Design Information

Photo Chemical Milling is a process in which close tolerance and exact size images can be transferred to almost any thin metal or alloy sheet (.0005-.062) and precision parts etched out. Almost any part in thin metal required by industry can be produced quickly and economically with a high degree of precision.

By "thin" metals we mean anything from foils 1 Mil (0.001 inch) to materials upwards of 0.062 inch thick. The thinness of the metal is a major consideration in determining limits on dimensions and tolerances. This results from the nature of the photo etch milling (PCM) process in which etchants attack the metal vertically. The specific metals being used and the variables in the PCM process are, to a lesser extent, also considerations.

 

Dimensions - Hole Size vs. Metal Thickness

Holes,slots, and RADII have dimensional limits which are related directly to the thickness of the metal. As a general rule, the smallest diameter, which can be produced by the PCM process, cannot be less than 1.2 times the thickness of the metal. Exceptions to this occur at the opposite ends of the scale : The minimum practical diameter of the holes in the foils must be determinated by test. "Tricks of trade" permit holes smaller than stock thickness in special circumstances.

Thickness Practical Hole Size Tolerances Attainable
0.0020"
0.0050"
0.0070"
0.0100"
0.0200"		 0.0030"
0.0060"
0.0080"
0.0120"
0.0350"		 ± .0005"
± .0010"
± .0015"
± .0020"
± .0030"