Lights-out machining of multiple small batches pays dividends

The benefits gained from automating the machining of prismatic components in a high-mix, low volume production environment are no better exemplified than at Alitech Precision Parts, Silverstone. Since 2019, the subcontractor has invested in four German-built Hermle 5-axis, trunnion-type machining centres from UK agent Kingsbury, two of which are equipped for automatic exchange of pallets with fixtured workpieces between a storage system and the machining area.

Alitech’s owner and managing director Darren Cudd commented, “The essence of making this type of production profitable is to buy a high quality, powerful, reliable machining platform, equip it with accurate zero-point clamping systems, in our case from Lang, and use top-end carbide tools, mainly Ceratizit here, that can be pushed to the limit of their performance.

“Overlaid on this sound basis must be a second, essential factor if you want to produce a series of small batches, perhaps even one-offs, rather than a long run of the same part. It is to have the confidence to program and simulate a new cycle in CAM – we use hyperMILL – never having cut the part previously and leave it to run overnight without anyone present.”

This is exactly what Mr Cudd has been doing since a Hermle C 22 UP machining centre, equipped with a PW150 storage and handling system for eighteen 320 mm square pallets, was installed in 2020, six weeks before the start of the Covid pandemic. He credits the production cell, which has a 450 x 600 x 330 mm working volume, as having saved the subcontract business through its ability to produce efficiently, with minimal operator attendance, batches of typically 10 to 20 motorsport parts, but often ones and twos for Formula 1 teams.

Two years later, a Hermle C 42 U prepared for automation, which may be retrofitted in the future, arrived on the shop floor. Then in October 2024, the second automated Hermle cell was installed, a 650 x 600 x 500 mm capacity

C 32 U machining centre with an HS Flex two-level store housing twelve 400 mm square pallets. Its 3-axis handling unit has rotary, lift and linear motions for transferring a pallet either from the set-up station or one of the store positions into the machining area, and then back again after the cycle is complete.

Mr Cudd calculates that, disregarding this latest purchase, the other automated C 22 UP cell accounts for less than 30% of machine tool investment in Silverstone, yet has for the last few years generated up to 50% of Alitech’s turnover, a performance-to-cost benefit approaching 2:1.

Another way of viewing the value of automated machining is to anticipate the return on investment in the new C 32 U cell. The cost of adding the HS Flex increased the investment by about 50%, but time trials carried out by Kingsbury indicate that the output will be equivalent to that of three unautomated machines, again a 2:1 performance-to-cost benefit. It is down to the raised efficiency with which work is presented to the spindle and removed afterwards, compared with manual loading and unloading, as well as the ability to produce parts lights-out without operator attendance, allowing an extra daily shift to be gained.

These calculations, showing that every pound spent on an automated production system works twice as hard as one spent on a stand-alone machining centre, are not rigorous but a clear indicator of significantly better value for money. However, as sales and production manager Ben Phillips points out, there are many extra benefits to automating machine tools.

He said, “The main one is lower labour costs. In the case of the latest C 32 U cell, only one operator is required rather than three had we bought three stand-alone machines. Moreover, the operator is able to walk-away for extended periods to carry out other duties in the factory.

“Consistency of production output is a further advantage, as robotic systems do not need breaks, holidays or time off sick. There are other upsides to automation as well. Fewer machines take up a reduced area of expensive real estate on the shop floor, and they consume less power, leading to substantial ongoing cost savings.”

Alitech’s rising turnover year on year reveals similar positivity. With a few CNC lathes, three 3-axis vertical machining centres and five 5-axis models (although the first to be installed, in 2017, is of a different brand and now used mostly as a 3-axis machine), the subcontractor has trebled turnover in the five years since before the pandemic – and despite it.

Approximately two-thirds of the company’s business derives from machining metals and composites for the motorsport sector, with another 20% coming from high-end road car OEMs or their supply chains and a similar amount from general engineering, including aerospace.

The subcontractor has largely distanced itself from 3-axis prismatic machining, preferring higher added value 5-axis work, a majority of which, unusually, is fully interpolative rather than positional. As cycle times tend to be long, often many hours, a considerable amount of roughing is completed on the 3-axis machines due to their lower hourly rate. In a recent instance, this policy reduced a 24-hour cycle on a 5-axis machine to 14 hours.

One-third of work going through the Silverstone factory involves machining either titanium or 13-8 PH hardened stainless steel. Parts are produced to a general profile tolerance of ± 0.1 mm, but bore and slot tolerances go down to 15 µm and 27 µm respectively. Generic surface finish is 0.8 Ra. Machining tough materials to these accuracies requires the machine tool to have a combination of high precision and robust build, hence the decision to opt for Hermle. The prospect of also machining nickel alloys and tungsten in 2025 only serves to reinforce the subcontractor’s decision in favour of this German machine manufacturer.

The relationship started back in 2019 with the purchase from Kingsbury of a 5-axis C 400 having an 850 x 700 x 500 mm working volume. It is of slightly different specification in that the trunnion is driven from one side only, whereas all the other so-called dynamic Hermle models on-site have a twin-drive system as well as a rotary torque table for in-cycle turning operations. Nevertheless, extensive inclusion in the early machine of temperature sensors continue to allow very fine tolerances to be achieved, down to ± 4 µm.

Historically, it has saved a lot of manufacturing cost through not having to hand-finish components. The machine has recently been repurposed by retrofitting it with dust extraction equipment for dry machining of composites, especially solid carbon alloy plate from which, for example, F1 wishbones and steering wheels are machined, the former in a 14-hour cycle.

The future for Alitech looks bright. Its consistent growth in turnover and diversification into serving industry sectors other than motorsport and automotive has given Mr Cudd the confidence to relocate the business to a new factory unit nearby, four times the size of the current premises. It is presently in build, so the move will take place towards the end of 2025.