RE: powder packing density!!!

From: Scott A Schroeder <>
Date: Wed Mar 03 2004 - 22:39:21 EET

Attaining theoretical (or near theoretical) densities can be extremely
difficult, if not impossible. The simple models assume that every void is
filled by every available particle of the correct size.
Obviously, this is not very likely. Also ignored are such variables as:
surface roughness, particle irregularity, true size distribution,
electrostatic and hydrostatic forces, deposition technique, powder
segregation and inhomogeneity, and subsequent processing (vibration,
compression, etc)

It is entirely possible to have two powder blends (one monosize, the other
7:1 bimodal), that show no measurable difference in final packing

Cheers, Scott

Scott A. Schroeder, Ph.D.\ phone: 805-373-4427
Rockwell Scientific Co. \ fax: 805-373-4775
1049 Camino Dos Rios \ email:
Thousand Oaks, CA 91360 \

"Neil Hopkinson" <>
Sent by:
02/23/04 09:58 AM

        Subject: RE: powder packing density!!!

I seem to remember reading that the ideal diameter ratio for one mode to
next is 7:1. So ideally particles would be mixed with diameters with 1st
mode = 1 micron, 2nd mode = 7 microns, 3rd mode = 49 microns, 4th mode =
microns etc. I'm not suggesting the use of 1 micron powder but hopefully
you get the idea.


-----Original Message-----
From: []On
Behalf Of Miller, Michael W
Sent: 23 February 2004 14:04
Subject: RE: powder packing density!!!

I've always wondered, what's the packing density for spheres?

Bear in mind most powders have a range of sizes, hence tighter packing =
is obtained as the smaller particles fill up the spaces between the =
bigger ones. Also when dealing with powder, other factors such as flow =
are affected by non-round shapes.

Michael W Miller ( =20
The Boeing Company M/C 45-17 A-2329 206-655-3289
Rapid Product Manufacturing 655-4366 655-4365 655-2262 =20

Disclaimer: Engineer and out the other!
Experience is something you get right after you need it.

-----Original Message-----
From: Toby Gill []=20
Sent: Friday, February 20, 2004 4:34 AM
Subject: powder packing density!!!

Thought this may be of interest to some,

It has just been published that M& M sweets pack together more densely =
perfect spheres when randomly jumbled in a container.
It was also discovered that by stretching the M&M shape (so elliptical,=20
like an almond) in computer simulations, a packing density approaching =
packing fraction of 0.74 was achieved.

This seems to me to be important to anyone involved with producing=20
components from powders, be it by conventional methods or by rapid=20
manufacturing techniques. Does anyone have any comments/thoughts on this =


P.S. I have just finished a PhD based on SLS and am currently looking =
employment. Anyone who has any vacancies arising in the near future =
contact me at the email address above.


Toby Gill
Received on Thu Mar 04 10:07:33 2004

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