Commatech Proves Dmg 5-Axis Is The Solution For Complex Racecar Parts

Over 600 different jobs were produced for the autosport industry in 2007 on DMG of Luton supplied Deckel Maho machines using five-axis universal machining centre technology by CommaTECH (Braye). Each job, of which more than half were new, involved very intricate features in problematical to machine materials such as Titanium, high-grade stainless steels and aircraft alloys using five Deckel Maho DMU 50T, two DMU 50 eVo and the very latest installation, a linear driven DMU 50 eVolinear. CommaTECH (Braye) is a small batch specialist where quantities rarely exceed 10 and are produced out of free issue materials from the leading F1 race teams and their demanding Tier 1 industry suppliers. Such is the level of complexity required that it is not unusual for cycle times on a single part to take eight hours while machining times between two to five hours are more commonplace. According to Managing Director Graham Saunders: “Sometimes a combination of part design, material and the intended function of the part dictate extra special attention.” He was referring to one particular racecar suspension fixing bracket in Titanium that chalked up 40 hours in a single cycle on one of the Deckel Maho machines to produce just one end of the component. The process involved considerable 3-D contouring of the outer form with a cross bore and various holes. However, the pièce de résistance was at the opposite end to the cross bore that involved a fairly narrow, around 12 mm tapered cavity, about 60 mm wide at the mouth and around 75 mm deep with a wall thickness of under 1 mm. The internal cavity, blendings and outside contour had to perfectly smooth without any machining marks being visible. Said Mr Saunders: “Most of the parts we produce will be highly stressed and often have recorded life cycles on the racecar. Almost all are very weight critical involving very narrow sections as they are used on suspensions, in transmissions and as part of the on-board hydraulic systems. Due to their very nature, most are produced out of solid so we combine as many features as possible into a single operation – hence the need for all our machining centres to be highly flexible to enable a five face approach to the job.” He explains further: “Although five-axis can be quicker – especially when lead times are considered, our goal is to maintain very strict geometric relationships of different features and it is the presentation of the tool to the job that is important. We also save on fixturing and the possible introduction of errors that could creep in if we had to relocate the part.” Most toolpaths followed by the Deckel Maho machines have very convoluted 3-D profiles, any numbers of cut outs, reliefs and forms with the added complexity of compound angled features requiring drilling, boring and milling cycles. According to Graham Saunders: “The DMG supplied machines were selected partly for their accuracy and flexibility of positioning, but especially their ability to enable negative angle machining in-cycle. The machines also provide very good tool access but also important in the decision is their excellent track record machining the type of work we produce. We also enjoy the commonality of controls, tooling and machine operation, which is important on the shopfloor, and the Deckel Maho design only requires a small footprint which helps on space requirements. The specialist operation of CommaTECH (Braye), which has a turnover of some £2M, shares the facilities of another group division CommaTECH (Hertford). This division has the capability to provide a complete project management service from its 60,000 ft² facility covering design, prototyping, pre to full production machining involving sheetmetal, fabrication, assembly CNC machining and power press work. Both business operations at Hertford are part of the CommaTECH group of companies that has, as its focus, high precision machining. The group employs 500 people with sales of some £40M. Other group businesses include CommaTECH (Northampton), CommaTECH (Leicester) and CommaTECH Holdings based in Birmingham. Within the group, DMG of Luton has installed eight five-axis machines at Braye and another DMU 50 eVolinear at Northampton to produce racecar engine components. Prior to the acquisition by the CommaTECH group and relocation in Hertford with the name change to CommaTECH (Braye), Braye Precision operated out of Cricklewood and built a track record of component supply to motorsport, medical and aerospace industries over some 40 years. Today, 95 per cent of production is motorsport orientated with just five per cent or so going to aerospace. Programming of the five-axis machines is totally dedicated to Open Mind HyperMILL® with only minor edits or offsets carried out on the machines. Solid carbide tooling predominates with the facility of a small toolroom alongside the main machine shop to easily alter radii and forms on tooling to meet the varying requirements of the different race teams. General tolerances vary according to the customer and intended use of the part. Most vary between 0.02 mm and ±0.05 mm with positional tolerances within 0.05 mm. However, 12 and 15 micron limits are very common on critical parts and, of course, due to the focus in avoidance of stress points plus the production of porting and sealing faces on hydraulic components, surface finishes are always strictly monitored. This means that speeds, feeds, step-over and depth of cut are always critical but according to Graham Saunders, the inherent rigidity of the machine and axis drive performance plays an important part. To ensure machines are maintained in a fully capable state, CommaTECH (Braye) has recently engaged DMG to progressively refurbish and upgrade the drive systems on its five DMU 50T machines on site which have all seen six years of sterling service. The latest DMU 50 eVolinear, like the other DMU 50 machines, uses the flexible concepts of a universal milling machine to provide the capability of a vertical machining centre for five-face tool to component positioning. Here, CommaTECH makes good use of the 500 mm by 380 mm dynamic swivelling NC table that has a 40 revs/min rotational speed and a swivelling range in the B-axis for machining at angles between 0º and 100º. Travel in the X-axis is 500 mm while, through linear drive technology, rapid traverse speeds of 80 m/min can be achieved with an acceleration of 10 m/sec² giving a major advantage when repositioning the tool during 3-D contouring. Travels in Y-axis are 450 mm and 400 mm in Z. Again ideal for autosport work, when machining materials as tough as Titanium, 6ALV4, 1M1318, and 7075 aircraft alloys and 13.8 PH and 17.4 stainless steels, is the rigidity and power at the spindle. Here, according to Mr Saunders, the 35 kW spindle drive, that has the benefit of 130 Nm of torque and a rigid HSK-A63 tool mounting, is ideal. Also with 18,000 revs/min available, aluminium components can also be machined if required and very small tools used to best advantage. CommaTECH has the 30 tool magazine fitted as standard to the machine that creates a chip-to-chip time within 5 secs, and control is via Heidenhain iTNC530 control with DNC linking to the off-line programming centre nearby.