Category: Part: Dental Impant

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

9/30/2015

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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Masa Tool Introduces the Microconic™ Over-grip Collet

5/20/2015

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Masa Tool has developed the Microconic™ system specifically for holding workpieces from Ø0.15mm to 10mm (Ø0.006" to 0.390") in any machine that has a collet-type chuck. The system consists of two major components: The Microconic ™ cartridge, which fits into your CNC machine spindle replacing the standard 5C, 16C, TF15, Tf16 TF20 , TF25 or TF37 collets, and the Microconic™ collet, which fits in the Microconic ™ cartridge.

Part of the standard offering of Micrconic™ collets is the UM10W Over-grip series. The UM10W over-grip series is offered in the coverage range from Ø0.5mm - 7.2mm diameter (Ø0.020" - 0.283").

Microconic™ Overgrip Collet. A = Grip Ø, B = Largest Part Ø, G = Grip Land Width

Over-grip collets, also referred to as over-the-shoulder collets, are used in a pick-off /sub-spindle when it is required to clear a shoulder and grip on a smaller diameter beyond the larger diameter.

The Drill blank pictured at the left is a good example of this kind part.

Extra spread is required to open the collet wide enough to go over the larger diameter. The grip diameter (A), the width of the grip land (B) and the largest part diameter to reach over (G) are required to choose the off-the-shelf over-grip collet for your specific part.

Microconic™ Over-grip collets are a great way to expand your CNC machine's capability and reduce cycle time.

The Problem
Generally, pick-off collets grip short part lengths that only occupy the front section of the bore. All of the clamping force is on the collet angle, which is a considerable distance from the part being held. As a result the collet begins to collapse under the angle.

At that point, the bore is no longer parallel and does not squarely grip the part. This usually results in the parts running eccentric and slipping in the collet. At that point machine operators generally increase the clamping pressure in reaction to the runout. This eventually results in the premature failure of the collet.

Another problem that is peculiar to pick-off collets is that they are sometimes closed without a part in place. Having no internal resistance puts undue strain on the collet walls, which can contribute to premature collet failure.

Microconic Over-grip collet opens over bone screw thread to hold the workpiece on the shoulder.

Machinable Brass ejection guide sleeve blank installed in the back of Microconic Over-grip collet

Microconic UM10W Over-Grip collet

The Solution

Over-grip collets from Ø0.5mm - 7.2mm diameter (Ø0.020" - 0.283").
Opens up to 4mm (0.157") diameter larger than the clamping diameter. Some restrictions apply to larger sizes approaching the 7.2mm (0.283") max diameter
Grips with the same industry-best rigidity and accuracy as our standard collets.
Compatible with all Microconic M10 cartridges: F20M10, F25M10, 5CM10 & 16CM10.
Fatigue tested design to over 250,000 full-load cycles.
Microject™ Brass ejection guide sleeve blank is included with each Microconic™ over-grip collet.
All sizes available to ship in 2 days.
Reduce part cycle time by moving operations to the sub spindle that you might currently be performing in the main spindle.

Microconic™ Overgrip Collet. A = Grip Ø, B = Recessed Part Ø, G = Grip Land Width

Microconic Overgrip collet installed in F20M10 Cartridge with a typical medical part produced using the Over-grip collet

Microconic Overgrip collet and Microconic F25M10 cartridge installed in the sub spindle with standard extended nose capability.

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

Collet wear & bad parts

Masa Tool Introduces the Microconic™ Over-grip Collet

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