Dear Cameron Smart,

Thank you very much for this suggestion, and I am sure this can be definitely help me. But this research article is not subscribed by my institute.

would you please share this research article through email: [email protected]

Thank You

What is the problem indeed?

What is the yellow vector on the picture? It seems to me that it should have the opposite direction (?)

Dear Mr.Rétfalvi Attila

yellow vector shows input force direction of effective part, this part is fixed with internal shaft.

here due to this there is a relative motion & friction between yellow part and pink part.

With the application of the force(Yellow vector), the collet moves against stationary mandrel(pink part) and hence the collet expands due to slots(not shown in this figure) made on the periphery of the collet parallel to the axis. This expansion fixes the job which is kept around this collet. So, we(Prof. Tejani and Me) are interested in finding the optimized design parameters like, clearance required, deformation, thickness, cylindricity etc

The easyest way would be to define the angle, the outer diameter, one of the inner diameters as variable, and to put pressure (which depend on the angle) on the inner surface. But as i see, you want more than that. So you you have to analyse the assembly, to define contact surfaces, gaps, and so on.

Thanks Mr. Rétfalvi Attila  for your guidance. Actually I am working according to your suggestion. Bigger challenge to me at this state is to model elasticity of the collet and the gap between the collet and job.

First you need to specify the grip force. From that you will specify collet’s outer diameter and length. Some factors affect the grip force:

D (see photo): high axial forces will result in higher gripping forces

Angle : defines the force amplification.

Friction : depends on material selection, heat treatment, surface roughness and lubrication.

To arrive to optimum gripping force you should consider the followings:

1) Machining force

2) Good ratio of amplification

3) Collet should be capable to rapidly release the workpiece. To this end self,ocking angle should be avoided.

4) Centrifugal rotational force should be considered, etc.

Thank you very much for your mathematical explanation. It is really helpful to me. The way in which you replied with the scanned image is wonderful.

Now what I want to do is to check about the amount of force using simulation as well as experimental setup. My sponsoring company will help me for experimental setup, but I have problem with simulation. I have selected Creo dynamic extension option for the same, but I am unable to model the constraints for collet as it is expanding(elasticity will matter) and also there is a gap of about 10 microns in between the job and the collet. How to make the collet elastic and how to model the gap is another challenge.

I would be very very thankful if you can suggest something in this direction.

Dear Hassan Radvar-Esfahla & Rétfalvi Attila,

Thank you very much for your kind support.

This would definitely help my friend Chetan Patel, who is working on this topic

Thanks ones again