Resin Casting Pickup Covers etc. - Have You Tried It?

Discussion in 'Tele Home Depot' started by Deed_Poll, Aug 20, 2019.

  1. Deed_Poll

    Deed_Poll Tele-Meister

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    I designed a rounded-edge pickup cover to take a standard humbucker, but more in the style of a dogear P90 mount for a guitar design I'm working on.

    My original plan was to have the covers 3D-printed in black, and to buff out the layers to a gloss. But that's really not happening. The plastic is too tough, and not black enough. Besides it's an expensive and time-consuming way to go, even if it had been as easy as I originally thought.

    This is the aborted 3D printing experiment. It's really not working for me!

    [​IMG]

    Here's a picture to show the HB sized covers in context. You can see what I'm going for aesthetically, sort of an SG Jr dog-ear look, or like an early cherry ES-330, but in a kind of lozenge-shape. They have to be deep black and shiny, or they will stick out against the pickguard like a sore thumb.

    [​IMG]

    I figured if I can make a decent reusable mold, maybe I can get the finish I want with a black gloss resin. But most of the tutorials I've found on YouTube for using this technique, they are replicating existing objects, besides they are not thin-walled shells but big solid chunky things.

    I'm guessing this will require an inner and an outer mold, the outer will have to be something like highly polished aluminium and the inner is less important. But I'm really lost on this stuff.

    I'd love to hear from you if you have any experience resin casting / molding pickup covers, knobs or any other bits and tell me what worked or didn't work for you!

    Cheers
     
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  2. scelestus

    scelestus Tele-Meister

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    I don't have any advice but wanted to say I love the look of those. I was going to ask in your other thread yesterday but didn't want to derail (here I go!).
     
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  3. Freeman Keller

    Freeman Keller Tele-Afflicted

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    Mike Doolin did an article about it in American Lutherie some time back. I could hunt it up for you or you could go to his website and ask.
     
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  4. draggindakota

    draggindakota Tele-Meister

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    This might not be feasible for a production run, but what about CNCing the covers from ebony (or some other wood and ebonizing it) and then polishing? I think that would look great with the vibe you've got going on that guitar.
     
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  5. dkmw

    dkmw Friend of Leo's

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    I’ve been around around a lot of mold-made parts, but none that small or thin. IME you’d need some fiber in there with the resin, so it’s an FRP (fiber reinforced plastic).

    Pure resin is not going to be very strong. If it has some thickness it’ll be stronger than thin obviously. Most small parts that don’t use a separate fiber in the layup are injection-molded, which is a little beyond diy for most people. Polycarbonate or ABS would be likely materials for a tough part. Infusion or resin transfer molding are other possibilities.

    A hand layup with a veil mat for fiber, and a lot of trimming and assorted finish work - that could work though! If it were me, I’d make the part close enough for finish, then paint the outer surface gloss black. I’d consider that a short cut rather than trying to get a perfect surface out of mold, and/or polishing straight plastic part.
     
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  6. Freekmagnet

    Freekmagnet Tele-Meister

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    Casting a thin plastic cover might be tough, unless you’re doing injection molding. I don’t know weather or not injection molding has reached the “doable for DIY” level yet.

    I’ve seen guys on the pickup makers forum getting good results for stuff like this using vacuum forming. You might want to go over there and check it out. There’s tons of guys doing their own P90 covers and stuff.

    Personally, I’ve only really done resin casting with the entire pickup dunked into a block of epoxy. I’ve had great results, but resin casting isn’t for everyone.
     
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  7. Deed_Poll

    Deed_Poll Tele-Meister

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    Thanks for the ideas, guys! Definitely some food for thought.

    Scleestus, thanks for the kind words! Very much appreciated :)

    Freeman Keller, thanks for the lead. I did a little digging and found an article about casting pickup rings out of resin? That could be useful bit it's behind a paywall I think. But I might return to that if I get stuck elsewhere. Researching Doolin's instruments was very interesting in itself though! He obviously knows what he's doing :

    Draggindakota, yes the thought had crossed my mind. Ebony would be really nice and fairly do-able, I could do a facing of ebony on another wood and that would be nice just to see another timber around the edges. but sitting next to a black pickguard I can't help but feel the ebony would lose some impact. Maybe this is the way to go, but it's got me thinking that perhaps what I want is to bond a piece of ABS to a wooden core or something, and machine that away? So the top 1/4" or something is milled black plastic and the back is mahogany or something as it disappears into the route? Might actually be a nice little detail. But then we're back to the question of how easily I could polish up a piece of tough plastic, and I'd probably have to make the walls a good bit thicker for it not to break.

    DKMW, you obviously have a lot more experience than me with these things, thanks for chipping in! I hadn't really considered the strength difference between an injection moulded part and a resin cast part, though it makes intuitive sense. I guess if you have a rock solid injection molding solution under high temperature and pressure, then you can use stronger and more suitable plastics. Whereas under standard pressure, you're limited to softer materials to cure chrmically at room temperature and atmospheric pressure, if I understand correctly. Your idea of putting some strengthening mesh in there might be do-able on the face, but it's opened up a can of worms as regards the wall thickness.

    Cheers Freekmagnet, that sounds interesting - so you are basically setting the whole coil in a block of epoxy? As if you are wax-potting it almost? Something like that would be really interesting if I was winding my own pickups, but one of the reasons for doing it this way was for the pickups to still be interchangeable with other humbuckers.

    The way I plan to mount them is kind of like a P90. I will bore out the threads on the humbucker legs, stick a P90 mounting screw through the top cover and then through the pickup leg, and have a spring on the bottom to hold it all up and together when the screw is threaded into the wood. So the cover is sandwiched between the pickup and the screw head.

    Thanks all for your ideas, I did find a company here that does something called vacuum casting which seems like it might be suitable?

    https://www.renishaw.com/en/our-vacuum-casting-technology--15268

    It looks like they make a 3D printed part, but then they put some work in to smooth it and polish it off to be perfect. Then they follow a more traditional copycat casting process. It might be worth investigating for a quote, I can send them a .STL model so that's convenient.

    Cheers!
     
  8. Freekmagnet

    Freekmagnet Tele-Meister

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    I have a current thread that’s basically a general build thread. It covers some aspects of my pickup making process.

    More Fun with the Modelo Uno: Forward and Lateral Motion

    I have an older thread that covers virtually all of the painfully gory details.

    https://www.tdpri.com/threads/build-3-thread-1-my-new-thinline-bass-guitar.713982/
     
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  9. 10orgtr

    10orgtr Tele-Meister

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    Use urethane resin and silicone rtv for the molds. The resin can be dyed black. Check out Smooth On's website for their products. Yes you will need a two part mold. I've cast model airplane parts as thin as 1/16" wall thickness (fuselage halves) with no problems.
    Cheers,
    Woody
     
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  10. Deed_Poll

    Deed_Poll Tele-Meister

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    That's awesome! Cheers, Woody. Just to clarify a couple of things -

    So the molds are silicon, correct? So I should make a master copy of the part as smooth and shiny as possible on the CNC out of aluminium or something and then take silicon molds from that as and when I need them? I guess I won't need a draft angle with silicon molds?

    Thanks!

    Dan
     
  11. pixeljammer

    pixeljammer Tele-Meister Ad Free Member

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    Could you not just enamel/paint the covers with enough high-gloss coats to get the shine you want? Or just pour black nail polish over them?
     
  12. Engraver-60

    Engraver-60 Friend of Leo's

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    Contact https://www.protolabs.com/services/injection-molding. They do prototype molds and parts, but cost may be prohibitive. They might do it for a calendar piece. They have done large pieces for the company I work for, and their quality is excellent. Also look through Preeb's threads. He did parts from existing pickup rings for his LP thread.
     
  13. slick4772

    slick4772 Tele-Meister

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    Thanks for the info. I’m looking for something similar - Fender Performer pickup covers.
     
  14. 10orgtr

    10orgtr Tele-Meister

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    Deed_poll, yes the molds are silicone, no draft angle needed. However make sure the interior is not undercut. Any imperfection in the master will show up on the finished product, this can include finger prints. Silicone molds can be used repeatedly until such time as the surface of the mold starts to erode from use. Make sure you use plenty of mold release when you pour the second half of the mold to prevent the liquid silicone from welding itself to the previously hardened first piece.
    Cheers,
    Woody
     
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