In my previous post I listed some of the best practices when creating sketches in Solidworks. I decided to tackle the topic of parts next, because it is the next logical step in the design of, well, anything. Have you ever bought an assembly without parts?
Best practices
Design before you sketch
If you want to create a good design, you have to know what you are going to draw up before you open up SolidWorks. You can’t iteratively design a part without having a clear image of the overall design. If you do start modeling immediately, chances are that you end up with an optimal design of a poor solution. So turn off your monitor, grab a drawing pad and test your first ideas on paper first.
Keep the manufacturing process in mind
After I graduated from university, I started working at a small mechatronics engineering firm. Since I was the only employee with a true background in mechanical design, I was responsible for the 3D and 2D drawings of all the parts that had to be made.
There I quickly learned that I knew very little about how products were actually made. I frequently had conversations with suppliers, with them asking me how something like that could possibly be made, or me asking them why the quoted parts were so damn expensive.
The lesson here is: go learn how your parts are made. Talk to a lot of suppliers about your parts. Or even better: go work at a firm that has a workshop in house. Go learn what tolerances are acceptable in the process that you have in mind, so you won’t pay top dollar for simple parts. I’ve heard stories about simple spacer plates that costed hundreds of euros because the tolerances were insanely strict, because the designer was used to adding those tolerances to each of his parts.
Pick the form of the raw material
Is your parts going to be manufactured mainly on a lathe? Then start your part design with a Revolve. Could your part be made from a thin walled or thick walled tube? That is going to save manufacturing time, so money and weight. The center of a circular part usually doesn’t carry any of the load anyway. Are you going to add a tolerance to a surface to fit a bearing? Consider using a bar with an h7 or h9 tolerance, turns out you can just buy those.
Is your part going to be milled? Start with a rectangular block and virtually mill away the material. Are you planning on laser cutting your part? Make sure you can actually buy the thickness you need.
Use the proper planes
By now you know what you are going to draw and you have a rough idea on the shape and type of raw material. It’s time to draw the first sketch. I’m going to repeat myself here: make sure the planes that you use actually make sense. I’m never going to remember that the front view of the house will show me the roof, so get your act together.
Add XYZ axes
I recently learned about this item from a colleague and I have benefitted from it since. Add three axes to your part template and assembly template and label them X-axis, Y-axis and Z-axis. Now you will have these axes ready in every part that you will design from now on. This means you will no longer have to use part edges for linear pattern, edges that will cause you trouble when they get modified or deleted. This means far fewer broken patterns, which in turn means more happy engineers.
Use the mid plane feature
When you create an Extruded Boss/Base or an Extruded Cut, don’t blindly use the standard Blind option. Consider extruding it in both directions equally by selecting the Mid Plane option. This will make adding mates later on so much easier.
Use the Hole Wizard
I hope you were doing this already. Or maybe you are the guy that creates all of his threaded holes and slots by hand, and then later complain about how much work it is to add fasteners and mates.
The Hole Wizard can save you a lot of time. It allows you to create simple or stepped holes, threaded holes and since 2014 even slots. You can use the Hole Callout feature in drawings to label the holes/slots in a single dimension.
If you create the holes or slots with the wizard, you can use them later on to pattern other parts. This assembly feature is now called Pattern Driven Component Pattern. It used to be called Feature Drive Pattern but can still be found under the Linear Component Pattern button. A video tutorial on this feature can be found here.
Make your parts smart
Chances are you are going to mess around with the design of your part quite a bit and chances are features will break in the process. You can keep this to a minimum by selectively using references and equations. Do you want some holes to remain at a fixed distance from the edge? Then add dimensions that specify just that. Do you want a line to end at another line but SolidWorks adds a midpoint relation? Replace it with a coincident relation immediately now that the sketch still works.
Start again if case of a major change
If you’re making major changes to the design of your part, you might as well start over by deleting all of the features and sketches. Yes you will mess up your assembly slightly, but repairing assemblies has never been easier than in the latest SolidWorks versions. Whatever you do, avoid the worst practice of cutting away everything using an Extrude Cut.
Final words
Here it is, my first set of tips or best practices on parts according to me, myself and I (remember Jive Jones? It’s as bad as I thought it was). Do you have any advice on what to do or what not to do? Please let me know and I’ll edit them into this post or in a future second part.