Automated valve fitting
In 2002, TM Robotics (Europe) Ltd and one of its longest serving integrators completed a project in partnership with a major UK manufacturer. The project saw three SCARA robots fitted as part of an automated system to increase output in pneumatic valve production.
It isn't always easy putting one's trust in a robot. There are a lot of statistics to put into the equation: the cost of the robots, the cost of installation and maintenance and the training required for key staff to manage the operation. All of this has to be weighed up against the cost of a manual alternative. One must also bear in mind potential downtime if the automated system is replacing an existing manual one.
After weighing up the options, one significant UK manufacturer of fittings isolated its 'push in fittings' assembly as one process where the installation of an automated system could increase productivity and profitability. However, conventional automation presented an unattractive proposition because of relatively small batch sizes (sometimes as few as 1000) and frequent changeover periods. As a result, the decision was taken to automate the assembly process using Toshiba Machine SR-654HSP SCARA robots.
The key factors in the success of the automation process were accuracy and flexibility. Accuracy was provided by the +/-0.02mm repeatability of the Toshiba Machine SCARAs and the degree of flexibility allowed the system to cope with 240 different product variants, all consisting of at least five component pieces.
The series benefits from parallel processing to offer smooth, fast motion combined with an extremely sophisticated set of control instructions to suit all applications. The SCARAs have traversing rates of 300mm in 0.63 seconds, carrying a 2kg payload. The robot's reinforced arm can handle up to 20kg at half-acceleration/deceleration, or 10kg at full capacity.
One of the key factors in the installation process was in ensuring a quick changeover period between different product variants to minimise downtime. This was where a manual process can be advantageous, the worker simply finishing a batch of one product type and collecting the components for another, with no long changeover period required. In order to make the installation cost effective, the automated alternative had to be designed with optimum efficiency in mind.
The required changeover efficiency was achieved through the use of the Toshiba Machine SCARAs in conjunction with a PC containing all of the component information. The PC linked to a PLC, which drove the inputs and outputs and automatically prompted the operator to choose the correct components.
The only information that had to be submitted manually was the fitting number. The result of this was that the average 'chip to chip' changeover time was just 15 minutes, giving an impressive operating efficiency of 90 percent.
The total cycle time for the three robots to assemble the fitting is just 7.8 seconds, 4.2 seconds faster then the manual method. Furthermore, the automation has the obvious advantage of constant running. Put bluntly, it doesn't slow down when its tired, it doesn't take coffee breaks and never takes long lunches. This improved cycle time and constant output delivers a very favourable payback.
Case Study originally published on Thu 23 Aug 07 13:27