Table of Contents
Design for Manufacturability
It is very important to consider how a part will be machined when designing it, even if you will be sending it out to be manufactured by somebody else. The design of a part has a direct influence on what machine tools and tooling is used to manufacture it. Poorly designed parts can be expensive to produce or sometimes impossible.
Mill
- Design the part to be machined in the fewest number of clampings possible
- Radii should usually be greater than 1/8". A 1/8" end mill is a common small end mill size
- Features requiring an end mill longer than 4 times it's diameter are usually difficult to machine
- Fillet internal corners
- A boring bar can be used on the student shop manual mills to bore large diameter holes
- External radii are usually difficult to machine accurately on a manual mill but you can alway use a file to add cosmetic fillets
- Steel is more difficult to machine than aluminum
- Tight tolerances will likely increase cost and manufacturing time
Lathe
- A wide variety of threads can be machined onto external diameters fairly easily. Even in the student shop
- Deep bores can be difficult to make because of tool deflection
Water Jet / Laser Cutter
- Very quick and inexpensive way to make parts with simple 2D geometry
- Holes with important diameters should be undersized and drilled to size on the drill press
- For tapped holes can be tapped after cutting
- There is usually some draft on the cut edges
- The surface finish of the cut edges is usually quite rough with water jet parts but can be easily cleaned up with files
- Water jet pats usually need to be submerged during cutting
- Flexure mechanism can easily be cut on a water jet
3D Printing
- The most practical application for 3D printing is to prototype injection moulded parts
- MS doesn't do any injection moulding but 3D printing can still be of use to us where a plastics might be used on a real car or where complex geometry is required but strength is not important
- Try not to design with geometry that can only be manufactured using 3D printing (bad practice)
- FDM 3D prints have orthotropic tensile strength
- You can use heat set inserts or helicoils to put tapped holes into plastic parts
Welding
- Welds should be easily accessible: welding out of position is difficult and welding in tight corner is sometimes impossible.
- Aluminum is far more difficult to weld than steel
- Welding can distort the geometry of your part
Solidworks
Sketch Geometry
- PUT THE ORIGIN IN A USEFUL POSITION
- Try to use relations whenever possible. For example, if you want to put a hole in the middle of an object use center-lines and midpoint relations rather than dimensions.
- Don't do fillets or chamfers in sketches
Fasteners and Off the Self Parts
- We will be using metric fasteners whenever possible
- Do not use toolbox fasteners. Try to use fastener already in trunk whenever possible. Otherwise find a CAD model on McMaster and download the model. Make sure to delete the default custom fields and add the VendorNo field. Fasteners should also have "Y" set in the "IsFastener field"
- Try to spec Spaenaur fasteners whenever possible. If you want to use a fastener that Spaenaur does not sell, check with a Mech lead first.
- Make sure to suppress threads in fasterners.
- Save the fastener according to the naming convension if you are adding it to trunk. Update the drawing number registry accordingly.
In Context Mates
- In context mates should be used when two parts are propertly mated
- These mates can help make the models more dynamic
Fits
Press Fits
A good rule of thumb for a press fit diametral interference is 1/1000th of the diameter you are trying to fit. So if you have 10mm shaft,