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Multitask Machines Use Modular Tool Indexing to Optimize Gear Milling
Author: Brian Lane
Source From: IMT Machining Journal
Posted Date: 2013-08-22
In the past, gear milling required machinists to perform complex machining processes such as hobbing and milling across a suite of different machine tools. However, new processes and technologies have allowed companies to optimize multitasking tools to save time and money in gear machining applications.
DMG/Mori Seiki USA has worked to develop new solutions for gear milling that limit the need for lengthy setup times and expensive tool changes. Nitin Chaphalkar, a manager for advanced solution development and the head of DMG/Mori Seiki USA’s gear machining initiative, recently explained to IMT Machining Journal how the company addresses these challenges with technology.
“For over two-and-a-half years we have developed new technologies for machining different types of gears on a single machine,” Chaphalkar said. “Our philosophy is that when our customer buys a traditional machine that can do only hobbing or gashing, they are limiting themselves. But if they have a multitasking machine, they can hob, 5-axis machine, gash, as well as broach or shape, so they are not locked into a process.”
Chaphalkar and DMG/Mori Seiki will appear at the Gear Expo in Indianapolis, Ind., Sept. 17-19. During this time, DMG/Mori Seiki will demonstrate several of its gear machining solutions, while Chaphalkar will deliver two presentations on multitasking solutions and gear machining processes.
DMG/Mori Seiki will demonstrate its NT series of multitasking machines and its 3-axis lathe series, called the NLX. The NT series of turning and milling machines offer two spindles and operate under nine total axes, allowing users to take advantage of a broad range of operations. Additionally, the company will demonstrate the versatility of its NLX series by producing spiral bevel, spur, helical, and internal gears on site.
Referring to the first of his presentations, Chaphalkar stressed the difficulty in manufacturing gears. One issue is that gear machining traditionally requires matching cutting tools to the specific type of gear to be machined. Then, there is also the issue of moving the workpiece between machines for different operations.
“Ninety percent of gears are soft-machined and then get pretreated and finish-grinded,” Chaphalkar said, underscoring the benefits of a multitasking machine. “We have done some work in heat-treating the gears inside the machine.” This way, an entire part can be machined and finished on one machine.
“[This option] offers immense flexibility to the customers, which means that their machines will be running all the time,” he said.
DMG/Mori Seiki will also display the InvoMilling process, a widely adaptable process developed bySandvik Coromant and under exclusive commercial license to DMG Mori Seiki. InvoMilling is a process for machining spur and helical gears without the use of dedicated hobbing or other gear machines. An example of InvoMilling is shown in the video below.
The InvoMilling process relies on indexable insert carbide cutters to centralize the gear cutting operations into one 5-axis machine under one setup, which reduces technology costs and greatly reduces the amount of time required to machine gears. Sandvik Coromant says that traditional hobbing can take 30 minutes for single-pass milling and much longer for double-pass hobbing. InvoMilling on a multitask machine takes only 23 minutes.
Sandvik Coromant Marketing Project Manager Aaron Habeck told IMT Machining Journal that the real boon of the InvoMilling process and the cutting tool maker’s compatible insert technology is the flexibility it offers in short-run part production.
“The strong points [of InvoMilling], I would say, are when customers are doing small batch sizes,” Habeck explained. “They want the flexibility of a tool that can make multiple, different gear tooth sizes, so they only need a handful of tools. That way there’s not a lot of investments in hobs for different gears in small batches. They can make, one, two, 10 different parts [...] and not have to wait for customized hobs to be made and the delivery times and costs associated with that. With a relatively small amount of tools and inserts they can produce a pretty wide range of gears.”
“That’s where flexibility is generating cost savings for the customers,” he added.
Mori Seiki has integrated the InvoMilling process with its Mori-AP software to further simplify the process. The user simply enters the gear type, form, number of teeth, and other characteristics into a user interface and then can watch simulated machining of the part to ensure proper production.
Sandvik Coromant will be displaying its gear cutting solutions, such as the CoroMill 172 cutting insert pictured here, during Gear Expo, Sept. 17-19, in Indianapolis. Credit: Sandvik Coromant.
Sandvik, which will also host a booth (335) at Gear Expo, also provides disc cutters for use with its InvoMilling process. The CoroMill series of indexable carbide cutters is precisely designed for allowing gear machining in non-dedicated machines.
The CoroMill 172 disc cutter can handle applications in the module range of four to eight in multitask machines and machining or turning centers. The CoroMill 176 is designed for gears in the module range of four to nine, while it can be used in hobbing machines, multitask machines, or 5-axis machines. Sandvik will also display some of the smaller CoroMill inserts for cutting lower module gears.
