TriparTech: Hybrid Manufacturing, Options to Metal Fabrication vs Metal Stamping

Sheet Metal fabricated parts can be produced by many processes. The two broad methods are metal stamping and metal fabrication. To understand where each comes into play, you must first understand what each is, and what the differences are.

Sheet Metal fabricated parts are those which are typically produced without the use of a metal stamping die (sometimes referred to as “hard tooling”), but instead use dedicated or specialized equipment.
In its simplest/lowest technology form, such equipment would consist of shears, modular tooling such as C-Frame Pierce-All® to pierce holes, slots, etc., and press breaks to do the bending.

Moving up the chain of modern technologies to the opposite end of the spectrum, most of this would be replaced by Computer Numerically Controlled (CNC) punch presses (often called a “Strippit”), CNC Lasers, or CNC Punch/Laser Combination machines, followed by bending if/as required using CNC Press Brakes.

CNC Laser

CNC Punch/Laser Combo machine

CNC Press Break

Full sheets would be placed on either a CNC Laser machine where most holes & slots would be punched or cut, or on a CNC Punch Press, where the same features could be punched or cut, and also knockouts, shallow forming* and sometimes tapping could potentially be done, and the entire perimeter of the part punch or cut from the sheet. Some tooling may be required using these processes for custom hole sizes, shapes, or forms, but this is not usually too expensive, ranging from $50-150 for a simple punch and mating die, to perhaps $1500-$2000 for complex forming tools.

*such as extrusions, flanges, louvres and other shallow forming, whose heights are limited by each machine’s specifications.

A CNC Laser can only cut, but can also cut both intricate shapes due to no tooling requirement, as well as large cut-outs, that might otherwise require punching forces (tonnage) that exceed the CNC punch press’ capabilities.

A CNC Punch/Laser Combination machine can achieve both of the above; pierced holes, formed features, and intricate and fine cutting without tooling.

The fully pierced and cut pieces would then be bent if/as required using a CNC Press Break, where programmable and moveable back gauges and stops permit the workpiece to have multiple bends done, often at different bend heights and angles to meet the drawing requirements. These typically require no tooling, or limited tooling, such as small matching punches and bushings for the piercing, and male & female press break tooling for the bending. Most metal fabrication shops have an arsenal of these to suit a wide variety of such requirements, so the customer should bear little or no tooling cost.

Part costs are commensurate with the time it takes to cut parts from each sheet, how they nest within the sheet (which establishes how much material it takes to produce each part), and if/what secondary operations are required such as bending, which consists primarily of labour.

Metal stamping is typically done using mechanical or hydraulic presses of increasing tonnage, and one or more metal stamping dies used to form many or all features of a sheet metal part. These dies can cost anywhere from a few thousand dollars, to $50,000, $100,000, and even more, all depending on the part size, complexity, and to what degree of part completion the die will yield. Small parts that are not overly complex can often be fully produced (i.e., no secondary or subsequent operations) in a progressive die and have the shortest ROI. Larger parts typically involve higher die costs, which can grow exponentially with part complexity.

The primary advantages in having a die that can fully produce a part, are high production rates, and in a single operation, thus relatively low labour cost, resulting in the lowest possible unit part cost, provided volumes can justify/amortize the tooling cost and provide an acceptable ROI.

One way to reduce die costs is to produce the part without all required features, which removes some die complexity, thus die cost. To complete the part, either secondary operations or dies (often simpler and less costly dies) can be used to complete the part. Alternatively, secondary operations without dies (e.g. bending in press breaks) can sometimes be employed to complete the part. This however comes with added labour expense due to multiple operations and part handling.

Where your supplier has one or more existing dies to make an acceptable variant of the part you require, or if any of those dies can be modified to do so, you may be able to obtain what you need with little or no tooling expense, and low part cost since the part is made as a metal stamping. This can also be beneficial in the case of a new product where the design is either not stable enough, or unknown volumes may not be able to justify the expense of a die.

This is where Metal Stamping and Metal Fabrication become seamless, through a supplier that has both capabilities; CNC metal fabricating equipment and stamping presses, ideally with a great many open (supplier owned or non-proprietary) dies, that you may be able to benefit from.

Examples include;

• Progressive dies that blank out the part, but do only limited or no bending because volumes could not justify such a complex die. In such situations, parts may be made in two steps; the blank done in a less costly die, followed by CNC bending. Unit part cost may be higher than a fully progressive die, but tooling costs will be reduced.

• Capitalize on a supplier’s existing item that is produced in a die, but have it customized or modified to suit your requirements using their CNC equipment. For example, your supplier has a die that can produce a pan or yoke with a limited range of hole sizes. They may be able to make that part without any hole, and then mount that part on their CNC laser or punch press to cut your custom hole. Better yet, if they have a CNC Punch/laser Combination machine, they may be able to cut holes without any tooling, (including irregularly shaped holes), and add the many other features previously discussed, all in the same secondary operation.