Short-run and medium-run metal manufacturers can produce a diverse array of parts for customers across industries and project types. In metal manufacturing, there are four main categories of processes that are used:
- Shearing and forming
- Casting and molding
Shearing and forming processes are combined with what is known as metal stamping. Stamping is the act of pressworking sheet metal to change its shape either with or without accompanying shearing or punching. Each metal stamping or fabricating project has its own techniques and design considerations, and each project can benefit from innovative ideas that produce more efficient, higher-quality parts.
It’s important to note, however, that in stamping there is no final machining away of metal. Instead, the scrap areas of a part are removed in the initial operations and a piece is created from this blank. The elimination of this additional operation reduces manufacturing costs.
Parts made as metal stampings can be found in nearly every industry and everywhere you look in daily life. Stamped parts can serve many functions from holding, joining and aligning simple shims and plates to enhancing the safety, design and critical part stiffness of highly engineered parts used for complex enclosures and mechanical brackets. The application of these parts is only limited by the imagination of the designer or engineer creating them.
Short-Run Vs. Long-Run Stamping
Whether you should choose short-run or long-run stamping depends on your exact application. If your project requires millions of identical parts with several complex operations to form, then long-run stamping is likely the most economical option as the price-per-part will be lower.
However, short-run stamping can substantially save you both money and time. Savings are generated from short-run stamping’s extremely low initial tooling costs, which, in most instances, saves approximately 80% compared to conventional permanent dies. Additional savings are generated each time you change die design of an item, as the tooling can be altered for a small fraction of the original charge. Short-run stamping also allows you to get small quantities of stampings delivered quickly – which enables you to maintain very low inventories and, in turn, see additional savings. Time is saved because tooling can be made in a fraction of the time it takes to design permanent dies. As a result, finished stampings can be produced quickly.
The advantages of short-run stamping are especially prominent when you’re:
- Designing and checking new products
- Changing existing products
- Supplying limited markets
- Making pilot runs
- Doing experimental work
- Making runs of parts that change in design frequently
- Meeting unusual time schedules
- Testing the market before securing production tooling
While short-run stamping can generate savings when quoting and ordering parts, there are many design decisions that can further reduce stamping costs.
How to Receive the Lowest Total Cost
More than any other single factor, the specifications in an engineered drawing will determine the price you will be quoted for a part. This is why it’s imperative to carefully consider the ways in which your specifications will affect the price you’ll be quoted. Don’t include excessive tolerances, limitations or any other specification that is not required by the design.
For example, it can be common practice for some companies to mark all prints with a tolerance of plus or minus 0.001″ for all dimensions. This makes it mandatory to hold that tolerance on all dimensions and, in return, it may make it necessary to carefully inspect 100% of the pieces. This will cost you extra money when you may only need one of those dimensions to be at plus or minus 0.0001″. Similarly, making material specifications without thinking through the requirements of your part can lead to selecting materials that are difficult to obtain – which will determine whether you receive a reasonable quotation.
This type of careful consideration should be applied to design requirements, finishing methods, quality assurance and every other step in the manufacturing process, or else you, the customer, will be footing an unnecessarily high bill. Luckily, manufacturers are frequently looking for ways to increase efficiency and decrease costs. It’s always worth discussing your job and how your part will be used with your metal stamping supplier since they know the operations and shortcuts that will lead to the most economical production methods.
Anyone who works on a project that requires metal stamped products will inevitably have a question about material selection. In some cases, your design needs will dictate a specific material property, such as strength or conductivity, and your viable options will be limited, often to a few materials or less. In these situations, it’s imperative to reassess each design choice to maximize the economy and efficiency of production. However, in most cases, there will be a wide range of material options to choose from, and selection may not take place until the design is finalized.
Start by Considering These Material Qualities
There are many material qualities to consider in the decision-making process. Some of the most important include:
- Stock thickness and tolerance
- Material strength and ductility
- Whether it’s a ferrous or non-ferrous alloy
- Whether it can be plated
- Whether it’s available for sourcing
- Associated material certifications
- How much it costs
Most projects will have only a few critical requirements, and it will be clear that the most commonly available materials are right for the job. But if you can’t find a material that meets every requirement, you may need to order custom-made metals from a specialized metals company—however, this will cost more than steel mill or warehouse prices.
Pay Close Attention to Material Thickness
It’s important to remember that when a material is sourced for metal stamping its thickness is expected to fall within an acceptable range. These tolerances are provided by mills and warehouses and are specific to the provider, the material and the thickness of the sheet, coil or bar.
Fortunately, ASTM International develops and publishes standards for material production that are easily accessible and widely accepted. These standards are occasionally updated and should be researched at the time of sourcing to ensure accurate expectations. This table provides a few of these standards for cold rolled steel, hot rolled steel and hot rolled pickled and oiled steel.
|Gage #||Decimal Equivalent||Cold Rolled Steel||Hot Rolled Steel & Hot Rolled Pickled and Oiled Steel||Pounds per Square Foot|
(Based on ASTM A568)
What to Consider After Selecting Material Type
Once a material is chosen, a designer should be able to confidently answer “yes” to the questions below. If after asking these questions you discover ways to safely reduce part requirements or widen tolerances, your bottom line will undoubtedly be improved.
- Is the part strong enough for the function it has to perform?
- Can the part be assembled, disassembled and serviced using the most economical methods?
- Are all the necessary symbols for finishing, grinding, etc., shown in the drawing?
- Are locating points and proper finish allowances provided?
- Are material and heat treatment specifications given?
- Are plating and painting specifications, either for protective or decorative purposes, given?
Most material warehouses have up-to-date listings on their website or can supply catalogs free of charge. These listings will most often show the commercial name or material type, along with the thickness, width, temper and thickness tolerance, but additional research may still be required. In general, if a particular material is listed, it can be procured without delay, shortening the lead time for part manufacture.
In every case, the ready availability of a material may make the difference between you getting a reasonable quotation or not. Excessively tight material tolerance requirements will unnecessarily raise sourcing costs and may be the cause of a project being scrapped. Luckily, manufacturers are frequently looking for ways to increase efficiency and decrease costs. It’s always worth discussing your project and how a part will be used with your supplier. They will know the operations and shortcuts that will lead to the most economical production methods.