Stäubli Six-Axis Robots Benefit Plastic Molder

Designing, manufacturing and installing cost effective automation systems requires a detailed knowledge and appreciation of the capabilities of robotics, control software and integration protocol. Once applied, this expertise will ensure that the system delivers the expected benefits, is easy to use and reliable in performance. While many companies have this type of expertise 'in house', frequently the demands are outside the capabilities of small and medium sized companies. This is where System Integrators, specialists in all aspects of automation, are able to bring the benefits of these advanced solutions to a wider range of applications.

Only a few years ago, six-axis robots were considered too expensive for use in many applications and they were also quite complex to program. Now they represent a good value, providing a payback period to operators, often in less than one year. The developments made to the control software by manufacturers like Stäubli have ensured that the programming will now be much easier with the added benefit of interfacing directly with other PC software.

One recent application illustrates the benefits achievable by the adoption of six axis robots. An installation of this type has been integrated on a manufacturing line that produces a range of large plastic storage boxes which require handles as well as wheels and other fittings and assemblies to be fixed into position.

The handles and wheels were being fitted to the plastic storage box by hand. This required two operatives per shift working on a three-shift basis who were positioned alongside the injection-molding machine. The operators were finding it difficult to keep pace with the production rate of the machine. The opportunity to incorporate these finishing and assembly activities along with the mold unload were solved using a six axis solution. It also enabled the six operatives to be employed on more useful work elsewhere and significantly reduced overall manufacturing costs. Because a typical 3 axis pick & place robot would not have the flexibility and range of movement to accommodate these additional operations, a six-axis robot was required.

Stäubli RX robots feature high speed and acceleration and are capable of following complex trajectories even at high speeds. Joint speed ranges up to 1125 degrees per second. The high degree of accuracy and repeatability makes the RX ideal for the performance of detailed, meticulous tasks. At the heart of each RX robot is the patented, unique, JCS gearbox providing zero backlash and consistent performance. The range includes models with load capacities from 1.5kg to 60kg with a reach at the wrist from 665mm to 2135mm. The movement in six axes provides an extremely large work envelope. User-friendly software permits easy programming as well as re-programming to bring the added degree of flexibility that is often a benefit in automated systems.

At the assembly site, the RX 130 robot first extracts the box from the injection molding machine, rotates it and places it in the handle assembly machine. While the box is gripped securely, it press fits the handles, wheels and any other fittings and assemblies into position. After checking functionality, the robot places the finished box onto the exit station.

Where box dimensions and assembly locations vary in this application, the ability of the RX robot assembly cell to accommodate process and product variables was also very important. Design modifications could also be readily programmed into the sequencing of the robot providing a level of flexibility not achievable with dedicated overhead pick & place units.

The advantages achieved so far have already opened up the real possibility of replacing more and more of the overhead pick & place units that have traditionally been regarded as standard in the plastics industry. The much more versatile RX robot assembly cell can readily perform many additional assembly functions in the same assembly cell and timeframe. Functions such as label application, part verification and marking, box measurements (such as temperature, weight and material shorts) and packaging are already being looked at, as is the final palletizing of finished parts.