Small Shop Sees Big Gains from Right-Sized Automation

A three-person German machine shop applies quick-change workholding and flexible robotic automation to succeed in a high-mix/low-volume production environment.

When Simon Oreskovic established his Zelos Zerspanung machine shop in 2017, he knew automation would be key to success. The 30-year-old managing director’s goal was to leverage quick-change workholding and robotic machine tending to establish an effective process for high-mix/low-volume work. For this to happen, he had to identify the type of automation technology that would enable his three-person startup shop, located in Bessenbach, Germany, to machine a wide range of parts. 

Mr. Oreskovic believes some robotic machine-tending solutions can be intimidating to small job shops. This can cause them to delay their transition to automated manufacturing because they think they need to invest in complex, expensive, process-specific systems that rely on highly trained specialists. “That’s not true,” he says. “You need to automate your job shop to remain competitive, but you can start small and adjust your level of automation to your future needs.”

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This is especially important in high-wage countries such as Germany. In starting small with automation, Mr. Oreskovic first implemented quick-change workholding technology to speed setups. After that, he added a robotic loader and pallet-pool system to one of his three-axis machines. This enabled new jobs to be set up offline and installed in the pallet pool while the machine continued cutting another part, maximizing spindle uptime. Next, he integrated robotic systems for two machines in which the robot grips not the parts themselves, but standard-sized vises holding parts positioned atop a trolley parked near each machine. That way, only one gripper is required to load various types of parts. This type of automation enables the shop to focus on parts no bigger than the size of a fist (which represents 80 percent of its business), while providing the flexibility to efficiently process batch sizes ranging from 10 to 1,000 pieces.

Stage One: Quick-Change Workholding

Prior to opening his shop, Mr. Oreskovic gained machining and manufacturing experience working at his father’s manufacturing company, Automated Sewing Systems AG, also located in Bessenbach. His Zelos shop machines parts for his father’s company, but also for general engineering, machine tool, stage building and railway industries.

While working at Automated Sewing Systems, Mr. Oreskovic became familiar with quick-change workholding devices from Lang Technik, located in Holzmaden, Germany. (The company’s U.S. division is Lang Technovation, located in Hartland, Wisconsin.) This led him to purchase Lang Zero-point clamping systems and Makro-Grip 5-Axis vises for his shop to speed setups and provide high process reliability and repeatability, he says.

The Zero-point system uses an interface plate that mounts to a machine table to enable quick attachment of devices such as Makro-Grip vises to a repeatable position. Clamping studs installed on the bottom of devices such as the vises install into the plate’s receivers.

The Makro-Grip vises grip part blanks in an unconventional way. A 20-ton stamping machine is used to squeeze either side of a blank along its bottom and uses “teeth” that create multiple indentations in the blank. The blank then installs in the vise that has jaws with mating indentation profiles. This form-fit connection is said to provide high holding force even though the vise grips on only a small portion of the blank. It also provides ample access to five sides of the part during machining. After machining is complete, the indentations are milled away.

This is similar to workholding techniques in which a dovetail is machined into the bottom of a blank, and the blank is installed in a vise with a mating dovetail profile. However, a machine tool is required to create the dovetail profile while the indentations for the Makro-Grip are created using the compact stamping machine.

Stage Two: Robotic Loader and Pallet Pool

Lang provided support to help select the type of automated process that made sense given the size of Mr. Oreskovic’s shop and the parts it primarily would be machining. “Automation is typically associated with high-volume production runs, but it also pays off to automate low-volume, high-mix parts in job shops,” says Guiseppe Semeraro, Lang sales manager. “Once you have a more in-depth view of a shop’s needs, very often you can increase its productivity with simple, affordable and retrofittable automation solutions, including robots.”

The Lang Eco-Compact 20 workpiece palletizing and handling system was the first robot-loading automation system installed at Zelos. This system, which was added to the shop’s DMG MORI Milltap 700 three-axis mill, features 20 pallet stations each with the capacity to hold 40 kilograms. The pallet pool enables the shop to set up and queue jobs while the machine is running. Each pallet features Zero-point clamping for repeatable positioning.

Stage Three: Robotic Loading of Vise-Clamped Parts

The Lang Robotrex was the second robotic machine-loading system installed at Zelos. In fact, the shop purchased two, one for its three-axis DMG MORI Ecomill 1100 machine and one for its five-axis Ecomill 50.

The Robotrex installs within an enclosure at the front of a machine and features a 12-kg-capacity FANUC robot. Each part blank is clamped in its own Makro-Grip vise, and those vises install in rows atop a trolley that is delivered to the Robotrex (the system can accommodate as many as four trolleys). Vertical orientation of the vises enables multiple vises to be installed on the compact trolley. Each trolley has a capacity to hold 30 vises with a maximum part size of 120 by 120 by 100 mm or 42 vises with a maximum part size of 120 by 100 by 70 mm. (These sizes fall in the range of the type of parts Mr. Oreskovic wanted his shop to primarily focus on.) The vises install in the machines’ Zero-point clamping system.

Because the robot picks a common vise from the trolley and not parts of different sizes or shapes, only one gripper type is required, and there is no teach-in process needed to accommodate new grippers for new jobs. “The beauty of this system is that it takes the fear out of many companies’ intimidations as far as robots and grippers are concerned,” Mr. Oreskovic says. “Systems in which the robot grips the part to feed the machine might be efficient solutions for series production, but shops like ours need to have the simplest automation solution without the fear of robot re-programming when parts change.”

Mr. Oreskovic says the most appealing feature of the Robotrex system is that it is compatible with almost any machine tool, and can be retrofitted to machines that do not have air or hydraulic supply, which is typically required for conventional automation systems. “The robot communicates with the machine tool via one M-code, which triggers the loading/unloading cycle,” Mr. Oreskovic explains. Loading is done through the machine door or a side window added to the machine. When needed, Lang adds the side window during Robotrex installation. Lang also connects the robot to the machine and programs the robot per the vises used at that time.

Mr. Oreskovic also appreciates the relatively low price point as well as compact design that require only 1.70 by 2.20 m of floor space. Plus, automation frees machine operators to work on the next order, set up new jobs on vises and to prepare new workpiece blanks using the stamping machine. He admits that he had concerns about running machines unattended overnight. However, the DMG MORI Messenger machine-monitoring system sends alerts when problems arise, and on-machine probes are used to measure cutting tools during the process. Mr. Oreskovic says this increases machining accuracy and reduces scrap and rework. Moreover, he and his team can monitor a machine’s status via their smartphones anytime. That said, for parts with very tight tolerances, the shop might split the job into two shifts, whereby roughing is performed unattended at night and finishing is performed during the day with an operator monitoring the process.

Mr. Oreskovic says the shop’s investment in automation has paid off, enabling it to achieve as much as 20 hours of spindle uptime per day. “We can also flexibly plan incoming short-notice orders, run the machines lights-out and also run them unattended over the weekend so we have some spare time for our families, even being a small team,” he says with a smile.