Compact approach to tool changing

A new product from HepcoMotion is more than just a space-saving tool changing solution. The combination of precision positioning offered by this play free vee guidance system, coupled with the ability to follow almost any two-dimensional shape, opens up the possibility of new concepts in tool change design. Systems can be constructed to suit individual loading and rigidity requirements by making the vee guidance track size and shape to suit the application.

The main body of the 1-Trak solution is effectively a mounting plate that is designed to be sufficiently rigid to be fitted to any suitable member of the machine structure with the minimum number of fixing bolts. The vee guidance track is machined into the plate as an integral component so there is no requirement for setting. 1–Trak tool changing systems are supplied as a unit, just requiring the tools to be located to the tool carriages. In turn, these are indexed around the track to the required position through an efficient drive system.

Case study 

The company comments that fitting a 24 carriage tool changer into a compact machine envelope can be challenging if the system has to follow a conventional tool changer style and this was one of the challenges facing Walter Machines GmbH who required both 12 and 24 carriage tool changers, for a new range of Helitronic tool grinding machines, to be fitted into the same space envelope. There was an additional problem in respect of locating 24 cup grinding wheels close enough together in the space available. By CAD plotting the required track shape to avoid 'clashing' of the wheels, the path was CNC machined into the plate, using specialised software, to ensure an exact replica of the path was produced. The result for Walter Machines was a compact 1-Trak double 'U'-shaped solution. 

The carriages that transport the tools around the system incorporate a special three bearing design, enabling tighter curves to be achieved than normal, the bearing sizes selected to suit the load and life requirements.

All carriages are linked so that any tool can be indexed to the required position for the pick and place unit to select and transfer into the machine. Typical indexing accuracies are in the region of ±0.1mm, but for the Walter machine 0.020mm was required. This, tighter than normal, tolerance was necessary in order to prevent any possible misalignment damage to the shaft that locates into the high precision bore of the grinding spindle. In turn, the required accuracy was achieved by solidly locking the carriage, when in position, using a cylinder.

The indexing mechanism is a simple no maintenance solution using drive pins running in a cam shape machined into the main mounting plate. The drive pins locate into a drive wheel that is fitted to the gearbox shaft. The gearbox itself locates onto the rear face of the main mounting plate with motor flanges customised to suit the requisite drive motor.

1-Trak can be manufactured to suit any vee bearing from the HepcoMotion range (the largest is 150mm). This diameter is unlikely to be required even for the heaviest duty tool with most requirements being satisfied by the 54 or 64mm diameter bearing. The ability to produce a wider track width for the space available will often enable smaller bearings to be used and still provide sufficient capacity to accommodate the tool load offset. Lubrication for the guidance track is important to ensure long life of the hardened track and 1-Trak can incorporate a bleed lubrication facility enabling direct coupling to the machines lubrication system or coupling via a separate canister.

Vee guide technology is known for its reliability due, in the main, to its simple principle that provides low friction with good rigidity and an ability to work in hostile environments.

HepcoMotion expects this version of the 1-Trak product to interest existing tool changer or machine tool manufacturers who want to improve their current solution and further review the potential cost savings from this advanced technology.