New and Improved Manufacturing Methods
Look what's coming!
By Robert B. Aronson
Make it faster, more accurate, smaller or bigger, from fewer parts, in one setup, with less labor, simpler to operate, and of course, cheaper. These customer demands keep the makers of manufacturing equipment hustling to improve existing processes and finding new ones. Here's a look at some of them.
Compact Graphite Iron (CGI) has been around for some time, but only fairly recently has it been called into active duty. It has a number of properties that make it attractive:
- It's 75% stronger and stiffer than gray iron
- It has good thermal and damping characteristics,
- It has at least double the fatigue resistance of gray iron and aluminum, even more in high-temperature applications,
- It';s more difficult to machine than gray but easier than ductile.
These features make CGI a good candidate for diesel engine blocks as well as other products that require good thermal conductivity and high-temperature strength. Another big plus is its weight is significantly lower than a conventional diesel engine block of the same power.
"European and Asian car makers were quick to take advantage of CGI," explains President Steve Dawson of SinterCast (a Swedish company with US headquarters based in Naperville, IL).
"More than 20 manufacturers now use it as an engine block or cylinder head material," Dawson continues. "Worldwide, each month about 30,000 engines are being produced with SinterCast technology."
All of the US Big Three have CGI engines under development. And it is predicted that some gasoline engines will migrate to CGI engine blocks. Many analysts regard the diesel engine as the savior of the SUV. Replacing the gasoline engine with a diesel would increase fuel economy by an estimated 40%.
"We predict that by 2011 there will be one million passenger car diesel engines operating in the US," says Dawson.
The move to titanium beyond aerospace applications, particularly in the automotive industry, has repercussions for many machine-tool manufacturers. Because cutting titanium generally requires higher torque and greater accuracy, machine tool makers are responding with new designs. For example, Makino has developed a machine tool specifically to fill this need.
In developing this design, they found that faster isn't always better. Sometimes a little slower and a lot more rugged is a better idea. This is the design philosophy behind the new high-torque M-series spindles.
These high-torque and high-thrust spindles are particularly suited for long reach and large-diameter boring operations that require high torque, particularly at low rpm. For example, tapping, where a significant amount of spindle stopping, starting, and reversal occur.
Among the newer fastening and joining methods is friction drilling, a process akin to friction welding, but limited to holemaking in thin materials. Usually, when a material is too thin to thread, it's necessary to add an insert or nut. In the system offered by Flowdrill Inc. (St. Louis) this step is eliminated by creating a hole with a threadable boss.
In this process, a tungsten-carbide tool with a cone tip spinning at speeds up to 3500 rpm is forced against a workpiece. The heat generated softens the workpiece and punches through. Thickness of the formed boss can be up to three times the workpiece thickness. Available as an automated or manual tool, it can make holes up to 2" (50-mm) diam.
Lasers have both created new processes and cut into some of the more conventional machining processes. Improvements include simpler operation, greater reliability, and increased power.
"In general we have been doubling output power," says Andy Appleyard, SPI Product Line Manager, High Power Lasers (Santa Clara, CA). "Our air-cooled products have gone from 100 to 200 W and water cooled from 200 to 400 W. The changes are due to our own research and the availability of more powerful pumped diodes from suppliers. Pumped laser diodes are very reliable, and based on technology originally developed for long-distance power-transmission systems. At the same time, our designs have been reduced in both complexity and cost."
A long-term trend in lasers has been the move to fiber systems. In this design, the fibers deliver the beam instead of mirrors. They offer a number of advantages over the more conventional types such as:
- Ease of integration into manufacturing systems,
- Low maintenance requirement,
- Minimal setup adjustment needed.
Because the laser cavity and pumping system are integrated into a monolithic structure, there are no optical interfaces that might become misaligned, and no optical surfaces to clean.
The fiber laser provides high power density in the target area because it is single mode. For example, a 200-W laser can have a 10 µm-diameter focus size.
The high productivity of punch presses has been challenged by highspeed laser-cutting machines, having the advantage of higher flexibility of cutting any hole diameter/shape without the need for tool changes or new tools. "Lasers have no limitations of contour complexity," explains Pieter Schwarzenbach, VP of Laser Technology, Prima North America (Chicopee, MA).
With synchronized ultra-highspeed cutting machines, the complex contour is easy to process, providing improved parts at a lower cost.
High-speed lasers are an advantage for customers cutting 0.020 x 1" (0.50 x 25-mm) thickness range in mild steel, aluminum, and stainless steel, although the maximum advantage is in the material thickness of 1/8" (3.2 mm) or less. Speeds can be more than 800 ipm (20 m/min).
One of the fast-curing UV adhesives is offered by Dymax Corp. (Torrington, CT)
In operation, the adhesive is placed on the parts to be joined, the parts are fitted together, then the adhesive is quickly hardened by UV light.
The light (UV or visible light) must see the adhesive by line-of-site. The adhesive will cure as long as light can get to it, whether by direct exposure around a seam, or bonding through a transparent or even translucent plastic/glass.
Loctite, a brand of the Henkel Corp. (Rocky Hill, CT), has long been known for its anaerobic adhesives for thread locking and has a significant line of structural adhesives. In one of the company's success stories, a company initially manufactured a trailer by first welding the frame together, then riveting on the exterior walls. This costly and slow operation was replaced by using Loctite H8000 Speedbonder structural adhesive. It is manually applied with a pneumatic cartridge dispenser, then a flat panel is clamped in position and the excess adhesive is removed. After a two-hour curing, the panel is structurally bonded to the frame. No additional reinforcements are added.
Life of the trailer's paint has also been increased. In the past, corrosion that degraded the paint started at the rivets. Now that the rivets have been eliminated, there is less potential for corrosion.
Cutting tools continue to proliferate, with variations in base material, geometries, and coatings. The main emphasis is on efficiently cutting higher-strength material, high-temperature resistance, and life.
At Sumitomo (Mt. Prospect, IL), a company specializing in inserts for turning, the major research emphasis continues to be coatings. The challenge is to efficiently cut superalloys such as Hasteloy and Inconel.
The more recent developments are Super ZX coatings.
Adding titanium, aluminum, and chromium improves hardness and oxidation resistance, extends tool life, and improves cutting-edge fracture resistance.
The National Center for Manufacturing Science (NCMS; Ann Arbor, MI) is an organization that works with a variety of manufacturing companies to resolve common problems.
Their Product Lifecycle Management (PLM) program has been rather successful.
"The goal was to bypass the human interface, and get paper out of the cycle when developing new products," explains Tony Haynes, director of advanced manufacturing technology programs.
One of their projects helps eliminate machine tool errors before any cutting is done. The starting point was the US Navy's need for a more efficient way to make ship propellers, chiefly those for submarines. Their existing system was to use a large five-axis gantry milling machine to do the work. If, after machining, tests showed too much metal removal, that section had to be built up by welding, then remachined. Too much metal required another machining pass. Making one propeller can take several months.
Using technology developed in the project, the machine tool is made more accurate to minimize machining error. A sensor is attached to the machine's spindle holder and a program is run that positions the spindle at several hundred random points over the entire working volume of the machine tool. At all these points, the program position data are compared to where the spindle actually is. Any deviation detected is the result of a machine-tool accuracy problem. A computer system then calculates necessary corrections and feeds them to a Siemens 840D NC controller that makes position corrections in real time. "The result is a machine tool with volumetric accuracy within 0.005" [0.013 mm]," says Haynes.
A third project used technology originally developed by the Cincinnati Machine division of MAG Industries to monitor customer usage of its machine tools, automatically gathering information on such things as machine utilization, spindle RPM, and torque in cutting processes. Realizing that the technology could be used to monitor any machine, not just machine tools, MAG transformed it into a product offering, Freedom eLog, by its Infimatics division.
The NCMS project applied Freedom eLog to a wide variety of applications in both defense maintenance and aerospace manufacturing.
"This project showed that in many manufacturing operations there are often wide discrepancies between what someone believes is happening and what is really going on," says Haynes. "The data are available, if you ask the right questions."
"Many of the advances in abrasive waterjet [AWJ] are evolutionary, such as greater pump reliability and ease of maintenance," says Mohamed Hashish, Flow International (Kent, WA). At Flow, some of the more recent developments are in adding remote diagnostic capabilities. That is, software that monitors the health of the hardware and makes it simpler to diagnose problems and forecast maintenance schedules.
With today's software for flat stock cutting, you need only dial-in jet parameters such as pressure, abrasive flow rate, and the required surface finish. The software will automatically select the cutting speed to give you the most accurate part. Future software will enable 3-D operation on complex parts with advanced jet models.
"And, of course, we are always looking for ways to increase pressure, as well as make the pumps quieter and smaller. Right now, we are on the limits of material technology," he says. "The strength of the pump metals and seals along with a need for a better understanding ultra-high pressure tribology are our challenges. That includes more knowledge of properties under pressure, friction, wear, and lubrication," Hashish concludes.
Research underway at Missouri University (Rolla, MO) under the initial direction of David Summers, Curators' Professor of Mining Engineering, Missouri University of Science and Technology, is developing several ways to use AWJ to resolve machining problems.
Removing material from sensitive metals is increasingly being achieved using higher rotational speed cutting tools. One problem with this technique is the quality of the end surface, particularly when cutting narrow ribs. Heat and vibration from the cutting process can distort the rib. "One solution being developed by Greg Galecki, associate research professor, is to add a small flow of highpressure water along the cutting face of the tool itself," he says. "This jet, which has to be at sufficient pressure to enter the chip/tool interface as material is being removed achieves several benefits. It keeps the tool cool, so it retains its sharpness for as long as five times normal life; the forces required for cutting [both thrust and cutting] are significantly lowered, so there is much less vibration, and thus better control of surface quality."
In the earlier days of the powder-metal industry, applications for these parts were limited by low strength. This was because of the low density of the powder-metal part compared to solid metal. Today these products have a much wider appeal because of their improved properties. Densities are now greater than 90%. A major positive feature is the ability to make PM parts with a shape close to or in some cases equal to that of a machined part. Another plus is the ability to tailor the characteristics of the final part by blending powders of different types. In the process, mixed powder is compressed into a mold. In some operations, core rods are added to the mold to create holes in the finished parts. The newly formed or "green" part is then sintered. The green shape can be machined before or after sintering, to make a form closer to the desired end products and reduce machining.
Parts can weigh tons, or be fingertip size. Parts as thin as 1/16" (4 mm) have been made, but the general rule is the L/D ratio should not exceed 8/1.
"Most of the research focuses on methods of increasing the density of the finished part and deriving new powder blends to increase the physical properties available," explains James R. Dale, vp of member and industry relations for the Powder Metals Industries Federation (Princeton, NJ).
"There is an alternate process called powder forging," says Dale. "The part is formed conventionally, then reheated and placed in a die for further compaction in a step that is much like conventional forging. The end result is a product that is more dense than conventionally made PM parts."
Another more advanced process is metal injection molding, which is much like plastic injection molding. Its major advantage is the ability to produce smaller, higher-density parts. Elements of surgical tools used in laparoscopic surgery are one application. This process competes well with die casting.
This article was first published in the October 2008 edition of Manufacturing Engineering magazine.