October 23, 2003
As one manufacturer of automotive exhaust assemblies recently discovered, selecting the most appropriate lubricant for a tube bending operation can have a dramatic impact on part quality, workplace cleanliness, and economic efficiency. Although the liquid lubricant it was using was reliable and inexpensive, the manufacturer was concerned about lubricant waste, workplace cleanliness, and bacteria that multiplied in the lubricant collection trays.
Each time the liquid lubricant was ejected through the mandrel, it flowed out of the tube, over the bender, onto the floor, and into lubricant collection trays (see left side of Figure 1). Empty 5-gallon pails were used to capture any lubricant that drained out of the tube. Absorbent mats were used to pick up excess lubricant that flowed out of the tube during bending and cutting operations.
|Figure 1Using a gel-based lubricant eliminated pools of lubricant and prevented bacterial growth.|
The manufacturer's goals were to improve the work environment while reducing overall costs. When studying the feasibility of using a gel lubricant, the manufacturer chose to test it on its most difficult part, an exhaust riser. The 6-foot, 1.5-inch-diameter stainless steel tube has 14 compound bends. The objectives of the test were to minimize lubricant waste, improve tool life, reduce or eliminate the bacteria odor, and reduce overall maintenance costs.
Results From the Initial Tryout. The initial tryout with the gel showed a reduction in lube waste and consumption. The manufacturer had been using 40 gal. of lubricant per bender per day. With the gel, the consumption was reduced to 5 gal. per bender per day. Using the gel eliminated waste, thereby keeping the work area cleaner and safer.
The manufacturer observed that with the gel, the length of the finished tube decreased, indicating that wall thinning on the outside diameter (OD) of the tube had decreased, which indicated more effective lubrication. Also, the manufacturer noticed that the gel provided a better barrier between the mandrel and the tube, creating less heat. The reduction in heat on the mandrel balls extended tool life by reducing scoring.
Applying the gel through the mandrel required a pump that develops more pressure than that used for a liquid lubricant. The manufacturer changed from a 20-to-1 displacement pump to a 50-to-1 pump. Also, the actuation time for the pump was changed. Formerly, 14 ejections of the liquid lubricant were dispensed for a completed part. With the gel, the number of ejections was reduced to six.
Manufacturing Compatibility. To ensure that the gel would be compatible with other manufacturing processes, the company performed several other evaluations, including laser cutting, washing, and welding. Because the gel contains no petroleum, smoke was minimal and posed no problems for its laser cutting lenses. The gel also proved satisfactory for the washing and gas metal arc welding processes.
Quality Control. To verify the initial findings, the quality control department tested the gel and collected information over a three-week period. In addition to verifying that the wall thickness on the OD of the bend had increased, quality control checks found less splitting at the seams and less scoring on the radius of each bend.
Waste Reduction. Whenever the equipment was idle, liquid lubricant drained out of the mandrel, requiring repriming before the next start-up. Gel doesn't lose its prime, which reduces waste and allows immediate start-up after a shift change or break.
Changing to a gel reduced other expenditures as well. For example, liquid lubricant tended to wash grease off bender armatures. After changing to the gel, the manufacturer was able to reduce grease application from once a week to once every two months. The company also saved money because it did not need to purchase absorbent mats to pick up excess lubricant.
|Figure 2Trays and absorbent mats were used to collect excess liquid lubricant.|
Hazard Reduction. Because the gel doesn't pool in trays, it does not provide a breeding area for bacteria (see Figure 2). After the three-week trial, operators noticed no bacteria odor. Also, because the gel doesn't splash onto the operators, it can't cause skin rashes or dermatitis.
Liquid lubricants are still the best choice for many applications. They are well-suited to bending thinner-gauge tube, easy to handle and apply, and provide adequate lubrication.
However, some operations may benefit from a gel lubricant that can improve cleanliness, reduce hazards, and improve economic efficiency.
Keith M. Karbum is vice president of sales for Metal Mates Inc., 6650 Highland Road, Suite 217, Waterford, MI 48327, phone 248-666-1880, fax 248-666-3359, e-mail e-mail firstname.lastname@example.org, Web site www.metalmates.net. Metal Mates develops and manufactures lubricants and specialty chemicals for the metal forming and fabricating industry.