Design Guide for Photochemical Machining
Specialty Services
ELDRE etches many metals including: Copper and Copper Alloys, Beryllium Copper, Stainless Steel, Nickel,
Nickel Alloys, Spring Steel, Cold Rolled Steel, Aluminum and some exotics. Metals range in thickness from
.0005” to .125” depending on the specifications listed.
This design guide provides some of the “basic rules” for Photochemical Machining. Your specific project
will be engineered by the ELDRE design team to meet your requirements.
Design Guide for Photochemical Machining
Dimensions and Tolerances
There are characteristics associated with the etching process that affect dimensions and tolerance.
As you photo-chemically machine metal, holes “grow” larger, concurrently “lands” or spaces between holes become smaller.
While ELDRE continues to advance our photochemical machining capabilities, the relationship of material thickness to
feature size is inherent to this unique process. The most common design rules are as follow:
In most instances the diameter of a hole or slot should be 20% greater than the material thickness.
Holes or Slots
| Metal Thickness (T) | | Diameter or Width |
| .001”-.005” | | At least metal thickness (.004 min.) |
| .005” and over | | At least 110% metal thickness |
The relationship between material and line width is shown in figures B & C.
In photo etching you can accomplish ratios between holes and material left not
possible with traditional machining techniques.
Line Width
| Metal Thickness (T) | | Spaces Between Holes (B) |
| .001”-.005” | | At least metal thickness |
| .005” and over | | At least 120% metal thickness |
An inside corner radius is typically equal to the material thickness,
i.e. in .005” material you will have an inside radius of .005” minimum. Figure IR
In an outside corner radius will etch more sharply than an inside radius.
Outside radius can be approximately 50-75% of material thickness. Figure OR
As you chemically etch through material you also etch laterally.
A bevel or “etch edge” is created. The relationship between bevel and material
thickness is shown in the “Edge view of material”. Typically you will see a profile
(P) of 20% of the material thickness.
Company logo’s, part marking and bend lines for hand forming can be accomplished
with the photochemical machining process. Partial depths are etched to produce these features. Figure D.
Much like dimensions there are general rules for tolerances with regard to photochemical machining.
Material choice, thickness and size are common factors in determining tolerance for etched blanks.
Center to center dimensions are controlled on our artwork and will be duplicated
in prototype and production. Following are typical center-to-center tolerances.
Center-To-Center Tolerance
| C/C Dimensions (C) | | Tolerance |
| 1.0” or less | | +/- .0005” |
| 1.0” – 3.0” | | +/- .0010” |
| 3.0” – 6.0” | | +/- .0020” |
| 6.0” – 10.0” | | +/- .0030” |
Feature dimensions much like sizes are based on material thickness,
material choice, and the panel size. Generally tighter tolerances can be held in
thinner materials and prototype runs. The next table shows general design rules for tolerances.
Etched Dimension Tolerances
Thickness (T) inches Tolerance in .000”
| | |
| .001” | | +/- 1 |
| .002” | | +/- 1 |
| .005” | | +/- 1 |
| .010” | | +/- 1.5 |
| .015” | | +/- 2 |
| .020” | | +/- 3 |
| .040” | | +/- 5 |
|
