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The Strand Mill

"Laboratory Preparation of Powder Coatings"

Introduction

Laboratory development time is critical to any industry. Therefore, to maximize the effort the best tools need to be used. In the development of powder coatings, there are many pieces of equipment that have been developed to reproduce large scale production. Included in this equipment are various laboratory grinders used in an attempt to match the particle size distribution achievable with an ACM (air classifying mill), common to most powder production lines. however, none of these devices have been found to be as effective, low cost, or efficient as the Strand Mill portable table top grinder. This review will compare the efficiency, ease of use, and ultimate particle size achievable with some of the common pieces of equipment used in the laboratory preparation of powder coatings.

Types of Mills used to match a production ACM mill

The most common pieces of equipment used in the laboratory preparation of powder coatings including the following: coffee grinder, Vitamix, Brinkman, Bantam, and a bench top ACM mill. This equipment ranges in price from $25 for a coffee grinder up to $30,000 for a bench top ACM. A simple coffee grinder consists of fixed blades, a small stainless bowl, and a plastic top. It is limited in capacity, inefficient, and includes plastic parts which cannot be solvent cleaned. Overall, contamination and durability is poor. Another common grinder is stainless steel Vitamix. A Vitamix is no more than a high speed blender, It' odd shaped container with corners, and small blade to height ratio is very inefficient for grinding dry powders. A more expensive option is a Brinkman SR3 mill. This mill grinds with a hammer tooth ring and a classifying screen. The product is ground by the hammers until it is small enough to pass through the screen. These mills are very difficult to clean and generate a lot of heat which frequently fuses the powder. Another choice is a Bantam mill. In principle, the Bantam mill works much like the Brinkman mill, however, it comes with a liquid nitrogen accessory which enables cooling during grinding. The Bantam contains many parts, is difficult to clean, and is not practical for fast evaluations or small samples. The final option is a bench top ACM mill known as the ACM-1. In principle an ACM-1 duplicates the mechanics of a production ACM mill. Although production particle size can be matched, cooling is a problem, it is not difficult to clean, and settings do not always coincide with production equipment.

Equipment

Cost($)

Efficiency
(Yield)

Ease of
Cleaning

Particle
Size

  Coffee Grinder

  25-100

  20-30%

  Poor

 Too Coarse

  Vitamix

  350-450

  20-40%

  Excellent

 Too Coarse

  Strand Mill

  1,300-1900

  40-50%

  Excellent

 Slightly Coarse

  Brinkman

  13-14,000

  70-90%

  Poor

 Too Coarse

  Bantam

  20,000+

  80-90%

  Poor

 Too Coarse

  ACM-1

  25,000+

  75-95%

  Poor

 Excellent

What is the Strand Mill

Non of the above options enables the fast, efficient, cost effective, preparation of laboratory samples of powder coatings. However, now there is a solution, The Strand Mill. The Strand Mill is a unique portable table top grinder that can quickly reduce flake into powder in less than 10 seconds. The mill consists of a motor housing, stainless steel bowl, two blades, and a stainless screw on top. The key to the Strand Mill is the construction of the blades and the geometry of the container which creates a unique mixing action. With this unit, it is possible to grind up to about 150 grams of flake at a time. Cleanup is easy, and it has been found to most accurately duplicate the particle size distribution of a production ACM mill. No other laboratory piece of equipment can match the easy of use, efficiency, and results of the Strand Mill.

Particle Size Comparison

In order to compare the performance of the Strand Mill with the other equipment, a standard 50/50 polyester epoxy hybrid was extruded using a Buss PLK-46. The sample was split and ground on the five different pieces of laboratory equipment. All samples were then sieved using a 140 mesh screen, and analyzed for particle size using a Coulter LS-130. The following table is an overlay of the particle size distributions for each piece of equipment.

 Equipment

Partical Size 

 Coffee Grinder

 200 microns
 Vitamix 190 microns
 Strand Mill 170 microns
 Brinkman 170 microns
 Bantam 170 microns
 AMC production 160 microns

Note: It was assumed that the laboratory ACM-1 could match the ACM production particle size and there it was not run. Comparing the other pieces of equipment it can be seen that the Strand Mill comes close to duplicating an ACM production mill. The following table compares approximate costs, efficiency, ease of cleaning, and particle size for each unit.

STRAND MILL (LAB GRINDER) COMPARISONS
     SMALL LAB GRINDER             MODEL # S101DS          

        LARGE LAB GRINDER           MODEL# S102DS                  

S101DS 2S102DS pg2

 Strand Lab Grinder Specifications

      

 Model

Volts

Amps 

RPM 

Bowl Capacity 

Dim. 

Wt. 

 S101DS

110 

10 

25,000 

150 Grams 

 9d x 8w x 15h

18 lbs 

 S102DS

 110

 15

25,000 

350 Grams

 9d x 8w x 18h

23 lbs 

STRAND LAB GRINDER
Replacement Parts List

Model S101DS

 

Model S102DS

 P/N               ITEM

Price US $ 

 P/N              ITEM

Price US $

DS101-01  Nut/Lockwasher

 

DS102-01  Nut/Lockwasher

DS101-02  Blades Set
              

 

DS102-02  Blades Set   
              (1 upper, 1 lower)

DS101-03  Dust Cover

 

DS102-03  Dust Cover

DS101-04  Bearing, Upper

 

DS102-04  Bearing, Upper

DS101-05  Brush Set

 

DS102-05  Brush Set 

DS101-06  Motor
DS101-07  Bowl/Lid

 

DS102-06  Motor
DS102-07  Bowl/Lid

DS101-09  Bearing, Lower

 

DS102-09  Bearing, Lower

DS101-10  Felt Washer, (2)

 

DS102-10  Felt Washer, (2)

DS101-13  Cap, Brush

 

DS102-13  Cap, Brush

DS102-15  Switch

 

DS102-15  Switch

*Call For Pricing

 

*Call For Pricing


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Strand Manufacturing Co., Inc.   1515 5th Street South #C   Hopkins, MN 55343
Phone: 952-935-8699   Fax: 952-935-8799   Email: jlkolb@strandmfgco.com
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