Looking for feedback on my first 3D printed Model

jonathan_drury

Hi Forum members, 

I recently completed my first modeling of two broken toy parts.    I was able to sketch/extrude/shell and remove areas to get the shape I wanted and I was able to print it successfully. 

However, I felt like it was a little clunky.   If anyone can take a few minutes to look at the approach I took and give feedback to improve my features, please do. 

https://cad.onshape.com/documents/50662148e63537e5c5201345/w/f20f58bb7ecf9a2cefc019e2/e/b762347149fdb7efd3e8fe32?renderMode=0&uiState=6691dba76331925a54d7dc01

Thanks,
JOTS

jonathan_drury

I was hoping someone would view the model and comment.... did I share it correctly?

nick_papageorge073

I looked at it last night. It’s not bad for a first attempt. I’ll send some details later. 

robert_scott_jr_

Clunky? Is it intended to be aesthetically pleasing and be utile? If looks aren't the first priority, I'd say it looks good and you made it friendly to handle. What is it? How did it perform as intended? - Scotty

nick_papageorge073

Geometry feedback:




The rounds are too big. Should not come to a sharp edge. Make them about half as big.






Rounds can't be mitered like this with most manufacturing processes. They can with 3D printers, but if you are trying to simulate a mass produced product, it most likely would not be like this. Instead, put a round on all of the vertical edges first. Then put a round on the top horizontal edge. It will wrap around the entire perimeter because the vertical rounds will make all the horizontal edges tangent.




Small steps don't look like they serve any purpose.




Tiny gaps are no good for injection molding. Will work for 3d printing, but still kind of suspect. Better to connect them with ribs.




The bosses and the perimeter touch simultaneously. It's a good idea to force the perimeter to touch first, this way there are no gaps due to manufacturing tolerances. The way to do this is to put a small gap where the bosses touch, about .5mm. When the screw pulls the bosses tight to bottom out, it will flex the plastic slightly, forcing the perimeter to bottom out.





There is nothing to align the top and bottom except for the screw. It's best to add a half lap joint around the perimeter. (its also often added to the screw bosses). Besides providing alignment, it adds a reveal to visually hide mismatches on the top and bottom. Look at any plastic clamshell item in your house and they will all have this.




Half-lap example. Note .5mm reveal, .1mm clearance gap, and 5 deg draft lead-in to aid assembly. The clearance gap is what you can play with after printing the first one to get the fit just right.

nick_papageorge073

https://cad.onshape.com/documents/507b8eb97bcf3256bb753ea8/v/808e7c17f6e36d408096ba54/e/85918a59950a0feb5b90ad65

Here is a clamshell design with the half-lap from the above screenshot. Take a look at how I made it. There are many cad methods to make a half-lap. I've found this one is easy, quick, and reliable.

Also before getting to the half-lap, check out how I build the basic top and bottom of the clamshell. It can give you some ideas for your next project.

nick_papageorge073

CAD feedback:

The model is drawn logically on the default planes. The hole (main feature) is on the front plane, and the top/bottom separation is on the top plane. This is great.

The variables for all of the features are unnecessary. If you are planning on making multiple sizes of this box as a configuration, then the variables make sense (some of them, not all). But if not, it's just a waste of time. Also I'm not sure why you have shell thickness twice.

For making the main shape, see my clamshell document linked in the post above. Your model has the top and bottom built separately. See my model, they were built together, and then split. Slightly quicker and less features this way.

Generally for plastic parts for mass production, the wall thickness must be constant throughout. It doesn't matter for 3D printing, but it will make your design more professional. To aid this, I like putting the major rounds on before doing the shell. This will ensure the wall thickness is maintained throughout the corners.

The top sketch is not fully constrained, and it has a very short line segment on its upper left corner. I don't think that is intentional. You are also dimensioning to that line segment instead of the main line.

Nice job overall considering this was your first model.