How to Avoid the Issues of Non-Standard Material Size

June 18, 2018 Joshua Jablons Ph.D.

Whenever Possible, Keep It Standard!

In the process of sourcing material for small metal parts, customers sometimes ask if they can use a non-standard material size for their parts. The question may arise because an engineer has specified a non-standard size in the design. Perhaps a buyer hopes that starting with a material that is closer in size to what the end part needs to be will save time and money in the cutting process. Or, a customer may be trying to avoid specifying a very tight tolerance by asking for a material sized to the very top or bottom limit of the material’s standard tolerance range.

The reality is that using any non-standard material size poses challenges in sourcing.

What’s Wrong with Non-Standard?

Any non-standard material may be difficult to get — and it may even need to be manufactured to the requested size by special order. Either way, that can increase both production time and cost (in the case of a special order, perhaps significantly). At the very least, different mills will have different minimum quantities and other requirements that may a small special order completely cost prohibitive. That’s why at Metal Cutting, whenever possible we try to guide customers to opt for using a standard size material that is readily available and therefore, easy to obtain, and more cost effective.

Even sourcing just a few feet of material at a special size to be used for R&D can be very pricey. When your purpose is to simply to validate a design, here, too, we recommend that you use a standard size material that is easily available at a minimum quantity. That way, you will be reserving the added cost of special-order non-standard material for the final product and a proven design — and then, too, only if the non-standard size material is absolutely necessary. (Who knows? Your testing may provide proof that a standard material size will deliver precisely the part characteristics and functionality you need!)

“Non-Standard” vs. Tighter Tolerance

Sometimes a customer will ask for a specific measurement within a standard tolerance range — say, for example, a flat piece of 14 gauge stainless steel that is 0.0781” thick. This, too, may pose issues and require a special mill run.

That’s because in general, the goal of manufacturers is to achieve material that is at the central, nominal tolerance, such as 14 gauge stainless steel at a thickness of 0.0750” with a tolerance of ± 0.0030. Asking for the material at the high or low end of the tolerance range is, in effect, asking for a tighter tolerance — which in turn might still require a special order and raise the cost.

It’s a Global World — and That Can Be a Problem, Too

Another factor when considering the use of a non-standard material size is where in the world that material comes from. In today’s global market, it is not unusual to have (for instance) an IVD machine designed in Germany, validated in the United States, and manufactured with most parts made in Singapore but other key parts made in Europe. Mergers and acquisitions can mean a company may be making a part or assembly using drawings that were generated by another company on the other side of the world.

This international melting pot of parts, specs, and materials poses its own challenges. In the United States, there are industry standard sizes of tubes and plates that are readily available in various materials. In the international marketplace, suppliers in different areas of the world may use different codes for identifying materials. Drawings from different countries may use metallurgical type designations that are not universal. In addition, the chemical composition of material may not be consistent across the globe. And what is one to do when dealing with a proprietary metal from a particular manufacturer?

There are tables available online that can be helpful; however, there is no guarantee they are accurate, and at this time there is no one unifying source that provides definitive cross references and translations for material sizes, gauges, chemical composition, and so on. There are legal implications, as well as safety and quality issues, associated with such differences. That means if a slight discrepancy in material composition will make a difference in the functionality of your end part, then you need to be wary when sourcing raw materials from different sources and areas of the world.

Is Non-Standard Really Necessary?

The fundamental questions we at Metal Cutting ask our customers are, Why is the material non-standard? and Can it be standardized to improve production costs and capacity?

If you really must have a non-standard material size, your vendor may be able to adapt a standard material to the size you request, as an alternative to a special order from a mill. For example, rather than your having to order 5’ of custom tubing for testing, Metal Cutting could take a standard size solid rod of the correct length and material type, and machine or grind it into a tube of the size you need. While that would require removing a large percentage of metal from the piece and would add the cost of machining time, it might still be less expensive than a special order. (Keep in mind that the farther from standard size you want it, the more metal must be removed, the higher the cost, and the greater the risk of instability in a machined tube vs. when you use standard gage tubing.)

Above all, when you are designing a part, be sure to think about the feasibility of actually producing it and always consider the cost and ease of obtaining the proper standard material(s), if at all possible. Many common sourcing problems can be averted by avoiding designing issues — such as non-standard material — into a part in the first place. For example, supposed you are designing a tube to carry liquid between two endpoints. Rather than calculating the flow over the necessary length and then determining the tube diameter, is it possible to test your application using a standardized tube size?

Remember, even in customized manufacturing, there is standardization. So, designing with standard size materials wherever possible will help you to control costs and keep the manufacturing process streamlined.

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