Stamping – A Cost-Effective Alternative to Machining

By Peder Peterson

By Russ Sabac, Brunk Industries Inc

Overview

Machining has sometimes been considered the only feasible manufacturing alternative for buyers to source low-to-moderate quantities of metal components. Because of the modest volumes or the complexity of the components, customers have often not considered stamping the part. However, with up front discussions, stamping can offer a range of cost-effective alternatives for components that are complex and require high-precision tolerances. There are a number of cost and design advantages that can be obtained by converting to stampings. Engineers looking to decrease material waste, increase the strength of their product because of grain direction, incorporate complex features, reduce the number of components, or reduce costs should consider stamping over machining.

There are four parts to the success of any stamping project – experience, the tooling, the equipment, and the quality inspection equipment. These variables are critical for obtaining a stamped component to specification.
Attempts to stamp components using conventional methods could fail. It is important that the buyer understands the capabilities of the stamper and equipment being utilized. They then can make an informed decision, as to whether or not the stamper can provide a successful product.

Advantages of Stamping vs Machining

There are a number of benefits that can be achieved by converting to stamping the part.
One major reason companies convert is the cost savings they receive per part. That’s because the amount of time it takes to stamp a component is a fraction of what it takes to machine a component. The stamping process produces finished parts on each cycle of the press no matter how complex, compared to machining needing multiple passes, cutter changes, and set-ups. Another benefit is stamping gives more freedom to designers to place intricate features in products thereby enhancing their ability to create more innovative products. Stamping can be a stable production process, because of the controlled consistency of material thickness, mechanical and chemical properties, and also the better natural surface finish of the rolled strip materials.

Stampings can also be a suitable replacement for MIM parts. Stamping can eliminate the need for secondary operations associated with holding part tolerances because of shrinkage associated with the metal injection molding process. Stampings are also well suited for any manufacturing assembly process that may include laser welding, riveting, etc.

Example case

It is very common to save high percentages on each stamped part. Here is an example of an actual cost savings project that changed to a stamped part.

The project was for a medical device manufacturer. The EAU is 10 000 parts.
The customer noted the main problem was the high cost of the machined component, but also some dimensional issues.
The customer was paying approximately $8.85 each.
The equivalent cost for a stamped component is $0.92.


Cost saving of Stamping VS. Machining
EAU 10,000
Machined part EAU cost = $88 500
Stamped part EAU cost = $9 200
Annual part savings = $79 300

The savings offset any tooling costs during the first year, meaning the continued value of low cost / high quality parts after that time period.

Stamping Materials

Some of the materials that can be stamped by a stamping company with the right experience:

• All Grades of Stainless Steels
• Full Hard Flapper Valve Material
• Low Carbon Steels
• High Strength Steels
• Kovar
• Various Grades of Titanium
• Niobium
• Tantalum
• Various Grades of Nickel
• Moly
• MP35N
• Bi-Metal (Butt Welded, Inlaid, or Laminated)
• Brass and Copper

Another major plus is many materials can be pre-plated when necessary, compared to the cost of post-plating machined parts.

Experience

Prior to evaluating tooling and equipment, the buyer must first determine if the stamper is a fit. In other words, does the stamper have the technical experience and a business strategy that will suit their needs? A company with business strategies and manufacturing systems in place can design and build tooling for all production volumes and will be more attuned with the goals and objectives of your company.

Tooling

One factor buyers must consider is the cost of the tooling. Quality tools make quality parts, so buying lower cost tools to save a few thousand dollars could jeopardize the quality of the part. The right tool is one that is designed and built precisely. In the past, one of the drawbacks to converting to stamping had been the lack of flexibility a tool had when design changes were required. Today, this cost can be minimized by inserting the tool correctly, so only small details would need to be changed to modify the part.

Equipment

Another important factor the buyer must consider is the type of stamping presses, since the quality of the presses can affect the consistency of the part. There are different types of presses, and it is important to understand how they affect part quality.
Other important items are; The need to have a strong preventive maintenance program in place for the total press line; and a robust sensoring system to monitor the part, the strip, the material thickness, the press, and any part of the material feeding process. Well-maintained press equipment, and detailed sensoring systems equal more accurate consistent product.

Quality

The last factor to consider is the quality of the inspection equipment, including proper fixturing of the part. Buyers must verify whether or not the stamper has the capability to measure the stamped parts correctly and accurately. A CMM has certain value to check some measurements, but optical measurement inspection systems are better suited for the majority of the workload. For visual in process inspection a microscope is required to look for the smallest required or unwanted features. In some processes a live camera inspection system can be incorporated in the production line. It’s very important to have the proper inspection equipment, and when needed, design into the process the correct equipment to meet the part and process requirements.

Conclusion

Stamping can be an excellent lower cost alternative to machining. Every stamper is different; therefore, the buyer must find a supplier who matches their business strategy and can make the part meet all the requirements. The stamper must explain the differences in the processes, so the buyer will have a thorough understanding and can ask the right questions to determine whether the stamper will have the capability to stamp the component.

The stamper will than need to provide the data and samples, to demonstrate to the buyer that changing to a stamped part will be successful.

Consider all the above mentioned benefits your company can achieve by converting your machined components to stamped parts. The stamping company of choice will use its experience, precision sensored tooling, well maintained press equipment, and advanced quality equipment, to provide the best opportunity to create innovative cost-effective parts.

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