Metals can be processed in a variety of ways. These can be classified roughly into casting, forming and machining. The following table gives characteristics of different processes for metals, although some may also apply to non-metallic materials such as plastics and composites.
General characteristics of metal processes :
| Process | Economic quantity | Materials (typical) | Optimum Size | Minimum section (mm) | Holes Possible | Inserts possible |
| Sand casting | Small/barge | No limit | 1-100 kg | 3 | yes | yes |
| Die casting, gravity | large | AI, Cu, Mg,Zn alloys | 1- 50 kg | 3 | yes | yes |
| Die casting, pressure | large | AI, Cu, Mg,Zn alloys | 50g-50kg | 1 | yes | yes |
| Centrifugal casting | large | No limit | 30mm-1m diameter | 3 | yes | yes |
| Investment casting | small/large | No limit | 50g-50kg | 1 | yes | yes |
| Closed die forging | large | No limit | 3000cm3 | 3 | yws | yes |
| Hot extrusion | large | No limit | 500mm diameter | 1 | - | yes |
| Hot rolling | large | No limit | - | - | no | no |
| Cold rolling | large | No limit | - | - | no | no |
| Drawing | small/large | AI,Cu,Zn,mild steel | 3mm/6m diameter | 0.1 | no | yes |
| Spinning | one-off, large | AI,Cu,Zn,mild steel | 6m/4.5m diameter | 0.1 | no | yes |
| Impact extrusion | large | AI, Pb, Zn,Mg, Sn | 6-100mm diameter | 0.1 | - | no |
| Sintering | large | Fe, W, bronze | 80g-4kg | 0.5 | yes | yes |
| Machining | one-off, large | No limit | - | - | yes | yes |
Labels: Manufacturing technology
Carbon steels
Their use is restricted to the cutting of soft metals and wood. Performance is poor above 250°C.
High-speed Steels
These are used extensively, particularly for multi-point tools. They have been replaced to a large extent by carbides for single-point tools. Their main application
is for form tools and complex shapes, e.g. for gearcutting and broaching. They are also used for twist drills, reamers, etc.
Carbides
These consist of powdered carbides of tungsten, titanium, tantalum, niobium, etc., with powdered cobalt as binder. They are produced by pressing the powder
in dies and sintering at high temperature. They are then ground to the final shape. They are generally used as tips and can operate up to 1oo0"C.
Laminated carbide
These consist of a hard thin layer of titanium carbide bonded to a tungsten carbide body. The surface has very high strength at high temperature, whilst the body has high thermal conductivity and thus efficient removal of heat.
Diamonds
These are the hardest of all cutting materials with low thermal expansion and good conductivity. They are twice as good as carbides under compression. A good finish can be obtained with non-ferrous metals and final polishing can be eliminated. Diamonds are particularly good for cutting aluminium and magnesium alloys, copper, brass and zinc. They have a long life.
Labels: Manufacturing technology