Making Meticulous Metal Parts

Precision Metal Work and Finishing
Written by Nate Hendley

Precision metalwork centers on tight tolerances, strict specifications, and repeatability to create parts or entire assemblies out of metal. In machining, material is removed through milling, turning, grinding, or drilling. Another common method of metalworking is forming, in which the material is reshaped through bending, cold-forging, rolling, or stamping.
Companies looking to achieve the standards expected in precision machining or forming often rely on computer numerical control (CNC) machines that guide the metalworking process with computer software. Once programmed with a computer language referred to as a G-code, the CNC machine automatically controls feed rate, speed, tool position, and other functions, allowing for repeatability, and predictability. These CNC machine tools offer the kind of precision that a human operator might be incapable of achieving.

CNC technology is commonly used with lathes, mills, and plasma cutters which cut metal material using a plasma torch. It also controls electric discharge machines (EDMs) which use electrical sparks to remove material and water-jet cutters which use high-pressure blasts of water to excise material.

The Hansford Parts and Products blog cites several reasons why CNC is the way to go when it comes to precision machining. These include a low error rate as human operators are far more likely to make a mistake than a computer program, less material waste, and consistent quality. Other benefits include enhanced workflow, reduced turnaround time, speedier production cycles, and easier prototype testing.

Another point mentioned by the blog is the potential for the technology’s use in producing small runs of experimental products. “Precision machining offers your business an opportunity to explore smaller niche markets with potential for high returns. Precision CNC machining can allow for a flexible product-development phase as the niche opportunity is determined. If the market has a demand, the machining can be shifted into a full-scale production mode.”

“Precision machining also allows for prototypes to have functional parts, as opposed to a more concept/design prototype. Functional prototypes instil more confidence from investor stakeholders than concept-only,” the blog continues.

Summit Steel & Manufacturing in Reading, Pennsylvania, offers metal bending and forming along with CNC machining. This company uses CNC hydraulic press brakes and other machine presses for bending and forming operations. The result is greater efficiency, shorter lead times and “increased precision in the finished product,” states Summit.

“CNC bending and forming helps to establish and maintain optimal performance and facilitates increased precision and control. When performed by top-quality bending equipment, the process will deliver high-precision bends in sheet metal, while minimizing the risk of workpiece damage caused by an improper fit,” continues the company site.

Tools used for precision work, besides CNC machines, included what is known as computer-aided design or computer-assisted design (CAD) software and coordinate measuring machines (CMM).

Like many of its counterparts, Summit utilizes CAD and computer-aided manufacturing (CAM) software for consistent output. Indeed, the growing popularity of computer numerical controlled machines has been matched by a trend towards the use of CAD software for metal parts and product design. Designs made with two-dimensional or three-dimensional CAD software programs are incorporated into the computer code driving the CNC machines.

Imperial Machine & Tool Co. of Columbia, New Jersey, notes that it uses CNC machine tools and CAD/CAM software programs. “Imperial has extensive capabilities in three, four and five-axis machining of large and small workpieces. While it is certainly work-specific, we regularly hold tolerances of .0002 inches in machining envelopes as large as 30 inches by 40 inches by 84 inches,” states the company.

Ensuring accurate measurements is a vital step in precision metal working. Companies that want extremely accurate measurements often turn to coordinate measuring machines (CMMs) for doing inspections. CMMs use probes to measure the geometry of metal parts and other physical objects. They offer arguably the most accurate measurements of any metrology equipment typically found in a machine shop and are becoming increasingly important given a growing trend towards tighter tolerances.

Once a metal part has been created, it generally goes through a finishing stage. This is done to enhance the part’s durability, tarnish resistance, adhesion, or appearance. Finishing can also alter electrical conductivity, friction, or adhesion properties Metal finishing processes include grinding, buff polishing, powder coating, sandblasting, plating, painting, and more.

Metalworking companies have trade associations looking out for the interests of the industry.

The Brecksville, Ohio-based Precision Machined Products Association (PMPA) represents businesses that either make precision machined parts or provide equipment or services for the sector. The PMPA has been in operation since 1933 and has roughly 440 member companies, including manufacturers, machine shops, and machine tool builders. Most of these firms are based in North America.

“The precision machining industry accounts for over 99,400 jobs with payrolls of $5.1 billion and shipments of over $18.4 billion,” within the United States, states the PMPA.

Metal forming companies are represented by the Precision Metalforming Association (PMA). Founded in 1913 and based in Independence, Ohio, the PMA has 800 member companies and 80,000 individual members in the United States and Canada.

Metal forming, according to the PMA, is a $137 billion industry in North America. In addition to advocacy work, seminars, and networking, the PMA co-sponsors the massive Fabtech trade show known as “North America’s largest metal forming, fabricating, welding and finishing event.” Fabtech 2017 in Chicago drew almost 45,000 industry people and 1,700 exhibitors.

Metal forming and metal working companies alike have expressed concerns about the impact that the aluminum and steel tariffs introduced by the U.S. government will have on the respective industries. In a report released in August 2018, PMA members worried that steel tariffs might raise expenses and make it more difficult to compete with Asian and European counterparts.

A PMPA press release from March of this year outlined similar sentiments. “The Precision Machined Products Association today expressed concern that the imposition of tariffs on imports of aluminum and steel will lead to the loss of manufacturing jobs that will far outweigh any employment gains in the steel and aluminum industries,” reads the statement.

Tariffs aside, precision metal machining and forming companies seem highly optimistic about the future. The PMA’s August report indicated that nearly one-third of participants expected an economic improvement during the next three months.

“Metal forming companies expect an upward trend in incoming orders during the next three months, with thirty-seven percent predicting an increase in orders (up from twenty-six percent in July), forty-six percent anticipating no change in orders (compared to fifty-four percent in July) and seventeen percent forecasting a decrease in orders (down from twenty percent last month),” added the report.

Precision machining companies seem equally upbeat according to a September 2018 press release about a PMPA member survey for the previous month. “Eighty-percent of our respondents reported sales increases. Fifty-one percent of shops reported sales increases in the double-digits.”

For now, precision metalworking remains as in demand as ever.



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