54    CALCULATING TRANSFER EFFICIENCY OF A
LIQUID FINISHING SYSTEM
John P. Owed
ITW Ransburg Electrostatic Systems
AUTOMATIC SYSTEM CONSIDERATIONS ECONOMIC JUSTIFICATIONS
Essential to all manufacturing processes is a good understanding of the cost related to a specific product. Within the paint shop there are many things that contribute to the coating cost of a
finished product. These included pretreatment chemicals, labor, utilities, waste disposal, paint
filters, coating materials, and many other things. The objective of this paper is to help the manufacturer identify the per unit cost of their coating material. Typically, this number will be one of
the larger percentages of the total finishing cost. This number can easily be calculated by dividing the number of parts coated per minute, hour, day, or year into the number of gallons of coating material used in the same time frame. Once this number is identified the manufacturer can
calculate the per unit cost of the coating material. It has been said that you pay for coating materials four times:
1. You pay someone to buy it originally.
2. You pay someone to apply it.
3. You pay someone to clean it up.
4. You pay someone to dispose of it.
With this in mind, any opportunity to identify a potential savings in the above-mentioned areas
should be pursued. Once the manufacturer identifies the per piece cost of their coating material,
they have also identified how much material is being applied per piece. This number or volume
of material can then be used to evaluate the performance of the finishing process. The manufacturer then knows how their existing system is performing and can compare it to known performance characteristics of other systems.
The following items will be covered in detail:
• Fluid Flow Measurement and Methods
• Calculating "Parts per Gallon"
• Calculating Actual Transfer Efficiency
• Theoretical Transfer Efficiency
• Calculating Return on Investment
FLUID FLOW MEASUREMENT AND METHODS
Fluid flow is a measurement of how much material is flowing per applicator in a given amount
of time. Typically, fluid flow rate is identified in cubic centimeters per minute (cc/min) or ounces
per minute (oz/min). In an effort to have a repeatable process, the manufacturer must monitor
and/or control the fluid delivery system.
Some manufacturers do not know where their fluid flow rates are set. They have operators that
adjust fluid deliveries by "I": "I think it looks good." This can be a very costly method; note the
following example. Example #1 - Assume that the target fluid delivery for a particular part is 200
cc/min. And at this rate the desired film thickness of 1.0 mils dry is obtained. What if 1.1 mils is
actually being applied because the fluid flow rate is at 220 cc.min (10% high)?
52nd Purdue Industrial Waste Conference Proceedings. 1997. Ann Arbor Press. Chelsea, Michigan 48118. Printed in
U.S.A.
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