using casting resin to make milling fixture

j ferguson

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I'm building R/C planes using a 3d printer and *.STL files published by an outfit in Czechia. The models are quite good but the one which I just built cries out for retractable landing gear which, alas, is not an option. The STL files are too complex to easily modify so my plan is to mill out a box volume in the bottom of the wing center section, 3d print the hard points and the box to receive the gear when it is retracted and glue said box into the space I've cut out of the wing. My assumption is that with ample use of CA glue, the result will be strong enough to support the plane on the gear and the structure of the wing will not be compromised. Besides, this is an oportunity to learn something the old fashioned hard way, by trying it.
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The problem is making a fixture to hold onto the center section of the wing while the cutout is being milled. The wing is quite delicate. At first I thought I'd convert the STL file to a solid and subract it from a rectangular block to get a cavity which would fit the top of the wing. This turns out not to be the simple thing I thought it would be.
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What I'm planning now is to make a rectangular dam on an aluminum plate which will hold casting resin and be deep enough to accept the center section of the wing wrapped in saran wrap which I will push down into the resin far enough (and hold down) to make a good cavity which will later support this section while I mill the box volume out of it.
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I'm expecting the milling will be done with very light cuts and that I will hold the wing section in the cavity with custom clamps - likely wood cut to fit.
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If the above isn't clear, let me know and I'll try again.
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If it is clear, can anyone see anythilng nuts here, or better yet offer suggestions of aspects I may not have thought of?
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I'd also be grateful to learn if I should have posted this in some other place.

john ferguson
 
John can you tell us what the 3d printer feed material is. I have done some modifications to things made out of polymers and have used solvent bonding were appropriate.

The other reason for knowing what material you are using is to determine what the cutting loads will be.

Having said this I think what you are suggesting for a fixture would work ok. Do you have a picture so we can see the shape and size?

David
 
David, material is PLA is polylactic acid. stuff glues wonderfully well with CA. I still need to find a subsstitute picture hosting site to replace PhotoBouquet. so unless i can post photos directly here....
 
David, material is PLA is polylactic acid. stuff glues wonderfully well with CA. I still need to find a subsstitute picture hosting site to replace PhotoBouquet. so unless i can post photos directly here....
Try imgur and yes you can attach files (images) directly here. Just hit attach files
 
What I'm planning now is to make a rectangular dam on an aluminum plate which will hold casting resin and be deep enough to accept the center section of the wing wrapped in saran wrap which I will push down into the resin far enough (and hold down) to make a good cavity which will later support this section while I mill the box volume out of it.
Don't know much about 3D printing , but I have plaster of paris for similar projects.
 
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