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  1. #41
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    The dragonfly guy sometimes talks about a "day job", and he does things like buy used kuka robots and makes them actually do useful work - so I suspect he has deep roots and training. And given that he seems to be the kind of guy who can go from "customer needs part" to "running a batch..." direct - well, there's probably money in that, at least if you have customer connections.

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    Oh for fucks sake! He just wants to make some simple molds and get plastic parts out of them. I say plastic parts because that is easy, getting properly packed, low stress parts is a lot more involved. He already said the grip is a very complicated part that can wait and has a few simple parts to try first.

    As for the hats you will need to wear. If you can learn mold making the rest is easy and will come to you just by doing it. Read all you can but don't take any of it as gospel, it's just good for ideas. Draft is nice but nearly all my parts couldn't have it. Even wall thickness is nice but again the parts I made it was not possible. If you get sink foaming agent is a great fix and an awesome tool for your toolbox, if it works with your plastic. It really works well with polycarb, PVC, and I think ABS and styrene.

    To design:
    A computer and Fusion 360. I made mine in 2010 for around $600 and pay $300 a year for Fusion. This is WAY more than I had as a professional mold maker, incomparably more!

    You need a milling machine, I prefer a cnc but a 9"x42" Bridgeport knock-off is how I got started, a simple manual lathe, and a way to cut your pins and grind them to length. If you are really cheap an abrasive blade on something that will spin it and a block with holes in it to align the pins on a bench grinder will work. The only "special" tools you will need are a boring head and a way to hold the plates at an angle to drill the pecker pins if you do slides, the rest you should already have. A surface plate is real nice but you can use your mill table if you need to.

    No sinker edm! Put your money in a good cnc mill instead. Edms are great for detail and surface finish but they are higher maintenance and add a lot of time to getting things done.

    Jig grinder and wire edm. What for? Really, they have zero value for the op.

    Molding stuff:
    Molding machine, depends on what you can afford and hopefully fit in your garage or shop. Do your research as each machine can fit several different shot sizes. Careful here as there are a lot of $$$$$ wear related things that can be wrong with it. Check valve, screw and barrel are the most obvious. Many older VMCs and mills are valued at scrap and often sold as such, older molding machines are far less useful.
    Dryer, with a hopper. Damned important to get this right! Especially if you want to run Nylon.
    Mold temp controller, this you can get real cheap on. You need to heat your molds to around 200f for nylon, Polycarb, and urethanes to start molding then you will need to cool them to maintain that temp. Chiller makes me think closed loop so I don't use that term, too spendy.
    A sensitive scale.
    Loader to get the plastic in the hopper. This could be a bucket if you are really cheap, or just dump the bag in directly and save the bucket.
    Old engine hoist to load molds, or a board and blocks to get it in there, which I have done as it was just easier. Remember we are cheap so they are aluminum molds, which are a lot lighter.
    Grinder, what for?? You think he's going to make enough scrap to justify it?

    Since you don't know what you are doing your first molds are for education, just use whatever aluminum is cheap. 1/2" dowel pins for leader pins, just drill and ream the B side instead of installing bushings. If need be you can always do that later. I have seen molds like this last well over 100,000 shots. A thermal insulator plate between the aluminum and platens is a great idea, but one I never got to try out.

    This is a budget operation, how much you spend really depends on how creative you are. The less you spend the more creative you will have to be, and in many ways the more you will learn dealing with your limitations. If there are a dozen ways to machine a part then there are 1000 ways to make a plastic part, the chances to learn are endless. The plastics available as pellets are hundreds of times greater than what is available as rounds and plates, and some of them are really interesting.

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  4. #43
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    Hi DavidScott:
    You are taking an interesting position and much of what you say is certainly a good and sensible way to frame the discussion.
    I am in full agreement with you and with the OP that he can do this.

    However, the sample part the OP described in post #12 has some challenges to make and many more challenges if the OP insists on trying to make both halves of the grip as one piece, rather than two halves.
    I contended that this was not a great entry point into moldmaking unassisted if he'd never done it before and I stand by that assertion, having built hundreds of molds of all kinds of mold specs and complexities over a 40+ year career in the business.
    This is not to puff up my bona fides; it is a simple assertion of my experienced opinion.

    So by all means, let the OP dive into the subject; I think we are in full agreement that a brand new guy can build a simple mold in today's technological environment, and he can find creative ways forward and see success.
    But it's still an obstacle course, and I think anyone diving in can profit from having some of the obstacles pointed out before he's halfway in and tearing his hair because his $10,000 fantasy turned into a $50,000 reality.

    With regard to how he tools up...tastes vary and of course he is free to choose what machine tools and goodies he prefers.
    But I've been building molds since the 1970's...long before CNC was a common thing, and I know what I found useful then, and what I still find useful enough that I would not want to be without it.
    My taste in tools is obviously different from yours....OK, I can live with that, but he still has to have SOMETHING, and that something is going to cost him some money in ways he may not have thought of.

    You and I could debate for a hundred yeas what the merits of any particular choice are, but if he wants to make a tool for what he shows in post #12, I'd like to have what I outlined at a minimum.
    Could I find a way to do without it?
    Sure I could, but for this particular part, knowing already how I'd like to build the tool, I'd insist on a surface grinder and I'd like to have a sinker.
    If I get lucky Fleabay can be my friend and I can put both machines on my floor for a fraction of my total spend for the toolroom.

    Regarding the molding setup, yeah there are lots of ways to approach it, and as with toolroom gear you can improvise.
    But you still have to find a way to hang the mold in the press and whether you choose beater forklift, or a lift truck or a chainfall is up to you, and you might spend 500 bucks instead of 2000 bucks but you still have to find a way.
    You can ditch a granulator if you don't mind tossing the sprues and the short shots; but you can't really ditch the drier and you can't ditch the press.

    All of these things are obviously seat of the pants estimates propped up by quick Ebay searches, and numbers I've swiped from my own beginnings, and there are things the OP may already have, so clearly this is not a comprehensive list locked in stone, but it does offer an order of magnitude kind of estimate, and that's all it's supposed to do.

    The OP is clearly determined to pursue this , and I'm happy to help as I can...I'll never say never, and I hope I communicated that, but if he goes into this totally blind, he's gonna get a bloody nose if he doesn't have any idea what this is going to take.

    So jhov, let's see some of the simpler parts you hope to mold, and we can all put in our two cents' worth as before.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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  6. #44
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    I did say the part in post #12 is advanced and out of his range to begin with, best to forget that part for now.

    Most of my experience with molding happened at one shop where we made our own products for sailboarding, true art to part. They were structural, cosmetics were flexible, and the budget was cheap. While I never got to do things "right" I did get to learn just how cheap one could get and still make good parts. My opinions about mold making are heavily influenced by running them too, I can't imagine separating the two. Kind of like programming for a cnc mill but never running them. We definitely live in different worlds where mold making and running them are concerned.

    Most of the aluminum molds for the 200 ton press I ran were easier to load by hand than with a forklift or hoist, so that is why I am saying those things are not must haves. I did say the drier was critical, in a way more important than the press.

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    Hi again David:
    You wrote: While I never got to do things "right" I did get to learn just how cheap one could get and still make good parts.

    Yeah, I know exactly where you're coming from.
    I've built a lot of those kinds of molds too and violated a lot of the "rules " I'd learned when I did my apprenticeship.

    Back in the day, bragging rights in the toolmaking world were predicated on what kind of micrometers you had (Etalon was best) and what a genius you had to be to even square up a block.
    That culture was often encouraged as a way to elevate the art, much as puffers in modern jobs often inflate their critical indispensableness and lard you with bullshit to help sustain their fragile little egos.
    I swallowed it all until I was mentored by a crusty Dutchman starting in 1980, who had cut his teeth in the prototype department for Phillips in Holland, was a brilliant toolmaker and absolutely detested bullshit of that kind.

    I learned a tremendous amount from him about what you could get away with because his business catered heavily to a market that was ruthless about keeping costs down and wouldn't pay premium prices to get the best we were capable of.

    But his was also the premier toolroom in Vancouver at the time, so we still got to build high class, high volume tooling from time to time too, and I learned a lot about how different the needs for tooling capable of a million parts a month was to tooling that might make 5000 parts in it's whole lifetime and could be rougher than guts where it truly didn't matter.

    It was a great eye opener and I owe that man a huge debt of gratitude.

    So yeah, I think we fundamentally agree about how to think about this trade...taking nothing away from what it can take in skill and experience to design and build a high end tool, but recognizing that they do not all need to be jewels of perfection in order to make successful parts.
    I also agree with you 1000% that experience running a press makes you a much better toolmaker when it comes to your design decisions...sadly very few toolmakers or tool designers ever get to see their stuff run, and fail, and get fixed and run some more, and get fucked up by the screwdriver monkeys, and get fixed and...

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    David and Marcus have indirectly touched on an important point without explicitly stating it; nobody, NOBODY does this on their own, we all need someone to learn from. Truth be told, that guru who sits by himself on the mountain top doesn't attain enlightenment, only loneliness, and that nagging feeling... "What do I do if I fuck up? I have no one to bail me out!"

    The normal way to learn this stuff is to go to school, or apprentice, or in the case of molding setup, on-the-job training. I think back across my last thirty five years. My partner and I started a small business were we added custom paint and decoration to someone else's plastic parts. Molding our own was something we thought about; I had worked in an injection molding shop part time in high school and knew it was no big deal, but tooling was the stumbling block. So, I was searching for used tooling when I came upon a set of "orphan" cavity inserts. These had been built to run in someone else's four slide mold base; when the company was sold these inserts didn't go with, but the new owner of the mold base also refused to run them. Thus, they were for sale cheap. With the hard part secured, we went looking for someone to design and build a mold base. Through that one man tool shop we found a molder that would run our piddly production.

    We needed another part, and our toolmaker was closing shop (to follow his dream - building steel guitars) so he referred us to another shop. My design skills were sorely lacking; I could design the part but not the mold, so this shop jobbed the design out to a design firm. The next tool I wanted competitive bids, so I went directly to the design firm. The point is, I was able to learn something at every stop along the way. I made more than my share of mistakes; my partner had a cute name for the re-work fees... tuition.

    Meanwhile, run sizes were becoming an issue with the molder, the economy was picking up and he no longer had press time to waste. After the second molder damaged a tool, we decided it was time to bring molding in-house, so bought a used press. Kawaguchi was not a well known brand in the states, but our tool shop had a customer who had a shop full of them, although they were phasing them out. They put us in touch with the maintenance foreman, kind of the black sheep of the family who owned the business, and he was agreeable to come in and check out our press, for cash. He was also a good source of technical info, and parts as they became surplus to their needs. That beater is long gone, but I think I still have a spare motor for it, somewhere.

    Eventually we decided to bring toolmaking in-house, too, so we hired a toolmaker... before we had a tool shop. A round of auctions solved that problem. Now I designed the parts I wanted, and the toolmaker would suggest better ways to do things, and I would refine the design. I learned a lot from that man. Eventually, he wanted to go on to other things, and we realized that our business really couldn't afford a full time toolmaker AND a full time designer (I had divested myself of both artwork and molding set-up) so I became the full time designer/toolmaker. Am I an well rounded toolmaker? No, I'm not, I'm just very focused on the type of tooling we need.

    The point is, without all the exposure to others, and a willingness to listen and learn, I never would have gotten even this far.

    Dennis

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  11. #47
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    So I received the books and I'll be reading them cover to cover. In the mean time, I'm keeping an eye out for a suitable machine, but I don't have a clue what to look for to know I'd be buying a good machine. How would one go about inspecting a used injection molding machine? David mentioned the check valve, screw and barrel as costly high wear items. It sounds like it would require some disassembly to see them visually, or it would need to run a shot to ensure it builds and holds pressure to ensure they are working. Not all machines for sale are under power. How would you inspect these items? Shaun mentioned all electric machines; my budget will be around $10-15k, so I'll be limited to an older machine but I have seen a few at the top end of that range. Are they worth the extra expense? How do these compare to hydraulic machines for maintenance costs and repairs? Are there any high wear items unique to them compared to a hydraulic machine?

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    I used to work for a place that refurbished injection molding and die casting machines. Back in the day, injection molding was a cut throat, super thin margin business and every company I saw ran their machines hard and fast to the point of destroying them trying to crank out parts as fast as humanly possible. I've seen owners dial up speeds so high the machine was jumping off the floor trying to get cycle time down by a few seconds. And I've seen mechanics literally cut chunks out of the machine and molds trying to squeeze a mold in an undersized machine so they can save tonnage. You can find used machines super cheap, but they are likely to be pretty well worn out. Not as bad as the die cast guys, but plastics guys were pretty well know for doing the most hackjob repairs to keep things cranking as fast as possible (the die cast guys were a special breed of hateful gorillas, when you used a 2" cube of steel welded on 4 sides to mount a 1/2" conduit, we called that 'die cast duty.' And they would still break it off...)

    Also, as to plastics for the firearms industry, if you are planning on using anything fiber reinforced, like PA6 glass filled nylon, it can be highly abrasive on your mold. I seem to remember they were coating hardened steel molds with hard chrome or PVD titanium nitride or nickle boron nitride to reduce wear. Aluminum isn't likely to last long under those conditions.

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    The check valve is pretty obvious if it's bad because the screw will move as you hold pressure. The screw and barrel need to be removed and measured to know what shape they are in. You will go through about 3 check valves per screw and 2-3 screws per barrel. If you need a new screw and barrel then you can change the shot size. How much injection pressure you need is very dependant on your gates. Good gates, and venting, will drop your boost or first stage injection pressure by up to 50%, and reduce how much clamp pressure you need too.

    I think I would rather get a hydraulic toggle press than the other variants if I was shopping used. They have been around forever, are a pretty solid design, and their only limitations are of no concern to me. There is a shit load to worry about but the most obvious are the toggle joints and that the "feet" of the platten have been kept adjusted so it isn't ridding on the bars and bushings. The screw, barrel, and check valve are just a crap shoot, but they are standard wear items and there are benefits to replacing them. Another worry is what type of screw is in there? Is it a general purpose or specialized for a certain plastic? Oh, the joys of used machines!

    I found 4140 ph gates lasted less than half as long as QC-7 aluminum gates with 10% glass filled polycarbonate. Harder does not mean more wear resistant.

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    Quote Originally Posted by jhov View Post
    I'm keeping an eye out for a suitable machine, but I don't have a clue what to look for to know I'd be buying a good machine. How would one go about inspecting a used injection molding machine?
    You really can't, it's a crap shoot. Ideally, you want to see the machine run; not just move back and forth, but actually run parts on a cycle. The theory is, if it ran parts for him, it should be able to run parts for you.

    But machines can have a lot wrong with them and still run parts. Even if the seller thinks it is in good shape, it may be a breakdown waiting to happen. After all, there's a reason he's getting rid of it, even if it's just advancing age / high mileage. I've bought two toggle presses used, and ended up having to do extensive work to the toggles on both.

    My buddy with the shop full of used Van Dorns lucked out. Early on, when looking for work, he visited the major molders in his area, looking for overflow work. One molder offered him a part, but he didn't have a press large enough. The molder offered to sell him the press it was running on. Large, high production molders regularly replace presses based on age and hours; that's how they avoid down time. This press was due for replacement, and the job wasn't a good fit for what they were replacing it with, so they were trying to sub out the job. He parlayed that job into the purchase of a bunch more used presses. Since there is a continuing business relationship there, they wouldn't offer him a press with known problems.

    Best I can suggest for you is to try to find a machine that's led an easy life in a school training program or R&D lab. Otherwise, you pays your money, and takes your chances.

    Dennis

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    Default Injection Moulding Books

    Just been sorting through my book collection to see what is no longer needed, and found these.


    These two books will give you an understanding of what is involved in designing injection moulds.

    Edit add link.


    https://www.hanser-elibrary.com/doi/...?download=true
    Attached Thumbnails Attached Thumbnails injection-moulding-books.jpg  


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