How to Avoid the Issues of Non-Standard Material Size

June 18, 2018 Joshua Jablons Ph.D.

Why Non-Standard Size Is Rarely a Cost Saver

In the process of sourcing raw materials for small metal parts, customers sometimes ask if they can use a non-standard material size for their parts. The question may come up for any number of reasons. For example:

  • An engineer has specified a non-standard size in the design. 
  • 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.
  • The customer wants 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 size poses challenges in material sourcing.

What’s wrong with “non-standard” in material sourcing?

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 have different minimum quantities and other requirements that may make a small special order 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.

The risk of busting the budget in R&D

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 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 sourcing for the final product and a proven design — and then, too, only if the non-standard size is absolutely necessary.

(And who knows? Your testing may provide proof that a standard size will deliver precisely the part characteristics and functionality you need, saving you the cost of special sizing.)

When non-standard = tighter tolerance

Sometimes in material sourcing, a customer will ask for a specific measurement within a standard tolerance range. For example, the customer might request a flat piece of 14 gauge stainless steel that is 0.0781” (1.9837 mm) thick.

This, too, may pose issues and require a special mill run. That's because a manufacturer's standard production run can be anywhere within the allowed tolerance.

So, 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.

Global complications in material sourcing

Another factor in material sourcing when considering the use of a non-standard size is to think about where in the world that material originates.

In the United States, there are industry-standard sizes of tubes and plates that are readily available in various materials.

However, in today’s global market, it is not unusual to have (for instance) an in vitro diagnostic device (IVD) 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 material sourcing:

  • 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. 
  • The chemical composition of a material may not be consistent across the globe.
  • A proprietary metal from a particular manufacturer may not be universally available.

There are tables you can find online that may 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 potential 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?
  • Can it be standardized to improve production costs and capacity?

If you really must have a non-standard material size, your supplier 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 ordering  5’ (1.524 m) 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 the material, 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 gauge tubing.)

Whenever possible, keep material sourcing standard!

Above all, when you are designing a part, be sure to think about the feasibility of actually producing it and 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, suppose 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 custom manufacturing, there is standardization. So, designing with standard size materials wherever possible will help you to control costs and optimize the manufacturing process.

 
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