Precision Stamping

Nibbling:

Nibbling is the process in which a single punch and die are used to shear small bits of material from a sheet of material. Accuracy and processing time is determined by the number of ‘nibbles’ taken by the punch and die. However, even very small position increments will produce edges that will be scalloped and relatively rough since the shape of the punch and die does not match that of the blank.

Chemical Etching:

Chemical etching can be used to create blanks on sheets of material. The blanks are free of burrs and can be quite intricate using this process. A number of blanks can be developed on a single sheet of metal, leaving only enough material to support the blanks through the etching process.

Advances in laser cutting have made it a viable option for thin-stock prototypes. However, tolerances are somewhat limited and small features cut from thin material can be greatly effected by heat generated. Laser cut edges will contain a heat affected zone and some recast from molten metal splatter. Highly reflective materials cannot be laser cut since energy is reflected from the workpiece.

Water Jet Cutting:

Similar in application to laser cutting, water jet cutting is a process that uses abrasives propelled by water to remove material. Cutting forces can be minimized but will have adverse effects on thin material.

Wire EDM:

A wire EDM (Electro-Discharge Machining) machine can be used to produce blanks by EDM’ing around the perimeter of the part. A small hole for threading the wire can be drilled into the scrap portion of inside features. By stacking several strips of material together, several blanks can be produced at one. Nearly every tool manufacturer has access to a wire EDM.

Punch and Die:

In order to best simulate the metal stamping process, a punch and die can be created to stamp the blanks. Usually inexpensive tooling materials can be used due to limited quantities. Some stamped component manufacturers have developed standardized blanking modules that easily accept custom punch and dies solely for this purpose.

Standard Shape Tools:

Using devices such as press brakes, a manufacturer can use standard shape tools to create bends. The selection of tools is often limited to standard bend radii and angles, thus limiting the feature sizes and shapes of the final product.

Custom Shape Tools:

By creating metal forming punches and dies with custom forming features, the manufacturer can replicate the production metal forming process. The methods with which the tools are guided and actuated vary from small hand presses to standard press brakes. Some stamped component manufacturers have developed standardized forming modules that easily accept custom punch and dies solely for forming custom products.

Single Part Transfer:

Single part transfer is a method in which single parts are moved from station to station for blanking and metal forming. Any of the blanking and metal forming methods previously mentioned can be used with single part transfer, often depending upon the need to replicate the actual production process.

This option offers the advantages of less expensive tooling as long as the manufacturer has standard system for designing, manufacturing and holding tooling inserts. However, individual prototype part costs will be high due to the slow manual methods of transferring each part through a series of stations. Limitations include part size and feature tolerances. Miniature parts are often too small to properly handle and locate, increasing the chances for part damage and misalignment. For repeatable results on all sizes of prototypes, it is important that each station contains reference features for accurate and repeatable part location.

Progressive Strip Prototyping:

Progressive strip prototyping refers to the method of containing a part on the stock material as it is moved through various operations. A progressive die is used to guide and actuate the individual stations necessary to produce the prototype part. In this operation, every cycle of the die performs an operation on parts on the strip and the last station produces a completed component. The strip can be moved through the die by hand or by an automatic feeder actuated by air, a servo motor, or by a mechanical linkage to the press.

Progressive strip prototyping is used to overcome many of the limitations of single part transfer, including part size, feature tolerance and prototype production speed. This method often simulates the final production method exactly with the exception that the tool is designed and manufactured for slower speeds and fewer cycles. It is also advantageous for the component manufacturer since the production tool can easily be designed using feedback from the prototype die design.