Material for program tryout
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  1. #1
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    Default Material for program tryout

    We are quoting on some making several different large 1 of a kind parts out of Delrin (5 by 10 by 40" $$$). They have a lot of detail and I would like to machine a tryout piece before we start cutting the Delrin. Is there an inexpensive material that we should consider? I don't want to use any kind of foam as it will contaminate our coolant and make a mess. I've even thought of using wood, but a lot of fine detail I'm not sure would work well, and again don't want to foul my coolant. Any suggestions?

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    I usually use aluminum, but that's a big piece. Maybe some small pieces strategically placed where the detail is that you want to check?

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    I think HDPE is cheaper and machines roughly the same. Grey PVC and Polypropylene are a couple more somewhat similar though a tad softer. Especially the Polypro.

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    Hello RJT,
    I've not seen this product for many years, but also, I've not had to look for it either. It is a Machining Wax that can be melted and cast into any blank size you care to build a wooden mould for.

    The swarf created during machining is collected and melted down for repeated use.

    Regards,

    Bill

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    Is the time spent machining a sample part worth it? Leave stock on whatever features you're concerned about, measure, adjust and cut. If the customer is not paying for it, it sure seems like a waste of time and money.

    I would take the time to tape plastic all over in the machine and just use foam. Wood will make just as much of a mess and is much more abrasive on your tooling. Rig up a shop vac to/near the spindle to collect dust.

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    Different plastics cut and warp differently, so a test part in another material won't help you much. First, see if you can use generic acetal copolymer; it's cheaper, doesn't warp as much, and doesn't have centerline porosity like name brand Delrin. Second, as mentioned above, cut leaving stock and dial it in. First part good.

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    Another one here stressing the warpage issue. All Poly/Co Polys play different and a piece of Delrin that size with a significant amount of material removal will draw into another zip code if you don't keep flipping it and letting it relax.

    Get the skin off of it and cut some small features then flip. Don't whack it down with a dead blow, it needs to be relaxed. Rinse and repeat/keep creeping up on your target sizes and you'll be fine.

    Since you’re doing several parts take note of the grain. Those big blocks are usually cut from a sheet and depending on the saw guy saving material you get some pieces with the grain cut the perpendicular direction. Nothing like getting a process figured out and the saw guy ruins your day.

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    On warping, you can control the warping direction. The ends/edges of the part will bow towards where you remove the most material; the surface is in compression. I just did some acetal lids, and I placed the part in the stock such that when the lids are screwed down the warping keeps the lid from gapping. I conferred with my client before doing so of course.

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    Are you looking to test your code or find out about tolerances, warping, etc?

    If it's just to verify your code, take the money and time you are thinking about spending and invest in software to verify the code.

    If you want to see how the material behaves after machining then the only reliable way will be to use the real material.

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    I used to use MDS filled nylon for testing prior to cutting expensive plastic. It machined very well, and for a while it was very cheap. I have also used laminated MDF (medium density fiberboard). It makes a ridiculous mess both in the machine and on every surface in the shop, but that was our go to for patterns back in the miserable foundry years.


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