for less than buying them directly from 80/20. Many of the fasteners are easily acquired from McMaster Carr. The best price on the router spindle was from amazon. If you like what you see, I can provide you with details. It might be a good test run to see if providing kits and construction support is something I want to start doing. It's a very nice little machine, easy to scale up or even upgrade in the future.

I can definitely say that this design is better than just about anything else at the entry level you will find. A complete machine could easily retail for $7,500 to $10,000. The other machines I've seen for the same price range are made from MDF or some other non-metallic material, and I personally don't like tolerances that drift depending on relative humidity in the shop. If you want to go for it, let me know and I can compile some information you will need as well as answer any questions you might have.

There is too much information out there, it's poorly organized, and most of it pertains to poor build quality. A CNC router should not brag about having a resolution of 1/32" because that is nothing short of awful.

Are you comfortable using at least one CAD environment? If not, you should definitely take that on first.

[David King]

Hugh, Thanks, I'll start a new thread where we can get down to brass tacks and rubber cement.