How to design separate parts

kenneth_croft

I learned the basics of Onshape 3 or 4 years ago and because I have not used it since, I have been going through the learning lessons again. I am happy with my progress but I am stuck on something very basic. I have gone as far as I want to go as a hobby model engineer, but I am stuck. I have drawings of one of my model aircraft engines and I am trying to model it in Onshape. I have completed the crankcase [see picture] and then I designed the crankshaft.

Now because both items were based on the origin, one part is in effect on top of the other. So when I created a flat on the crankshaft , because I extruded “through all”, it punched a hole right through the crankcase. So the question after this long explanation, is how do I design individual separate parts, which will be later use in an assembly, so features of one part do not impact other parts? I realise that I can hide the part I am not working on, but that seems not to be good enough. The public document is called "Megow19 crankcase".

Oliver_Couch

Either use separate part studios, or check the merge scope of your extrude feature is set to only affect the part(s) you want it to.

nick_papageorge_dayjob

I could not find your document in the public space. Please include a link.

Anway, the root problem is the way you located the two parts. When drawing multiple parts in one part studio that will be used inside of one subasm, they should be drawn in the locations they will be at in real life. Not on top of each other on the origin.

And check the merge scope as Oliver mentioned.

joshtargo

That studio only shows one part. Perhaps when you made the second one, you had it ADD to the original instead of made as NEW.

MDesign

Found it.https://cad.onshape.com/documents/088d56cd8b2e6e0639c3b9f5/w/60619b2d3b6ab412dfff8595/e/27b478082b8c2a2c78b2ffee

glen_dewsbury

My personal preference would be to build all parts for this project in one part studio. This won't always be the case. As the number of parts increase some separation into more than one part studio to manage the details. That's up to you when it will be necessary.

Just have to pay attention to what's new and what's added/subtracted to parts and what the merge scope is for part features.

rick_randall

@kenneth_croft - I got to agree with all of the above advice, in particular the red circled areas in @justin_martin524 post. The UI box has a lot of details in it, pay close attention and make sure you tick all the right info - otherwise you get bad output. Also you can't go wrong, going over the training lessons (in the learning center) over and over - it's surprising how many things that make sense 2nd or 3rd time through, that didn't the 1st time. My advice is to look at multi-part, part studios again, lots of good stuff in there.

nick_papageorge_dayjob

One other comment, if you are designing this engine from scratch, then 100% make the major engine parts in one part studio. For example, you could start with the cylinder bore diameter, and then make the piston fit it with a set clearance. Then if you decide to make the bore diameter larger, the piston diameter would automatically increase. This is called "top down modeling ".This is super powerful during the design phase.

However, if these parts are already designed and you have a dimensioned drawing of them from a hobby kit or book, I would not bother with that. If you are simply duplicating in CAD what already has been designed, I would model each part in its own separate part studio. This is called "bottom up modelling". It will make each part studio much simpler and more focused.

Afterwards, in either case, you would combine all the parts in an assembly.

joshtargo

You should get some insight and inspiration from this: https://www.youtube.com/watch?v=T-VRYm3kMDA