A premier provider of workholding solutions, Hainbuch can minimize your production challenges while increasing profitability.
In an era of domestic and international competitive pressures, gear manufacturers with fabrication sites throughout the United States and internationally are constantly faced with the pains of production challenges and quality control. As a result, gear manufacturers are continually in search of the latest state of the art workholding opportunities. The trend remains in the direction of increased flexibility, efficiency, and accuracy in order to gain the competitive edge. These challenges include, but are not limited to, setup and changeover times, rigidity, and precision.
Manufacturing gears is a very intricate process, and that’s why Hainbuch invests deeply in employee know-how and the latest technologies. We focus on industry needs and strive to be a step ahead of the competition to provide customized solutions. If you can machine it, Hainbuch can hold it. Consequently, to ensure this process the company is continuously involved in research and development as it pursues improvements in providing answers to gear-manufacturing challenges.
Workholding Tool Selection
Gear-cutting machines are typically outfitted with a factory standard workholding component. While acceptable, the factory standard unit does not provide the most flexible, accurate, or efficient solution. One of the most significant yet overlooked opportunities in which gear manufacturers can gain the competitive edge is by means of improved workholding solutions. The perfect clamping and centering device can minimize the workpiece changeover times by as much as 50 percent while concurrently improving rigidity and precision, increasing the value of machines and profitability.
What to Consider
The ideal workholding solution for gear manufacturers enables quick part-to-part changeovers that can locate and lock on the gear’s pitch diameter, work with pieces having virtually any number of teeth, and can compensate for varying teeth spacing and pitch values. While changeover time is essential, be sure that your workholding tool also ensures maximum repeatability and rigidity. “You don’t want to sacrifice manufacturing quality for speed,” according to Jurgen Bettray, president of Hainbuch America, which is located in Milwaukee, Wisconsin. “That’s why our engineers have endeavored to develop and design some of the most innovative systems that give you the best of all worlds, such as Hainbuch’s Centrex Interface Centering system and the Mando T212 segmented mandrel.”
Sylvia Rall, marketing director of Hainbuch Spannende Technik in Marbach, Germany, says that “Hainbuch is not only the original designer, developer, and manufacturer of the mandrel, but we have been the experts in the field since 1994. We have the knowledge and experience that supports this incredible workholding device.”
The Centrex Interface Centering System
The need for increased precision and rapid setup times has resulted in the development of the high-precision Centrex Centering System, the compact patented solution and first automatic zero-positioning pallet system already in use with various Hainbuch products. Figure 1 This simple system uses precision steel ball bearings in a rubber ring in conical positioning elements integrated into the pallet system and guarantees an exact repeatability of less than .003 mm, as well as a perfectly level contact. The four bushings and positioning cones are ready mounted, allowing the pallets to be fitted to each other with exact repeatability. With a mini zero position system in Hainbuch standard pallets, it will save users space with part specific equipment, time, and money. If you have not seen this centering system in action you will appreciate that a plate fitted with Centrex is mounted with exact repeatability, and that a dial indicator reading 1 micron shows no deviation. This system allows the changeover of the entire chucks to be performed while retaining process reliability and without alignment. The Centrex Interface System performs the centering function, with centering accuracy of less then 3 microns. In addition, due to its diversity of applications, this system drastically minimizes setup times and interruptions in production. Here’s how it works:
• The taper bushing is pressed into the carrier pallet, and the taper mandrel is pressed into the base plate.
• If the carrier pallet is positioned onto the base plate, the pallets will initially have no face contact. Under these circumstances the internal and external cones make only indirect point contact through the bearings. If a force is now applied to the carrier pallet, the superficial surface of the tapers deforms in the elastic range.
• The clearance for the bearings thereby becomes greater, and the taper bushing can move in the direction of the base plate until face contact occurs.
• As the superficial surfaces of the tapers have the same hardness universally, the mandrel always has the tendency to move toward the center of the taper bushing.
• Through the use of two Centrex units, the carrier pallet is exactly aligned between two defined points.
Trend-Setting Clamping
The obstacle to complete machining is often the lack of a sensible workholding device that is able to clamp a workpiece from the inside. A jawchuck offers only limited help, and mandrels currently on the market leave much to be desired regarding accuracy, rigidity, stoke, and usability. The central element is the clamping bushing.
Because conventional clamping bushings are made out of spring steel and are only annealed and therefore soft, they have to “bend” to clamp the workpiece. Hainbuch’s segmented bushings are made of chrome/nickel case-hardened steel that is very hard, extremely wear resistant, and rigid. All contact surfaces are ground in one operation, guaranteeing optimum concentricity.
The mandrel type T212—known as the Mando T212—without a draw bolt is just what the doctor ordered to eradicate the pains of the gear manufacturers’ production challenges. The Mando T212 offers a solid and minimum ID clamping range for blind bore Ø of 8mm (.31496”) and up to 100mm (3.937”) with pull-back effect. This T212 segmented mandrel has long been in use for customer-specific solutions because of its versatility. It can be used in both rotating and stationary applications, and it has an added clamping length, eliminating the need for a projecting draw bolt. The utilization of a pull-back effect provides the powerful holding strength needed for maximum rigidity while also offering concentric precision of less than 10 microns. Due to Hainbuch’s own vulcanization process, there is virtually no vibration.
The proven mandrel principle is also available as a stock item in a standard series. The T212 is particularly impressive with short distances and expressly for blind bores and small components, including gearing. Since it works without a draw bolt there is no loss of clamping length, and the workpiece can be gripped with the pull-back effect in the secure manner gear manufacturers call for and are accustomed to. Also available even with the smallest Ø, a sensational 8mm (.31496”), the new mini mandrel in XXS size naturally has the typical Hainbuch segmented clamping bushing with the vulcanized rubber-metal connection. The T212 offers maximum accuracy and holding power in the clamping range of 8mm (.31496”)-100mm (3.937”) Ø. Due to the easy-to-operate coupling on the segmented clamping bushing, changeover times are minimal.
Addressing Clamping Range
Figure 2 Small batch sizes are an everyday fact for Hainbuch, but clamping ranges up to 420mm are the exception rather than the rule. This is exactly the clamping range that was requested by one customer. The international transmission and motor manufacturer builds to order and was looking for a precise, user-friendly setup solution requiring no time-consuming adjustment of the various clamping devices. The company found a solution at Hainbuch. It weighs an impressive 1.3 tons, and it also has visually imposing dimensions—the largest segmented mandrel ever produced by Hainbuch.
Expert Engineering
The patented Centrex Centering System in this segmented mandrel, which was developed for China, automatically provides for proper adjustment during changeover, in addition to exact repeatability of the position.Figure 3 The giant mandrel, which has a segmented bushing equipped with a specially developed rubber compound, can clamp gears with an outer diameter of up to one meter with concentric precision on the Gleason-Pfauter hobbing machine. Figure 4 In internal tests, the repeatability was even below 0.005mm. “The great challenge was not only the large clamping range, but especially the coordination of the various processes that we were unable to carry out internally,” says Peter Gerster, a section manager in production. Figure 5 “With more than 200 production orders, the engineering by our team of experts for the end-stop production and nearly 200 external order items—from raw material to the welding construction and heat treatment—all of that has to be managed, and the timing has to be right in the end.” Figure 6 Apparently this was achieved, with a follow-up order involving a Liebherr LC800.
Test results have proven that ideal workholding solutions will provide gear manufacturing with the accuracy and rigidity that are essential for product excellence, while easing the pain of production costs and prolonged setup and changeover times.
