Installation of a Hurco vertical machining centre (VMC) in the toolroom at the Ross-on-Wye factory of rubber mouldings manufacturer, Wye Valley Precision Engineering, has resulted in much faster availability of mould tools compared with when the company was using a manual-tool-change CNC mill. A typical middle plate in P20 tool steel is now programmed and machined in six hours, whereas the same job used to take a week. Said machine operator, Matthew Griffiths, "Programming was very time-consuming using our previous machine because the control system did not accept the DXF file output from our CAD system. So after a mould was designed, I had to program every feature manually at the control and the complexity of the tools meant that there was a risk of making errors, which were subsequently difficult to find and correct."This contrasts with the user friendliness of the Ultimax control fitted to the Hurco VMX-24 VMC, installed in April this year (2003). Mr Griffiths advised that the twin-screen CNC system not only reads DXF files directly and automatically generates tool paths from them, but also has powerful on-board software to simplify creation of the entire part program.
For example, a rubber mould might contain, say, 1500 holes in four blocks which used to take several hours to program. Using the Ultimax control, it is simply necessary to program one block, highlight it on the right hand graphics screen, and then rotate and repeat it three times around the appropriate PCD. It is then possible to input the commands for centre drill and drill for all holes at the same time, instead of individually. Another feature is the unlimited number of islands that may be created within a pocket boundary (the previous maximum was 12) and the automatic, gouge-free machining.
A further area of programming that is speeded is the generation of 3D parts from 2D contour profiles followed by automatic creation of roughing and finishing cycles after telling the control which tools to use. This is a real benefit to Wye Valley Precision Engineering, as more and more it is being asked to design and produce 3D moulds for the manufacture of keypads, for example.
"The Ultimax control is by far the best on the market for one-offs,” said Mr Griffiths. “It is so quick to use that sometimes I have difficulty believing the program is right. I have more confidence in this CNC system
after one month than I had in the previous control after 10 years." When the machine is cutting metal, various features within the control contribute further to faster mould production. Conversation touch-probing of the tool allows periodic checking of the tip for wear, with the appropriate offsets sent automatically to the control. Alternatively, if necessary, a command is sent to replace the cutter with a sister tool from the 24-station magazine. Mr Griffiths also highlights the recovery/restart feature within Ultimax, whereby after the spindle has been stopped it is possible to resume cutting immediately at the same point, without having to cycle through from the beginning of the last whole program block.
Certain design characteristics of the machine itself promote high productivity with minimal operator attendance. Flood coolant is effective at washing swarf to the front of the machine, from where a spiral augur transfers chips into a bucket at the side. It is not necessary to stop the machine to clear swarf from the working area. Notable also is the high speed of the Hurco VMC
compared with the previous CNC mill
. 10,000 rpm is 2.5 times higher than the previously available spindle speed, and cutting feedrate is double at 2 m/min with the possibility of 8 m/min utilising new tooling currently under investigation.
Paul Nelson, manufacturing director of family-owned Wye Valley Precision Engineering, was surprised at the variability of response from the eight machine tool vendors he contacted when he was researching the market. One well known supplier had an old fashioned showroom, derided the competition's machines and failed to keep its website up to date. Some had outdated looking machines and / or controls. Others wanted to make an additional delivery charge to take account of the restricted height of the door at the Ross-on-Wye factory. "In the end, Hurco was the obvious choice," said Mr Nelson. "All the machines in the range are modern and good value for money, the Ultimax control is a clear advantage and the approach of the company was very positive and helpful. We felt that it conducted its business in the same way that we do.”
In conclusion, Mr Nelson confirmed that he had proceeded with updating his toolroom after the company had rejected the option of outsourcing the manufacture of mould tools. "We like to be in charge of our own destiny," he said, "and rapid availability of tools is important to us in order to ensure a prompt service to our customer's. "We can turn round a rubber mould in one week, including design and manufacture, or perhaps in two weeks if the tool is particularly complex. We could never match this by going to overseas suppliers.
"In any case, the high quality and low price of foreign-sourced moulds appears to be a myth. We had a tool made once in France which was very poor quality; and a number of Portuguese toolmakers sent us prices that were not far below those quoted by UK suppliers. In the end, it made sense to keep this important function in-house."