Design for Manufacturing and Assembly (Week 9) Flashcards
What is the manufacturing process?
- Machining
- Forming
- Joining
- Finishing
What is machining
Machining is the process of removing or separating pieces of material from a workpiece (i.e., material removal).
What is forming
Forming is the process of giving shape to a workpiece without adding material to, or removing material from, the workpiece (i.e., material
deformation, casting, and injection molding).
What is joining
Joining is the process of fastening workpieces together, permanently or semi-permanently.
What is finishing
finishing is the process of modifying a workpiece
surface for the purposes of protection and/or
appearance (i.e., surface treatment).
What is design for manufacturing (DFM)?
Design for manufacturing is the need to consider capabilities and limitations of chosen manufacturing process as well as the part geometries optimized for particular process.
What are design guidelines for machining?
-Allow run-out for tool
-Avoid completely spherical surfaces
-use through holes wherever possible
-provide boss to avoid drilling into an inclined surface
-do not design very difficult (or impossible) to machine hollows or overhangs
-Design for reasonable internal pockets radii
-use standard dimensions
-avoid long narrow holes
-avoid thin walls, they break when machining
-place holes away from the edges
-provide access for holes
-design parts that are easy to hold (fixture)
-avoid deep pockets that require long tools and cause tool vibration
-avoid long thin sections that cause vibrations when machined
-remember that holes cannot change directions
-avoid external rounds which are difficult to machine, use chamfers instead
What are design guidelines for casting and molding?
-Avoid sharp corners
-maintain uniform section thickness
-stagger ribs to avoid hot spots
-facilitate flow of molten material
-provide draft angle to be able to remove part from mold
-avoid abrupt changes in section thickness
-avoid deep narrow ribs
-design with mold flow considerations in mind
-avoid staggered split lines
What are design guidelines for molding?
-Avoid using “sliders” in mold design
-use uniform wall thickness
-do not design sharp corners, they create stress concentrations and obstruct material flow, but do not use radii that are too large either
-keep section thickness uniform around bosses
-attach bosses to walls with ribs
-keep rib thickness less that 60% of the part thickness to prevent voids and sinks. Space out ribs as shown.
What are design guidelines for sheet metal?
- A narrow web will cause bulging
-Provide an ear in the blank or include the hole as a notch
-offset bends
-A cut-out is needed to bend flange
-Use separated flanges when possible
-Avoid sharp internal and external corners
What is design for assembly?
Design for assembly is product design that can be measures in terms of the efficiency of its overall assembly and ease with which the components can be retrieved, handled and mated.
What is a product with high assembly efficiency?
A product with high assembly efficiency will have very few components, they will be easy to handle, and they will virtually fall together during assembly.
What is the objectives of Design for Assembly?
The aim of design for assembly is to simplify the product so that the cost of assembly is reduced.
What are the consequences of design for assembly?
the consequences of applying design for assembly include improved quality and reliability, and a reduction in production equipment and part inventory.
