page 455
66. PROCESS PLANNING
•Process planning is the selection of operation and parameters required to manufacture a part.
•A process plan is a list of operations required to manufacture a part.
•This technique is quite inexact, and never perfect.
•Some strategies that can be used to do process planning are,
-Technology driven features
-Most significant feature first
•In general a process plan is put together in pieces, but at all times we will be trying to convert features on the design to operations on the process plan.
•Many of the parameters that effect the process planning decisions are related to a part, and to a process being considered.
-lead times
-processes available
-tolerances
-feature geometry
-standard features
-surface finish/roughness
-geometry complexity
-material types
-material properties
-part shape
-largest dimension
-section thickness
-length to width ratio
-hole diameters
-corner radii
-quality control
-quantity produced
-economic batch size
-capital costs
-tooling costs
-lead time
-material waste
-production rate
-tool life
-environmental impact
page 456
OPERATION SHEET
Part No. |
|
CLP023456-4-92-023 |
Material |
|
steel 1040 |
||
|
|
Widget |
|
|
|||
Part Name |
|
|
|
|
|
||
H.Jack |
|
|
|
||||
Orig. |
|
Changes |
|
|
|||
|
|
|
W.H.ElMaraghy |
|
D.Corrin |
||
Checked |
|
|
Approved |
|
|||
No. |
Operation |
Machine |
Setup |
Time (hrs.) |
0010 |
Saw off and slug 1.75 dia. hole |
Dept 12. Saw 3 |
|
.3 |
0015 |
R’Turn 6.00 dia. stock to 5.210/5.190 |
G.E. Turn Lathe |
Hold in counter centrifu- |
1.2 |
|
R’Bore 1.75 dia to 2.00 |
|
gal Chuck |
|
|
F’Bore 2.00 to 2.005/2.015 |
|
|
|
0025 |
Deburr all edges |
|
|
5 mins. |
66.1 TECHNOLOGY DRIVEN FEATURES
•Some parts have features that are so advanced or specialized that they can only be produced with one technology. Consider a ferrous part with a high strength that requires a specific heat treating operation.
•The general approach is to start at the end of the process plan, and work backwards. When the design features left are normal
66.2 MOST SIGNIFICANT FEATURE FIRST
•Generally we can identify the most significant geometry. Some things to look for are,
-the features are all cut from a base piece - cutting
-there is a natural parting line - welding/molding/casting
-features seem to be stuck-on a base piece. - assembly/molding/casting
-large/small mass
-material
•An example of this is an angled block with a hole,
page 458
•Thin walls can be difficult to manufacture and will collapse under force,
<0.25 in. Sand Casting (0.125”)
<0.1 in. powder metallurgy (0.06”)
Investment casting (0.025”)
Die casting (0.025”)
Injection molding (0.03”)
Structural foam molding (0.09”)
Blow molding (0.015”)
Rotational molding (0.06”)
< 0.01 in. Hot extrusion (1.5% of circumscribed dia.) Spinning (0.004” sheets)
Sheet Metal Stamping Bending (0.001” sheets)
< 0.001 in. Electroforming
• Small hole diameters can be difficult to produce,
page 460
<0.01in. rotary swagging (0.003”) Hot Extrusion (0.005”)
turning (0.001”) milling (0.002”) drilling (0.008”) reaming (0.001”)
electrochemical machining (0.001”) electro discharge machining (0.001”) investment casting (0.002”)
die casting (0.002”) injection molding (0.003”)
structural foam molding (0.003”) impact extrusion (0.002”)
<0.001in. boring (0.0005”) broaching (0.0005”)
grinding (0.0008”)
<0.0001in.
<0.00001in
• Surface finish can be difficult to obtain, (micro-inches),
