Quality

Quality The industry offers various levels of quality. There are light-duty presses that are capable of "spanking" the work momentarily and reversing, and there are heavy-duty machines designed for general purpose metalworking applications.

Here are just a few construction points that will provide a basis for comparison of one machine with another:

1. Frame. Look at frame construction-rigidity, bolster thickness, dimensional capacity, and other factors.

2. Cylinder. What diameter is it? How is it constructed? Who makes it? How serviceable is it?

3. Maximum system pressure. At what psi does the press develop full tonnage? The most common range for industrial presses is 1000 to 3000 psi.

4. Horsepower. The duration, length, and speed of the pressing stroke determines the horsepower required. Compare horsepower ratings.

5. Speed. See separate page  to determine the speed of a hydraulic press.

Speed. There are no hydraulic presses today that are as fast as the fastest mechanical presses. If speed is the sole requirement and the material feed stroke is relatively short, the mechanical press remains the best selection.

Stroke depth. If a limit switch is used to determine the bottom, the stroke depth is not likely to be controlled much closer than .020".

Many hydraulic presses can be set to reverse at a pre selected pressure, which usually results in uniform parts.

Generally, if absolute stroke depth accuracy is required, "kiss" blocks must be provided in the tooling.

Automatic feeding equipment. Hydraulic presses require some external or auxiliary power to feed stock. The feeder must have its own power, and must be integrated with the press control system.

There is, however, an increasing selection of self-powered feeding systems available: roll feeds, hitch feeds, and air feeds.

Shock after breakthrough in blanking. Both mechanical and hydraulic presses experience this problem. But, the hydraulic system of a hydraulic press must also be isolated from the shock associated with decompression. If the hydraulic system does not contain an antishock feature, this shock can affect the lines and fittings.