Filtered for success

Air dryer boosts CMM's productivity

Brackett & Cochran Manufacturing Inc. is a contract manufacturer that supplies individual component parts and subassemblies to a variety of industries. Much of the company's production is related to the healthcare industry, such as parts for hospital beds and operating room tables. The company is equipped with state-of-the-art CNC machining and CNC turning centers as well as conventional job shop and welding equipment. To ensure high quality of machined parts and assemblies, ISO 9002 certified Brackett & Cochran monitors its processes with test equipment, and when necessary manufactures its own test equipment.

Membrane air dryers have become a factor in a manufacturer's quality control.

Recently, oil in the air supply to a CMM caused inaccurate measurements, resulting in scrapped parts. A check valve that passed CMM inspection, for example, later failed functional testing and had to be scrapped, indicating that the CMM measurements were inaccurate. Oil contamination also required the CMM to be taken out of service at least monthly to be thoroughly cleaned.

The CMM, a Brown & Sharpe Microval model, is used to compare new parts and finished parts against customers' drawings. Manual measurements are also taken, but the CMM is preferred because it is faster and provides the ability to program the inspection process. For example, the QC department can program the CMM to guide the technician through an inspection process, displaying critical dimensions and allowable tolerances as he takes measurements. Another benefit of the CMM is that it can get accurate measurements on parts that are too complex to inspect adequately with manual tools.

Fair-operated CMM

The Microval CMM operates on air bearings that allow the operator to easily move the arm around the part being inspected. The bearings have 0.020´´ air holes so it is important that the compressed air supply is clean. At Brackett & Cochran, the air supply for the CMM is the same compressed air used in the rest of facility. The Microval includes both a particulate filter and coalescing filter that are supposed to remove both oil and water particles from the air supply. At Brackett & Cochran, they controlled water effectively but did not prevent oil from reaching the CMM. The QC department tried installing another air drying filter system upstream of the CMM but it did not prevent oil contamination either.

When oil permeated the filters, the holes in the air bearings clogged. With less air passing through the bearings, the CMM became difficult to move. Because the operator must carefully move the probe of the CMM all over the part, the sluggish motion compromised accuracy. At times, parts that passed a CMM inspection failed functional testing, indicating that the measurements obtained with the CMM were wrong. The device was then taken apart and cleaned but this was not a simple process because all the tubing that supplies air to the bearings had to be cleaned as well. Old filters were replaced with new ones, costing $600 annually.

A different approach

One possible solution to this problem was replacing the compressed air system for the entire building. That would have been expensive and the CMM was the only device that required a clean air supply. Another option was presented by a salesperson from Whatman Inc., Tewksbury, MA, who came by to demonstrate a new type of compressed air dryer. The Balston Membrane Air Dryers offered by Whatman use membrane separation technology. In the demonstration, the salesperson used a compressor to inject oil into the air supply, then showed how a regular coalescing filter reduced oil permeation by 50 percent. The Balston dryer, which provides clean dry compressed air through the use of state-of-the-art membrane technology, reduced oil permeation by 99 percent.

This demonstration convinced the QC department to install a Balston Model 76-25 Membrane Air Dryer. The dryer was installed downstream of an air regulator that reduces pressure to the CMM. The compressed air goes into the Balston system but prior to entering the membrane drying portion of the system, the air passes through two high efficiency coalescing filters. The filters remove oil and water droplets and particulate contamination with an efficiency of 99.99 percent at 0.01 micron. Next the air passes into Balston dehydration membranes. These consist of bundles of hollow membrane fibers, each permeable only to water vapor. As the compressed air passes through the center of these fibers, water vapor permeates the walls of the fiber, and dry air exits from the other end. A small portion of the dry air (regeneration flow) is redirected along the length of the membrane fiber to carry away the moisture-laden air that surrounds it. The remainder of the dry air is piped to the CMM.

Liquids removed by the filter continuously drain from the filter cartridge into the bottom of the housing, where they are automatically emptied by an autodrain assembly. The air leaving the prefilter carries only water vapor, which is removed in the membrane module. The dryer delivers air with a dewpoint of 35 F. Selective permeation membranes remove water vapor from compressed air. The Balston Membrane Air Dryer is designed to operate continuously, 24 hours per day, 7 days per week. No electrical supply is required to use these dryers. The only maintenance required is changing the prefilter cartridge once a year. The time required to change the prefilter cartridge is approximately five minutes.

Excellent results

After passing through the Balston dryer, the compressed air goes through the CMM filters as well. Since the installation of the Balston dryer six months ago, the filters on the CMM have not shown any signs of use, nor has the CMM needed to be cleaned. Downtime due to contamination has been eliminated, and the company is no longer buying new filters for it every month. So far, the filter on the Balston dryer has not needed to be changed. When it does, the fact that the filter is an off-the-shelf part will simplify the process because it will not be necessary to order filters eight weeks in advance as it was in the past.

In addition to installing the Balston dryer, the Brackett & Cochran QC department completely overhauled the CMM. In all, they spent several thousand dollars--including the purchase of the new air dryer--to get it back in good working order. Since then, the CMM has performed perfectly. Now that the air bearings no longer clog, the unit is easily operated and all parts are effectively measured. The scrap that resulted from inaccurate measurements is no longer produced. In addition, since parts are more easily measured, the process takes less time so productivity has increased.

A new approach to air filtration spared Brackett & Cochran from replacing its entire compressed air supply, and gave the company the well-functioning CMM it needs for quality assurance. With something as simple as cleaner air, Brackett & Cochran has boosted productivity, reduced scrap, and improved the operation of an important piece of equipment.

Whatman Inc., Tewksbury, MA, http://www.OneRS.net/101tp-351 or circle 351.

A whiz of a Wiz

Coolant unit keeps machine shop racing

It's hard to believe that a successful manufacturer like Dickey & Son, Indianapolis, IN, would trust a single, portable coolant reconditioning unit to service its 22 lathes and mills--and that the unit would pay for itself within its first year. But that is what happened to Dickey & Son, Indianapolis, IN.

The Coolant Wizard hunts down tramp oil.

"We had invested more than $3 million in new equipment and were hoping to get a coolant reconditioning system to help extend the life of our coolant," says Scott Dickey, shop supervisor. "Our Coolant Wizard unit has helped our machines run cleaner and reduced our coolant disposal costs."

Dickey & Son has more than its investment to protect. The ISO 9001-certified company has a reputation for machining high-quality parts for locomotives, generators, and gearing for transmissions.

In addition, the company has been heavily involved for nearly four decades in the custom manufacturing of tube-end forming machines. This equipment is built to meet the challenges presented by heavy industrial production: accurate tolerances, quick tool changes, and operator safety. Dickey & Son has machines that can accommodate copper, brass, stainless steel, and carbon steel sizes from 1.5´´ to 6´´.

The company has built an impressive customer list--all from a company founded in a small garage in 1947 by Edgar Dickey and his son, Jack. Ed and Jack were both lathe operators who put a premium on price and quality. Today's Dickey & Son holds to that belief.

From those humble beginnings, Dickey & Son has moved into a 60,000-sq-ft facility on Indianapolis's west side, where Jack's son, Jack Jr, runs the company. As Dickey & Son grew, the company became busier and busier. This meant machines were worked harder. A typical by-product of this was the need to purchase more coolant to use in the machines. This provides a ripe environment for bacteria to breed and grow. The bacteria causes problems that usually require changing the coolant often.

For the company, the single Coolant Wizard unit has changed the dynamics of this process. "The Coolant Wizard gets tramp oil out of the coolant so bacteria doesn't have a food source," says Scott. "This year, we've saved 11,760 gallons of coolant waste on our lathes and mills. We used to change coolant every four to six weeks. Now we change our coolant once a year. I've measured our net savings at nearly $8000 per year."

The Coolant Wizard is simple to set up, and for Dickey & Sons, the only maintenance to the unit has been changing the filters every two weeks.

Coolant Wizard Inc., Indianapolis, IN, http://www.OneRS.net/101tp-260 or circle 260.

Racers dig speed of rapid prototyping

Formula 1 Team crosses finish line
with CastForm patterned parts

The latest Minardi Formula 1 (F1) race car features several high performance titanium components. These parts were investment cast in titanium and other metals from patterns made by the team's technical sponsor, CRP Technology of Modena, Italy.

A titanium component for the Manardi Formula 1 race car cast using rapid prototyp[ing technology.

CRP, a division of the Cevolini Group, used its DTM Sinterstation systems to rapidly produce the CastForm PS patterns for the uprights, suspension supports, clutch box, steering box, and gear box for the Minardi F1 car. These rapidly produced patterns were then shipped to CoastCast Corp, a foundry in Rancho Dominguez, CA. There they were investment cast in a modified version of Ti 6246.

Within five to eight weeks, depending on the specific part, the titanium parts were cast, machined, tested, and installed on the Minardi F1 car in time for the 1999 championships.

"Formula 1 racing is a difficult, technically demanding field," says Franco Zucchelli, marketing manager for CRP "These teams are willing to try anything to get the results they want."

Parts with a purpose

Among the most critical parts for the Minardi F1 car were the uprights, the four parts that hold together the upper and lower wishbone of the wheels. This is an important part of the car; the area where the suspension comes together. The uprights hold and support the caliper for the brakes, as well as the hubs of the wheels.

These "out-of-fender" parts have to be strong because they are directly in touch with the ground through the wheels. Imagine the abuse these parts have to take on a car that races at very high speeds

"The uprights are sensitive parts in the geometry of the suspension and have to be strong and stiff, yet very light," Zucchelli explains. "It is really hard to combine all these characteristics. To do this we had to design a very complex and intricate geometry and use the titanium."

Process Design

"We designed the pattern for the uprights and some of the other parts knowing they would be patterned on our Sinterstation system," Zucchelli adds. "There were a lot of undercuts, hollow areas, dropped angles, and other features that would have been difficult to create via tooling." These features and details are easily created with the layer-by-layer SLS process.

As the CRP staff developed the uprights, they knew that creating the patterns with DTM's new CastForm PS material and the SLS process would offer certain advantages. The process would save them time and the patterns would work well with reactive alloys, including the modified Ti 6246.

The team needed 10 sets of four uprights for a total of 40 parts. Several other parts for the car were also cast at CoastCast at this time.

"We actually had the uprights cast in both Ti 6246 modified and Steel 17-4PH, just to compare the two," explains Zucchelli. "The steel is a relatively high strength alloy that would have worked well also, but it is heavier than titanium."

CoastCast also cast the steering box in the modified Ti 6246 and a variety of other alloys, such as Al 206. The clutch box and suspension supports were cast only in the modified Ti 6246. The Al 206 and the Ti 6246 are both light, but titanium offers more strength where it's needed most.

The results

One lesson learned: the new titanium parts are a big improvement over those used on the previous year's Minardi F1 car.

An F1 part in casting stages.

The parts were used in the Minardi F1 car for every race in 1999. They even survived several mishaps, including one that destroyed the wheels on the car.

"There wasn't so much as a deformity," notes Zucchelli. "These parts are much lighter, yet stronger."

And, unlike the machined and welded versions used on other cars, the one-piece upright design requires little maintenance.

"They are checked after each race out of principle," says Zucchelli, "but the maintenance crew has never had to do any repair or rework on them."

Other benefits include:

• Time savings. "You can go from CAD design to casting and to the finished part in six to eight weeks. Normally it would take at least 10 weeks just to make the tool, plus it might take an additional six weeks for the rest of the process. We essentially cut our time in half," says Zucchelli.
• Changes made easily and often. In addition, CRP and Minardi could make design changes throughout the process without endangering project costs or missing deadlines. They even made six design changes to the rear upright for the Minardi car--changes that, with traditional tooling, would have been next to impossible with regard to time and cost.
• Significant cost avoidance. Tools for the four uprights could cost about $25,000 to $50,000. A more complex design could go as high as $50,000 to $75,000 for the four tools.

Zucchelli adds, "Another option, machining the part in titanium, would be expensive as well. With the casting method we used, you only need a relatively small amount of material and even then it is practically impossible to acquire and very expensive."

• No welded joints. Titanium parts are cast in one piece with no major welds or joints, avoiding the destructive testing and rework often necessary with welding and machining.
• More metal choices. With the SLS/CastForm formula, CRP also had the freedom to cast parts in the alloy of choice.
• Foundry approved. Even foundries agree that CastForm PS works very well in investment casting, even with sensitive metals such as titanium.

DTM, Austin, TX, http://www.OneRS.net/101tp-258 or circle 258.

Originally published in the January 2001 issue
of Tooling & Production.
Please Note: some pictures or diagrams are only available through the printed media.