Microconic™ Over-Grip Collets W-Type
Now you can over-grip and do REAL MACHINING in the sub-spindle!
No other product on the market can “overgrip” as much as the Microconic™ W-Type Over-grip Collet with the Masa Cartridge. The Microconic™ W-Type Over-grip Collets can open up to 4mm over the chucking diameter and run within 5 µm/.0002" TIR. The are currently available in the UM10 size.
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 machine's capability, eliminate secondary operations and reduce cycle time.
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.
Have Longer Parts?
Be sure to take a look at our "T-type" over-grip collets, which have a longer gripping surface than our original W-type depicted here. The "T-Type" is designed specifically for applications that require holding longer length parts.
How to use the Microguide™ Sleeve
Due to the extreme opening capability of our overgrip collets , workpiece ejection must be very reliable to prevent a part from becoming stuck in the slots of the collet. Therefore we have developed the Microguide™ ejection guide sleeve to prevent parts from falling inside the collet instead of ejecting into the part catcher.
Each Microconic™ Over-grip collet is supplied with a brass Microguide™ ejection guide sleeve blank. The Microguide™ sleeve can be bored, drilled or machined to match the part profile and support the part and guide it for reliable ejection into the part catcher.
You will need to machine the Microguide™ to fit your particular part setup. We suggest using programmed cycle stops while validating the production setup to make sure part ejection is reliable.
The Microconic™ over-grip collet is extremely rigid and precise. If it closes onto a part wrapped with chips the collet may be over-stressed and break. It is critical that the workpiece be free of wrapped chips. High pressure coolant is recommended to blast away chips.
There are many other techniques that can be applied to keep the part clear of chips, such as chipbreaker inserts, speed/feed optimization, chipbreaker G-code cycles and cutter path retracing, amongst others.
It bears repeating that we suggest using programmed cycle stops while validating the production setup so the operator can confirm the part is clear. Once chip control is proven reliable that won't be necessary.