By replacing its existing deep hole drills with the new BT-A drill from Allied Maxcut, engineers at Cummins' diesel manufacturing plant in Daventry have achieved a 40% productivity increase and doubled the tool life on its crankcase manufacturing line.
To drill the 26 mm and 38 mm diameter oil rifle holes in large cast iron industrial diesel crankcases, ranging from 50-litre V16 to 78-litre V18, Cummins drill half of the 2.2 metre depth required from each end to help maintain rigidity and ensure coolant flows and pressures are maintained.
Cummins was already working alongside AMEC in developing specialised tooling for one of its other plants in Europe and was keen to improve the performance of its main manufacturing line, where it believed the deep drill tooling from its existing supplier was the limiting factor to further progress, as any improvement in speeds and feeds reduced the tool life and caused higher tool failure rates.
Cummins adopted AMEC's new BT-A drill following extensive trials, which allowed them to increase cutting speeds from to 800 to 980 rev/min on the 26mm diameter drills and 540 to 670 rev/min for 38 mm diameter. The corresponding feed rates were also increased by 48% and 57% on the 26mm and 38mm drills respectively.
Employing the latest evolution of AMEC's widely used T-A® insert range, Cummins used the K20 carbide with AMEC's high performance AM200® coating, which enabled twice the number of holes to be drilled before the insert required replacing. Also, the purpose designed BT-A drill holder uses a standard thread mounting so is directly interchangeable with other existing deep drilling tube systems and enables improved swarf evacuation through large ports within the drill body.
Cummins also found that replacing the inserts was a less complex and much simpler process as the BT-A drill uses only a single T-A insert and its previous system used 5 inserts of 4 different types, which has also helped reduce the number of items required to be held in stock.
One of the tool failure issues experienced by Cummins related to the high level of cutting forces generated, causing individual cutting inserts or hole guide inserts to fail, which then blocked the axial swarf evacuation ports and in some cases caused the holder to collapse in spite of sophisticated coolant flow and spindle power monitoring on their deep drilling machines.
As the BT-A drill uses a single insert with a 132-degree angle, the cutting forces are balanced and spread over a larger cutting area. Also, as the BT-A holder is designed using two large evacuation ports in the sides of the body, it allows a higher mass of metal to support the cutting insert in the nose of the tool, giving greater rigidity.
Gareth Plackett, one of the engineering team responsible for the main engine case production at Cummins, explained: "Like many businesses, we are constantly looking to improve manufacturing performance, efficiency and costs and AMEC's BT-A drill system has enabled us to achieve some significant productivity increases."
He added: "In addition to the key improvements of tool life and productivity, we also discovered a number of supplementary benefits. As a result of the BT-A drill's longer hole guides of around 3 times that of our previous system, the hole alignment had improved with a virtually invisible join within the casting. Also the cutting noise had reduced considerably, which helped the working environment."
The AMEC BT-A deep drilling system covers diameters from 12.95mm up to 47.80mm and is part of a wider deep hole manufacturing programme including AMEC XL and 3XL drills, which extends the range from 9.5mm to 114.48mm diameter.