Motorizing rolling mill?

Jewelry Discussion
1

Hi Richard,

I happen to be in the midst of this project at the moment. My
analysis has been this:

  1. The torque requirement all depends on the metal and how much of a
    reduction per pass one choses to make. The common hand mills with
    ratios of 3:1 and 4:1 seem to work out with about 30 foot-pounds on
    the handle.

  2. The speed should be “comfortable” to allow you to feed and pickup
    without feeling rushed and out of control, 5 to 10 rpm seems
    reasonable.

  3. A motorized unit is on the market listing; 2 1/2 HP 110 V
    yielding 5 to 40 rpm. My guess is that a major part of the speed
    control is by voltage reduction and consequent loss of torque. A
    postor who is more engineering educated than I can surely educate all
    of us, but my gut tells me that 2 1/2 HP at 5 rpm is way beyond
    necessary.

  4. I’m trying the following:

A. HP mini mill with 3:1 ratio and a 12 inch pulley.

B. A surplus tread-mill DC motor rated at 3/4 HP with a 1 1/2 inch
pulley.

C. A surplus pulse-width modulated DC power supply yielding broad
range motor speed control with essentially full torque.

  1. Parts cost thus far appear to be, mill + about $60.00.

I’ll be most interested in other comments and especially
criticisms–and I"ll let you know what happens!

Dr. Mac

2

I have a friend who motorized his rolling mill. He doesn’t like the
computer so I’ll see if I can get some info from him about ratios,
motor, etc.

Donna in VA

3 
A motorized unit is on the market listing; 2 1/2 HP 110 V yielding
5 to 40 rpm. My guess is that a major part of the speed control is
by voltage reduction and consequent loss of torque. A postor who is
more engineering educated than I can surely educate all of us, but
my gut tells me that 2 1/2 HP at 5 rpm is way beyond necessary.

My 1 HP power mill works well but can be easily stalled on larger
pieces with too great a reduction. The speed controlled mill you
refer to has a three phase motor driven by a VFD (Variable Frequency
Drive) The speed reduction is achieved by gearing down then it is
variable within the listed range by changing the frequency of the
supplied current not by reducing the voltage. The torque remains
relatively constant. Depending on the design of the VFD it can run
on either single or three phase input power.

James Binnion
@James_Binnion
James Binnion Metal Arts

4

Mac

Check for a posting by Dave Arens he has done this and very
inexpensively.

A larger pulley or gear at the mill will certainly give you lower
speed.

3/4 HP is the least that you will need 1 HP will be better. A
Reversible slow speed motor with high torque is desirable

Maximum Speed should be around 35 rpm. A lower speed is desirable.

A decent Reversible Drum switch would cost you around $80.00.

A brand new 1 HP motor wired with drum switch is sold for $300 and
these are heavy. If you can find one in your city it would be better.

Whatever you use Belts or Chains safety is an issue no French Cuffs.

Kenneth Singh
46 Jewelry Supply