[HN Gopher] How to build your own injection molding machine (2023)
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How to build your own injection molding machine (2023)
Author : danboarder
Score : 80 points
Date : 2024-01-21 00:21 UTC (22 hours ago)
(HTM) web link (www.machinedesign.com)
(TXT) w3m dump (www.machinedesign.com)
| zer00eyz wrote:
| Though this is cool and I appreciate the ethos here the article
| doesn't really spell it out.
|
| All the cost, difficulty, time and money in injection molding is
| in the molds. They are expensive.
|
| When done well they can make 1000's of parts if not more.
|
| It's a great project, an amazing POC. There is the potential for
| small scale (garage sized) manufacturing to exist, the equipment
| is the cost of a (nice) car...
| mildchalupa wrote:
| 1000 pieces is a soft tool Millions are expected out of hard
| tooling.
| throwup238 wrote:
| I think the small scale, as in the footprint, is the point.
| They'd be much better off buying a used IMM if they want
| production parts but those are huge compared to TFA's design.
|
| If they can make their own molds at a machine shop, this could
| hit the sweet spot for a product that's too high volume for 3d
| printing but not enough to justify a professional mold. Set it
| up and run it once a week to make a few hundred parts, that
| type of schedule. Just practical enough for a hacker-run
| lifestyle business.
| londons_explore wrote:
| I wonder if it might be possible to make moulds out of other
| materials for hobby-scale things?
|
| For example, a mould which is made of plaster/concrete with an
| inner layer of silicone?
|
| That would be pretty easy/cheap to manufacture. You'd use a 3d
| plastic printer ($150), dip the print in casting silicone, then
| float the result in concrete, with the concrete surface being
| the parting line.
|
| Then use a scalpel to cut the silicone along the parting line
| and add more concrete to make the other half of your mould.
| SOLAR_FIELDS wrote:
| The design the buster beagle uses is an aluminum box you drop
| your molds into after printing them. Though this idea is
| interesting, I think, for people who are injecting with
| variable size molds that a single casing would not suffice
| for.
|
| A desktop CNC at that scale to make simple stuff like casing
| boxes is probably going to be more affordable and less
| hassle/mess than your suggested setup pretty quick though.
|
| Desktop is definitely not going to be good enough to make
| aluminum molds themselves though. I think you need a 5 axis
| CNC for that. Surprisingly my makerspace actually has one of
| those and I considered learning how to use it but decided
| against it.
|
| In practice however on these molding setups I've found you
| are already kind of constrained on your mold sizes a lot
| simply by virtue of your machine's volume capacity. The one I
| have goes up to 3 cubic inches, but in practice you can't use
| all of that capacity and you get weird/bad results for too
| small of capacity too so the actual ranges of shot volume I
| can produce in a mold are actually constrained to something
| like 1-2.5 cubic inches
| jacquesm wrote:
| 1000's would for most molds be considered a failure and very
| much excessive wear. You'd normally look for orders of
| magnitude more than that.
| say_it_as_it_is wrote:
| It's only a Three-Dimensional inversion of an intricate model
| that requires very precise depths and must be reusable for
| hundreds of thousands of jobs. How hard can it be?
| jacquesm wrote:
| And where both the material and the mold shrink at different
| rates and it would be nice if the product released from the
| mold after the injection phase. At most a weekend's work ;)
| supermatt wrote:
| There are many videos on YouTube using 3d printed resin moulds.
| SOLAR_FIELDS wrote:
| Total cost to do this is roughly (2021 USD when I went through
| this)
|
| $1000-1500 USD to build out a buster beagle with COTS
| components $700 for an anycubic photon plus a an anycubic
| treatment chamber $300 for all the ancillary materials like
| resin (Siraya tech is a great option), mold spray, pellets
| (purchased off eBay), $30 toaster oven from Walmart to keep the
| molds warm, etc etc
|
| Design your molds in fusion 360 and print them on the Anycubic
|
| So if you are patient and have more time than money it is
| theoretically possible to have a full fledged injection molding
| machine with up to 3 cubic inches (50 mL) in your garage for
| under $2000 USD
|
| It takes a lot of time and research to do this properly
| however. Designing the mold has lots of caveats and is very
| custom work. This process is not at all as simple as operating
| an FDM printer, there are a ton more variables and failure
| modes that go into injection molding so you have to be able to
| create an environment where you control all of them.
|
| One thing that could probably save a lot of time and heartache
| for people on this journey is finding someone on fiverr to
| design the mold for you for a few hundred bucks rather than
| trying to teach yourself some hardcore industrial engineering
| concepts. But it's doable, I read an injection molding book and
| was able to produce something that worked after leveling up my
| Fusion 360 skills.
|
| I do want to underscore that yeah, as your comment implies,
| even though recently the money component has significantly
| improved with innovative designs like these that use COTS
| components the time and difficulty part is still there.
| Injection molding is not for the faint of heart, it's
| definitely one of the more hardcore industrial processes out
| there. I have seen the endgame of this journey so I am happy to
| answer any other questions if people have them
| zer00eyz wrote:
| How long did your molds last? PTFE and PTFE with glass? What
| kinds of plastic.
| SOLAR_FIELDS wrote:
| Molds last between 150-500 shots depending on all sorts of
| factors in my experience. Once you have the design dialed
| printing a copy of the mold is not terribly expensive,
| however, takes several hours and perhaps $5-10 of resin.
| Buster beagle sells an aluminum casing to surround the mold
| that greatly increases the life of it since the vast
| majority of the beating it takes is from pressure from the
| clamps.
|
| Not sure if you are talking about the PTFE molding process
| or not but this is just straight single shot injection
| molding, though it is possible to design multi shot
| processes with this setup. It's just more complicated.
|
| I used polypropylene which imo everyone should start with
| first because it's by far the easiest to work with and
| pretty easily sourced off of eBay. It's suitable for a wide
| variety of components for indoor use. For outdoor use you
| would want something like polycarbonate. I think working
| with polycarbonate would not be as lucrative in a home
| machine and here's why: temp and pressures for
| polycarbonate are often a bit harder to achieve and the
| temps you need for molding polycarbonate are often at the
| upper limits of what these resins used to make the resin
| molds will tolerate. I think it's possible though, but
| requires careful selection of a particular polycarbonate
| with the correct thermoplastic properties (such as lower
| melt temp) to operate within the acceptable ranges of your
| setup.
| zer00eyz wrote:
| Need more coffee before questions!
|
| Were you using a PTFE release agent? Like this:
| https://www.antiseize.com/PTFE-SPRAY-HEAVY-COAT-Anti-
| Seize-L...
|
| Polypropylene... Did this have (fiber)glass added?
| SOLAR_FIELDS wrote:
| No though I know people have literally just used stuff
| like PAM in the past. Mine was a purpose made mold
| release agent that I picked up off McMaster Carr. They
| sell a lot of different ones
|
| The polypropylene I've used does not have fiberglass
| added. Though there are a LOT of options for
| thermoplastics, both ready made and custom
| mixed/compounded. You really learn to just go straight to
| the data sheet when thermoplastic shopping because that
| has all the relevant info you need
| skybrian wrote:
| They don't really talk about why. When would you want to switch
| to this over using 3D printing for prototyping?
|
| If you just need a few parts (likely at home), waiting for the 3D
| printer seems a lot easier?
| zonkerdonker wrote:
| I think small[er] scale injection molding has a ton of
| potential for local/recycled/lower volume projects that 3d
| printing isn't necessarily suited for. Brothersmakes [1] sells
| recycled plastic combs and more using a similar process,
| products that really wouldn't work well with any modern 3d
| printer. I've seen similar projects for disc golf discs as well
| from TrashPanda. [2] The market for hyper-local small scale
| products is growing, and I think downscaling injection molding
| fits in well to this. I could order a custom steel mold (that
| I've designed) from a machine shop for a few hundred bucks, and
| with an injection machine and a supply of some plastics,
| conceivably make a few thousands parts on a relatively short
| time scale, with minimal manual labor.
|
| [1] https://www.brothersmake.com [2]
| https://youtube.com/@TrashPandaDiscGolf?si=LWdw3gV9rtNQdlUD
| iancmceachern wrote:
| Thank you for this! I just started exactly this! I bought a
| couple injection molding machines and started Golden Gate
| Molders. We injection mold parts right here in the SOMA
| neighborhood of San Francisco! Not only do we use traditional
| metal tools, we also provide 3d printed tooling options for
| lower volume prototype tools.
|
| www.goldengatemolders.com
| SOLAR_FIELDS wrote:
| If your part is small enough you can do small scale (several
| hundreds to low 1000s) of your units in house for a machine so
| cheap money wise to build that it's better than outsourcing
| even without the QC concerns. Also even prototyping sometimes
| gets old on the 3D printer when you have a 5 hour per you need
| to make 10-20 of that you could do in an hour with the molding
| machine.
|
| Though IMO faster prototyping is not a good reason for getting
| a molding machine, it's just a nice bonus. There are plenty of
| shops in the USA you can send your STL file to and they will
| print a bunch of them for a reasonable price. The real reason
| that you want a molding machine is fast small scale production
| runs because oftentimes what you produce on a 3D printer is
| either not professional looking enough to sell (the lines look
| very hobbyist) or FDM cannot achieve your product requirements
| long term (outdoor plastic enclosures, for example, need
| waterproofing with FDM but not with molded parts)
| cjnicholls wrote:
| This project Precious Plastic shares machine design, resources
| and a store to encourage localized recycling within communities.
| They are already globalised if your interested there may be a
| project near you https://www.preciousplastic.com/
| SOLAR_FIELDS wrote:
| Great guys but the design they offer is a lever operated
| machine which IMO does not give you the consistency you need
| for production runs. The problem is that your arm applies an
| inconsistent amount of pressure whereas a pneumatic machine
| like the one from OP does not. I looked at their design and the
| holipress when I looked at low cost benchtop molders and that
| was one reason I decided against them. I actually built a lever
| machine first and disassembled it when I wasn't happy with the
| results
| londons_explore wrote:
| Can injection moulding be done into a hot mould which is later
| cooled down?
|
| Clearly a cold mould is better for mass production speed, but if
| you had a hot mould then you could probably just use a 3d
| printers nozzle and low pressure to do the injection - or even
| just keep the whole mould in an oven and pour plastic pellets in.
| jacquesm wrote:
| That's more or less how it is done. Thermal cycling of the
| molds is one of the bigger factors in determining the
| operational life of a mold. Moldmaking is a very advanced art,
| the people that do this have a formidable array of software at
| their disposal to model how the mold and the plastic will
| behave as well as a massive amount of accumulated trade
| knowledge. I know several, one of which is outstanding and in
| very high demand because he can reduce the number of trials to
| a minimum. Materials science is nice compared to software
| because you can actually learn something and build on it for a
| whole career instead of the next five to 10 after which you
| have to re-learn everything.
| SOLAR_FIELDS wrote:
| I have my own injection molding machine in my garage, DIY all
| the way. Everything about molding is precise, and it has to be,
| it's not nearly as forgiving as FDM printing in terms of
| failure modes. To achieve what you are describing I have two
| molds that I rotate in and out of a toaster oven, not kidding.
| Every thermoplastic pellet has a detailed data sheet on
| expected temps and the like and mold temp is simply one of
| those.
| 55555 wrote:
| Just FYI this machine can only inject 44ml of plastic. It makes
| tiny parts. Great progress for DIYers though!
| jacquesm wrote:
| That's true but it's already quite impressive at that and
| usually when you have something working the path forward is
| incremental so I think over time you'll see larger and more
| capable units.
| SOLAR_FIELDS wrote:
| Buster beagle sells a variant that goes up to 50 mL but once
| you get beyond that I think the price point is going to
| significantly increase. You need more pressure and capacity
| that an off the shelf air compressor might be able to give,
| for instance. So unless the availability of COTS stuff
| changes I think there is somewhat of a ceiling of capacity
| you can get at this price point
| jacquesm wrote:
| This article could be vastly improved by adding some sketches and
| diagrams.
| mdaniel wrote:
| weird, the linked video from the article is their original
| design, but then the auto-play after it takes the viewer to the
| "v2" they repeatedly reference in the first video:
| https://www.youtube.com/watch?v=M28Pbrm7wzE
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