Quote:
Originally Posted by Bart
What I need is a new cable retainer for a QHY9.
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General principles for creating a 3D model file for a custom part:
If it's based on an existing design, take accurate measurements of the original part (digital calipers are invaluable for this!), and create a sketch. Make a note of which dimensions are critical (e.g. has to be an exact fit to or inside another part), and which are non-critical (it wouldn't matter if the dimension increased or decreased by a few mm).
Think if there's a "better way" of ensuring good functionality and fit up - e.g. if the part has to be screw-fixed to another part, rather than trying to place precision holes at exact locations, could we use slightly oversized holes, and use screws and washers to join the parts? If the original injection-moulded part uses some sort of snap-fit, can we achieve the same precision of fit with a 3D-printed part? Mechanical hinges can often be replaced with a one-piece 3D-print with a hinge incorporated into the design.
Think about the limitations of the manufacturing technology - e.g. 3D printed parts shrink a bit after printing; you may want to print it slightly over-size if it has to fit over another part, or slightly under-size if it has to fit inside another part. "Precision fits" are often best achieved by printing with a bit of over-size "wastage", and then grinding or sanding down to fit after the print is finished. Overhangs can be difficult to print cleanly; very thin walls can be a problem; parts can be printed truly hollow, or with a honeycomb core of variable "density", or truly solid (rarely needed); etc. Modify the design if necessary to optimise the print.
I create my model files using a proper professional MCAD package, but amateurs without 3D CAD skills may be limited in what they can create using low-cost or free tools such as TinkerCAD or Sketch-Up. With professional MCAD, you can create very complex shapes, with variable fillets and blends, etc, but with basic tools, you may be limited to using simpler graphical "primitives" such as cubes, cylinders, wedges, etc.
Do a quick trial print to see how accurately the part prints, whether it can be improved for printability and / or functionality, and whether it is robust enough to survive the intended duty.
Modify the design if necessary, and run a slower, higher-precision print.
) - about $10 - $12 for most typical parts if the 3D file is provided or easy enough to generate, maybe a bit more if I need to spend a bit of time to create the CAD model.
