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Abstract

The U.S. Environmental Protection Agency (EPA) has funded

a pilot project to assist small and medium-size manufacturers

who want to minimize their generation of waste but who lack

the expertise to do so. In an effort to assist these manufacturers, Waste Minimization Assessment Centers (WMACs) were

established at selected universities, and procedures were

adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). That document has been superseded by the Facility Pollution Prevention

Guide (EPA/600/R-92/088, May 1992). The WMAC team at the

University of Tennessee performed an assessment at a plant

that manufactures several varieties of electrical rotating devices. Metal stock is machined, cleaned, and surface-treated if

required. Laminations, which are used in rotor, stator, and

stepper assemblies, are manufactured in-house from strip stock.

Rotors, stators, and steppers are manufactured through a series of operations and are then assembled into the finished

devices. The team’s report, detailing findings and recommendations, indicated that spent solutions from the four-stage aqueous cleaner are the waste streams generated in the greatest

quantity and that significant cost savings could be achieved by

discontinuing the use of FreonTM vapor degreasing for precision

parts cleaning.

This Research Brief was developed by the principal investigators and EPA’s Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of an ongoing research

project that is fully documented in a separate report of the

same title available from University City Science Center, Philadelphia, PA.

Introduction

The amount of waste generated by industrial plants has become an increasingly costly problem for manufacturers and an

additional stress on the environment. One solution to the

problem of waste generation is to reduce or eliminate the

waste at its source.

University City Science Center has begun a pilot project to

assist small and medium-size manufacturers who want to

minimize their generation of waste but who lack the in-house

expertise to do so. Under agreement with EPA’s Risk Reduction Engineering Laboratory, the Science Center has established three WMACs. This assessment was done by engineering

faculty and students at the University of Tennessee WMAC.

The assessment teams have considerable direct experience

with process operations in manufacturing plants and also have

the knowledge and skills needed to minimize waste generation.

The waste minimization assessments are done for small and

medium-size manufacturers at no out-of-pocket cost to the

client. To qualify for the assessment, each client must fall

within Standard Industrial Classification Code 20-39, have gross

annual sales not exceeding $75 million, employ no more than

500 persons, and lack in-house expertise in waste minimization.

The potential benefits of the pilot project include minimization

of the amount of waste generated by manufacturers and reduction of waste treatment and disposal costs for participating

plants. In addition, the project provides valuable experience for

graduate and undergraduate students who participate in the

program and a cleaner environment without more regulations

and higher costs for manufacturers.

Waste Minimization Assessment for a Manufacturer of

Electrical Rotating Devices

United States

Environmental Protection

Agency

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-94/018 September 1994

Richard J. Jendrucko*, Thomas N. Coleman*,

and Gwen P. Looby

* University of Tennessee, Department of Engineering Science and Mechanics,

Knoxville, TN

** University City Science Center, Philadelphia, PA

E AP
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Methodology of Assessments

The waste minimization assessments require several site visits

to each client served. In general, the WMACs follow the procedures outlined in the EPA Waste Minimization Opportunity

Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC

staff locate the sources of waste in the plant and identify the

current disposal or treatment methods and their associated

costs. They then identify and analyze a variety of ways to

reduce or eliminate the waste. Specific measures to achieve

that goal are recommended and the essential supporting technological and economic information is developed. Finally, a

confidential report that details the WMAC’s findings and recommendations (including cost savings, implementation costs, and

payback times) is prepared for each client.

Plant Background

Several varieties of electrical rotating devices are manufactured by this plant. It operates over 4,000 hr/yr to produce

more than 250,000 units annually.

Manufacturing Process

Carbon and stainless steel, aluminum, brass, and copper bar

stock, nickel strip stock, plastic powder, fiberglass pellets, and

powdered metal are the principal raw materials used in production.

The various types of metal bar stock are machined into component parts using automatic screw machines. Metal shafts that

are produced are sent to the four-stage aqueous cleaner consisting of an alkaline wash tank, two rinse tanks, and a rust

inhibitor rinse tank for carbon steel parts. Other parts produced

by the screw-machines are machined further and then washed

in the four-stage cleaner. Stainless steel and aluminum parts

undergo surface treatment after cleaning.

Almost all of the stainless steel parts and all of the aluminum

parts undergo a protective surface treatment to prevent corrosion. The stainless steel parts are submerged in a passivating

bath, rinsed, dried, and cleaned in an ultrasonic vapor degreaser. Aluminum parts are submerged in a chromium dioxide

solution and rinsed.

Laminations, which are used individually in rotor assembly and

stacked and fixed together in stator and stepper assemblies,

are produced in the plant. Individual laminates are cut from

strip stock in a punch press and then washed in the four-stage

washer and heat-treated. The laminations are transferred individually to the rotor assembly area or to spray painting, or are

stacked and held in place by shrink wrap or by welding. The

welded laminates are then sent to painting, and unwelded

stacks are transferred to the stator and stepper assembly area.

Injection molding machines are used to press plastic insulating

rings onto metal shafts and to press fiberglass pellets, plastic

powder, and powdered metal into various component parts.

The resulting parts are stored until needed for assembly.

In the rotor and stator assembly line, individual laminations are

pressed onto metal shafts. Magnet wire is machine-wound

onto the laminations and onto painted and unpainted laminate

stacks. An insulating coating is manually stripped from the end

of the contact wires using a stripping compound. Then, the

stripped wires are welded to a contact point. The wire coils are

impregnated with epoxy and oven-cured to fix the coils to the

laminations. The resulting rotors and stators are machined,

washed in the four-stage cleaner and in an ultrasonic vapor

degreaser, and transferred to final assembly.

For use in stepper assembly, laminate stacks are preheated in

an oven and powder-coated in a fluidized bed. The parts are

cured in an oven and, after manual removal of excess coating,

cleaned in an ultrasonic vapor degreaser. Magnet wire is wound

onto the laminate stacks. Insulating coating is manually stripped

from the end of the contact wires with a stripping compound

and the stripped wires are welded to a contact point. The wire

coils are impregnated with epoxy and oven-cured to fix the

coils to the laminations. The resulting steppers are machined,

washed in the four-stage aqueous cleaner and in an ultrasonic

vapor degreaser, and transferred to final assembly.

In the final assembly area, a bearing is inserted into a housing

at one end of the stator or stepper. The insulating ring end of

the rotor is inserted into a bearing plate. The rotors are matched

with stators and steppers and inserted into them. The bearing

plates are fastened, and a brushblock is fastened to ring

contacts on the rotors. The completed units are tested, the

motor housings are wiped clean and stamped with identifying

markings, and the finished parts are packaged and shipped.

The flow diagrams shown in Figures 1-7 depict the operations

used by this plant.

Existing Waste Management Practices

This plant already has implemented the following techniques to

manage and minimize its wastes:

• Distillation units are used to recover usable TF-FreonTM from

contaminated FreonTM in the plant’s vapor degreasers.

• An in-drum waste compactor is used to reduce the volume

and disposal cost of paper towel waste.

Waste Minimization Opportunities

The type of waste currently generated by the plant, the source

of the waste, the waste management method, the quantity of

the waste, and the annual treatment and disposal cost for each

waste stream identified are given in Table 1.

Table 2 shows the opportunities for waste minimization that the

WMAC team recommended for the plant. The minimization

opportunity, the type of waste, the possible waste reduction

and associated savings, and the implementation cost along

with the simple payback time are given in the table. The

quantities of waste currently generated by the plant and possible waste reduction depend on the production level of the

plant. All values should be considered in that context.

It should be noted that the economic savings of the minimization opportunity, in most cases, results from the need for less

raw material and from reduced present and future costs associated with waste treatment and disposal. Other savings not

quantifiable by this study include a wide variety of possible

future costs related to changing emissions standards, liability,

and employee health. It also should be noted that the savings

given for each opportunity reflect the savings achievable when

implementing each waste minimization opportunity independently and do not reflect duplication of savings that may result

when the opportunities are implemented in a package.
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Figure 1. Process flow diagram for machining and surface metal treatment.

Metal bar

stock

Machining Metal shafts

Aluminum

parts

Passivating

Stainless

steel

parts Stainless

steel

parts

to stock

Ultrasonic

vapor

degreasing

Chromium

anodizing

Anodized

aluminum

parts to

stock

This research brief summarizes a part of the work done under

Cooperative Agreement No. CR-814903 by the University City

Science Center under the sponsorship of the U.S. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.

Other

metal

parts Lathing Precision

grinding

4-stage

aqueous

cleaning

Metal parts

to stock
4

Metal

shafts from

stock

Molded plastic

parts to

assembly

Fiberglass

pellets,

powdered

metal,

plastic

powder

Metal shafts

with insulating

ring to assembly

Contact

wires

Gold

rings

Assembly

Injection

molding

Manual

trimming

Nickel and

cold rolled

strip stock

Welded

laminate

stacks

Cutting

4-stage

aqueous

cleaning Annealing

Individual

laminations

Stack

welding

Manual

stacking

Laminate

stacks

Stack

fixation

Figure 2. Process flow diagram for injection molding.

Figure 3. Process flow diagram for laminate production.
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Figure 4. Process flow diagram for rotor manufacture.

Individual

laminations

Painting

Assembly Coil

winding

Stripping

Soldering

Epoxy

impregnating

Shafts with

insulating

ring

Magnet

wire

Curing Precision

grinding

4-stage

aqueous

cleaning

Ultrasonic

vapor

degreasing

Rotors to assembly
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Figure 5. Process flow diagram for stator manufacture.

Ultrasonic

vapor

degreasing

4-stage

aqueous

cleaning

Precision

grinding Curing Epoxy

impregnating

Painting Assembly

Coil

winding Stripping Soldering

Painting

Laminate

stacks

Magnet

wire

Motor

housing

Stators to assembly
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Figure 6. Process flow diagram for stepper manufacture.

Ultrasonic

vapor

degreasing

4-stage

aqueous

cleaning

Precision

grinding Curing

Epoxy

Soldering Assembly impregnating Stripping

Assembly Coil

winding

Ultrasonic

vapor

degreasing Trimming

Preheating Powder

coating Curing

Laminate

stacks

Steppers to assembly
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Figure 7. Process flow diagram for motor assembly.

Rotors

stators

steppers

Subassembly

Fastening

Testing

Finished motors shipped
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Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Generated Source of Waste Waste Management Method Generated (lb) Management Cost

Oil-based lubricant Machining and alkaline wash tank Shipped offsite for use in fuel-blending 45,190 $3,350

Water-based lubricant Machining Shipped offsite for disposal 36,530 4,900

Metal scrap Machining and assembly Sold to recycler 40,000 (57,370)1

Aqueous cleaner and rinse water 4-stage aqueous cleaner Sewered 1,195,200 5,250

Rust-inhibitor solution 4-stage aqueous cleaner Sewered 250 220

Spent passivating solution Passivating of stainless steel parts Shipped offsite for disposal 660 940

Passivating rinse water Passivating of stainless steel parts Treated in onsite WWTP; sewered 102,960 920

Spent Stoddard solvent Water removal following passivating Shipped offsite for disposal 920 1,400

Evaporated Stoddard solvent Water removal following passivating Evaporates to plant air 2,830 0

Spent TF-FreonTM Vapor degreasing Distilled onsite; reused 23,760 1,820

Evaporated TF-FreonTM Vapor degreasing Evaporates to plant air 39,510 103,520

Spent chromic acid solution Anodizing of aluminum parts Shipped offsite for disposal 1,650 1,200

Anodizing rinse water Anodizing of aluminum parts Treated in onsite WWTP; sewered 597,600 4,100

Plastic flashing Trimming after injection molding Shipped to municipal landfill 40 140

Evaporated cooling water Injection molding machines Evaporates to plant air 796,800 160

Paint waste Water curtain paint spray booth Shipped offsite for disposal 27,500 30,200

Evaporated solvent Painting Evaporates to plant air 2,180 1,440

Stripper waste Assembly of rotors, stators, and steppers Shipped offsite for disposal 1,450 2,800

Waste solder Soldering Sold to recycler 200 (250)1

Epoxy waste Assembly of rotors, stators, and steppers Compacted; shipped offsite for disposal 18,000 20,180

Waste powder coating Powder coating during stepper assembly Shipped offsite for disposal 4,400 3,200

Acetone-wetted rags Wiping and cleaning in final assembly Shipped offsite for disposal 6,340 5,360

Wastewater treatment sludge Onsite WWTP Shipped offsite for disposal 24,750 21,890

Still bottoms Onsite solvent recovery still Shipped offsite for disposal 2,640 9,940

* Includes waste treatment, disposal, and handling costs and applicable raw material costs

1 Net credit received
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Table 2. Summary of Recommended Waste Minimization Opportunities

Annual Waste Reduction

Implementation Simple

Minimization Opportunity Waste Reduced Quantity (lb) Per cent Net Annual Savings Cost Payback (yr)

Discontinue the use of the water curtain Paint waste 27,500 100 $33,2701 $78,44 2.4

 paint spray booth and install an electro- Evaporated solvent 1,250 57

 static powder coating system. A small

 amount of powder overspray waste will

 be generated and disposed.

Minimize the use of paper towels during Epoxy waste 14,400 80 17,850 760 0.04

 adhesive and epoxy application by collect-

 ing drip waste for convenient clean-up or

 glass table covers and in small trays. Re-

 use collected material before it dries.

Discontinue the use of FreonTM vapor Spent TF-FreonTM 19,010 80 49,4001 3,150 0.06

 degreasing for cleaning of precision parts. Evaporated TF-FreonTM 31,610 80

 Use the existing 4-stage aqueous cleaner Still bottoms 2,110 80

 for precision cleaning. Generation of

 aqueous cleaning waste will increase

 slightly.

Install a sludge drying oven to reduce the Wastewater treatment sludge 12,380 50 8,5301 37,200 4.4

 volume of sludge shipped offsite.

Cover the vapor degreaser tanks except Evaporated TF-FreonTM 19,760 50 51,760 2,060 0.04

 when parts baskets are being lowered into

 or taken out of the tanks.

1 Total savings have been reduced by an annual operating cost required for implementation of this opportunity.
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-94/018