I am making a study of intermediate drawing machine and there are some things I still don't understand.

- Why does the slip increase backward instead of being constant?
- Can I calculate the diameter of the capstans in the case there's no slip then?
- Can I increase the capstan diameters according to the slip percentage?

My drawing machine has 4 step cones and a final capstan (17 dies type). The 4 step cones are geared but the final capstan is driven by belt.

- So what is the advantage of using a belt? Why don't they use gear for this capstan.

Sorry for my bad English.

Please advise.
Best regards

Here are some pictures of the machine.

Hello gbanana and welcome to the WAI Forums,

Here are the answers to your questions:

Answer 1
Please think of your drawing machine this way.

- There is nothing that says the dies in a slip-type drawing are exactly on size and that they do not wear to a larger bore.
- There is nothing that says capstans do not groove or wear to a smaller diameter.

Now lets us think of the final die in the machine.
- Because of the above statements, more metal (In your case copper.) must be supplied to the die than is actually used by the die. The excess metal must there slip out of the machine and the only way this is possible is to send it backwards by slip to the entry wire.

This then happens at every die in the drawing machine and all excess is cumulative back to the entry wire.

Answer 2
- Zero slip machines are dry like a series of dry capstans, each with its own speed controlled or torque controlled capstans.

Answer 3
- Although capstan diameters could vary to reduce slip a bit, the diameters are generally of constant size or are similarly stepped as in your machine. This means that they are easier and cheaper to manufacture and of course easier to repair or replace.

Answer 4
- Your dry capstan has no slip. If it did, the wire would slip and friction would burn the wire off the capstan. It is easier and cheaper to use a high capacity flat belt than to add more gearing and weldments to the machine. Thus the capital cost of the drawing machine is reduced. The drawing machine is also quieter with a final high capacity belt drive.

I wrote a simple paper on wet drawing machines and slip some years back. Think of it as a refresher.

www.stewart-hay.com/pshslip.htm

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212

Dear Mr. Stewart-Hay.

Thank you so much for your answers.

So if the step cone's size and the ratio of the speed between each step cone are constant, the reduction at each die is constant (20.7% etc). How can they set the different slip on each capstan?

If I want to design a gearbox for the machine, first I will calculate the step cones according to the reduction. Then I will have the speed of each step cone. but now I'm stuck with slip problem. Is there anything wrong with that?

please advise
Best regards

Hello again,

Please re-read the link I provided and then accurately calculate the surface speed of each of the capstans starting with the dry capstan (line speed) on your existing machine. This should give you your answer.

Please note that a strobe is not accurate enough if you decide to do it this way.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212

Thank you so much, Mr. Stewart-Hay
This helps me a lot
hope you have more success in the future
Best regards