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Have I understood the document / part hierarchy correctly?
wobblycogs
Member Posts: 2 ✭
I'm about to start drawing up a CNC machine I've been planning for a very long time. I designed it originally (many years ago) in SolidWorks but I no longer have access to that software so I'm redrawing it in OnShape. I would like to check I'm approaching this in the correct way.
As I understand it a Document is essentially a complete project so I've created a document for my CNC design. Inside that I was planning on having a PratStudio for each of the three axes but it just occurred to me that things like stepper motors should probably live in their own PartStudio and then be pulled into an assembly. Looking at the x-axis, the frame there will be a total of maybe 20 unique parts so I don't think that will overload a PartStudio (I hope). I will be using extruded aluminium profile for the frame, would you include this in the PartStudio or make it it's own PartStudio? Thanks
Answers
How to split up the parts into studios can be subjective. Start playing around with the larger items first, and you may get a sense of what you want to include in the same studio. Also make sure you understand modeling in Context, and how a Master Sketch, top down design would work.
I personally like to do projects like this by a couple of heuristics.
Shared components (motors, lead screws, sensors) can live in their own documents because they're reusable; just make a version and reference them at that version from your main doc. People often make entire designs in a single Part Studio because that makes referencing things easy, at the cost of simplicity and organization - to avoid this, I make an automatically inserted Variable Studio where I keep project-wide constants. That way, you can drive common dimensions globally without having to overcrowd your Part Studios (it's easier all around to keep feature trees lightweight).
Your thinking is pretty good. A CNC made of extruded aluminum probably won't overload a single part studio. Lots of simple, square, parts. Nothing organic with a ton of features.
You'll have a lot of imported items, such as ballscrews/nuts, linear ways, linear trucks, servo motor, possibly spindle, etc. Each imported item gets its own part studio. (that's an OS thing, you can't change that). You def don't want to draw those parts. Import them, and then insert them into the assembly.
You can put everything into one document, especially to start. Or, if you were sharing the imported parts across multiple CNC designs, it would make sense to do what Anton mentioned above and put the imported parts into their own document(s).
You might want to make a draft CNC, all in one part studio to start. Just simple square shapes representing your extrusions, and blocks representing the spindle, etc. Just to get your machine size, travel, and xyz envelope good. Then, when satisfied draw it for real with all the details.
Also do the training module on Frames. It will save you a ton of time on an extruded t-slot machine.
I assume you are making a gantry type router, since you are using extruded alum t-slot? If so, that could be broken down into one part studio each for the frame, the gantry, and the Z. Each would also get a subasembly. Then the top level assembly would put all the sub-asm's together.
You want the assembly motion to work properly, so you can adjust your travels, make sure the ball screw and linear rail lengths are good, etc.