Flexible, Durable, and Yet Accurate, Collet System for Job Shops

Jan. 27, 2011
Vulcanized rubber is critical design feature for achieving quick changeover and accuracy
Vulcanized rubber bonds together the hardened, chrome-nickel steel collet sections of Hardinge’s FlexC collets.

Vulcanization is a chemical process that coverts rubber or polymers into more durable materials — and it’s the process that gives its name to Hardinge’s FlexC vulcanized collet system. It’s an effective name, too, because the process is used to bond hardened, chrome-nickel steel collet sections together … permanently.

Hardinge claims that because of their durability and flexibility, the FlexC collet systems are ideal for the job shops where machines must endure multiple changeovers and stock variations every day. The quick collet changeover can increase output and lower manufacturing costs, while the special accuracy could qualify that machine to handle a wider variety of jobs. It indicates that testing results from repeated collet actuation indicate a “highly durable, fully sealed gripping solution.”

Vulcanized rubber is especially value in a collet head because of its elasticity. The collet can sustain repeated opening and closing without deterioration. The Hardinge devices’ elastic design makes it possible for a manual wrench to be used to compress the collet providing quick changeover in seconds, rather than minutes. The timesavings can reduce the total cost of manufacturing.

Hardinge indicates the FlexC collet system is guaranteed to be accurate within 0.0004 in. (0.010 mm) TIR for both collet system styles A (pull-back stationary stop) and D (pull-back through-hole) and 0.0008 in. (0.020 mm) TIR for style DL (push-to-close dead-length). These systems achieve the same gripping capability as conventional collets but use less drawbar force.

Also, variations in bar stock will not be a concern for the users. The FlexC collet head has a gripping range of ±0.020 in. (0.5 mm) of its nominal size to allow variation in bar stock without having to change the collet. Because there is no collet body, the collet segments will remain parallel to the stock even when there are variations in the bar stock. This parallel clamping minimizes stock "push back" that could create inconsistent part lengths.

Hardinge FlexC collet systems are compatible with many CNC lathes and are interchangeable with other brands. The developer recommends substituting a FlexC collet system for 16C, 20C and 25C collet applications to meet special accuracy requirements, or mounting it on a chuck-style lathe or rotary indexer to increase versatility. The spindle mount will fit on A2-5, A2-6, A2-8 and some flat back spindles (main and sub). Once the FlexC spindle mount is attached, different collet head sizes can be interchanged from job to job. Hardinge stocks 42- and 65-mm collet sizes in round smooth and serrated styles. Hex and square sizes are made to order. Some examples of custom-manufactured applications include stepped holes, special shapes and off-center work.

In addition, FlexC collets can be shared with vertical machining centers using Hardinge FlexC modular collet blocks, which are compact with a low profile for increased axis travel and also may be used on fifth-axis rotary trunnions.

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