Machining Solutions Automated grinding of workpieces with different lengths

Editor: MA Alexander Stark

Switzerland — The manufacturer of high precision grinding machines Kellenberger, has developed a new solution for a tool manufacturer that simplifies the automation of grinding workpieces of different lengths.

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Z2-axis sample application assembly
Z2-axis sample application assembly
(Source: Kellenberger)

When it comes to machining solutions, the machine manufacturer is responsible for the entire process, including all upstream and downstream operations. The steady advance of automation in production processes also challenges the flexibility of machine tools.

In the Hardinge competence center in Studen, Switzerland, the focus is on customer-specific systems solutions. There, highly integrated cylindrical grinding systems for large-scale production are equipped with automatic loading, measuring devices and other additional operations as the case requires. Every year, a wide variety of turnkey solutions are delivered to customers, including automobile manufacturers and other suppliers.

At the Kellenberg production site in St. Gallen, the “Customer-Specific Special Constructions” department develops solutions that are particularly challenging and are not yet available on the market.

A well-known tool manufacturer was searching for a solution for the automated grinding of workpieces such as drills and tool holders. The challenge in machining is that the parts have different lengths. This means that the clamping force must be changed manually for the necessary length compensation during grinding. Automated machining seemed to be impossible.

The designers in St. Gallen met the challenge: They developed a positioning axis (Z2 axis), that ensures automatic length compensation by a robot or gantry loader during the fully automatic loading.

The newly developed Z2 axis for automatic length compensation
The newly developed Z2 axis for automatic length compensation
(Source: Kellenberger)

The Z2-axis is mounted on the Z-axis and moves there. The automatic zero point shift is done using a longitudinal button (KEL-Pos). Dressing is not possible on the Z2 axis. The grinding dressers are mounted on the Z-axis.

Workpieces with a diameter of up to 250 mm and length compensation from 50 to 300 mm can be machined. Non-circular parts can also be ground. These can be centered fully automatically.

Technical details:

  • Hub 250 mm
  • Center height min. 250 mm
  • Axial force max. 1200 N
  • Load capacity for live spindle grinding 100 Nm (max. 80 kg)
  • Positioning speed 10 m/min
  • Load capacity between the tips max. 150 kg

When using a synchronous tailstock (available as an optional feature), no chuck is required because of the friction drive. An in-process measuring control covers a diameter range of 25 mm. Manual retooling is no longer necessary.

The Z2 axis was developed for the universal internal and external cylindrical grinding machines of the K100 and K1000 series with Fanuc control. The obvious question: can the Z2 axis be retrofitted on such machines? Patrick Gähler, Design Engineer at Kellenberger answered in negative. “Retrofitting is not possible because the function of the Z2 axis must be incorporated in the design of the machine beforehand.” In the showroom at Kellenberger in St. Gallen, interested customers will be able to see a K100 with Z2 axis from June, on which tests can also be carried out.

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