Chemical Etching vs. Other Manufacturing Methods
Precision is the goal of every manufacturing process in the production of thin metal electronic and mechanical components.
Industries, such as aerospace, automotive, electronics, medical, and R/F microwave, rely on precision parts to increase the safety, strength, functionality, conductivity, and corrosion resistance for optimal performance.
The goal is to find the best manufacturing process for a part's design. When precision is the most crucial factor, there are questions to consider when choosing a manufacturing process.
Which manufacturing process achieves the highest precision for my part design? Which method delivers the best results for function, metal thickness, and dimensional tolerances?
For instance, lead frames, filters, encoder disks, and fuel cell plates all have either one or more of the following features: small, intricate, complex designs or numerous apertures such as holes and slots.
Some components, such as board-level shielding, are expected to be free of any metal deformations or burrs to ensure proper fitting or protect against electromagnetic and radiofrequency waves.
Likewise, burrs or distortions prohibit proper contact in mating components such as electrical connectors.
In the Design For Manufacturing phase, the engineer carefully evaluates manufacturing processes to determine which one is the best fit to maintain a part's specific dimensions and dimensional tolerances.
These dimensions include edges, the center to center tolerances, inner and outer radii, angles, holes, slots, or other features.
There are several options for the production of thin, flat metal fabricated components.
Here are how some of the most common manufacturing processes can affect a part's precision.
This process commonly uses an optic laser beam to cut through sheet metal. This method can cut through very thin metal as well as a thickness above .060".The operator programs the G-code into the CNC (Computer Numeric Control) with the part's dimensions. The laser beam will cut by melting, burning, or vaporizing away the unwanted metal. The laser is usually a very accurate and precise method. Problems can occur when the code is entered inaccurately or with mechanical issues due to poor maintenance. Additionally, micro burrs and thermal stress can occur on the surface and edges, where both can interfere with part performance.
Water Jet Cutting
Like laser cutting, a G-code is used to recreate a digital image of a part's dimensions. Instead of a laser, a stream of high-pressure water mixed with abrasives makes a clean cut into the metal part. This process works well on metals where high temperatures can affect their properties. Water jet cutting is usually precise unless there is an operator error or machine malfunction. There is also the possibility of micro burring since the metal is blasted at high pressure. And for this reason, thin, fragile metals may not hold up to the stress.
A wire electrode emits a spark that cuts through the metal with pinpoint precision. Although the process is limited to conductive metals, wire EDM machining is an effective method for small parts with intricate features. However, because the process involves heat, thermal expansion, tempering, and structural changes can affect precision. Micro-burring can also occur. Incorrect G-code or machine maintenance also affects accuracy.
A hard tooling die is created and then used to stamp out the part's dimensions and features. This type of force can cause stress deformations, particularly on thin or brittle metals, and will, therefore, affect precision. So, it depends on the metal thickness as to how precise the cut is. For this reason, anything requiring precision under .020″ (.5 mil) is not suitable for the stamping process. Small parts with intricate designs are also a challenge to manufacture.
Photo Chemical Etching
Unlike the hard tooling from stamping and the G-code used in other manufacturing processes, a repeated digital image of the part is transposed onto a film called a photo tool. This flexible tooling adheres to photoresist-coated metal sheets where a UV light hardens the part that remains in the chemical etching process. The chemical etchant simultaneously dissolves the unwanted metal. The process of dissolution allows the parts to remain burr-free without metal deformation. Factors affecting precision in this process can include inaccurate tooling placement on the metal, machine malfunction, or improper rate of speed and amount of time in etcher.
Comparison of Precision in Manufacturing Processes
|Processes||Laser Cutting||Water Jet Cutting||Wire EDM||Stamping||Chemical Etching|
|Burrs||Microburring||Microburring||Microburring||Partial Burring||No Burrs|
|Stress||Possible thermal Stress On Edges||Some Stress On Edges||Possible Thermal Deformation and Structural Changes||Stress On Edges For Thinner Metals Or Complex Parts||No Stress or Structural Changes|
|Metal Variety/Hardness||Large Variety - no problems with hardness||Large Variety - no problems with hardness||Only Conductive Metals - Possible issues with hardness||Not Suitable For Soft, Hard or Brittle Metals||Large Variety - No Problems With Hardness|
|Tolerances/ % of Metal Thickness||+/-5%||+/-10%||+/-10%||+/-15%||+/-10%|
All of the above processes can provide some degree of precision for flat metal parts.
It is best to review the part's requirements such as metal type, metal thickness, design features, inner and out dimensions, and dimensional tolerances to determine which process is the best fit.
Consideration should also include how the part integrates with other components in mechanical or electronic systems.
For instance, if it is a mating part, then any burrs or stress causes friction. Or, if heat exposure alters the metal's properties, it could affect the following:
- Electrical Resistance
- Thermal Expansion
Photochemical etching is the best manufacturing process if your part must be burr-free and stress-free without any metal deformations or unaltered properties. Photo etching can deliver smooth surfaces, precision edges, and low dimensional tolerances whether the parts are flat blanks, mesh screens, or lead frames.
It is the most cost-effective method for parts with numerous features or small intricate designs.
Whatever process you choose, it is beneficial that the manufacturer has experience with many types of industrial components. Experience with processes ensures a low margin of error and provides the best quality and precision.
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