Sizing a lid for a box  

RE: Sizing a lid for a box

An honest answer is that It depends.

On material used, printer used, design, layer height, presicion of extruded material etc.

On most printer, a tolerance of around 0.2-0.3 is a good starting point.

If you have a hole that is 150mm wide and 50mm deep, a print of 149.8mm x 49.8mm is a good starting point. Try a simple model, say 3x3mm frame and make it 0.2 less wide and deep.

It also depends on if you print the box and lid on the same printer, or box on one printer and lid on another.

Each printer may have it's own needed clearence and tolerances. They might even differ between X and Y value between printers.

RE: Sizing a lid for a box

PLA.  150x90mm.  .3mm layer height.  Done on the same printer.

I can do some trial and error but useful to have some idea to start with.  I'll start with 0.2mm and take it from there.

Thanks for your advice

RE: Sizing a lid for a box

You're welcome.

Most printers can do away with 0.2-0.3mm tolerance for parts that interconnect.

There are alot of parameters that play into designing for FDM-printers.

For example a dovetail, you will never get a perfect angle on the inner and outer corners and tips. 

In these circomstances you will need to make a fillet or chamfer to the inner and outer points to allow for the printingpath of the plastic to make the slightly rounded edges fit together.

Example of this is the outside corner of a box. It is now square, but ever so slightly rounded. The same behaivior is on the inside corner.

I think is was Maker's Muse on youtube that has a good starting tutorial for desinging for FDM-printing.

Happy printing. (Oh, and dont mind my spelling, i'm not very good at that 🙂

RE: Sizing a lid for a box

And because of the different tolerances of different printers I would expect that whatever you do will work great for some people, will be too tight for some, and too loose for others. There are many ideas for working around this, including using some sort of clasp mechanism to secure the lid or magnets. 

One of my favorite approaches is to make the clearance a bit larger, say 0.3mm, and use a couple of nubs on each side of the lid. Here's a video that explains the general idea using crush ribs: I keep it simpler by simply extruding a few circular nubs from the lid or the top of the box. 

RE: Sizing a lid for a box

That is a very elegant solution.