Applying and handling die lubricants

Effective application of die lubricants typically is overlooked in many stamping facilities. Many companies try to get by with applying as little lubricant as possible, just so they don't have to deal with the mess.

However, metal stampers need to move away from thinking of in-die lubrication as a necessary evil and instead view it as a powerful tool that, when applied effectively, can improve die life, press speed, and part quality.

Figure 1 In many applications, the lubricant first is applied to the stock. Some companies use roller coaters for this job. However, for operations in which the lubricant must be reapplied in the die, spray lubrication often is required.

Die Lubrication Methods

In many applications, the lubricant first is applied to the stock. Some companies use roller coaters for this job. However, for operations in which the lubricant must be reapplied in the die, spray lubrication often is required (see Figure 1).

If possible, spray line and nozzle location should be determined during die design (see Figure 2). If that cannot be done, the next step is trial and error. During the initial setup stages of running a new die, magnetic-base spray assemblies can be used to determine the best placement for the nozzles. Once determined, the hard plumbing for the spray lines and nozzles can be installed.

Figure 2 If possible, spray line and nozzle location should be determined during die design. During the initial setup stages of running a new die, magnetic-base spray assemblies can be used to determine the best placement for the nozzles.

Locating a central manifold on the die will assist quick die setup. From the manifold, all lines are routed to each spray location and hard-plumbed to the die. For large dies or applications that require longer spray lines, consideration must be given to the type of spray line that will be used. For these applications and ones that require the use of a high-viscosity lubricant, a harder or rigid spray line typically is recommended. A soft spray line could result in a loss of line pressure, producing a less effective spray pattern.

Proper punch lubrication sometimes may require introducing the lubricant directly onto the punch, rather than spraying it (see Figure 3). A groove is machined in the stripper plate of the tool, allowing the lubricant to be pumped directly onto the tool. This allows the lubricant to fill the groove and "weep" around the punch.

If space is limited, spray nozzles may be buried in the die. Figure 4illustrates three spray nozzles mounted in the bottom of the die. In this process, the lubricant is applied to the bottom of the part before the extrude station of the tool.

Figure 3 Proper punch lubrication sometimes may require introducing the lubricant directly into the punch, rather than spraying it.

Using one pump to feed multiple spray lines is not recommended because it can cause unequal distribution. The spray nozzle closest to the pump typically receives an adequate amount of lubricant, while the location farthest from the pump doesn't receive enough. For best results, each spray line and nozzle should be supplied by its own pump or valve.

Also, the use of couplings and other fittings to extend the length of spray lines may cause ineffective spray patterns, points of restriction, and leaks.

Pumping high-viscosity lubricants can require higher pressure and thus a higher-pressure-rated spray line, such as hard nylon, copper, or steel.

Figure 4 If space is limited, spray nozzles may be buried in the die. In this process, the lubricant is applied to the bottom of the part before the extrude station of the tool.

Containing the Lubricant

Containment of lubricants is critical when they are applied to the stock and in the die. When companies allow lubricant to fall and build up on the floor, they not only are spending a lot of money on lubricant, but they're also risking possible injuries to their employees.

Spray nozzles can be mounted with magnetic bases in the press window area, but then lubricant containment becomes a challenge.

One option in this case is a spray cabinet or chamber. The cabinet is an enclosure that incorporates nozzles and works in conjunction with a spray system. In this noncontact method, only the lubricant comes in contact with the stock. The spray is contained in the cabinet, and any excess that is captured may be recycled. Since the cabinet usually is mounted to the feeder, it moves with the feeder when the passline is adjusted.

Figure 5 Die space enclosures (die doors) are a practical method for lubricant containment in the die area.

Die space enclosures (die doors) are a practical method for lubricant containment in the die area (see Figure 5). Die doors contribute to the cleanness and safety of the pressroom. Not only do they help contain the lubricant, but they also provide a point-of-operation barrier guard. Sometimes enclosures eliminate the need for additional guarding, such as light curtains.

When sprayed, die lubricants, especially water-soluble ones, can create a lubricant mist. In many cases, this mist is actually the steam produced when water hits the hot tooling or part surface (see Figure 6). The steam carries lubricant into the air and through the pressroom, where it settles on floors and equipment. In addition to using die doors, some companies install exhaust or filtering systems to evacuate the vapors.

Figure 6 When sprayed, die lubricants, especially water-soluble ones, can create a lubricant mist. In addition to using die doors, some companies install exhaust or filtering systems to evacuate the vapors.

Collecting and Recycling the Lubricant

Collecting the lubricant is a crucial step in the lubrication process, especially if the lubricant can be used again. Companies should plan for the lubricant runoff and develop a collection system.

Today many press manufacturers supply troughs around the bed of the press for lubricant collection (see Figure 7). Existing presses can be retrofitted with troughs fairly easily. Once collected in the trough, the lubricant can be routed to a central collection area, such as the press pit. It can then be pumped out and used again or held as waste lubricant. If the lubricant will be used again, it must be filtered first. Many spray lubrication systems are equipped with their own filters.

A spray cabinet also can assist with lubricant collection. The lubricant then can be routed to the central collection area or directly back to the spray lubrication system.

The Employee Factor

The application and handling of die lubricants are critical in all metal stamping facilities. Of the many benefits associated with proper lubrication, however, the most important is the effect it has on employees.

Figure 7 Many press manufacturers supply troughs around the bed of the press for lubricant collection. Once collected in the trough, the lubricant can be routed to a central collection area, such as a press pit.

No one wants to work in a messy, unorganized facility, but implementing lubricant containment procedures takes a lot of commitment and cooperation from all employees. Companies must be patient in implementing these practices, but it is worth the effort.

Stan Reineke is sales and marketing manager with Pax Products Inc., 5097 Monroe Road, P.O. Box 257, Celina, OH 45822, 419-586-6948, fax 419-586-6932, sreineke@paxproducts.com, www.paxproducts.com. Pax Products is a manufacturer of in-die lubrication systems and under-die conveyors.