Q. I am planning to equip my shop with more sophisticated sheetmetal equipment, and I have been hearing a lot about Pullmax machines. What exactly do these machines do, and how can I get more information about using them?Ted FosterVia the Internet
A. Pullmax is the trade name for an electric reciprocating machine made in Sweden. They have been around for decades, and have a broad range of uses. First, let's make a distinction between the Pullmax (or electric reciprocating machines in general) and some other machines with which they are frequently confused. I'll use the name Pullmax here in a generic way, since it is widely known, but there are many makes of similar machines, such as Noland, Trumpf, Vibra-Shear, and others.
While Pullmax machines are still made new, most people buy these machines used, since the price of a new machine, coupled with the shipping costs, is exorbitant. Just a few years ago, these machines could often be found used at bargain prices, since many of the large metal fabrication shops that originally purchased them have replaced them with newer CNC equipment. Now that more people are familiar with the great utility of these machines for automotive sheetmetal work, it is more difficult to find them at bargain prices, but they are often available used in the range of $3,000 to $5,000.
The Pullmax has a stationery lower die and a reciprocating upper die. The stroke length is set with a lever, and some machines have multiple speeds. One of the key reasons these machines operate the way they do is that the stroke length of the top die always repeats exactly. The position of the lower die can be adjusted up and down, so the clearance between the dies can be set with precision. Additionally, the lower die can be positioned inline with the upper die, or offset, as it would be when the machine is set up for shearing. These machines generate a repeated squeezing force between the dies-distinctly different from the hammering action of the machines we'll talk about shortly.
One of the major benefits of these machines is that the tooling is based on square bar stock, usually 5/8-, 3/4-, or 1 inch. This means you can easily make your own tooling by creating complementary (male and female) profiles on the ends of two pieces of bar stock, thereby creating the upper and lower die. Simple dies for stepping, beading, and flanging are easy to make and modify. With a little ingenuity, you can make more complicated dies for profiling, shrinking, or even louvering! The louver dies are especially interesting, since they enable you to make louvers of any length, and by using simple guides, the louvers can be either straight or curved if you like! Pullmax made several different sizes of these louver dies, and they are highly desired, since this particular die profile is rather difficult to make. The lower louver die has three different positions on a turret-one for making the center portion of the louver, and one for crisply setting each end of the louver.
Further, "thumbnail" style shrinking dies, similar to those used in power hammers, can be used on Pullmax machines, and they allow you to shrink deeply into a panel, with little limitation on the amount of shrinking possible. While some people make their own shrinking dies, it is tricky to create the profiles needed for proper use, and even tiny deviations from the ideal shape will cause them to stretch, rather than shrink, or to leave nasty marks in the metal.