Cascading Failures stopped by Precision, Hardened & Ground Microconic UM collet for Dental Implant

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 chip wrap of the dental implant part was periodic due to tool wear.  Clamping on the chips, that where wrapped around the implant in the TF25 sub spindle collet, led to two collet wear problems in less than 10,000 parts on a swiss screw machine:

• Deformation of the ID clamping surface of the collet
• Bell mouthing of the face of the collet
  

​Concurrently, there was a mushrooming of the Titinium head of the workpiece from the uneven clamping pressure due to the collet bell mouthing.  Scrap rates and collet replacement times where not predictable in a lights out production environment.

Fig. 1: 6Al4V Titanium Dental Implant chip wrapping during threading on the main spindle

Fig. 2: Bell mouthing of competitors collet after 10,000 parts

In the competitors collet, the Titanium material started to yield where the chucking occurred  (Fig.2) This caused an out of round situation and caused micro movement in the workpiece..

Fig. 3: ID wear and damage of competitors collet after 10,000 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.

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Microconic UM Collet to the rescue

​We installed a Microconic UM standard collet with a TF25 Cartridge on the sub spindle.

We ran the 10,000 parts through the sub spindle changing no other cutting parameters.

After 10,000 workpieces produced the Um collet has no discernible signs of wear even after chucking on multiple parts with chip wrap.

In the words of our customer, "It's a beast!"

Concentricity was checked after 10,000 pcs and still concentric within .0001 TIR.

The Microconic TF25 cartridge with UM collet installed. Dental implant and human hand for scale.

Fig. 4: No bell mouthing and substantially little wear on the Microconic UM collet after 10,000 pieces.

Titanium Dental Implant held in Microconic UM collet