CITIZEN TAKES DRIVING SEAT POSITION AT HEELER ENGINEERING

Since it was founded in 1963, Northants based Heeler Engineering has built its subcontract turned parts business around seven CNC lathes, 16 cam autos and nine sequence controlled lathes producing a wide range of shafts, adjusting nuts, pivot pins, spacers, nuts, bolts and washers for a commercial vehicle seating company.

However, since making the decision to purchase a Citizen L32 CNC sliding head automatic lathe from NC Engineering of Watford, directors Martin Heeler and Julie Malin cannot believe the effect the latest machine tool technology developments have had on their business. Says Martin Heeler: "Not only are we producing parts in half the cycle time, they are now so totally consistent in size and surface finish. We have also eliminated secondary operations involving de-piping, milling and drilling and can now include certain operations that always had to be sent out to another subcontractor."

He explains that while most of the 200 or so different turned parts produced aren’t exactly what you would call high tech, they still have to be accurately and efficiently. The major part of the business is now geared to parts supply to a leading manufacturer of commercial vehicle seats and so, the 15-strong company needs fast, reliable and cost-effective production.

Indeed, so successful was the Citizen L32 installation that very quickly another sliding head CNC lathe was installed at the Kislingbury factory. This time, however, the company bought a second-hand Citizen L20 machine from NC Engineering’s previously owned machine operation which runs alongside the Park Avenue headquarters at Watford.

Julie Malin outlines the thinking behind this move. "We had to increase output on five variants of piston rods for suspension seat damper units, as our existing cam auto could not keep pace with the schedule. But with only a limited budget for this project, we initially thought about buying a Citizen B12. However, NC Engineering was able to offer us a used L20 lathe which had a known history and was more appropriate because it gave us a larger turning capacity plus the ability to handle cross-drilling and milling operations in a similar ‘one hit’ cycle as the new machine." Installed in May 2003, the Citizen L20 lathe is currently producing some 1,200 of these 9.5 mm diameter by 152 mm long piston rods each day.

Heeler Engineering is a family run business with the second generation now controlling the day-to-day operation. The majority of its work is for local customers producing batches between 2,000 and 15,000 parts against daily just-in-time delivery schedules.

The decision to switch-over to CNC sliding head technology was not taken lightly and there were some reservations. As Martin Heeler explains: "Investing in such an expensive machine was a big move for a company of our size. However, after looking at the options and other machines on the market the Citizen L32 was seen as the best machine in terms of capacity, features and all-round performance."

One major factor in the decision, apart from the machine’s capability, was NC Engineering’s whole attitude to the project which Martin Heeler felt would ensure a high level and long term technical back-up and support. "What’s more," he said, "Geoff Bryant, NC’s managing director was so confident in the difference the machine would make to our production that he even agreed to buy-back the L32 after 12 months for a fixed price, if things didn’t work out as planned."

Now he maintains the performance of the machine, since it was installed in November 2002, has more than vindicated the decision. The six-axis slant bed design enables the vast amount of swarf produced from Heeler Engineering’s parts to fall away from the cutting zone and the main and secondary spindles, coupled with its 16 tool capacity gives so much flexibility when setting.

The tooling configuration has five tools available for external turning and three for internal operations. Four further tools are driven and five tools are available for back machining and with both a C-axis and Y-axis, enables the driven tools to traverse across the workpiece. The Y-axis also simplifies tool centre height setting through offset input at the control.

Compared with cam autos, the L32 has demonstrated major performance benefits across the range of seating elements it is producing. Heeler Engineering has also adopted unmanned, ‘lights-out’, working at night and at weekends and plans are laid to capitalise further on the ability to increase production capacity ‘at almost no additional cost’. The Citizens are also left virtually unmanned during the 10 hour day shift utilising the capacity of the 20 bar magazine. And the cycles, which tend to be very reliable, involve turning, recessing, drilling, threading, cross-drilling, knurling and the milling of flats.

On one component, a 12 mm diameter by 220 mm long steel seat adjusting shaft, which has a 100 mm length of thread and is required in batches of 15,000, Heeler uses a die head in favour of single point cutting and one set of chasers lasts around 3,000 parts. Other features machined include a 5 mm diameter cross-hole in the threaded portion, a short knurling section and a blind drilled hole in the reverse end which is accessed by holding the part in the L32’s subspindle. Total production time on the Citizen is 59 seconds against over the two minutes before with the added benefit of saving time and effort to set up for three additional separate operations.

It’s a similar story on a 12 mm diameter by 135 mm long steel adjuster stud – required in weekly quantities that vary between 1,500 and 2,000. With a 90 mm long threaded section, two cross- holes of 3 mm and 4 mm diameter are required in the threaded portion plus general profiling and chamfering. The L32 can completely finish a stud in 60 seconds ready for packing. Previously, turning times were around 95 seconds but the part then had to be transferred to another machine for the cross-drilling followed by manual deburring.