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Adventures of an Amateur Machinist – August

SwarfySteve

Plastic
Joined
Jun 5, 2017
Background

Last month’s g-code file was used as it yielded a quality wax part. The file was reused this month using Delrin stock material instead of wax. The part design is a half-scale 1-2-3 block.

Tool

The Pocket NC is a 5-axis CNC mill. The only tool used is a 0.125 inch, single flute, flat end mill. It is optimized for cutting wax and plastic, and is made of uncoated carbide. When installed in the tool holder, the tool reaches roughly 1.125 inches.

Workpiece Material, Fixturing, and Machining Strategy

Stock used is a 2” x 2” x 2” (really 2.05 ± 0.05 inches per axis) block of Delrin plastic. The stock would only be fixtured once with a final parting off operation.

Speeds and Feeds

The program was written with a max spindle speed of 9,000 rpm and max feed rate of 40 inches per minute. However, it was programed with wax in mind and not Delrin. To compensate for the difference in material, the feed rate override was set to 80%.

Conclusions

Here is a picture of the finished half-scale 1-2-3 block.

Delrin Block.jpg

Just like last month, this month yielded a sufficient part but now in Delrin. Only one of the six sides was left with a rough finish that needed remedy with some light sanding. Next month, the feed rate override won’t be dialed back as much and instead of sanding, the part will be refixured and the machine tool operated manually to finish the rough surface by a more precise means.
 








 
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