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Jay W. Preston, CEO

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Safety Subject Information:


Power Presses are an exception to the workers’ compensation laws in California. This has an advantage for victims of injuries on machines that are considered "power presses." Because of Labor Code Section 4558 many machines can be considered to be power presses. Paradoxically, some machines that any machinist would consider power presses are not, under 4558. Naturally, a plaintiff's attorney will try to make a machine a power press under 4558 because that opens up the employer to unlimited damages under ordinary liability theory.

One of my areas of expertise concerns safety and accident prevention in metal working machinery. I have worked on a substantial number of accidents involving mechanical and hydraulic power presses, presses of many configurations, and similar machines. Background and experience includes on the job training in the safety of power presses and similar metal working machinery. I am familiar with metal working and machine operations from school shop classes as a youth and adult. I have studied the Liberty Mutual power press safeguarding courses and attended a PSC power press safeguarding seminar.

I have done considerable independent study of safety of power presses. I have taught the power press safeguarding course for the Los Angeles Chapter of the National Safety Council.

I have worked many machine guarding accident cases. My accident prevention clients have called on me for machine guarding expertise. I am intimately familiar with the ANSI, OSHA, CAL/OSHA, ISO, and other codes and standards which apply to the construction, care, use, and safeguarding of machinery including presses of most types.

So. Is this a Power Press?

One of my investigations was particularly to consider whether or not a wire net weaving machine met the legislative definition of "power press" which is cited as part of section 4558 of the Labor Code.

I inspected the incident machine and reviewed pleadings, interrogatories, and materials produced pursuant to requests for admission.

Multiple separate strands of wire are fed into the machine. As a cylindrical point of operation revolves, the wires are gripped and formed by bending to result in the woven hardware cloth sometimes referred to as poultry netting. A multitude of multi-part metal tools grip and deform by bending the incoming wire. These tools reciprocate back and forth as the point of operation cylinder revolves. The finished woven material exits the downstream side of the machine where it is roll wound by a winder.

I took photographs of the machine as it was operating on the day of my inspection which depicted the point of operation of the machine through which the wire strands are fed. These show that the strands of wire are deformed or bent into a new shape which becomes part of a new product which can be described as construction lathing. I had not been allowed an inspection of the machine while not in operation so as to more closely inspect the interior operating parts.

Based on my knowledge and experience, it was my opinion that after the wire strands are fed into the machine, the machine uses a multi-piece metal part or tool, which can be characterized and defined as a die, to grip, hold, and form, by bending, the inserted wire, which after being formed by bending becomes a part which is used in the manufacture of another product: construction lathing. The dies also appear to crimp the wire and perform other ancillary forming on the wire stock which further supports that the machine in question is indeed a power press in the eyes of the California State Legislature.

Key in my analysis is that the Legislature departed significantly from the American National Standards Institute's application of the mechanical power press safeguarding standard B-11.1. In so doing, it appears that the Legislature intended a broader application than to "machines commonly known as mechanical power presses." However, they also narrowed the definition to eliminate a large number of B-11.1 machines.

The Legislature had at its grasp and in its hands ANSI B-11.1 "American National Standard Safety Requirements for the Construction, Care, and Use of Mechanical Power Presses."

Within this B-11.1 consensus standard is the following statement of scope:

"The requirements of this standard apply only to those mechanically powered machines that shear, punch, form, or assemble metal or other material by means of tools or dies attached to slides, commonly referred to as mechanical power presses."

The 4558 statute puts the essence of what is a power press clearly on the presence of a die used for forming material in the manufacture of other products. It avoids any reference to "slides," and it does not cite common parlance.

Webster's New Universal Unabridged Dictionary defines "die" as follows: "5. in mechanics, any of various tools or devices originally cubical in form, for molding, stamping, cutting, or shaping; specifically, (a) a piece of engraved metal used for stamping money, medals, etc.; (b) the stationary part of a machine for shaping or punching holes in sheet metal, etc.; matrix; distinguished from punch; (c) the punch and matrix as a unit; (d) a tool used for cutting threads, as of screws or bolts; (e) a piece of metal with a hole through it, used in drawing wire, extruding rods, etc."

Some of the forming operations that are conducted with dies on various power presses and similar machines include bending, forming, drawing, extruding, embossing, engraving, coining, heading, swaging, crimping, folding, impressing, imprinting, stamping, rolling, seaming, necking, casting, riveting, cold-welding, joining, and laminating.

Dies are frequently multi-part devices, and machines, particularly in performing multiple identical operations, often use multiple dies.

Dies are frequently used in bending operations which are considered a kind of "forming." The material is forced into another shape by the action of the dies. Mechanical and tooling catalogs are filled with listings for "bending dies." Bending can also be done on a machine with slide-attached dies.

I reviewed a declaration of August 1, 1997 submitted as part of the Defendant's moving papers in this matter, and the facts in the case of Graham v. Hopkins, (1993) 13 C.A.4th., 1483. The Festo molding machine of Graham v. Hopkins is a machine with rotating cutting heads that resemble saw blades that can not be a 4558 power press. There is a fundamental difference in the mechanical process of the Festo molding machine versus a power press. The Festo machine shaped its product by removing unwanted material by knife cutting (carving) or abrasion, whereas forming is a process wherein the material is shaped by being forced into another shape by the tooling.

In the strictest and most precise machine tool language, the action of the Festo machine is not "forming" at all (neither is "punching," "shearing," or similar operations routinely carried out on ANSI B-11.1 machines). The Festo machine is a "molding" machine. The process it employs is not "molding." The product it makes is "molding." Molding is a decorative, carved strip of material, so named because the decorative embellishments replicated were once made by artisans in situ by manipulating (molding) plaster to form it into similar shapes. A molding machine such as a plastic injection molding machine, one that forces a fluid into dies or molds under pressure to form a product, would likely be a 4558 power press. The Festo machine is not a power press because it shapes its product by cutting away unwanted material.

The wire net weaving machine I observed utilizes what could be considered to be "dies" for bending, forming, crimping, and perhaps other operations not as readily apparent, on the wire stock being fed to it. Therefore the machine is within the definition of "power press" as defined by Section 4558 of the Labor Code.

There appears to be nothing in the legislative intent regarding Section 4558 that would rule out the wire net weaving machine as a power press. It forms material utilizing a die for use in the manufacture of other products.

Based on my inspection, its apparent operating characteristics, my knowledge and experience in the specific manner in which power presses with dies operate, it was my opinion that the machine meets the legislative definition of a power press.

So, just what IS a 4558 power press?  I can help you figure it out.

I can help you win power press cases.




Copyright 2000 - 2011, Jay W. Preston.  Distribution permission granted when this notice is printed in full.  For questions or comments: contact  The J-P, Plus Design and SAFETYBIZ. are registered service marks of Jay William Preston. Permission for use of specific Safety Subject Information is only granted when this notice is printed in full and Preston has been contacted by phone, fax, or email prior to use.