When Quality Demands Clean Parts

Combination of cleaning steps removes chips and oil from deep, blind holes

Published by Metlfax Online

One critical quality issue is a part's final condition after manufacturing. It must be oil-free and completely clean. Meeting or not meeting these conditions can make it usable or scrap.

This is a challenge for VMP, Inc., Valencia, CA, a screw machine shop that produces thousands of parts per day. To solve this problem, they rely on a parts washer that provides the right amount of heat, chemical concentration, agitation and rotation to meet their cleaning requirements.

"Quality was our first concern," said Bob Schreiner, Jr., vice president/general manager at VMP, when describing his search for the right cleaning system. "At the time, we had a 40-year-old cleaning system. It was time to step up in technology."

Schreiner's second concern was durability. "When we were looking, I saw three- to five-year life spans on many of the machines we saw."

Schreiner found that special combination of capabilities, quality and durability at Magnus Equipment, Cleveland, OH, a manufacturer of standard and custom agitation washing systems for all types of industries.

Since its installation, the unit has allowed VMP to maintain a competitive product cost, while offering high quality parts and on-time delivery. Its speed and quality has enabled VMP to take on more large-volume customers, tripling sales volume.

Daily, thousands of screw machine parts produced by VMP, Inc., Valencia, CA, are run through the Magnus wash system.

A pleasant cost-saving benefit for Schreiner was the minimal amount of waste sludge left from the cleaning process. After two years of operation, VMP has only disposed of 55 gallons of sludge. And in California, with its stringent environmental laws, this can be a major concern.

High-volume, precision machining

VMP, Inc., is a family-owned business that started in 1960. Among its customers are General Electric, Boeing and Lockheed Martin-Marietta, as well as companies in the medical industry. However, the company is noted for manufacturing threaded and non-threaded inserts and fasteners, with many conforming to MIL-I-45208 specifications. They have a complete line of standard inserts and fasteners for industrial applications. Engineers will design or recommend parts for their customers' requirements, providing CNC screw-machined parts from four different facilities for rotational-molding, injection-molding, electronics and fittings applications. Materials offered include brass, aluminum, stainless steels, and Ludloy.

VMP's CNC department machines industrial parts using Acme Gridley and Davenport screw machines. The Swiss department can turn out precision parts to a tolerance of 0.000 05´´ to meet the requirements of the medical industry. The variety of machines within VMP can tackle parts ranging in size from a 0.032´´ diameter stock, up to a 3.5´´ diameter rounds or 2.5´´ hex stock.

Jobs often require VMP to cut holes and threads 0.08´´ to 3Ž8´´ in diameter with 3Ž4-10 threads and a pitch at the bottom on some of the parts," explains Schreiner.

Coordinated cleaning actions

According to Schreiner, the work at VMP required a cleaning system that offered minimal rinsing requirements, left parts clean and free of chips, and prevented any rusting or oxidation of the parts. "Rotation and vertical immersion agitation allows for constant flushing to get oil and chips out of all the nooks and crannies of our parts," says Schreiner.

Washer provides the right amount of heat, chemical concentration, agitation and rotation to meet cleaning requirements. Here, washer system's second stage shows three basket compartments.

Today, the Magnus washer accepts screw-machined parts from the four VMP machining facilities.

VMP's cleaning requirements were temperature, proper cleaning chemicals, rotation, combined with vertical immersion, agitation and time. Heating of the solution helps break down the oils, allowing the cleaning solution to eliminate the oil. The cleaning solution also contains a rust inhibitor to keep parts from oxidizing and rusting.

Aggressive rotation is needed to allow chips to come out of any blind holes. "With the rotation, the parts are constantly tumbling to loosen the chips. The machine we were looking to buy had to provide axial rotation," says Schreiner.

A continuous immersion agitation with rotation cycle flushes the chips out. Rotation outside of the wash tank removes any residual cleaning solution or chips remaining on or in the parts.

The rinse tank features an internal electric heater. "We run a lot of brass through the machine. If I set the water temperature at 175 degrees while we are running at full speed, the temperature might drop down to 168 degrees. We don't run as hot on the wash. The purpose of a hotter rinse is to put enough heat into the part so that it flash dries once it leaves the rinse water," explains Schreiner. This approach means parts don't need to sit long on the drying table which is not part of the Magnus washer.

"A lot of our competitors use solvent chemical cleaning, such as perchloroethylene, which requires the parts to be dipped in alcohol before use. Our parts can be taken out of their shipping box and placed on the injector pin of a molding system without any additional cleaning. This is a big savings to the customer," says Schreiner.

Fast and clean

Over 150,000 OEM and distributor parts machined by VMP will pass through the washer in a matter of 2.5 hours. "Our older system, a vapor degreaser built back in 1960 by my dad, ran 24 hours a day and took two operators," says Schreiner. "Today, the Magnus washer handles the same workload, starting at 7:00 am and finishing by 9:30 am, an improvement in time and cost."

VMP, is also very environmentally conscious. "We make a point of recycling our waste materials. We are trying to be a self-reliant shop. We are constantly filtering oils using chip spinners, coalescers and filters right at the machining systems," he says.The Magnus washer is an extension of that environmental mentality at VMP.

One of the Magnus washing units features a coalescer on its wash tank. Spent washing solution is circulated through the coalescer, allowing the oil in the wash water to split from the soap. The oil floats to the top of the water, where a skimmer collects the oil. "We can recycle the oil and put it right back into use during machining," says Schreiner.

Operator loading baskets into washer agitator/rotation receiver.

It automatically keeps the water levels to a preset level. Cleaning solution and water acidity is checked using a pH monitor and titration.

The waste water in the soap solution is evaporated off, leaving sludge. This sludge or waste from the cleaning system consists of minute debris that collects as sediment at the bottom of the coalescer. "We have had the system in operation for 21 months and we are just getting our first waste stream from the operation. From the volume we are seeing, we expect to generate only 55 gallons of waste sludge over two years. That's nothing compared to our previous method," says Schreiner

This minimal amount of waste generation does more than provide recycled washing solutions and oil, it also saves on disposal costs for VMP.

"It costs $200 a barrel to dispose of this waste," says Schreiner. By reducing cleaning sludge amounts to this level promises to give VMP significant savings in disposal costs.

Three baskets of parts complete the submersion/agitation process.

A ventilation stack attached to the system provides a small amount of draw on the parts, which removes any condensation on the inside of the parts. "This low pressure system draws out moisture from all the nooks and crannies in the parts. Then once the moisture leaves the parts and goes up the stack, we have a system in the stack to collect the water vapor and recycle that."

Components are easily accessible, making maintenance simple. "We already have the unit on a maintenance schedule. It only requires maintenance five to ten minutes a day. Every three months we do a more in-depth maintenance step that can take two hours. That maintenance procedure involves cleaning the airlines and ensuring they are free of debris. We also check the self-oilers on the system to make sure oil is being delivered where needed."

http://www.manufacturingcenter.com/metlfax/archives/0301/0301prt.asp