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Thread: Ultem and CF Peek in an aluminum mold

  1. #1
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    Ultem and CF Peek in an aluminum mold

    Hey guys -

    New to the forum, molding for a decent amount of time...

    Recently took a new position at a mainly CNC shop that purchased two brand new JSW 180 ton machines and all supporting equipment. Their general idea was to near net mold and save time and waste material.

    Seemed reasonable... They have an initial aluminum mold, two cavities, "L" shaped parts. Dimensions of each part are 3.75 x 2.0 x .625

    They wanted me to sample a wide range of material from ABS, to GF Nylon, various Ultem grades and today, they gave me PEEK 450G and GF PEEK.

    They have oil to get the mold temp up, but it's an aluminum base... Am I crazy, or is this a waste of time and going to turn out poorly?

    Any input is appreciated.

  2. #2
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    Re: Ultem and CF Peek in an aluminum mold

    I’ve found it easiest to place heaters in the mold base and use a mold heat controller to get the mold hot enough. Place rod heaters with thermocouples in the mold to get it hit enough. Also add an insulating board to get it to heat faster and not have to heat plattens.
    Make sure the ejector (pins) were ran in steel sleeves. This will stop mold base wear and extended repair times. If the sleeve galls up just replace them both. Make sure gate areas are hard inserts to improve replacement timing of worn parts. Also you may need place a hard insert opposite the gate for wear too. The mold can be DLC coated to slow wear of the base material.
    rick.

  3. #3
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    Re: Ultem and CF Peek in an aluminum mold

    After giving them feedback, they're in full understanding of what to expect with this mold and are completely happy to replace with a steel version if we can mold the parts.

    Thanks for the insight Rick.

  4. #4
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    Re: Ultem and CF Peek in an aluminum mold

    Rick:

    Have you been happy with the DLC you've used? Also which plater(s) have you used for this?

  5. #5
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    Re: Ultem and CF Peek in an aluminum mold

    Nikom,
    We have looked at it for SEVERAL molds. But to convince a company to try something new is ALWAYS a stretch. There’s a place in NC reasonably close to us that we want to use. Our thoughts were to do lifters and like ejector pins with slots for ribs cut in them. They used to be Sulzer but I think the parent company made a push to adopt their name.
    They brought in plated guide pins and round bushings for a mold. Ridiculous how slick they are w/o lube on them. I’ve seen molds Dynablued for glass wear resistance but hard to repair some damage. With DLC I think they can remove, repair and plate again.
    Rick

  6. #6
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    Re: Ultem and CF Peek in an aluminum mold

    My biggest sturggle has been making the parts without voids in the middle... I'm tried everything. The mold is 350 degrees, the material is at 735 degrees. Slow speed, high speed, low BP - high BP, High pressure, low pressure, short cool times, extended cool times....

    I'm near the point of just saying that I don't think we can mold a part that's as thick as this is without the voids...

    Any last suggestions?

    Currently the part is filling through a runner in the middle of the "L" shape... I'm contemplating having dual fill spots? Near the top and bottom? Or will that do nothing?

  7. #7
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    Re: Ultem and CF Peek in an aluminum mold

    What is the thickness of the part? What size and shape are the gates and runners/sprue?

    Click image for larger version. 

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    I'm hoping that only one of the 0.625 dimensions in this sketch is correct and your part has a much thinner wall.

  8. #8
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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 just low enough to not blow the mold open. But as Nikom says, I wouldn’t have much hope of making a good part with a .625” wall section.

    As for Ultem, if you’re going to machine the parts so appearance isn’t an issue: if you run the melt and mold very hot so the part cools very slowly, you just might be able to trade voids for sink.

  9. #9
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    Re: Ultem and CF Peek in an aluminum mold

    Unfortunately that is the exact shape and size of the part, only that there are two cavities in the mold. One facing up, the other upside down. Nearly in the shape of a square.

    As for the runner and sprue - sprue starts at .275 and opens / tapers to the runner at .400

    The runner is circular - undersized at .370 (I say undersized because typical runners are 75% of the part wall thickness - usually)

  10. #10
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    Re: Ultem and CF Peek in an aluminum mold

    Thanks Jay, yeah these are very thick parts. It makes sense why no company would give them a bid for doing it. Good for me, I have a great job. Bad for me, mission impossible. I'm going to try to add more heat to the mold and open the runner to the normal call out of 75% and spure gate the cavities. Hopefully that helps.

    Thanks for the insight all. Will post if I'm successful in my efforts.

  11. #11
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    Re: Ultem and CF Peek in an aluminum mold

    How are you heating the tool? Can you get it hotter? Perhaps the runner is freezing too soon hence the sinks or voids. Can you injection compression the parts? Maybe that would work.
    Rick

  12. #12
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    Re: Ultem and CF Peek in an aluminum mold

    I would try to buy some material bar stock and place it in the center of the cavity and over mold it this would help you cycle time also as it does reheat the the plastic to bond and does help to cool the part from the inside . Just try to find the same grade of resin to ensure there is no delamination . I would try place a .250 bar of plastics inside the cavity on spring loaded pins . Other wise I agree injection compression or a delayed core pin to keep the cavity pressure up during cool

    Also if you balance the tonnage and injection pressure close to the point of flashing you will see the mold blow open and the as shrink occurs it will close again If you were to try this I would take a drop indicator between plattens and watch for it to move .002 -.003 during pack and hold and it should if you did not flash the tool go back down during cool . It might work but obviously this is not very robust
    Last edited by cheeseyone1; 22nd August 2019 at 10:51 AM. Reason: more

  13. #13
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    Re: Ultem and CF Peek in an aluminum mold

    Rick:

    Currently heating with oil at 400 degrees... Could potentially go hotter, but it's an aluminum mold... I'm wondering if we tried filling from multiple positions if it would help? There's very little sink, and the parts look really nice on the outside. But when we CNC the top half off, there's always a couple of small voids. The issue is that these are near-net parts. The idea behind this was to prevent having the buy blocks of PEEK and waste 80% of it. However, if there are voids, then the parts we run are waste in the same sense that they cannot use them.

  14. #14
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    Re: Ultem and CF Peek in an aluminum mold

    How about making gate a fan style so you can get enough area to stay open during the entire pack/hold phase? Have you ran a gate freeze to see how long it stays open? Are you gated into the thickest area of the part? Maybe you’re not using enough pack/hold time. Run more time ev n if you must run low pressure and remove time from cooling portion of cycle.
    Next then I’d try multiple gates but you’ll have knit lines that may be bad.
    Rick

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