Photo-Chemical Machining - The Hong Kong Polytechnic University

Photo-Chemical Machining (PCM)5. The dimensional tolerances, an important specification, are about ±0.1T.6. The centre-to-centre and pitch-to-pitch dimension of PCM has atolerance of ±0.05% of the specified dimension, e.g. for a 10 mm pitch,a tolerance of ±0.005 mm can be easily achieved by PCM.4. Comparison of PCM to Metal StampingPCM is often compared with metal stamping because both methods produceprecision sheet metal parts.1. In nature, PCM has a relatively high part cost and a very low artwork andtooling cost. In contrast, precision metal stamping has an extremely lowunit production cost but a very high tooling cost, especially forcomplicated parts. Thus PCM has an economical edge for complex partsand small to medium quantity. For less complex parts and very largequantity, precision metal stamping would have the cost advantage.2. PCM lead time is short, it takes about 2-3 days to produce samplequantities, while in metal stamping, it normally takes several weeks tomake the tooling. If there is any design change required, PCM canmodify the photo tool easily at low cost within a short period of time.This gives PCM a definite cost and lead time advantages over metalstamping in making prototypes.3. The etched components from PCM are burr free. Metal stampingrequires further abrasive treatments to eliminate the burrs and to finishthe components.4. PCM is a process which does not affect the physical or chemicalproperties inherent in the sheet metal. This makes PCM the prominentprocess in magnetic material fabrication since it would not affect themagnetic permeability. Metal stamping will reduce the magneticpermeability significantly and cause stresses for which a time consumingand costly annealing process is needed to restore the permeability.5. Metal stamping cannot process pre-hardened sheet metal. Metalhardness has never been a concern in PCM manufacturing, which canprocess sheet metal of any hardness.6. Some other aspects of PCM and metal stamping can be compared in thefollowings:-Page 5IC Professional Training