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  1. Re: Chiller water is getting dirty and brownish color

    We also use glycol in our tower water. It solves some water quality problems, but keep in mind it can also be detrimental to heat transfer in the mold.
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    Re: Boy 50T2 no SEMI-AUTO or AUTO

    Screw position is defined by shot size set point plus decompression. If the screw is not at or beyond this position (the stroke is 'made'), then the press will not operate on auto/semi-auto.

    Also,...
  3. Thread: Nanotubes

    by JayDub
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    617

    Re: Nanotubes

    You start by mentioning IM, but then say the part is 3D printed. Is printing the permanent method of manufacture or just prototyping with the intention of molding later? Printing will limit your...
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    Re: Compressed air for cleaning?

    I would think vacuum is better than air anyway. If you suck up the fines/contamination it ends up stuck on a filter somewhere. If you blow it off, then it's back floating around in the air where it...
  5. Re: Three resin lots required for part qualification

    I work for a medical molder (regulated facility) and we write our PQ protocols to use multiple material lots "if available". The idea of PQ is to model long term behavior of the process and prove...
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    Re: Injection Molding Process Sheets

    We use machine-specific templates that we use to make job-specific set up sheets. Both the templates and set-up sheets are controlled documents, stored electronically in the doc control system. We...
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    Re: Overmold Possibility

    I like the idea of using plastic blocks to locate the part, but here are a couple of other issues to consider:

    The overmolded plastic shrinks, but the metal doesn't. You have thicker sections of...
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    Re: Liquid color issue

    You may not be able to get good mixing from the GP screw. If you read the Celcon processing guide (which I highly recommend you do), what you ideally need is a barrier screw with a high (3 – 3.5)...
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    Re: Soft TPU sticking in sprue bushing

    Have you done a gate-freeze study to be sure you aren't over-packing the sprue & runners? For small urethane parts we use very short (typically 2 -4 seconds) pack times and the sprues generally have...
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    Re: Melt Pressure before Transfer

    My work computer won’t let me open your links, so I’m just going off what you wrote.

    “We are seeing slight waviness at the open end of our tubes” – parts with a high ratio of flow length to wall...
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    Re: Ultem and CF Peek in an aluminum mold

    I used to mold a PEEK plaque that was around 2.5” x 2.5” x .375”. Mold temp 400 F and – most importantly – the cavity was sprue gated. Cooling time was very long – 60 or 90 seconds. Hold pressure...
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    Re: Recovery Issues at Start-Up

    Can you tell whether the material is getting to the screw or hanging up in the throat? If the latter it could be coming out of the drier too hot and soft and bridging. You could try drying at a lower...
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    Re: Proper Short Shot - What do you think

    All I would add to the above advice is to weigh the parts to see if fill speed has any effect on cavity balance. I'd be looking at within-shot (cavity to cavity) weight consistency, shot to shot...
  14. Thread: Flow Lines?

    by JayDub
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    1,306

    Re: Flow Lines?

    The images are too small for my old eyes to make out much detail, but the defect doesn’t look like what I would call a flow line, it seems to be more related to gate blush.

    Can you give us more...
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    Re: Nissei Press Training

    Some manufacturers offer free on-site training as part of the sale. Even if Nissei doesn’t normally do it, you might be able to negotiate it in the purchase contract.

    I haven’t worked on a Nissei...
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    Re: Changing holding pressure

    What controller do you have? Our Boy machines have the Procan controller, which is reasonably intuitive. Can you take a couple of pictures to give us an idea of what you are working with?

    I think...
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    Re: Shot Size Procedure

    Interesting procedure, but why? Myself, I pick up the phone and ask the mold designer to pull the sprue/runner/cavity volume off the CAD model for a pretty good estimate of shot volume.
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    Re: Cushion Changes with Pack Time

    As I understand it, the established process used to produce good parts, but now leads to under-packing. Additional packing gives good parts but inconsistent cushion.

    It might be worth checking...
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    Re: Cushion Changes with Pack Time

    Taken literally, your supervisor is correct – the whole point of a hot runner system is that the material between the nozzle tip and the part – including the gate – doesn’t freeze at all. If you...
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    Re: Silver Fibers show Up when Parts are Rubbed!

    If you look at the process graph, is there a sharp pressure drop at transfer? Just wondering if the flow front is hesitating & causing delamination.
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    Re: Over-molding Aluminium with PEEK

    One more thought - make sure the mold has half-inch thick insulator boards. If you don't insulate the mold, you'll spend the profit margin of the job on heating the machine platens.
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    Re: Over-molding Aluminium with PEEK

    PEEK runs hot but it will run on standard equipment, & you can get processing conditions from the manufacturer. The only difference may be that you need to have the mold at least around 375 or 400 F,...
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    Re: Injection volume calculation

    This is not injection molding - this is casting.
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    Re: Injection volume calculation

    Your calculation is correct. However, note that 80 g of material is a lot to melt just by external heat within any reasonable cycle time. Most bench top machines have cylinder diameters around half...
  25. Re: Can I do injection molding of a plastic mixed with a powered grit?

    There is a huge range of commercially available carbon filled plastics – people mold them on standard equipment all the time. I am a bit confused by your reference to carbon powder as “powdered grit”...
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