2018 saw SRD add three new Citizen sliding head (Swiss type) CNC turning centres – the company has trebled in size since 2015 when it moved to new premises.
A 20 mm bar capacity Citizen Cincom L20 Type VII lathe was installed in 2009 and helped contract machinists to weather the recession. Last year it added two further models for processing similar size stock in March and August, followed by a 32 mm capacity machine in November. The ten-year-old machine is currently running 24/7 and still holding tolerance well.
Precision is key for Bicester-based SRD as 60% of the company's business comes from Formula One, with most of the remainder received from customers in the aerospace and electronics sectors. Dimensional and concentricity tolerances down to 6 microns are held on some 50 to 60 mm long, 3 mm diameter components, for example.
To help achieve this level of accuracy reliably, even during unmanned running, all of the latest sliding-head lathes are equipped with Citizen's LFV (low frequency vibration) functionality. The patented system allows stringy swarf generated when machining aluminium, stainless steel, nickel alloys, copper and plastics to be broken into shorter chips, the length of which can be controlled by the cutting program.
Mark Bonham, joint managing director with his brother Paul of the 30 years established, family owned precision machinists commented, "We had no hesitation in choosing the LFV option on the new Citizen lathes, as being a subcontractor we have to process a broad variety of materials.
"Often they are not short chipping and it is difficult to break the swarf using chip-breaker geometry on the cutting tool and/or high-pressure coolant.
"With LFV, which acts in two CNC axes simultaneously and is part of the control's operating system, as distinct from a macro in the part program, it is possible to regulate chip size closely without compromising the life of the cutters - in fact, they tend to last longer and break less often."
The impetus last March for installing a 7-axis Cincom L20 Type XII LFV with a Y-axis on the counter spindle and a 135-degree B-axis spindle integrated into the gang tool block for both front and back machining was down to the original Swiss-type lathe being fully occupied, while enquiries kept coming in for large volume runs of typically 10,000-off per month. One of the contracts won involves producing a two-part, press-fit assembly with a threaded insert that forms a stainless steel oil restrictor used in the aerospace industry.
The machine is more or less devoted to this ongoing job, so a Cincom L20 Type VIII LFV was purchased on spec five months later and was immediately busy producing diverse parts for a number of existing and new customers.
The Bonham brothers and their father Steve, who is still active in the business, reckon that, as a rule of thumb, a Swiss-type lathe costs around twice that of a fixed-head machine, but the former is able to produce twice as many parts, allowing a subcontractor to invoice around double the amount per month per machine compared with fixed-head capacity.