From humble beginnings in 1958, Hofmann Innovation Group (which now operates under the brands Hofmann, Ihre Impulsgeber and Hofmann and Ihr Möglichmacher and which is based in Lichtenfels, Germany), has developed into one of the most renowned companies in the plastic processing industry. With distinct simulations and consistent part optimization, Hofmann designs and produces molds for the automotive, home appliances, medical, packaging and electronics sector. Around 400 employees and partners in Spain, China and Turkey generate a turnover of 56 million euros (as of 2016).
Managing Director Stefan Hofmann says that the key to success is automation and standardization throughout the entire manufacturing chain. He took up the reins of the family business in January 2018 from his father Günter Hofmann. More than 10 years ago, Hofmann reacted to pressure from low-wage countries by turning to automation and standardization in an effort to cap costs.
But, low-cost countries have not been the only sources of pressure. The market demands high flexibility, components are becoming ever more complex, and there is increasing pressure on manufacturers, including mold shops, regarding prices. Additionally, a skills shortage poses a challenge, and of course consumers demand components of high quality but are largely unwilling to pay a higher price. Therefore, even small and medium-sized enterprises, and perhaps even especially small and medium-sized enterprises, need to address the issue of automation.
Addressing Automation Is a Must for SMEs
But the topic of automation is diverse, ranging from zero-point clamping systems on milling centers with pallet changers to linked, fully automated manufacturing cells. Multiple clamping is the most basic type of automation. In a next step, for example, parts can be provided on a pallet in front of the machine, and the pallets can be changed either manually or automatically. The final step could be to link multiple machines through a handling system or robots, and this is what Hofmann has opted for.
The company started with its EDM department, which, according to Hofmann, was the ideal place to launch the first automation project in his mold shop.
“We started our first automation efforts in our EDM department,” he says. “Because electrode milling and EDM are time-consuming processes, they ideally are suited for automation. The implementation is relatively straightforward. It is a good opportunity to learn when you are just beginning with automation, because if something goes wrong at the beginning, throwing away an electrode is not a big deal. But, with a finished workpiece, it would not be that simple. Of course, you need to control the entire process and to do so, you should never start with the most complicated process. Today, we are milling around 25,000 electrodes per year—even the Chinese cannot work any more efficiently!”
To control the process, Hofmann works with transponder chips based on RFID in its automated EDM line that CERTA makes. CERTA is a medium-sized software and process consulting company and a 100 percent subsidiary of Erowa Group in Büron, Switzerland. The system assigns electrodes to workpiece holders and makes them available in the CERTA central process control system, preventing errors during the insertion of the parts into the machine. When machinists insert the workpiece (or in this case, electrode) into a magazine, the system immediately recognizes it in the corresponding magazine position. The system also provides the data centrally. Machinists therefore can change workpieces correctly and flexibly.
NC programs for processing, offset data for tools, tool positions in magazines as well as pallet and loading information are provided centrally in the CERTA process control system based on the order. All of the required information is on the chip. “We insert the tools via barcode, and the system does the rest automatically. Thus, clamping errors and the like are practically eliminated. But of course the whole process has to be simulated before going into production.”
The process for determining the offset data of the electrodes is fully automated at the presetting station. The necessary geometry data, dimensions and tolerances are automatically transferred from all popular CAD systems to the measuring machine. The required measuring points are defined in the CAD plug-in. If deviations occur in the target or actual comparison during the measuring process, the required process steps are automatically initiated. This may involve remanufacturing or reworking, for example.
After successfully automating its EDM department, the company also largely automated its milling lines. Hofmann runs two fully automated lines, a smaller line with two Hermle C50U units and a robot and a larger line with four Hermle C42U machines, a washing and measuring station, 60 pallets and space for 400 tools. According to Hofmann, the latter is as efficient as 10 stand-alone machines. “Even though automation makes up half the investment, it is still worth it,” Hofmann says.
Even though automation makes up half the investment, it is still worth it.
Automating the milling lines was not the easiest task, Hofmann says, because fully automated milling of hardened mold inserts involves much more tool wear and requires even higher accuracy than EDM die-sinking and electrode milling. As a result, the process has to be highly standardized and needs more than machines, pallets and robots.
Standardization Is the Prerequisite for Automation
“You need to organize the material flow properly, be transparent about planning and control operations and identify standardization and modularization potentials throughout the entire order-fulfillment process, from costing to design and programming to production.”
To ensure data consistency throughout the streamlined production process, Hofmann uses Siemens NX.
“Apart from designing and using our own standard components to build our molds, we count on standardized design,” Hofmann says. “You need standard elements that are always designed exactly the same. That is one key aspect of it, but you must also standardize the process itself. Reduction is key here. Take, for example, reducing the number of tools. When you have 500 tools, it is unrealistic to think you could operate an automated line. Fifty would be a good number, because your tool library remains manageable, and you can reduce potential sources for error. And these 50 tools will have to do, no matter what.” Hofmann explains that you must also standardize programming through libraries, configurations and attributes to execute the process in a secure and uniform manner. “An automated workflow from design to NC code helps reduce programming time and eliminates errors. Since we never manufacture the same workpieces, standardization and process reliability are crucial for us,” he says.
Automation Facilitates Higher Throughput and Increased Accuracy
For Hofmann, automation means 24/7 operation and fewer operators, but the important thing is that you can achieve a much higher throughput because “you do not need to tinker with the process all the time,” Hofmann says. He adds that automation frees his employees to focus on value-adding and creative tasks. Most of all, they can determine their working hours, which are more flexible. Automation prevents their hours from being determined by the machine. “The robot acts as a buffer—whether we work manned or unmanned, the process is always the same. Everything is standardized,” he says.
The robot acts as a buffer—whether we work manned or unmanned, the process is always the same. Everything is standardized.
About the Author
Barbara Schulz is Gardner Business Media’s European correspondent. She can be reached at email@example.com.
A review of the explosive potential of graphite dust and how to dispose of remnants that may be accumulating around the shop.
To achieve the ultimate capability and level of productivity from your wire EDM on a consistent, repeatable and reliable basis, regular maintenance is a required task.
This article explores the applications in which wire EDM has found its way. It will examine the reasons for this new interest in a supposedly unrelated machining method, and its impact on moldmaking, both physically and fiscally.