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    Default Help a new guy

    Hi guys,
    I'm looking to CNC machine a part. Could someone provide some tips on how to edit the design to reduce costs and machining time but not compromise its functionality? This is a custom lego part, I wouldn't mind 3d printing, but some walls are thin and CNC machining has tighter tolerances while having options for materials like aluminum. The + shapes are for technic axles, if that shape has to be edited, it still has to fit those axles without allowing them to rotate. For the 4 technic pin holes, the diameter of the holes can't change, but I don't know how the small rings around them will affect machinability. The STL file is available at the following link:
    Dropbox - susparmcustom.stl - Simplify your life

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    STL files are for printing only. If you want anyone to look at your design you need to put up a CAD format. STEP, IGES, Parasolid, etc.

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    That part looks designed for molding or printing. The pin holes are fine. If you want to machine those axle holes you need to have radii in the corners for a small endmill. It's not going to be particularly cheap. Can you tell me more about the "trailer hitch" at the end? What's the application, are you planning on selling these?

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    Some thoughts.

    1. The Technic axle through-holes are killer. With subtractive machining, sharp inside corners need to be cut with a non-rotating tool (like a broach or wire EDM) and that is adding cost. This is the most expensive feature on the part.

    2. Does the end with the cup have to be rounded on the top? 3D profiling is slow, it would be easier to leave the top flat.

    3. What's wrong with 3D printing this part? Do you actually need it to be made out of aluminum? What kind of tolerances are you trying to hold?

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    Bear in mind also, the original lego ball sockets depend on the elastic deformation of the plastic to push the ball into the socket and have it retained there. That won't work in aluminium.

  7. Likes mhajicek, TeachMePlease, Bobw liked this post
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    No problem at all with 3d printing-but maybe a couple walls may be too thin and the ball socket, pin holes, and axle holes may be impossible to print without supports. What would be the cheapest method to produce 5-10 of this part? I'm open to any sort of technique and optimizing the design for that technique. The material can be plastic too. Btw, the tips you guys gave are really helpful and I want to say thank you.

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    Do you really want to have that part machined in aluminium or would you not rather have a mold for that part machined so that you could mold any quantity you want with it.

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    Quote Originally Posted by BoredGuy View Post
    What would be the cheapest method to produce 5-10 of this part?
    Order them resin printed from 3dhubs.com. Choose a tough resin. I recommend only ordering two or thee to start and check your fits. For the axles you might want to make most of the X profile a close slip fit and have some small bumps or ridges to create friction.

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    Quote Originally Posted by BoredGuy View Post
    No problem at all with 3d printing-but maybe a couple walls may be too thin and the ball socket, pin holes, and axle holes may be impossible to print without supports. What would be the cheapest method to produce 5-10 of this part? I'm open to any sort of technique and optimizing the design for that technique. The material can be plastic too. Btw, the tips you guys gave are really helpful and I want to say thank you.

    Check with the guys at Additive Manufacturing | 3D Printing. They've been good to me in the past, and since there's no real setup costs, making 5 won't be much more expensive than making 500. Tell them your intended use and ask them for a suggestion on materials.

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    Sorry guys, gonna have to put this design on hold for a bit. Just started work on another project, moving this one to the back burner.


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