Mill throughput calculation

[res]

Is the a way to ballpark the throughput of a given mill at a given speed? :huh:

I'm running a monster MM3, Three rollers, six inches long, two wide. Proposed motor turning at 120 RPM.

 

[razz]

Do you mean how many kilos per minute it can mill?

 

[res]

Yeah. Approximately.

 

[razz]

Not sure on the theory but I think you will find most of us here have worked it out post set up. i.e., it takes two minutes to put through 5 kilos, that sort of thing. I think the important bit is that you will have approx 120 revolutions and that is in the ideal range for a grain mill.

 

[klangers]

To do it properly is rather complicated. We'd have to look at surface finishes, mill hardness, motor torque, motor power, grain size, hopper pressure, vibrations, grain friability/strength etc etc.

Agree with Manticle - in industry all the calcs for this are empirical - design a few good experiments, measure results, and use mathematical scaling principles to generate an empirical equation.

If you want a guess, I would suggest the following approximation:
Roller slip factor: Rs (unitless)
Roller diameter: D (mm)
Effective roller length: L (mm)
Grain density: P (kg/m3)
Mill speed: w (RPM)
Pi: (our good mate 3.14)
Mill gap: g

Roller slip factor is related to mill gap settings and grain consistency. Smaller gap - larger slip factor. It is basically a fudge factor to cover all the other variables that are near impossible to measure.

Approximate kg/hour = PiDLwgP/((1000^3)Rs)


For example:

Roller slip factor: 1.4
Roller diameter: 30 mm
Effective roller length: 150 mm
Grain density: 500 kg/m3
Mill speed: 120
Pi: (our good mate 3.14)
Mill gap: 3mm

3.14*30*150*120*3*500/((1000^3)*1.4)
=1.82 kg/minute

 

[res]

Thanks very much guys, sounds pretty workable
I'll post back when I have the empirical data.
Cheers. :beer:

 

[Ducatiboy stu]

Well my mill, 2 roller @ 50mm x 200mm spinning at 180rpm gets thru 5kg in about 1 minute

 

[klangers]

Well my mill, 2 roller @ 50mm x 200mm spinning at 180rpm gets thru 5kg in about 1 minute

Yeah the equation I developed (aka made-up, but I'm allowed to do that cos that's my job) is pretty loose. It's based on the volume swept by the rollers, and so there are huge variations depending on all the factors I initially mentioned.

I'm happy to develop an empirical equation etc based on everyone's info

 

[TheWiggman]

Yes Stu we all know how good your mill is...

 

[Ducatiboy stu]

Yes Stu we all know how good your mill is...

Just simple facts. Nothing else.

Unless you want to make something of it

AND if you have followed the MM mill thread with the fluted rollers then you would see that they are fairly similar in throughput

 

[klangers]

Well my mill, 2 roller @ 50mm x 200mm spinning at 180rpm gets thru 5kg in about 1 minute

Using my previous equation,

Roller slip factor: 1.4
Roller diameter: 50 mm
Effective roller length: 200mm
Grain density: 500 kg/m3
Mill speed: 180
Pi: (our good mate 3.14)
Mill gap: 3mm

3.14*50*200*180*3*500/((1000^3)*1.4)
= 6 kg/minute

Damn. That's pretty close to reality. I've still got it! :beerbang:

 

[Ducatiboy stu]

Using my previous equation,

Roller slip factor: 1.4
Roller diameter: 50 mm
Effective roller length: 200mm
Grain density: 500 kg/m3
Mill speed: 180
Pi: (our good mate 3.14)
Mill gap: 3mm

3.14*50*200*180*3*500/((1000^3)*1.4)
= 6 kg/minute

Damn. That's pretty close to reality. I've still got it! :beerbang:

You Da MAN.... :super:



I wont ask how you tried to work it out....Math was never my strong point

 

[TheWiggman]

Just fishing for a bite Stu But I certainly have heard about your mill before. I think you built it with Tony? My mill takes about 20 mins for 5kg, but that involves 3 children and a hand crank and halfway through a cranky dad.

3mm gap seems wide klangers, on the home scale I would have expected a gap of 1mm (0.9mm personally) which would have a significant impact on the result.

 

[Ducatiboy stu]

Just fishing for a bite Stu But I certainly have heard about your mill before. I think you built it with Tony? My mill takes about 20 mins for 5kg, but that involves 3 children and a hand crank and halfway through a cranky dad.

3mm gap seems wide klangers, on the home scale I would have expected a gap of 1mm (0.9mm personally) which would have a significant impact on the result.

Yeah Tony built it.

You need to visit Motion Dynamics and get yourself a motor. Kids get sick of that kind of stuff when they get older

 

[klangers]

3mm gap seems wide klangers, on the home scale I would have expected a gap of 1mm (0.9mm personally) which would have a significant impact on the result.

Yeah fair enough - just change the mill slip factor to compensate in the above examples. We have to "calibrate" the equation with real life examples, so to speak.

 

[Ducatiboy stu]

Wonder how many Calories you would burn hand cranking 5kg grain...?