Topcon Corporation
Precision Equipment #3: Perseverance
The customer inspects electronic components using an optical system mounted on a very precise table. The inspection system travels over the components at high speeds, which can create a lot of vibrations that affect the inspection. To prevent the vibrations, the table is made out of an aluminum silicon carbide casting. The customer had several tables to be built for new inspection systems.
Problem
The projects first big challenge was the material. Aluminum silicon carbide casting is an exotic material that’s extremely difficult to machine because of a 28% carbide content. Carbide is very hard and damages tools very easily. It creates dust that is very harmful to moving machine components (feed screws, spindles, bearings). Furthermore, there are grains of sand in the material left over from the casting process. Machining sand grains is the equivalent of machining glass – almost impossible.
The second challenge was assembling the precision table from the machined parts. There assembly had a tolerance of .001” (.0254 mm) on the parallelism and perpendicularity. Additional machining was also required after the assembly was complete.
Solution
Apex developed a custom dust recuperation system to protect the machine and its operator. The challenges presented by the material were overcome by extensive testing of custom diamond-coated tools (including taps and reamers) along with experimentation with feeds and speeds.
The assembly of the final product was done on a large CNC milling machine with glass scales. All the rails were aligned within tolerance using an indicator. Once aligned, the assemblies were match drilled, reamed and dowel pins were installed.
Results
Apex has successfully produced 20 Super Precision X-Y Tables. The tool wear was controlled and predictable, which allowed Apex to manufacture very precise parts with an excellent finish. The tables were assembled within the tight tolerance and are used to perform thousands of inspections per hour.
Apex achieves high precision machining of Aluminum Carbide
