A common question is what surface finish can I get when milling with PCBN-inserts? Well, it will depend on the setting of the milling cutter. When milling with PCBN, it is important that all inserts take the same load; any insert sticking out will result in reduced tool life and poorer surface finish. The inserts should be within 0.002 to 0.004 mm of each other. If a wiper insert is added, this should be positioned between 0.025 to 0.1 mm above the other inserts depending on workpiece material and operation. It is always recommended that the cutter should be set-up outside the machine in a pre-setter.
Since this a parameter that is difficult to control, it was decided to do the tests with only 1 insert. Grey cast iron was selected as workpiece material, and the parameters were:
- Feed rate 0.05 – 0.3 mm/tooth
- Insert nose radius 0.8, 1.2 and 1.6 mm
The average profile deviation, Ra, was measured after each test, and the results plotted as a function of feed rate for each of the nose radii and the wiper insert.
As can be seen, the Ra-value increases with increased feed rate and decreases with increased nose radius in much the same way as in turning. By far the best surface finish is achieved with the wiper-insert.
At low feed rates, it is possible to reach Ra -value of 0.5 mm, but to maintain that surface finish when increasing the feed rate, it is necessary to use a wiper insert. Even at the highest feed rate, 0.3 mm/tooth, the Ra-value is less than 0.6 mm.
Product Specialist SECOMAX PCBN/PCD/CERAMIC
SECO TOOLS Shanghai CO., Ltd. Level 2, Building 8, 456 HongCao Rd., Shanghai 200233, China
Office: +86 21 5426 5849
Mobile: +86 185 1520 6942