Over 600 jobs were produced for the autosport industry last year on DMG supplied Deckel Maho machines, using 5-axis universal machining centre technology by CommaTECH (Braye).

Each job involved intricate features in difficult to machine materials such as titanium, high-grade stainless steels and aircraft alloys. Five Deckel Maho DMU 50T, two DMU 50 eVo and a linear driven DMU 50 eVolinear were used.

"We chose the machines for their accuracy, flexibility, and negative angle machining"

Graham Saunders, CommaTECH MD

CommaTECH is a small batch specialist where quantities rarely exceed 10 and are produced out of free issue materials from the leading F1 teams and their tier one industry suppliers. The level of complexity is often so high 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.

Managing director Graham Saunders said: “Sometimes a combination of part design, material, and the intended function of the part dictate extra special attention.” He was referring to a particular titanium suspension fixing bracket that chalked up 40 hours in a single cycle to produce just one end of the component.

The process involved considerable 3D 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; it involved a narrow 12 mm tapered cavity, 60 mm wide mouth, and 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.

Mr Saunders continued: “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 added: “Although 5-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 convoluted 3D profiles, any number of cut outs, reliefs and forms, with the added complexity of compound angled features requiring drilling, boring and milling cycles.

Graham Saunders continued: “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 shares the facilities of the Hertford division of the group. This division has the capability to provide a complete project management service covering design, prototyping, and pre to full production machining (involving sheetmetal, fabrication, assembly, CNC machining, and power press work). Both operations at Hertford are part of the CommaTECH group of companies, which employs 500 people and has sales of £40million.

Within the group, DMG has installed eight 5-axis machines at Braye and another DMU 50 eVolinear at Northampton to produce racecar engine components. Programming of the 5-axis machines is totally dedicated to Open Mind HyperMILL, with only minor edits or offsets carried out on the machines. General tolerances vary according to the customer and intended use of the part. Most vary between 0.02mm and 0.05mm, with positional tolerances within 0.05mm. However, 12 micron and 15 micron limits are very common on critical parts; and, due to a 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 Mr Saunders the inherent rigidity of the machine and axis drive performance plays an important part.

The rigidity and power are ideal when machining materials as tough as titanium

To ensure machines are maintained in a fully capable state, CommaTECH 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 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 500mm x 380mm dynamic, swiveling NC table that has a 40 rpm rotational speed and a swiveling range in the B-axis for machining at angles between 0º and 100º. Travel in the X-axis is 500mm while, through linear drive technology, rapid traverse speeds of 80 m/min can be achieved with an acceleration of 10 ms, giving a major advantage when repositioning the tool during 3D contouring. Travels in Y-axis are 450mm and 400mm in Z.

The rigidity and power at the spindle is again ideal for autosport work when machining materials as tough as titanium; 6ALV4, 1M1318, and 7075 aircraft alloys; 13.8 PH and 17.4 stainless steels. Here, said Mr Saunders, the 35kW spindle drive, that has the benefit of 130Nm torque and a rigid HSK-A63 tool mounting, is perfect. Also, with 18,000 rpm available, aluminium components can be machined, and very small tools can be used to the best advantage.

CommaTECH has the 30 tool magazine fitted as standard to the machine, creating a chip-to-chip time within 5s; control is via Heidenhain iTNC530 with DNC linking to the off-line programming centre nearby.

Prior to its acquisition by CommaTECH, Braye Precision operated out of Cricklewood, having built a track record of component supply to motorsport, medical and aerospace industries. Today, 95 per cent of production is motorsport orientated.