SynthoTec has been making precision parts from plastic for almost 30 years and its bearing cage products are used extensively in two applications, the first of which is heavier-duty rotating mechanical and electrical applications (such as alternators, air conditioning units, motor vehicles, HGV axles and railway locomotives). Additionally, lighter-weight moulded plastic parts are also produced and these find their way into an equally wide range of lighter-duty products, such as child seats, security buckles and power tools.
Numbered amongst SynthoTec’s key customers are global manufacturers of rotating and linear bearings, including SKF and NSK. Because the bearings are used in so many applications across both industry and in consumer products, the precision plastic cages in which they run must necessarily be manufactured in a range of diameters from 20mm-250mm.
In early 2018 the company decided to further automate and install a new robot in the company’s bearing cage demoulding cells. “We targeted a new robot, as we wanted to move the production cell forward to a new concept, and a 6-axis robot enabled us to greatly simplify the cell,” says managing director Graham Ward.
In this particular part of the production cycle, the company wanted a robot to take the cages from the mould, retain them while dropping the waste sprue into a recycling granulator, and then place the finished cages onto pallet-mounted mandrels, all in one swift operation. Each individual mandrel needs to be stacked with up to 185 completed cages and the robot would need to ‘feed’ more than 150 close-packed mandrels in succession on each pallet.
The SynthoTec engineering team set about designing a system to update the cells and embrace the latest developments in robotic assistance. The proposed method, using an off-the-shelf multi-axis robot, was projected to make significant savings in material cost (by reducing wastage and recycling more), by cutting the elapsed time for the process itself and by reducing the number of moving parts in each cell by one third. The opportunity to reduce the number of PLCs used to just one was also embraced.
Having established what they needed, the team at SynthoTec wanted to do something unusual in the automation field: design, install and commission a robotic cell themselves, using the company’s own in-house team of design engineers, production engineers and skilled toolmakers.
As Ward points out: “Robots are an integral part our business, as is our desire to continue developing in-house automation solutions to exactly meet our own needs. It is just one of many facets that allows us to retain absolute responsibility for the quality of end product for which our business is respected by customers. We take this reputation extremely seriously and therefore sought a robot supplier prepared to work on our terms. After a series of meetings with a number of potential suppliers, a unanimous decision was taken to work with Kawasaki Robotics.”
Graham continues: “I would say that the early engagement with Kawasaki was extremely supportive in helping us understand the capabilities of the robot. It actually made us rethink our approach again. It was only the decision to take the integration responsibility back in-house that enabled us to get close to Kawasaki in a way that offered up these opportunities. Synthotec even took the decision to delay the project, in order to incorporate the full benefits of the Kawasaki robot.”
Project engineer Jon Hart states that the project goals included achieving higher throughput, reducing the production cell footprint, as well as the potential to do integration and training on their own.
The Kawasaki RS-20N was chosen. The medium-duty robot can handle a 20kg payload, offers a horizontal reach of 1,725mm and a vertical lifting capability of 3,078mm. In standard form, it offered the required high speed in every axis, could demonstrate repeatable accuracy to within +/-0.05mm across each axis for the lifetime of the robot, and could also be stopped instantly, should it be required. Brushless servomotors are used throughout. The robot’s compact size reduced the overall width of each of the demoulding cells on the shop floor by at least 1m per enclosure.
With thousands of moulding and demoulding operations taking place on each shift, repeatability, reliability and durability were critical elements in the justification matrix, and SynthoTec calculated that the payback period for all three Kawasaki robots in this application would be just 14 months. Kawasaki Robotics would expect a lifespan of at least 10 years for each unit, subject to no more than routine maintenance.
The robot was supplied and installed in 25 weeks, and in the SynthoTec application it has proved to be working to a tolerance of just 0.02mm over thousands of daily cycles.
Synthotec managing director Graham Ward concludes: “Although we have never thought of ourselves as such, as a result of installing and commissioning our new RS-20N robotic demoulding cells, Kawasaki Robotics have awarded us an ‘Approved Integrator’ certificate for their equipment, which makes us quite proud.”