3D Print Your Own Injection Molds, Ejector Pins And All

May 5, 2025 by 20 Comments

3D printing is all well and good for prototyping, and it can even produce useful parts. If you want real strenght in plastics, though, or to produce a LOT of parts, you probably want to step up to injection molding. As it turns out, 3D printing can help in that regard, with injection molding company [APSX] has given us a look at how it printed injection molds for its APSX-PIM machine.

The concept is simple enough—additive manufacturing is great for producing parts with complex geometries, and injection molds fit very much under that banner. To demonstrate, [APSX] shows us a simple injection mold that it printed with a Formlabs Form3+ using Rigid 10K resin. The mold has good surface finish, which is crucial for injection molding nice parts. It’s also fitted with ejection pins for easy part removal after each shot of injection molded plastic. While it’s not able to hold up like a traditional metal injection mold, it’s better than you might think. [APSX] claims it got 500 automatic injection cycles out of the mold while producing real functional parts. The mold was used with the APSX-PIM injection molding machine squirting polypropylene at a cycle time of 65 seconds, producing a round part that appears to be some kind of lid or gear.

This looks great, but it’s worth noting it’s still not cheap to get into this sort of thing. On top of purchasing a Formlabs Form3+, you’ll also need the APSX-PIM V3, which currently retails for $13,500 or so. Still, if you regularly need to make 500 of something, this could be very desirable. You could get your parts quicker and stronger compared to running a farm of many 3D printers turning out the same parts.

We’ve seen similar projects along these lines before. The fact is that injections molds are complicated geometry to machine, so being able to 3D print them is highly desirable. Great minds and all that. Video after the break.

Continue reading “3D Print Your Own Injection Molds, Ejector Pins And All” →

Calculating The True Per Part Cost For Injection Molding Vs 3D Printing

October 14, 2024 by 45 Comments

At what point does it make sense to 3D print a part compared to opting for injection molding? The short answer is “it depends.” The medium-sized answer is, “it depends on some back-of-the-envelope calculations specific to your project.” That is what [Slant 3D} proposes in a recent video that you can view below.  The executive summary is that injection molding is great for when you want to churn out lots of the same parts, but you have to amortize the mold(s), cover shipping and storage, and find a way to deal with unsold inventory. In a hypothetical scenario in the video, a simple plastic widget may appear to cost just 10 cents vs 70 cents for the 3D printed part, but with all intermediate steps added in, the injection molded widget is suddenly over twice as expensive.

In the even longer answer to the question, you would have to account for the flexibility of the 3D printing pipeline, as it can be used on-demand and in print farms across the globe, which opens up the possibility of reducing shipping and storage costs to almost nothing. On the other hand, once you have enough demand for an item (e.g., millions of copies), it becomes potentially significantly cheaper than 3D printing again. Ultimately, it really depends on what the customer’s needs are, what kind of volumes they are looking at, the type of product, and a thousand other questions.

For low-volume prototyping and production, 3D printing is generally the winner, but at what point in ramping up production does switching to an injection molded plastic part start making sense? This does obviously not even account for the physical differences between IM and FDM (or SLA) printed parts, which may also have repercussions when switching. Clearly, this is not a question you want to flunk when it concerns a business that you are running. And of course, you should bear in mind that these numbers are put forth by a 3D printing company, so at the scale where molding becomes a reasonabe option, you’ll also want to do your own research.

While people make entire careers out of injection molding, you can do it yourself in small batches. You can even use your 3D printer in the process. If you try injection molding on your own, or with a professional service, be sure to do your homework and learn what you can to avoid making costly mistakes.

Continue reading “Calculating The True Per Part Cost For Injection Molding Vs 3D Printing” →

Injection Molding Using A 3D Printer

June 25, 2024 by 16 Comments

Recently [Stefan] of CNC Kitchen took a gander at using his gaggle of 3D printers to try injection molding (IM). Although the IM process generally requires metal molds and specialized machinery, 3D printers can be used for low-volume IM runs which is enough for limited production runs and prototyping before committing to producing expensive IM molds. In the case of [Stefan], he followed Form Labs’ guidance to produce molds from glass-infused Rigid 10K resin (heat deflection temperature of 218 °C). These molds are very rigid, as the ceramic-like noise when [Stefan] taps two together attests to.

Injection molded bolt, with imperfections on the head. (Credit: Stefan, CNC Kitchen)

The actual injection process is where things get more hairy for [Stefan], as he attempts to push the clamped-shut mold against the nozzle of the FDM printer to inject the molten plastic, rather than using an IM press. With PLA at standard extrusion temperature the plastic barely gets into the mold before solidifying, however. Following this, higher temperatures, different materials (PETG, TPU) and high flow-rate extruders are attempted, with varying results.

Many of the struggles would seem to be due to poor mold design, rather than fundamental issues with using an FDM. The Form Labs document details some of the basics, such as opening up the injection gate (to decrease pressure inside the mold), adding air vents to improve flow and so on. Commentators to the video with professional experience point out many of these issues as well, along with the benefits of preheating the mold.

With the caveat that most of the challenge is in making a good mold, we’ve even injection molding done with nothing more exotic than a hot glue gun. If you’ve got a friend, or a long enough lever, you can even inject the plastic by hand.

Continue reading “Injection Molding Using A 3D Printer” →

Lessons Learned: Plastic Injection Molding For Products

October 14, 2023 by 23 Comments

Injection molding is one of the technologies that makes the world go round. But what does it actually look like to go through the whole process to get a part made? [Achim Haug] wrote up a blog post that does a fantastic job of explaining what to expect when getting plastic enclosures injection molded in China.

These air quality monitors required a two-part enclosure.

Injection molding a part requires making a custom mold, which is then used by an injection molding machine in a shop to crank out parts. These are two separate jobs, but in China the typical business model is for a supplier to quote a price for both the mold as well as the part production. [Achim] describes not only what navigating that whole process was like, but also goes into detail on what important lessons were learned and shares important tips.

One of the biggest takeaways is to design the part with injection molding in mind right from the start. That means things like avoiding undercuts and changes in part thickness, as well as thinking about where the inevitable mold line will end up.

[Achim] found that hiring a been-there-done-that mold expert as a consultant to review things was a huge help, and well worth the money. As with any serious engineering undertaking, apparently small features or changes can have an outsized impact on costs, and an expert can recognize and navigate those.

In the end, [Achim] says that getting their air quality monitor enclosures injection molded was a great experience and they are very happy with the results, so long as one is willing to put the work in up front. Once the mold has been made, downstream changes can be very costly to make.

[Achim]’s beginning-to-end overview is bound to be useful to anyone looking to actually navigate the process, and we have a few other resources to point you to if you’re curious to learn more. There are basic design concerns to keep in mind when designing parts to make moving to injection molding easier. Some injection molding techniques have even proven useful for 3D printing, such as using crush ribs to accommodate inserted hardware like bearings. Finally, shadow lines can help give an enclosure a consistent look, while helping to conceal mold lines.

Making An Injection Mold For Yourself

August 28, 2023 by 29 Comments

Injection molding is the obvious onward step from 3D printing when the making of a few plastic parts becomes their series manufacture. The problem with injection molding is though, that making a mold can be prohibitively expensive. Has the advent of affordable CNC machining changed that? [Teaching Tech] takes a look, and machines a mold for part of a bicycle bracket.

With a diversion into home-made silicone seals for the injection molding machine, he proceeds to machine the mold itself from a block of aluminium. It’s a basic introduction to mold construction for those of us who’ve never ventured in this direction before, and it provides some interesting lessons. As we’d expect he does a rough machining pass before returning with a ball-end tool to smooth off those curves, but there’s a lesson in measuring rather than believing the paperwork. The tool he used was a bit smaller then the spec, so his path left some rough edges that had to be returned to. Otherwise the use of a removable pair of bolts to form holes in the finished part is we guess obvious after watching the video, but it’s something we learned as injection molding newbies.

This video follows on from a previous one we also covered, in which we’re introduced to the machine itself.

Continue reading “Making An Injection Mold For Yourself” →

Repairing A Home Injection Molding Machine

August 5, 2023 by 10 Comments

When [Michael] over at the Teaching Tech YouTube channel bought a hobby injection molding machine a long time ago, one of the plans he had with it was to use it for grinding up waste bits of PLA filament for injection molding. Since the machine was bought from a US shop and [Michael] is based in Australia it required some modifications to adapt it to the local 220+ VAC mains, followed by adding a PID temperature controller and a small compressor to provide the compressed air rather than from a large shop compressor.

Although [Michael] had discussed using the machine for PLA with the seller to confirm that this would work, a user error meant that the now defective unit had been sitting idly for many years, until recently.

Since the machine had been gathering dust and rust in the garage, fixing the machine up took a complete teardown to remove corrosion and resolve other issues. After this the original fault was identified, which turned out to be a shorted wire near the heater which had been turned up to a too high temperature, leading to the release of magic smoke and banishment of the machine to the Pit of Despair, AKA the shadowy depths of one’s garage.

In this first installment, [Michael] cleaned up the machine and restored it to a working state. In the next part injection molding will be attempted again, which should give some idea of the feasibility of turning scraps of PLA and failed 3D prints into smooth injection molded parts, assuming you have the CNC machine or patience to carve out the requisite molds, of course.

Continue reading “Repairing A Home Injection Molding Machine” →

Hackaday Prize 2022: Recycled Plastic Skateboard Decks Demonstrate Small-Scale Injection Molding

October 21, 2022 by 25 Comments

Injection molding is usually focused on high-volume production, but that doesn’t always need to be the case. The Recycled Plastic Skateboard Deck project centers on the use of injection molding for a relatively low-volume production line using open-source tooling.

RPSD is part of the Precious Plastics ecosystem and uses the existing and open-source shredder and extruder to turn locally-sourced plastic waste into melted plastic. The core of the tooling is in the aluminum CNC-machined top, bottom, and edge mold sections bolted to a thick steel support structure that give the skateboard deck its shape. The edge section defines the deck’s perimeter, and 64 cartridge heaters are inserted into it to bring the mold up to temperature. The mold is mounted on a scissor lift mechanism to allow it to be aligned with the extruder, and temperature control electronics are housed in a laser-cut metal enclosure, which is bolted to the base of the mold structure.

To be clear, this is not a cheap way to make a couple of skateboard decks, but rather a way for small shops to do injection molded decks in-house. At ~$7500 for the components of this relatively large mold, excluding the extruder, you’d still have to sell quite a few decks to make it economically viable.

Although small-scale injection molding has become a lot more accessible, the cost of machined metal molds will remain high for the foreseeable future. However, if you only need small, flexible parts, you could probably do it for under $50 using 3D printed molds and silicone.

Continue reading “Hackaday Prize 2022: Recycled Plastic Skateboard Decks Demonstrate Small-Scale Injection Molding” →