Windows of opportunity

Prior to purchasing a Hurco DCX22 bridge type machining centre, Bridlington-based AB Graphic International – a leading manufacturer of narrow web label finishing and converting lines, subcontracted out the machining of large plates used in the construction of its equipment.

Even though free issue aluminium, mild steel and boiler plate was supplied to subcontractors, expenditure on machining was in excess of £80,000 per year.

So last year, the DCX22 installed and the work was brought in-house. The competitive price of the 2,200mm x 1,700mm x 750mm capacity machine means that it will pay for itself within 18 months, the company predicts.
Phil Robson, operations manager at AB Graphic, comments: "We machine a lot of ones and twos when producing larger structural plates; 12-off is a big batch for us. Rapid set-up is therefore very important for economical manufacture of components.

"We chose the Hurco machine partly because the Windows-based conversational control has the ability to import data files directly from our CAD system, speeding program preparation."

Machine operator Andy Playforth takes up the story: "Over our network or using a memory stick, I download a DXF file of the part to the Hurco Ultimax CNC and it appears on one of the two screens. The conversational menu within the WinMax software comes up on the other screen to guide me through the programming sequence.

"I extract all component features and dimensions from the 2D file – for example, the software will identify all holes of a certain size and put them automatically into the program. I just need to tell the machine which drill to use.
"Similarly, pocket coordinates are entered without having to key them in manually. Again, I simply specify the mill and the direction of travel and the next part of the cycle writes itself automatically.”

In this way, the program is quickly compiled. If a repeat job is being run and design changes have been made since the last iteration of the component, edits to the program are made easily on-screen from notes on the drawing.
Mr Playforth says that a large aluminium plate measuring, say, 2,150mm x 1,500mm x 20mm and containing over 100 features can be programmed in less than 45 minutes at the Ultimax control. In contrast, the same job would take many hours on a different control on the shopfloor, as all parameters would have to be keyed in manually, with a consequent risk of human error and potential for scrapped parts. He continues: "Having two screens on the Ultimax CNC system means I can see a graphic of the part created as the program is built-up. It is rather like having a CAD/CAM system inside the control. Similar software for other controls is available but it costs extra and we would need to retrofit different packages to all of the various CNCs on our shopfloor to achieve the same functionality."

Another big advantage of WinMax, he says, is that the program stores the position of the part on the table as well as the cutting cycle. So if the next billet is fixtured in exactly the same place and no edits are required, production can start immediately.

Apart from the machine's competitive price and the benefits of the Ultimax control, the other feature that impressed AB Graphic's production staff was the all round guarding, allowing aluminium to be milled at high speed without showering chips all over the shopfloor. Other bridge mills they looked at only had fence type or open guards.
In practice, the machine has proved to be very accurate. Some dimensional and positional tolerances – hole centres for the path rollers that transport the web, for example – are down to 10µm total to ensure accurate label production and printing.

Based on the success of the DCX22, when another machining centre on the shop floor had reached the end of its useful life, the automatic choice to replace it was another Hurco, a VMX42m with 1,067mm x 610mm x 610mm working envelope. It is fitted with a Max control, which has all of the Windows functionality of an Ultimax, but without the second screen.

Speed of programming is only one way in which AB Graphic maximises production efficiency. Both Hurco machines and indeed seven other machining centres on the shopfloor, carry drilled jig plates on the tables to reduce the time needed to locate and clamp components.

Renishaw tool length setting and probing for datuming components and post-machining inspection have been fitted to the Hurcos to ensure that machining starts as soon as possible after the component has been fixtured.
A further initiative has been to work with tooling suppliers to maximise metal removal rates. Solid carbide cutters are used, mainly from SGS for machining aluminium and Fenn for use on steel.

Hurco
www.hurco.co.uk