How it Works to Reduce Costs, Maximize Productivity
Controlling production costs is critical for today’s gear manufacturers, especially when factoring in global economic pressures. One key effective cost savings measure is using a quality quick-change workholding system (QCS). A quality quick-change workholding system can increase machine up-time, resulting in greater production on existing machines. Also, by minimizing the changeover time from one workpiece to another, investing in quick-change workholding for new machines can often reduce the number of machines needing to be purchased.
Controlling or reducing costs is paramount in gear manufacturing facilities due to the considerable investments to produce today’s high-quality gears. In gear manufacturing, being flexible with the ability to adapt to challenging workholding requirements is more important than ever. Utilizing a quick-change system across multiple operations is a great way to achieve this. For instance, the same arbor can be used for hobbing a green blank, as well as both end face grinding and finish tooth grinding operations after heat treat. This saves costs by not requiring an investment in complete dedicated arbor assemblies for multiple machines. Where production is high enough that machines run concurrently, having the same arbors saves on the amount of spare assemblies, spare parts and requires less operator and maintenance personnel training.
Emuge offers three quick-change designs, including the QCS-CM, QCS-CA and the QCS-HM, to suit a wide range of requirements. With all three quick-change systems, each machine spindle is fitted with an Emuge quick-change adapter. This allows for precision clamping devices to be interchangeably mounted with minimal changeover time. In most cases, after the clamping devices have been mounted to the adapter, there is no need to adjust the runout of the clamping devices. It is only necessary to check runout with the master to verify proper mounting to the adapter. And while the primary functionality is constant, the machine spindle and workpiece requirements will factor into the final design of the quick-change system.
The system QCS-CM (Fig. 1) utilizes a bayonet disc to uniformly secure the clamping devices to the adapter. Each clamping device has multiple studs that protrude through the bayonet disc. The bayonet disc is then rotated and locked into position, pre-mounting the clamping device to the adapter. The studs are uniformly tightened with a wrench, firmly mounting the clamping device to the adapter against the tapered connection flange. A draw piece attaches the drawbar of the machine spindle to a segmented collet within the EMUGE quick-change adapter. The segmented collet enables the machine spindle drawbar to operate various clamping methods, dependent upon the design of the clamping devices. If a customer requires air sensing or air pressure within the clamping device, a channel can be bored through the quick-change adapter. Air sensing is used to facilitate proper workpiece seating to the location points during loading and prior to centering the workpiece. This ensures the clamping device only operates when the workpiece is in the correct position. Air pressure is used for pressurizing the clamping devices to aid in preventing coolant from penetrating the device.
Advantages of the QCS-CM system include providing an extremely stable mechanical connection with few components, maintaining a highly flexible system with maximum force transmission from the machine spindle to the customer’s workpiece, and excellent resistance to chips and coolant penetrating the connection during use.
The system QCS-CA (Fig. 2) uses a bayonet to hold the clamping devices onto the adapter, like the QCS-CM. The bayonet is actuated from an internal disc spring package and released from the machine spindle drawbar via the thrust bolt. When changing the clamping device, the spindle drawbar is moved to the full forward position, compressing the disc spring package and releasing the clamping device. The clamping device is then rotated until the bayonet lugs are aligned to the load/ unload slots and can be removed from the adapter. After the adapter and new clamping device are properly cleaned, the clamping device is inserted onto the adapter in the reverse order of which it was removed. Once the spindle drawbar moves to the operating position, the disc spring package holds the clamping device firmly against the connection flange. Also, similar to the QCS-CM system, there is a segmented collet and draw piece, which allows the machine spindle drawbar to actuate the clamping device and enables air sensing or sealing air to be supplied through the adapter.
Advantages of the QCS-CA system include the highly flexible, user-friendly changeover without the need for tools. Also, the drawbar can be used for two functions: changing the clamping device and loading/ unloading of the workpieces.
The system QCS-HM (Fig. 3) uses a double bayonet system without the requirement of a drawbar from the machine spindle. The connection bayonet mounts the clamping device to the quick-change adapter. The second bayonet, the clamping bayonet, actuates the clamping device.
The connection bayonet uses springs and a hydraulic unit contained within the quick-change adapter to attach the clamping device to the quick-change adapter. To remove the clamping device from the adapter, the operator rotates one clamping screw charging the internal hydraulic system. This pressure compresses the spring force allowing the release of the clamping device. Next the clamping device is rotated, aligning the bayonet lugs from the clamping device with the loading/ unloading slots in the bayonet adapter. The clamping device is now easily removed from the quick-change adapter. After proper cleaning of both the quick-change adapter and the next clamping device, assembly takes place in reverse order of the removal process.
The clamping bayonet is actuated from the machine spindle hydraulic pressure connection. As the hydraulic pressure is applied to the quick-change adapter, the unclamping spring force is overcome, enabling the bayonet to pull on the clamping device drawbar and achieve workpiece clamping. After the machining operation is finished, the hydraulic pressure is removed for the unclamping springs to ensure the return of the drawbar and removal of the workpiece from the clamping device has been completed.
Advantages of the highly flexible QCS-HM system include the user-friendly centering of the clamping device by using only one screw, and fitting to machines where no draw bar is required.
Low Mix, High Mix – No Problem
All three QCS systems achieve more machine up time with smaller lot groups of workpieces, as well as facilitate easier preventative maintenance of the clamping devices. In smaller lot groups of workpieces, the Emuge clamping device can be mounted to multiple machine operations, reducing the number of clamping devices required. The clamping device can be moved from one machining operation to another, with minimal to no components needing to be exchanged. Where a machine is dedicated to one workpiece, having a quality quick-change workholding system installed will allow for the removal of one clamping device for preventative maintenance, while another identical clamping device can be installed to keep the machine running.
Emuge QCS systems are also suitable for a family of workpieces similar in size and geometry. Gear manufacturers can use the quick-change system to keep the machine running, while they are preparing for the next workpiece to run.
Whether production ranges from high volume using machine dedicated clamping devices, or smaller lot sizes that are changed over frequently, Emuge quick-change systems can be customized to meet the requirements of keeping production costs down and machine run-time up.
About the Author: Greg McLennan is sales manager – precision workholding at Emuge Corp. He previously held positions at the Mitsubishi Gear Technology Center and Liebherr Gear Technology.