Think before you scrap
Adapting old cast-iron frames to new technologies
Before you scrap your iron frame, think about the benefits of using the original frame. Adapting your old cast press frame to new technologies may be easier, cheaper, and greener than you may have thought.
In stamping press shops around the world, you can find a range of equipment from brand-new, state-of-the-art installations to workhorses that have been operating since the 1940s or even earlier. Business strategies drive the machinery investment decisions, whether that be taking the leap on a new piece of equipment and disposing of the old, or refurbishing existing equipment with new technology. A case can be made to evaluate an old press before sending it to the scrapyard, and it may actually have benefits you can’t even buy anymore.
When you look closely at the base elements of older cast-iron press equipment, it’s difficult not to appreciate the workmanship and quality of past manufacturing methods that are no longer economically feasible today. It is worth considering the structural and cost advantages of old cast iron, as it may be the foundation for a new future for your business. With such a limited access to capital these days, stampers may find that a refurbished system may be the most feasible solution for their operations.
The basic function of a press has not changed in over 100 years. Machines still employ a platen, a crank, a frame, and a slide, which provide the brute force necessary to form material. What has changed, however, are the outward components such as the motor, drive, feeders, sensors, and controls. In the right business situation, it makes sense to apply these newer components to a structurally sound old frame, enabling the old to become a new and competitive workhorse for tomorrow.
New Cast Versus Old Cast
Cast iron, the base material for most press designs, has had a remarkable history. In its most basic form it is a combination of ore, coke, and limestone. It is enhanced further by the addition of scrap materials to provide for most of the typical cast press components manufactured today.
Before World War I, cast was made in many small foundries using a variety of unique recipes. Castings were laid outside for months or even years to “cure.” To make up for poor casting methods, designs were made with additional mass.
Improvements in cast technologies, in particular the Meehanite® processes, started in the early 1920s. These techniques provided improved grain structure and overall strength to the casting process. This also eliminated the old curing method of stabilization. However, it is worth noting that stress-relieving processes are still employed to relieve built-up stresses during material cooling in today’s cast processes and have remained a standard to today. This ensures that the old cast will perform as well as new cast without degradation to form or function.
Structural Advantages: Bar Versus Bell
An important difference exists between cast bar and bell configurations used to cast press crankshafts. In a cast bar the grain is aligned with the pour shape and runs parallel with the bar surface. When the casting is cut into the shape of a crankshaft, the grains are cut, which reduces its overall strength. When a bell is cast, it is made as close as possible to the final shape of the crank. This causes the grain to follow the bell and provide a substantially stronger crank.
Typically OEMs manufactured presses with a cast bell process. While cost is slightly higher and delivery is longer for the bell process, it can equate to many more years of useful life of a crankshaft.
While it is common practice to make crankshafts from a forged bar as a solution to crankshaft repair, it does not produce a life cycle as long as a cast bell configuration.
Modernization—New Life for Old Cast
While the most difficult issue with older equipment is the lack of support and documentation, facilities still exist solely to refurbish old presses. With the advent of computer design and foam patterns, even difficult parts can be newly manufactured using the latest advances in materials. Any part of a press can be replaced, including frames, bolsters, crowns, and slides, at a fraction of the price of a new press.
Keeping in mind the benefits of old iron, it may make sense to incorporate new technologies onto existing frames in an effort to modernize.
- Drive Mechanisms. With inverters, eddy current drives, and servomotors, the press’s speed can be adjusted easily and the press reversed; that is, reversing the flywheel and jogging the press backward to release the die. The drives used with these motors can sense torque, current, spikes, and overloads.
- Tonnage Monitors. Load cells mounted in strategic locations can prevent press overloads and help prevent premature press failure.
- Temperature Sensors. With temperature sensors added in specific areas, the press can protect itself from costly repairs.
- Autolube Systems. These systems include sensing blocks to note when areas are not receiving lubrication. This, matched with a few temperature sensors, can help your press avoid one of the main causes of press downtime, burnt and/or spun bearings.
- Shut Height Indicators. Used with a preventive maintenance program and a good die setup instruction, shut height indicators can go a long way toward reducing press damage.S
STAMPING Journal is the only industrial publication dedicated solely to serving the needs of the metal stamping market. In 1987 the American Metal Stamping Association broadened its horizons and renamed itself and its publication, known then as Metal Stamping.