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Topic Tag: speed

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Hi there! As we posted in the welcome section, at TallerEsfèrica we built an injection machine. In the gif you can see Aniol perpetually working with it! We are still working on the molds, but so far we've finished the first one, which gives shape to the piece you see in the picture. These are a few things we found out to be important. We are sure some of these have already been mentioned in the forum. MACHINE DESIGN: In our case, our projected parts had cavities and thin walls (not too thin actually, but they aren't solid pieces), so we needed a stronger structure for the machine. We used 40x40 profiles so that the force we could do was bigger. Although we can inject our parts, speed is an important factor at the time of injection (for the final properties of the injection part). With this machine speed isn't as high as it should be, so we've thought of a few ways to add speed to the process. One is to add a pneumatic ram. We haven't tried it yet, as we found that you need a huge piston to get the right psi. Also, the whole point of these machines is to exist in a low scale production zone, and not be compared to normal production machines, so we discarded this option. A second option we thought about was to use springs. Have them in tension when the piston is up, so that when you release them they exert the force you need and fast. We didn't try it for similar reasons as the option of the pneumatic ram. A third option, which would actually not offer than much speed, is to use an hydraulic car jack to press the piston. It would offer a steady force all over the process of injecting (about 2 tonnes for a car jack that costs 16€). There are also the mechanical car jacks that offer similar pressures for similar prices. The main disadvantage of the hydraulic option is the return of the piston, which would need an aid to get back to the initial position. The mechanical jack sounds like an interesting option as it is moved manually both ways. An possibility would be to add a big wheel with weight to add speed to it, but again, we haven't tried these options. INJECTION PROCESS The process we found to give best results is to add the plastic bits once the machine is hot. Then press with the piston to compress these bits before they melt to remove the maximum air possible. Add more bits in case we want to fill up the cavity, press again and leave the piston at the lowest position the bits allow, having them as compressed as possible. If air is left inside, in between the plastic bits, we found problems to inject properly, leaving the mold nearly empty. Once the bits are compressed and melting we block the nozzle so that no plastic escapes, and after a few minutes we inject. TEMPERATURE CONTROLLERS: We are using the Sestos D1S 220v PID controllers. They work fine, but aren't super reliable with temperature control. We had to know the way they worked to adjust temperatures according to how they behave, not what they show on screen. They do the job perfectly for now, though. It helps to use a high temperature thermometer to know the actual temperature the machine is at. Hope this helps! Aniol and Marc from TallerEsfèrica.
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