Small Batch Manufacturing Gets Serious with Rapid Injection Molding

Protomold shop floor

Protomold shop floor Image credit: Protomold

Though the New Industrial Revolution sometimes makes people think it's all about 3D printers or rapid prototypes, those technologies are only a part of it. They've been getting a lot of press for the past few years, but even now they're still slow and the end result can be a bit rough, not as strong as a more conventional part and expensive if you're talking about making more than a handful.

If you're really entertaining the thought of making something for sale in any quantity, you need high quality and reasonable cost. For plastic pieces, the standard method for the big guys is injection molding, but anyone familiar with the process knows tooling is expensive ($20K or $30K or more) and time consuming, possibly months, to make. Sure, once it's done you can churn out millions of parts, but what about this small batch manufacturing we're talking about? Say you want to make five hundred, what then? Well, how about rapid injection molding?

Larry Lukis was designing printer mechanisms as the founder of a printer company (eventually acquired by HP) and needed some plastic parts. When he looked into the injection molding process he was amazed that it took so long and cost so much and eventually came up with the process of rapid injection molding.

ProtoMold, a division of Proto Labs of Maple Plain, Minnesota, can take your 3D CAD file and, using high speed CNC machining, create tooling in aluminum alloys. If you're one of those big companies you can use the aluminum tooling to check the injection molded parts to make sure everything is right before scaling up to massive quantities with steel tooling, or to produce an initial run of parts while waiting for your final production tooling to arrive, making 100, 1000 or 10,000 parts right away. But if you're a small batch manufacturer and you'll never need more than 10,000 total, you're not waiting for anything, you're in production!

Think about that, you can now have real injection molded parts, in a wide range of resins, for whatever you're building and get them produced fast in the quantity you need at low cost. Pricing starts at $1495 to produce tooling for a simple part. If everything checks out, you tell them how many you need.

Some examples of companies using the rapid injection molding process are fascinating, the Parrot A.R. drone is one of the better known, but another made a plastic lid for Mason jars to turn them into travel mugs, one made a kite camera mount for kite surfers, another was a housing for a race management system which is the RF tag attached to a race car to transmit information during a race and many more.

ProtoMold has actually been around for a number of years and seems to be well known, especially among medical device manufacturers, but I had never heard of them until I saw an article the other day and it just struck me how far we've come in this new technology of manufacturing. It wasn't long ago, this would have been impossible, now, you come up with a design, send off the CAD files and get injection molded parts shipped to your door. For those of us who like to see manufacturing here in the US, did you catch the fact these guys are in Minnesota, too? We need more of this. I like it.

Link: ProtoMold via Wired


  1. B50 Jim says

    Back in the 1980s CAD/CAM was new technology, but as we started learning to really use computers, it became the vanguard of the New Industrial Revolution. Now we’re beginning to realize that industrial production no longer means expensive tooling and huge production runs to overcome the high initial cost. Remove the expense for tooling, and production can show a profit immediately while costs for the finished parts are low. I have a feeling we’re just beginning to understand the potential of rapid prototyping, rapid injection molding and computer-to-part manufacturing. Very soon the process will be adaptable to making parts from alloys. Then it will get very interesting.

  2. David says

    This is not really news. In the Investment Casting industry, we have been making molds from aluminum for years. (I personally have been doing it for almost 25) Wax, being much less abrasive than plastic doesn’t eat up tooling much at all.

    We still use 3D printing and stereolithography for prototyping complex parts.

    • Paul Crowe says

      It’s not so much the aluminum as the speed at which this is done, they can do a quote in 1 day based on the computer’s analysis of the design and first sample parts for a project delivered in 15 business days, or much faster (for a price) if necessary and then making it possible for someone to do this for short runs. They can supply injection molded parts as fast as some 3D print shops can turn your design around. Fast turnaround for small batches of injection molded parts is what makes this different. I’m not sure if I stressed the speed in the article as much as I should have.

  3. Paulinator says

    We’re working with an Asian supplier for some parts right now. Same technology, but other serious limitations. We have to deal with a 12 hour time diffrential, language and document processing barrriers, accountability deflections for failures (when translated, everything sound like “love you LONG time”), two-month lag if shipping is “on the water”…or heavy logistics costs if its “by air”, specified material sourcing and substitution issues and, oh ya, Chinese New Years.

    Re-shoring is becoming a practical alternative.

    • lostinoz says

      Not to mention the ethical issues of an underpaid and mistreated labor force, loss of jobs in the U.S., quality control issues resulting in a 30% loss of parts or more (by my customers admissions), problems with customs by air, possiblility of mold due to leaking containers by sea, triple if not quadruple transportation costs for final products and the increase in greenhouse gasses… yeah re-shoring DOES look better.
      Chinese new year is the only time my business slows down enough to actually “take a break” and enjoy 10 hr days rather than 14 hr days however.

  4. todd says

    They’ve also been able to take their considerable machining resources and turn that into a nice rapid prototyping service as well. If you don’t want to commit to the soft tooling and you just need some prototype verification they offer “Firstcut” for one-day or more turn around. The really strange part is getting a phone call from them even though their quote process is so automated. You just assume this is a web site and a bunch of robots but then a real person is talking to you about your parts. They can’t do every feature on your parts sometimes but they’ve been adding capabilities as requests come in. They’re (Protomold+Firstcut=Proto Labs) a great bunch of people and do excellent work. Highly recommended.

    My favorite source however is John McKeown at Z-tech in Carson City. Same results as Firstcut but less expensive.


    • todd says

      in case that wasn’t clear, Firstcut is the same company as ProtoMold but offers “rapid” machining services for 1+ quantities with the same automated quoting process.


  5. jar says

    Have used Protomold on more than one occasion, they can definitely be an advantage to getting to short run parts. Would (will) use them again, and would recommend them as well to anyone looking to do this type of work.

    I will say, that the way the article was written, only two dollar amounts were described $20k-$30k and then $1495. While, with regard to the $1495 figure, the article does indicate “starts at…to produce tooling for a simple part”, I think there is an implied connection between the two prices….where in truth there is none. Meaning at part costing $20k-$30k to tool in a production sense, is not likely to be remotely close to $1500 to tool at Protomold, in aluminum. For comparison purposes, it would likely to be better to speak in terms of percentages…, a $20k-$30k production tool would likely cost 35% of that number to execute at Protomold.

    To be clear, I do not believe the author or Protomold was seeking with any degree of dubious intention to imply that the cost to prototype tool a part was 5-7% the cost of a production tool for the same part.

    Rather I was attempting to bring a little bit of real world expectation to those who may not be as familiar with the process. I think it quite likely that one could expect a prototype tool to be in the neighborhood of 25%-35% the cost of a production tool….obviously, dependent upon where your production tool may have been quoted