Motor selection centrifugal casting machine

Other Hardware Motors, Mechanics, Power and CNC
1

Hi there!

I want to start a new project: a spincasting/centrifugal casting machine for pewter and resin casting.
Gravity casting is okay but casting by forcing the material into the mold by a rotary force seems to produce better results.

Im stuck selecting the right motor for this kind of application. See attached my current thoughts.

I will have:

  • Loaddisc will weight approx 1-2kg
  • Disc with approx. 20cm radius (approx. 40cm diameter)
  • 1 toohed belt disc with 30 teeth underneath
  • belt to the motor disc with approx. 20-30cm length
  • 1 toothed belt disc with 15 teeth attached to the motor

My question (1) is:
How do I know which motor to buy?
How do I calculate the right parameters for the motor? Watt?? Newton Meters?? I find sometimes only the wattage of the motor and sometimes only the NewtonMeters per gramm, centimeters or milimeters.

My question (2) is:
Is there any formula with example how to calculate the force that is applied to the casting material into the mold at which rotation speed?

My question (3) is:
Has anybody expirience how much rotary force the disc needs to produce nice casts?

Thanks for your time in advance!

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2

Maybe take a look at commercially made products and see their specs and maybe part numbers to get an idea.

Otherwise it's on you to figure out torque and speed requirements of a motor. Weight distribution and acceleration needs all factor into what you need. Maybe just stick a corded power drill to it and see if it works.

3

Thanks for your advise!
Testing with a corded power drill is a good starting point.

But shouldnt be there a formula for calculating the required torque, NewtonMeters or wattage for a certain weight? Honestly, Im not sure if I want to buy 10 Motors to test... :smiley:

Later on I also want to integrate RPM measurement with Arduino buts thats another question :wink:

4

asuryan:
Hi there!

I want to start a new project: a spincasting/centrifugal casting machine for pewter and resin casting.
Gravity casting is okay but casting by forcing the material into the mold by a rotary force seems to produce better results.

Im stuck selecting the right motor for this kind of application. See attached my current thoughts.

I will have:

  • Loaddisc will weight approx 1-2kg
  • Disc with approx. 20cm radius (approx. 40cm diameter)
  • 1 toohed belt disc with 30 teeth underneath
  • belt to the motor disc with approx. 20-30cm length
  • 1 toothed belt disc with 15 teeth attached to the motor

My question (1) is:
How do I know which motor to buy?
How do I calculate the right parameters for the motor? Watt?? Newton Meters?? I find sometimes only the wattage of the motor and sometimes only the NewtonMeters per gramm, centimeters or milimeters.

My question (2) is:
Is there any formula with example how to calculate the force that is applied to the casting material into the mold at which rotation speed?

My question (3) is:
Has anybody expirience how much rotary force the disc needs to produce nice casts?

Thanks for your time in advance!

With a horizontal wheel on good bearings the motor only has to overcome running friction from
air and the bearings, and to accelerate / decelarate the load.

You need to know your maximum speed and some idea about the acceleration rate required
and the moment of inertia of the load.

Then you can start figuring out speed and torque requirements, thus gearing and power.

Since the load is hazadous I'd recommend limiting the max speed by design (ie enough reduction
gearing), rather than rely on a speed controller, and of course this gives the best efficiency
anyway.

A disc of radius 0.2m and mass of 1--2kg can have at most a moment of inertia of 0.08 kgm^2,
and if I guess the max speed is 200rpm (about 20 radians/s), that gives a g-force at the wheel
edge of about 4g, and about 1.6 Nms rotational impulse to accelerate to that speed from standstill
for MoI = 0.08. Tangential velocity is 4 m/s, which seems dangerous to me(!)

0.1Nm for 16 seconds will give 1.6Nms rotational impulse, suggesting 200 rpm, 0.1Nm as plausible
figures.

With a 3000rpm motor geared down by 15:1, that's 0.007 Nm not allowing for friction.