Cold forming, or cold forging, is becoming a more popular option for manufacturing precision engineered miniature and micro surgical and medical components. 1 Manufacturers that purchase custom cold formed components for their assemblies do so with a view to reduce raw material and labor costs while also improving yield and component reliability. While the parts are generally very small, a large percentage of them contain a wide variety of expensive — and often precious — raw materials, and any reduction of waste adds directly to the bottom line. Cold forming’s other advantage of retaining or even improving repeatable quality over alternative methods is another reason it is becoming increasingly popular.
So, while production efficiency, lower cost, and improved yield, strength, and quality are all extremely compelling reasons to choose cold forming, here’s an unexpected one: ecological. Many companies employing methods to reduce environmental impact do so either because of regulatory compliance requirements or because of the public relations value; that is, a perception of good corporate citizenship influences consumer preference in esoteric (if not real) terms. However, with cold forming, the ecological advantages translate almost entirely to cost advantages as well.
The naturally environmentally friendly methods used in cold forming can result in savings from the following categories: virtually no scrap, lower material and recycling costs, reduced overhead cost, and reduced oil cost and consumption. Note: The platform for cost comparison takes into consideration a significantly higher production volume for cold formed parts at an average of 100 PPM versus the typical 20 PPM for machined parts. The savings illustrated below are particularly effective over very long runs.
Virtually no scrap. Very little to no material is sacrificed in part manufacture, except in trimming, which may account for less than 2 percent of the part mass. Cold forming produces a “near net shape” (and frequently a complete net shape) part. Less scrap translates into a reduction in original material cost to manufacture the part.
Lower material and recycling costs. Recycling costs, especially for exotic materials such as gold, silver, and platinum, are much lower for cold forming because machining produces scrap, whereas with cold forming, all materials are near net shape. Recycling costs for exotic materials are higher due to challenges of reclaiming particles and screening impurities after recycling.
Reduced overhead cost. Fewer man-hours are devoted to producing the same number of parts; therefore, the cost per piece includes a much lower contribution of labor cost than machining does. Also, because of cold forming’s high production speed, there is a much lower utility cost contribution per part than with a slower process like machining, making the part significantly more energy efficient.
Reduced oil cost and consumption. Total oil cost is lower for cold forming. Even though it uses a more expensive type of oil that requires greater viscosity than lubricating oil for machining, the faster production speed means less oil usage over time. On average, this results in lubrication cost savings of 10 percent on every full production run.
To illustrate ecological savings using actual products, the following examples of specific parts compare manufacturing costs and savings with cold forming versus machining.
Example 1: Medical Device Insert Screw
A stainless steel medical insert screw is manufactured using cold forming and roll forming as a secondary operation. This net shape micro-screw produces no scrap and has an increased tensile strength due to work hardening through the cold forming process. The high run rates of cold forming positively impact cost and energy efficiency with a savings of 407 KWH per million pieces compared with traditional machining methods. Production runs for the insert screw are in excess of 50,000,000 parts annually (see Table 1).
Example 2: Cannula Hub
An aluminum tubular part that holds a medical needle and screws into a syringe body is manufactured using cold forming with secondary operations for threads. Minimal scrap and increased tensile strength are achieved through the cold forming process. Due to the high run rates possible with cold forming, when compared with traditional machining methods, 528 KWH were saved per million pieces, reducing not only energy cost but the carbon footprint as well. This part runs in excess of 2,000,000 annually (see Table 2).
Bottom line: Ecological imperatives, considered alone, may not be enough to convince medical device buyers to adopt cold forming to solve many of their small component manufacturing needs. But cold forming affords them an opportunity not just to claim a high road of environmental responsibility, but to save some additional cost along the way.