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  • I need help building a machine.

    My brother in law has asked me to help build a dip moulding machine.It is a simple machine that needs to move up and down but it will have a rack where aluminium moulds hang from. These need to be dipped in a liquid called plastisol, Which is liquid pvc. Candles are made in a similer fashion.

    At the moment it is manually done but mechanically assisted by a chain and counter weight.
    I was thinking if one made a frame out of angle iron and had four posts ,lets say 30mm in diameter that are held by a bronze bush . Or do they make off the shelf linear type bushes.?
    Then it would need a means to travel up and down. It would need to carry a maximum of 50kgs. I wonder if a leadscrew of some sort would allow this to operate smoothly. ? If he attached a vfd to the motor it would allow for a smooth and adjustable movement.

    What would be best for this , Some form of dc motor with a leadscrew or would a reduction gearbox and rack work.?

    There would need to be some kind of timer involved so it could sit for a few seconds in the liquid.It would also have to stop in exactly the same spot repeatedly .
    It will be a great help if I can get some feedback on this as there is not much on the net about it.It sounds like a nice project to make.

  • #2
    For the moving part, reads like you need a linear actuator, do you have piston type gate openers readily available there? If you run something off the shelf, replacement when it wears is a matter of buying another one of the same model, after that limit switches, a plc or arduino to control a automated cycle etc are all possible. In fact the system you are describing could almost be done by a normal gate opener setup...
    As for linear bushes, yes, they make masses of linear bearings in huge varieties. From round rail units to flat slideway ones, not clear which motion you need to have covered by it but there are so many types there's one for every job nowadays.

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    • #3
      A chain drive garage door opener would have all the limit switch's & parts you'll need & be very easy to adapt.
      "Let me recommend the best medicine in the
      world: a long journey, at a mild season, through a pleasant
      country, in easy stages."
      ~ James Madison

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      • #4
        The mold is dipped and waits for "x" amount of time and then you lift it out and after it is done dripping for "x" amount of time the part is removed or changing to a fresh mold and allowed to drip on a drain rack?

        Does he have an air compressor?

        Plastisol dipping search mentions heating to set it. Is there heating at some point in this process?

        2 tanks 2 molds and a teeter-totter. 1 DA air cylinder with speed controls and timers, =double production.
        Last edited by Abner; 12-10-2017, 08:31 AM.

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        • #5
          One product he makes is the plastic covers for a bakkies (suv) tow hitch. The aluminium mold of a tow hitch is heated in a gas oven and then slowly dipped into the tank of plastisol. Then its put back in the gas oven for a few minutes to cure. Then its cooled in water and a blast of air removes the tow hitch cover from the aluminium mold.

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          • #6
            Originally posted by Abner View Post
            2 tanks 2 molds and a teeter-totter. 1 DA air cylinder with speed controls and timers, =double production.
            A chain drive garage door opener might be a good fit for this. Just need a sprocket on the teeter-totters axle. The limit switches for controlling
            where to stop at each end are built into into the unit and screwdriver adjustable. The motors on these things utilize a worm drive so when it stops
            it stays put. No timers required. Change the rack on one side and push the garage door opener button. Change the rack on the other side and
            push the button. Then do the first side again.

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            • #7
              Oh boy! Sounds simple but isn't. His mold must contain multiple pieces( like 10 hitch ball covers= 1 mold)
              Full auto, big project - Horizontal loop of chain with molds evenly spaced, or a rotary carousel. Indexed motion. Probably easiest to have chain assembly/carousel to rise and fall. Stations- preheat, dip, reheat, cooling, removal. 5 molds needed for 5 station machine. Time at each station would have to be equal, could temperatures be adjusted to make this happen? <-That is a critical go/no go question, if times cannot be adjusted to be equal then it would get increasingly difficult. Molds could be changed saving $ vs. building another machine until production warrants.

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              • #8
                Look on Youtube for "how it's made" videos. There was one for PVC coated gloves. No rack or timer involved, the gloves hung from a track which descended and accended towards the liquid filled trough, gloves traveled along the track pulled by a continuous chain. Simple and effective.

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                • #9
                  Originally posted by reggie_obe View Post
                  Look on Youtube for "how it's made" videos. There was one for PVC coated gloves. No rack or timer involved, the gloves hung from a track which descended and accended towards the liquid filled trough, gloves traveled along the track pulled by a continuous chain. Simple and effective.
                  That sounds ideal!

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                  • #10
                    Originally posted by reggie_obe View Post
                    Look on Youtube for "how it's made" videos. There was one for PVC coated gloves. No rack or timer involved, the gloves hung from a track which descended and accended towards the liquid filled trough, gloves traveled along the track pulled by a continuous chain. Simple and effective.
                    That basic system is how Sinclair and Rush as well as MoCap have done it. There are details which I do not know, and they don't talk about, but that's the basic iidea. Of course they are making a huge number er day.

                    If doing batches, one would not have to have the chain-line, just a circular hanging track; bring the next mold assembly over by hand, dip it, move on for drying, and do the next. Then bring them around for the next coat (if any) until all are at the right thickness, and strip the molds.

                    The molds could hang by a two position chain where a lever in the hanging chain lowers the mold into the material when it is flipped down, and is then raised again and latched ed in position to hold the mold up for drying. The level of plastic material needs to be maintained so that the dipping is a constant distance.
                    1601

                    Keep eye on ball.
                    Hashim Khan

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                    • #11
                      One of several videos: https://youtu.be/RoDprCL-1sE

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                      • #12
                        The moulds are simply moved out of a gas oven by hand. They are attached to lengths of angle iron and placed on a frame that is then manually lowered into the tank of plastisol. They are then lifted out of the liquid and manually loaded back into the oven for curing. We cant go as fancy as the first video on gloves.

                        We just need it to be less tiring for the operator.At the moment it is working off a bicycle chain and a counter weight .But it needs some learning curve. We want to make it so that any operator can do it immediately.It really just has to be a frame that can go up and down but stop at a constant depth in the liquid.The garage motor sounds interesting.Would it be able to lift 50kg vertically.?
                        What would work for the posts.?

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                        • #13
                          Don't make it too complex.... it need not be.

                          The molds only need the roughest of vertical guides, if any, to prevent banging the dipped molds against the tank.

                          You could, if you used post guides, just put pieces of pipe the right length over the posts so that the frame only goes down until it hits the pieces of pipe. or a stop on the chain, etc. Lining up the frame with posts sounds fussy and a hassle.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Stay away from the garage door opener as they are carefully designed to last only a defined number of cycles and are programmed to fail at the most inconvenient time!

                            I not sure a bicycle or garage door opener chain would last long with that load but nonetheless I think the chain is a good idea just go up a size or two into the motor cycle range.

                            Chain, sprockets, belt reduction to a reversible electric motor.

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                            • #15
                              Originally posted by plunger View Post
                              .
                              I was thinking if one made a frame out of angle iron and had four posts ,lets say 30mm in diameter that are held by a bronze bush . Or do they make off the shelf linear type bushes.?
                              .
                              There are a few manuf that make lined linear bushing type bearings.
                              https://www.hepcomotion.com/product/...lock-bearings/
                              Also send for the Misumi cat, a wealth of info in there.
                              For a controller you could look at a SmartRelay, they have timers and you could integrate both manual and auto operation.
                              Max.

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