Machine retrofit is often seen as a stopgap solution – a compromise between limited budget and the desire for modern manufacturing technology. However, EWS Weigele GmbH & Co. KG in Uhingen demonstrates that this perspective is too narrow. Together with EMAG, the company has specifically modernized a VSC 400 DDS and adapted it to its individual manufacturing requirements. This has created a manufacturing solution that is at least on par with a new investment in terms of process reliability, availability, and cost-effectiveness. The key difference: the retrofit was not chosen out of necessity, but as a conscious technological strategy.
Retrofit strategy: Availability as a competitive factor
EWS Weigele manufactures high-precision tool holder systems with a depth of in-house production of 90 to 95 percent – from raw material to assembled product. A key component of this manufacturing chain is the production of bevel gears and spur gears for driven tool units. The typical batch size structure is two to five workpieces per order.
With this high vertical integration, every machine downtime directly affects delivery capability. When the existing gear manufacturing needed modernization, the central question was not only 'Which technology?' but above all 'How quickly?'
The decision for the retrofit of the VSC 400 DDS was based on a clear calculation: The delivery time for a comparable new machine would have taken eight to twelve months, plus several weeks for commissioning and process qualification.
The retrofit enabled the resumption of production after just a few weeks. The mechanical basic structure of the machine was intact, and the employees were familiar with the machine concept – ideal conditions for a quick modernization.
Technological enhancement: Automation and pick-up
The retrofit included a complete technological modernization while retaining the mechanical basic structure:
Control technology: Replacement with a current CNC system with expanded functions and interfaces for manufacturing data collection. The new control allows for direct integration into the digital manufacturing management system.
Automation interfaces: Adaptation of the machine-side interfaces to the factory-installed Varia quick-change system and the workpiece feed via a round conveyor.
The investment costs were about 70 percent of a comparable new machine – with full technological capability.
Pick-up principle: Process stability through mechanical guidance
The VSC 400 DDS is based on the concept of a vertical lathe with a pick-up spindle. The workpiece is not manually or robotically inserted into a clamping device, but is picked up by the work spindle itself from a defined position. The gear is located on a workpiece carrier in the round conveyor system. The work spindle retrieves the workpiece from the pick-up station and transports it into the working area.
This process eliminates insertion inaccuracies.
The repeat accuracy of the workpiece pickup is in the range of a few micrometers, as the positioning is mechanically defined by the workpiece carrier geometry. Unlike robotic systems with grippers, insertion errors due to contamination, workpiece mix-ups, or recognition errors are structurally excluded.
Process stability is demonstrated in practice: At EWS, the complete hard machining of gears takes place on the VSC 400 DDS – hard turning with PKD or CBN tools, grinding of defined functional surfaces, and final finishing. Batch sizes of several dozen workpieces are produced without intermediate measurement. The required tolerances are maintained throughout the entire batch.
Varia quick-change system: Set-up times in the range of minutes
With batch sizes of two to five workpieces and processing times of 4 to 7 minutes per part, the pure processing time per batch is between 20 and 100 minutes. Classic set-up times of two hours would negate cost-effectiveness.
EWS uses its in-house Varia quick-change system, available in three standardized sizes (VX3, VX4, V5). The system is based on a bayonet lock with a defined tightening torque.
The repeat accuracy is in the range of a few micrometers. Both static and driven tools can be accommodated.
The tool change follows a well-thought-out process: While the machine is running, the tools for the next job are assembled outside the machine in Varia holders, measured, and placed into a tool shuttle. The tool data is transferred to the control system. CAM programming is done with digital twins of the tools, allowing for collision checks to be performed before the physical change.
After the current job is completed, the tools are removed from the tool shuttle and inserted into the turret positions via the bayonet lock. The mechanical change process takes a few seconds per tool. The machine downtime during job change is reduced to 5 to 10 minutes for a complete turret.
Automation: Three hours of unmanned operation
The round conveyor system accommodates workpieces for up to three hours of unmanned operation. The workpieces are on workpiece carriers that ensure defined support surfaces and positioning. The operator loads the conveyor belt at the beginning of the shift and can attend to other tasks during the processing time.
This form of 'flexible automation' enables economical machine operation even with small batch sizes – a crucial difference from large series automation, where dedicated systems only amortize over high quantities.
Digital manufacturing control: From CAM system to machine
The manufacturing is based on a continuous digital process. Every tool and tool holder exists as a digital twin in the system. The NC programs are created with CAM software, using not abstract tool geometries, but the exact digital models of the tools actually used.
This allows for collision checks to be performed already in the programming phase, tool path optimization based on actual tool dimensions, and the automatic generation of set-up data. The operator receives a digital set-up list that precisely specifies which tools are to be set up in which order. This systematic approach minimizes set-up errors and significantly reduces the training time for new employees.
Quality assurance through process stability
At EWS, quality is not ensured by measuring but generated through process stability. The combination of process stability of the pick-up principle, repeat accuracy of the Varia tool system, and thermal stability of the vertical machine enables the production of gears with tolerances in the micrometer range – without 100 percent inspection.
Statistical process capability is monitored through regular sampling inspections. Only when the measurement values show that the process is stable are individual inspections waived. This manufacturing strategy significantly reduces lead time and quality assurance costs.
Retrofit as a conscious technological decision
The EWS project shows: Retrofit is not a stopgap solution, but can be a technically and economically superior alternative to new investment – especially when the mechanical basic structure can still be used for decades.
The central benefit aspects:
- Availability: Production resumption after weeks instead of months. With a high degree of in-house production, this is a crucial competitive factor.
- Process reliability: Pick-up principle eliminates insertion inaccuracies. Tight tolerances are maintained without intermediate measurement.
- Flexibility: Quick-change system reduces setup times to minutes. Frequent product changes become economically feasible.
- Economics: Investment costs at around 70 percent of a new machine with comparable performance capability.
- Sustainability: Extension of machine lifespan by 10 to 15 years with significantly reduced resource consumption.
For manufacturing companies with small series production, high quality requirements, and a high degree of in-house production, the concept offers a proven approach to modernizing manufacturing technology.
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