Tool-changing devices for machine tools are often standard bulky chain-driven systems that, in many cases, take up excessive space in the body of the machine. Mechanisms that can reduce the space requirements by offering a more compact tool indexing path will provide improved space utilization, ultimately leading to reduced overall costs.
1-Trak from HepcoMotion, though, is more than just a space-saving tool-changing device. 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. This is an approach not seen before in tool changing applications.
The main body of the 1-Trak 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 a highly efficient drive system.
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. This was one of the challenges facing Walter Machines GmbH, who required both 12 and 24-carriage tool changers for their 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, utilising 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 device.
The carriages that transport the tools around the system incorporate a three-bearing design enabling tighter curves to be achieved than normal, the bearing sizes selected to suit the load and life requirements. All the 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.
Customised to suit the drive motor
The indexing mechanism is a simple no-maintenance approach 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 popular 54mm 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 by users to offer excellent reliability due, in the main, to its simple principle that provides low friction with good rigidity and an ability to work in hostile environments. This version of the 1-Trak product is likely to interest existing tool changer or machine tool manufacturers who want to improve their current equipment and further review the potential cost savings from this highly advanced technology. Go to www.hepcomotion.com to learn more.