Element Six Hard Metals is a leading manufacturer of special tungsten carbide tools for the mining, construction, tunnelling and other industries around the globe. The company owns a number of presses that compress tungsten carbide powder, which is formed into shapes that will be machined into milling cutters, drill bit inserts and various other tools. Referred to as blank burrs, some of the more specialised of these can be manufactured only on complex three-stage presses. With this in mind, Element Six Hard Metals purchased a second-hand de-commissioned press, with the intention of using it to boost its production capability of the specialised products. The press was mechanically sound, but required new hydraulics, electrics and instrumentation and control equipment.
The scope of the problem
The upgrade posed several unique challenges, including the absence of operational knowledge on the press and no clear functional specification on how the system should be controlled to achieve the desired end products. The press has a very complex three-stage design, consisting of four moving axes, all of which need to move in an exact relationship to each other, the only difference being in the cam profiles. Three axes are servo driven and the other is hydraulically actuated.
The solution approach
To gain the knowledge required to achieve the correct automation philosophy, much time was spent studying a similar old press that currently produces the specialised burr blanks. Each of the different products required a unique setup of the machine, with different cam profiles for all the axes. Recipes for the products, consisting of over 20 variables, had taken decades to set up perfectly on the existing machine, with some trials taking months to achieve the required quality specifications.
Once the automation of the press was completed, it became clear that much time would be needed to develop the correct recipe data in order to produce the same products on the new press. Abacus Automation was selected to undertake the process, based on the company’s extensive experience and knowledge of Siemens control systems.
“The challenge became the transfer of all the intellectual property stored in the recipes of the existing press. The two presses are mechanically different so it was not simply a matter of getting one to mimic the other in every respect,” says Abacus Automation’s Warren Scott.
“By fitting instrumentation and recording equipment to the existing press we were able to record the behaviour of all the control components on the press, while each recipe was executed under production conditions. The new press was then set up and programmed to replicate the behaviour of all control components for each of the recipes recorded on the existing press,” he explains.
This process, which took six months to implement, was so successful that most products needed little or no fine tuning to be successfully manufactured on the refurbished unit, to the same quality standards that had taken years to perfect initially.
The cam profiles for the four axes are derived from the recipes and are then downloaded to the Siemens drives via Profibus from a Siemens S7300 PLC and WinCC Flexible HMI platform. A fifth virtual master axis is used to synchronise all the cam profiles on the four different axes. The resultant profile of each axis can be graphically compared to the required cam profiles for diagnostic purposes.
“Our level of delivery has improved greatly. This press is unique in that it is the only one of its kind in South Africa. We had originally approached the local agents but they were unable to assist. Abacus Automation’s service and performance has been exemplary and has given us the confidence to meet demand from clients by being able to spread the workload equally between two machines,” concludes Element Six Hard Metals production manager, David Hamilton.
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