I am becoming a bit more adventurous with my designs, and have started designing some ideas that would need to be injection moulded to be of any real practical use. There are also some aspects of the design that I believe would need to be rotomoulded to reduce material usage and weight to acceptable levels.
How can I move to this "next level" of prototyping and small scale manufacture? Is this something I can achieve myself with (limited) investment in specific machinery (budget ~15k USD)? Im only looking at small runs - but a number of parts, which I would assume would make more commercial offerings expensive?
I agree with the other points, injection molding would be difficult to get into and is designed for moderately big runs. That being said, I know of a guy who was in a similar position as you with a couple inventions he wanted to bring to market. The quote for plastic injection molds was coming out to low 6 figures, and there wasn't a guarantee they would work the first try, so he bought a 3-axis CNC mill and a plastic injection molding machine for the same cost and could iterate faster and cheaper. He now runs a decent size contract manufacturer in Iowa.
Depending on your designs and interests, I'd suggest checking if your nearby community college has welding classes. They're typically very cheap and professional guidance with a skill like that is invaluable. They may have other classes for other manufacturing skills which you could learn on YouTube, but again professional guidance can be invaluable for learning fast and avoiding poor habits that will hold you back later.
Take a look at the hobby offerings for Inventor and Autodesk if you feel at all limited. I recently tried using Fusion 360 but found the interface confusing coming from using Autodesk in school.
If you have more specific examples of things you're looking to make, we could give more tailored advice. There are tons of manufacturing processes available, each with a range of units and product features they're optimal for.
Back in school the manufacturing professors would have us bring in products if we couldn't determine the manufacturing method and they would help us figure it out.
First, if you'd like to take another step forward, I recommend silicone molding your 3D printed part. You'll need to spend a lot of time sanding/prepping, but you can achieve a surface quality similar to injection molding if done right. Your tooling investment will be well under 15k and you can do small batch runs to test the idea. I've seen some product runs under 1k parts that came out looking flawless and were 100% commercially viable.
You can experiment with the type of silicone you use and the type of polyurethane you pour into the mold. You should be working out all of the question marks here. Things like, strength, durability, weight, feel, aesthetic, and more.
BJB plastics has some great silicone products, awesome customer service, and a number of videos up on Youtube to guide you along. They aren't the only ones, but they sure are a great resource for asking questions.
Hope this helps. Good luck!
Not convinced it's the best, as I didn't really enjoy the class, but that was mostly due to a poor lecturer. I'm also not convinced that it's the most relevant for you, as you seem to be looking more into "small batch prototyping", rather than mass scale manufacturing.
Still, it's a good book for getting an overview of what is out there in terms of processes and figuring out what would be appropriate for your needs. It's not a good book for getting into the nitty of, say, injection mold design, which is highly specialized.
I do believe Protolabs offers small batch injection molding for "reasonable" cost, probably as reasonable as you'll get for small batch. From my memory they also have a design guide PDF that you can download or they send when you register. That's probably a good place to start. Also try searching reddit r/mechanicalengineering for "injection mold" and similar queries, I do remember a few people asking for resources and getting good replies.
You're going to have to be specific as it is entirely up to what you are manufacturing. How tight are your tolerances? Is it plastics? Metals? By small scale do you mean a batch of 10, 100, 1k, 10k?
There are first class machinists on YouTube that will teach for free and to be frank, I've yet to run into anything that couldn't be machined with a bit of skill, a lathe, a drill press, and a milling machine, all of which you can pick up on the cheap. I'd start there. What about it makes you need to use injection molding? That's a process used in bulk production. If it's tractor brackets and such then casting might be a better idea. If you're looking into injection molding, you'll have to get in contact with professionals - the tooling is in the range of hundreds of thousands if not millions. The "next level" of prototyping for you I think would be machining, not IM. You might be able to pay a contractor to do IM for you but it'd be a stretch at your budget.
On a tangential note, I'm currently working my way through MIT's "Principles of Manufacturing" MicroMasters program on edx and would thoroughly recommend it. It's more large scale systems then anything, but it's been great for me in terms of learning the vernacular and has helped me better communicate with manufacturers when I'm looking to scale one of my designs. Might be worth checking out.
https://courses.edx.org/dashboard/programs/452d5bbb-00a4-4cc...
Your wording here is a bit odd. Injection moulding is mostly a question of scale. Do you need to mass-produce your parts or are you just looking for mechanical properties that a standard 3D printer can't provide?
If it's mechanical properties, there may be other options like resin printing, casting or machining parts.
> How can I move to this "next level" of prototyping and small scale manufacture? Is this something I can achieve myself with (limited) investment in specific machinery (budget ~15k USD)?
You can get a (very) low end injection moulding machine for a bit over $2000 [0] and you can get a small desktop CNC milling machine for just under $3000 [1]. I would think about going for something more like a Tormach or SYIL but those are more like $10000.
You might also find Physics Anonymous' videos interesting. They bought a small injection moulding machine for a small run [2].
But there's going to be a huge learning curve here. Moulds are much more complicated mechanisms than static welded parts.
Before you get too invested in injection moulding, I'd really spend some time to see if you can manufacture the part some other way. Maybe talk to a job shop and ask them if they think they can fabricate it.
[0]: https://www.techkits.com/products/model-150a/
[1]: https://shop.carbide3d.com/products/nomad-3/nomad-3?variant=...
The problem is the tool cost vs. small production runs. Plus, designing good tools can get really tricky.
Here is what I would do on the garage scale:
* A CNC router like shapeoko or x-carve (you can buy or diy)
* This allows you to build large, but rather flat moulds
* Pouring epoxy resin mixed with e.g. cotton flakes or other additives gives you nice solid objects
* Laminating glass or carbon fiber can net you large surfaces
* Vacuum forming also nets you large surfaces and can be done with a diy machine
Old, used machines are also always a good idea.
It appears the company may be defunct, but the information is pretty good.
---
Edit: It looks like they were acquired - https://ir.avnet.com/news-releases/news-release-details/avne...
Part 12 for plastic forming and casting.
[1] https://www.youtube.com/watch?v=xMP_AfiNlX4&list=PLSGA1wWSdW...
Edit: And also there's a textbook which covers pretty much every method of making things:
Kalpakjian, S. Manufacturing Engineering and Technology.
You might be able to buy an injection molding machine for pretty cheap, but it's useless without the appropriate tooling which costs a fortune, and the learning curve for operating an injection molding machine is very steep. If you don't have the equipment and skill to machine your own tooling then trial and error is going to be real expensive - I'd definitely invest there before trying injection molding yourself.
I would recommend calling up a chinese injection molding shop and having them run your parts instead - they have the experience and volume to produce tooling quickly and (comparatively) cheaply, and that's all you really have to pay for. You could always go through the trouble and expense of producing things domestically after you've validated your design. The one downside is that they'll usually just make your design as is, whereas a domestic shop will usually assist you with some design for manufacturing to make sure you get something that actually works for you, but the cost is so high its still often better to screw up a few times with the chinese shops, and nowadays some of them are better with their customer service anyways.
But for short runs you really should consider alternatives. The appropriate one depends on what you're making. Urethane casting is great for making plastic parts with tolerances comparable to injection molded parts - you can even use 3D printing to make the master molds. CNC machining is also very economical for short runs.
Even with aluminum molds at a low cost focused prototyping CM, which are MUCH cheaper than steel molds, I think the pricing for just one set of tooling is going to exceed your $15k budget.
Finding 3D printing contract manufacturers who can manufacture with the materials you're interested in would be my recommendation if you're moving into plastics. The unit cost is going to be extreme compared to injection molding, but there's almost 0 tooling cost, so for prototyping 1 or 2 units will be significantly cheaper. Advanced 3d printing these days can rival (or even exceed) the performance of an injection molded part.
A lot of manufacturing knowledge seems to be "oral culture". Finding a local contract manufacture firm to partner with might be a good next step.
Depending on the size and complexity of your part might just make it for $15k to get the tooling done. The manufacturing itself most probably will never make sense to do inhouse.
If you want to learn more about manufacturing techniques , this is the book I used in college which had a great breakdown IMO https://www.amazon.com/Fundamentals-Modern-Manufacturing-Mat...
A lesson I've learned is: Never assume you know the cheapest / best way of making something. I've especially learned this from designers working in China, who have surprised me many times because they know their local industry way better than I do.
Some techniques to keep in the back of your mind are punched and folded sheet metal, cast / molded aluminum, and vacuum forming. "Soft" mold tooling is cheaper than hard tooling. Vacuum forming is done with wooden molds. There are now some aluminum alloys that can be used for injection molding with short lifetime, but cheaper to machine than hard steel.
Injection molding has a steep learning curve because of the cost of tooling plus issues such as mold flow, ejection, and shrinkage during cooling. You don't always get it right on the first try.
Look for raw materials and parts that are close to the net shape that you want, and only need finishing or modification. For instance, "plate with holes" can be done with plates cut to size by a raw material supplier and drilled using a plywood jig with carbide drill guides.
Try to attend the International Machine Tool Show when the pandemic cools down a bit. Just for inspiration. Bring good shoes.
Personally, the biggest hurdle for me is "finding" the cost of some of these processes so that I could adapt my idea and material early on. All places in my local area require you to submit a formal quote and plans without giving you an indication at all of how much it'll cost (which is inside info that people who use those services often know).
Oh and don't get sucked into the trap of ordering runs from Alibaba, even though you will find someone that does what you need at a cheap price there. It's a pit of time sifting through spam and incorrect info till you find a good reliable supplier, so rather deal with local providers in your area.
Speaking solely from what I have observed being on the IT side of two manufacturing companies, your budget for machinery investment is probably an order of magnitude low. Probably want a partner to start.
If you want a DIY approach to producing parts you could think about casting polyurethane parts in Silicone RTV molds from a 3D printed buck. This is something you could do at home without much extra support hardware, maybe just a vacuum chamber. Check out Smooth-On (smooth-on.com).
You mentioned rotomolding which sounds like you are looking for large parts. Because of the high cost of rotomolding tooling I would recommend looking into fiberglass construction for dimensionally large short run parts. If you can find a local CNC shop you can have foam bucks machined and then take them to a fiberglasser to create a run of parts or one-offs. DIY fiberglassing is also very possible on a reasonable budget.
For most molding processes you will need to get familiar with draft angles, part lines, minimum wall thickness, sprue placement, etc. These are things that will have an impact on your parts during the design phase.
Very generally speaking on manufacturing, it is good to get into the habit of defining your budget, how big the parts you want to make are, how many you need and what material you want them in. As you answer those questions the better fabrication methods for a part will become more obvious.
Final (and probably unpopular) piece of advice; I would stay away from buying a CNC machine or other large equipment until you know exactly what you need. If your goal is to make finished prototypes and products then it's usually better to spend your time understanding the various manufacturing methods vs learning to be a machine operator for a specific process.
Good luck!
To paraphrase: How/where do I start, as software engineer, to learn hardware, but not necessarily "computer" hardware?
*Not only limited to woodworking, they also build contraptions of some sort.
He covers the questions in your last paragraph, specifically for small runs and low budget. Even lower budget than you're thinking, so it's a perfect starting point.
Plus he's a hell of a lot of fun to listen to and the production quality is too sweet.
Start here: [0] Making silicon molds
[1] Cheap plastic injection molding using silicon molds + metal casing
[2] Making a complex toy with DIY injection molding
[3] Bonus: the best dubbing of a classic Star Wars scene you've ever seen.
Enjoy! And keep on steady craftin'.
[0] https://youtu.be/RC9TgAO5mGo
[1] https://youtu.be/78bM615koOo
Terminology is important.
Manufacturing is usually outlined by Industrial Systems Engineering for setting-up assembly lines.
Design for Manufacturing (DfM) is an engineering approach to reducing costs and manufacturing complexity of products.
These comprise different areas of responsibilities.
There is no single, universal answer but there are important questions to consider. At what scale? What are you making? What is the current cost per unit? What is the cost per unit target? How much would it cost to build it using powder-sintered FDM?
Without knowing the specifics of your part. Usually you can trade a more expensive process and still get a workable prototype part if you want to avoid molding. Eg, commercial 3d printing, (assemble panels together for larger parts), cnc milling.
Do you have a validated market for your product? If you don’t want to do the equipment purchase upfront but can demonstrate that your are a competent client, a contract manufacturer would be able to help you with the smaller first runs.
That said, contract manufacturers are easy to work with. They'll do the mold design based on your CAD model of the object. Making the molds is the most expensive part.
How big are the parts you want to make, and how many different parts are there? If you could send a link to pictures or parts on the open market you think are similar, it would be helpful to get an idea of type of thing you want to make.
Maybe opening a small lab for youngsters, schools and happy triggers in your neighborood? You would personally benefit from new, like-minded acquaintances while keeping your running costs covered and surveying business opportunities.
Injection molding machines get big and expensive quickly. But there are some hobby / education molding machines that are relatively inexpensive. They'll be limited in the part size, of course, but it will be very educational. You can find used industrial machines, but ones in a just-right size are harder to find.
You can make molds using high-temperature epoxy (hundreds of shots), high-temp SLA resin (presumably at least tens to hundreds), aluminum (thousands), or steel (often refurbished for very long lives). Having a CNC mill will be very helpful--something like a Tormach 440 is $7K or so new, and is useful for all kinds of things besides mold making. Depending on the complexity of the part and the finish you need, this is probably intermediate machining skill.
Machines are often rated in clamping force (e.g, "15-ton"), but shot size/volume (usually expressed as the weight per shot in polystyrene) and injection pressure are also important. Horizontal machines can take up a lot of space, but can use gravity to clear the part after it's made.
For smaller parts, Morgan makes some nice benchtop machines, but they're pricey. If I was going to buy a new machine, I might look at this cute little horizontal: www.robotdigg.com/product/657/ It's about $9K I think.
For me, it made all the sense in the world to buy an old import vertical 15-ton machine ($2,800 on eBay) and design and make my own aluminum molds for a product I sell. I learned a lot, and now can make other parts. I spent less than the cost of having a mold company make me a single mold (I think the quotes I had were $3,500 or so for my relatively simple, small part). But I have access and experience on a CNC mill, lathe, etc. If you don't have that, or don't live near a makerspace, then you'd need to factor in the machining equipment and tools.
I currently produce an ABS case for my product, actually resembles a DB-25 shell. About 2.5 x 1.5 x .8". I did use Fusion 360 CAD and CAM, and a Tormach CNC mill. Used aluminum for the two mold halves and spacers, actual ejector pins (they're inexpensive) for the ejectors. About a 40-second cycle time. It took quite a while to get everything put together (the manual is in Chinese, and actually is for a similar but not identical machine), and I'll probably add on some microprocessor control soon to make it a bit easier to run. It is extremely pleasing to be able to sit down and fill up a box with custom plastic parts. Need to add a logo or product name to the part? Throw it on the CNC mill and you're set.
How much would I pay to take a course to learn how to create molds and set up and run an injection molding machine? Right now I've spent less than I would having an outside company make just the molds. Your outlook may be different, but learning and creating actual products (subject to some size limitations) is very possible. It all depends on what value you place on learning new skills, versus the raw economics of it.
The booklet from Morgan called "Cutting costs in short-run plastics injection molding" covers simple mold making, and the case for using high-temperature epoxy for short-run molds.
The NYC CNC folks machined their own mold from a pre-built mold blank on their CNC machine, then had a company do the injection molding.
(I'm omitting the weeks I spent stripping and rebuilding a small pneumatic machine--it was just too small for my part. Another learning.)
By the way, I had a toy injection molding machine as a kid. Small but completely functional--came with a mold for a toy soldier, I think. I'd cut up sprues from plastic models. Probably burned my fingers more than once, but an excellent experience for a kid. Wish that was more common.
Has to be a really good balance when it comes to machine quality and capabilities.