Sizing Up The Management Challenge
The demand for extremely small precision components is growing. A look at one company’s thrust to meet this demand reveals what it takes to run a micro machining business.
by Mark Albert
Remmele Engineering is no stranger to the pages of this magazine. This company, which has a half dozen machining plants in the greater Minneapolis area, excels in numerous metalworking activities and is considered one of the country’s best and most diverse job shops. Remmele is perhaps best known for its innovative approach to the high speed machining of large aluminum airframe components and has been the subject of several articles on this topic.
However, Remmele has a growing reputation in the field of micro machining. The company began to look at micro machining in the early 1990s, then made the decision in 1997 to devote one of its plants entirely to the production of very small precision parts. This location, Plant 30, is next door to one of the company’s other plants near Big Lake, Minnesota. It so happens that this other plant handles some of the largest work that Remmele takes on—workpieces weighing up to 100 tons and as long as 100 feet.
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Fig. 1—These medical components are typical of the sub-millimeter work Remmele’s Micro Machining Division produces. These pieces are under 0.08 inch long and toleranced to ±0.0005 inch.
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Plant 30’s specialty, in contrast, is work that is roughly no larger than one cubic inch and often under one millimeter in length—about the size of a pinhead. John Bowden, one of Remmele’s VPs and head of the company’s micro machining division, has a clear idea of what it takes to be successful in this aspect of metalworking. A recent discussion with Mr. Bowden showed that managing the micro machining shop is a matter of paying attention to the important things, which often contrast with the priorities in other aspects of machining. Very small parts can be difficult to see, difficult to handle, and difficult to measure. The assumptions and expectations valid in general machining may or may not hold in the realm of micro machining.
One Definition Of Micro Machining
The term micro machining has no standard definition, Mr. Bowden explains. At Remmele, it means parts smaller than a one inch cube mainly because that’s how the company finds it convenient and appropriate to divide work among its four divisions (General Machining, Automation and Repetitive Batch Machining are the other three). Plant 30 is home to about 25 Swiss-type CNC turning centers, mainly Cincom machines from Marubeni Citizen. These machines represent the chief machining capacity of this plant. Several machining centers complement the turning equipment. A uniquely designed micro laser processing system is also located here.
Although sub-millimeter workpieces such those in Figure 1 are this plant’s forté, complex, tightly toleranced machined parts in sizes above 1 millimeter and produced in mid to high volume are a mainstay. One example is shown in Figure 2. This has proven to be a healthy mix of work. On one hand, skills developed in the sub-millimeter jobs, where tolerances are typically ±0.0001 inch, carry over to “larger” parts.
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Fig. 2—Larger workpieces such as this titanium bone screw are also produced in Plant 30.
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About 95 percent of Plant 30’s production is for the medical industry. Mr. Bowden expects the medical industry to remain a strong consumer of sub-millimeter parts as trends in medical research continue. For example, researchers are developing a host of new instruments small enough to insert through catheters for minimally invasive surgical procedures. Telecommunications and fiber optics are also likely to create a growing demand for micro machining.
Facilities Management
Attention to housekeeping is important in any plant, but it is especially important when dealing with micro machining. Cleanliness in Plant 30 is maintained scrupulously. “We had the floor stripped and resurfaced when the building was converted.” Mr. Bowden notes. “The light, high gloss finish doesn’t let you get behind on a cleaning schedule,” he explains. Walls are also painted in glossy, light colors.
The reflective surfaces of the walls and floor were chosen to enhance overall lighting in the building’s production areas. New lamps were installed to provide even, glare-free lighting throughout. Lighting makes a difference when working with small parts and fine detail and is essential for bench work, where parts are routinely inspected with microscopes.
All of the machine tools in this building are fully enclosed and equipped with mist collectors. The heating and air conditioning system is designed to maintain an even temperature (±2°F) throughout the shop area. Strict climate control is required because thermal changes have an exaggerated effect when tolerances measured in “tenths” are the rule.
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Cleanliness and good lighting are fundamental requirements for micro machining.
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The bright, freshly scrubbed appearance of the plant has an additional value. “With most of the work related to the medical industry, customers expect a laboratory-like setting in this production facility,” Mr. Bowden explains. With its strong lighting and stringent orderliness, it has even been compared to a surgical suite, he says, a favorable comparison that is certainly welcome.
Operations Management
Completing parts in one setup is a common theme being emphasized throughout metalworking today. One would certainly find this true if the Remmele plants represent a cross section of the industry. For micro machining, however, “done-in-one” takes on an added dimension.
“Many of our workpieces are simply too small for effective handling,” Mr. Bowden explains. “Performing secondary operations off the original machine is not an attractive option due to the likelihood of locational errors,” he continues. For this reason, almost all of the Cincom lathes are equipped with subspindles and live tooling.
Live tooling on these lathes is a major asset, allowing the screw machines to function as miniature turnmill machines in many cases. This approach simplifies workholding challenges because the bar feeder and spindle chucks solve the difficulty of loading and positioning very small workpieces.
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Workstations in the production area are equipped for cleaning, inspecting and packing finished workpieces. The company strives to perform all other machining operations in one setup on one machine tool.
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Deburring is an operation that gets considerable attention. Brushes of various diameters can be spotted in tool turrets and on tool slides in the screw machines. “We’ve devoted a lot of time to testing and developing our deburring techniques,” Mr. Bowden claims. “For example, finding the right combination of bristle type, brush speeds and feeds, and so on is not unlike finding the best feeds and speeds for a cutting tool,” he says. The goal is to produce, on one machine, parts that require only cleaning, inspection and packaging after cutoff and release into the parts catcher.
The whole issue of burrs on workpieces is critical, one that has to be dealt with carefully and thoroughly in micro machining, Mr. Bowden warns. When a customer specifies a “burr-free” condition, the precise definition of “burr-free” has to be spelled out, with no uncertainty remaining about what is acceptable or unacceptable. According to Mr. Bowden, Remmele has compiled a comprehensive handbook on burrs that classifies types of burrs, lists the techniques for removing those burrs, specifies methods of verifying that the burrs have been removed, and so on. This handbook has proven to be an invaluable resource for establishing agreement during production planning and for avoiding problems when parts are received by customers.
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A multi-sensor measuring system provides tough probe and non-contact measurement options. The Mycrona Primus system is based on digital imaging techniques.
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“It is not unusual for customers to turn to us to recommend how to handle burrs and establish procedures based on our experience,” Mr. Bowden says. “The main thing is not to underestimate the importance of deburring from the start,” he emphasizes. Proper handling of material is another item in micro machining that might not be recognized as a priority. At this plant, most workpieces are produced from bar stock, which is always delivered in a ground, heat-treated and straightened condition. Material storage is maintained inside the production area under the same climate control as the rest of the shop. Bars are stored in cardboard or PVC tubing to prevent marring or sagging. Even when bars are moved to the machines, provisions are made for supporting them along their full length. “We don’t have the luxury of ‘machining out’ any out-of-round, off-center or non-straight conditions.” Mr. Bowden explains.
Part cleaning and packaging also get their due. Wherever possible, parts are cleaned and packed at the work bench near where they are machined. Each work bench is equipped with an ultrasonic cleaner. In some cases, the company has had to design special holders for parts that would otherwise slip through the openings in mesh containers for submersion in the cleaning bowls. The company has also designed unique packaging for micro machined parts. Special “egg crate” designs, for example, protect delicate features and create convenience for the customer.
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