In part one of setting up for early sales we covered the parable of mice and cheese. And we also wrote a bit about making plastic parts for small-quantity production, the purpose of which is to demonstrate sales potential to prospective licensees, or to prove to ourselves and to prospective investors that we can increase sales rapidly. The main point is to use methods that simulate volume production, but to do so with lower cost tooling. Volume production molds for a typical small part may cost $20,000 to $25,000.
The majority of inventions are made, at least in part, from plastic. And the king of plastic processes is injection molding. For metal parts, the king of processes is stamping.
Stamping is done on a machine called a punch press. The machine has a heavy flywheel that stores energy most of its cycle, and releases it in a down-ward stroke that pushes the “punch” through the “die.” The metal is punched out similarly to paper punching action. Not hard to visualize.
Punching out a flat part is known as “blanking.” In addition to blanking, we have two other actions that are common to stamping: “forming” (bending), and “drawing,” which is the stretching of the metal to form a three dimensional object like a bowl or a pan.
Bending of volume-produced parts is most often done in the same die set that accomplishes the blanking. The parts are partially blanked, but held in place with connecting tabs, and are then formed into their specified shapes. After forming, the final blanking cuts are made, and the part drops into a box or bin of some sort. Such tool is called a “progressive” die-set.
Now, a progressive die-set is typically very expensive. It’s not uncommon for a die set to cost $20,000 or more. And this is not the kind of investment you want to make for low-volume production, especially if such production is intended to be temporary.
So, here are some ways to produce parts that look as though they were stamped on a punch press. First, let’s look at blanking. Three common methods are available: laser beam cutting; abrasive water jet cutting; and universal stamping die cutting.
Laser beam is mainly used for thin metals. Ask your vendor for the limitations in its shop. Thicker metals can be cut with reasonable accuracy using the abrasive water jet process. The laser beam simply burns through the metal. Abrasive water jetting cuts by forcing a slurry of water and small abrasive particles, impinging on the metal at a force of 50,000 pounds per square inch or higher. Both processes move the metal sheet under the beam or jet, as programmed. The program comes from the 3D CAD drawings (three dimensional computer assisted design drawings). Thus, professional 3D CAD drawings are essential whether made by an independent drafter, or by the cutting service, which sometimes offers drawing services as well as cutting.
Okay. Now you have a blank. The only tooling involved was a slight modification of your 3D CAD digital data, and that won’t cost more than a hundred dollars or so in most cases. The drawings will cost more, of course. So, next we need to form the blank. This is done by manually positioning the blank in a press brake, which is a relatively slow moving ram that holds a “vee” (male) top die and a “vee” (female) bottom die. These dies are usually in stock at the vendor, and no tooling charge is necessary.
Universal tooling may produce parts less expensively than laser or water jet cutting. Universal tooling consists of a wide variety of punch and die sets, such as rounds and squares of many diameters and side dimensions, and slotting obrounds and rectangles of various widths and lengths. Such tooling and machinery may not require 3D CAD drawings. The job-shops that produce stamped parts using universal tooling are known as “precision sheet metal shops,” as against shops that make rain gutters and air conditioning ductwork, etc.
Finally, drawing of sheet metal into shapes such as a bowl can be done by “spinning.” A sheet of metal is cut into a disk, clamped in a special lathe, and spun. A tool is manually applied to the disc, and the disk conforms to the shape of the mandrel, the special wooden form tool made to produce your part. The mandrel may cost a few hundred dollars.
The lowest total cost of tooling and parts from any of these processes can only be determined by soliciting and comparing price quotations.
Best Wishes,
Jack Lander
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