"Every time the collet would chuck on the parts with chip wrap, it would leave an impression in the collet. Sometimes the chip would stay lodged in that impression and the parts run from that point on are scrapped due to the chip impressions on the part and once noticed, the collet would need to be replaced."
Avinger Inc., based in Redwood City, California, designs, develops and manufactures precision medial device technology with the goal of helping patients keep their legs. Recently they began testing the Micoconic system on their Citizen L20 (7M8) Swiss Screw Machine using a Utilis 3000 series cutoff holder and an 1/5mm X 10mm insert. The bar stock was .225" OD round.
They where kind enough to share their test results with us.
Our customer was machining 6Al4V Titanium dental implants and scrap rates increased the longer our competitors collets where in use.
This root cause was primarily result of cutting the threads in the main spindle. Chips wrapped around the finished threads before the implant was handed over to the sub spindle collet for machining of the head hex and internal thread.
Collet wear & bad parts
The unpredictable periodic clamping on the wrapped chips on the workpiece embedded chip impressions in the collet (Fig. 3) which in turn marked the next part when it was chucked on.
As a result the competitor's collet workholding lost it's chucking power from the bell mouthing in the front. By becoming out of round, parts lost their concentricity.
When you need to make small parts, the size range of the 5C collet is where the best variety and value exist in machine tools and accessories. You don't want to sink capital into expensive, specialized machinery that will run nothing but small parts. But a 5C collet is pretty big compared to your 1/8-inch diameter part.
An adapter is available, however, that renders a common 5C machine tool capable of handling very small diameter parts. The new small parts adapter, manufactured by Masa Machine Tool Accessories, Oceanside, California, fits in any machine's 5C collet closer, just like a standard 5C collet, without any modifications or special mounting procedures.
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