Irish subcontractor Shannon Precision Engineering (SPE) has solved an ‘impossible’ one hit machining challenge with a turnkey Nakamura Tome system.
Supplied by ETG, the SC100X2 was purchased for a complex automotive part that was being produced on three machine tools - a 4-axis horizontal machining centre and two single-spindle turning centres. With an annual output of 40,000 units, the steel forged automotive tensioning assembly component was permanently absorbing the capacity of all three machines.
ETG Ireland’s Jamie Fletchmore said: “We were notified that other machine tool companies said the part could not be machined in one-hit. When I first saw the part, I was trying to think of ways that we could machine the job in one operation. I took inspiration from the technology from Nakamura - and also the art of Japanese origami. I wouldn’t accept that the part could not be machined in one hit, so I conducted my own origami project in the office where I took a sheet of paper and started tearing strips on the paper and folding it to get an impression of the particular part and how it might work. I moved the paper around my hands to replicate the spindles and how target points could be put on the centreline. Once I understood this in my head, I went back to Nakamura, they worked out a plan and the component is now used as one of their sales tools to demonstrate how this type of complex part can be produced on a Nakamura machine.”
Dominic added: “We’ve run this family of parts for more than 2 years and we have investigated the market for a solution on numerous occasions – without success. There just hasn’t been a machine on the market that can do the parts in ‘one hit’ - until now. The challenges have included the turning of two spigots on either side of the part that are 40-50mm off-centre. Added to this, we have to mill features that require long-reach tools to overcome interfering features.”
To explain how the part is machined on the Nakamura-Tome SC100X2, Jamie said: “Once we determined that we could handle this part inside the machine in one operation complete, the next challenge was workholding. Workholding is so fundamental to the process and we knew that if we didn’t get good clamping and repeatability, the project wasn’t going to work. We went to the workholding manufacturers and developed the solution. So, what we have on the left spindle is an offset three-jaw chuck with hard gripper jaws that have been designed so the part sits off centre - this means the main spigot is sitting on centreline.”
With forgings known to be inherently inconsistent in their precision, ETG Ireland developed yet another solution for this challenge. As Jamie states: “Inside each of the chuck jaws are two inserts with teeth that are both independent and rock. With the independent teeth and the rocking motion, this counteracts the inconsistency of the forging, as the teeth provide six points of clamping contact that is even - every time we clamp.”
Dominic concluded “There just hasn’t been a machine on the market that can do the parts in ‘one hit’ - until now. The challenges have included the turning of two spindles on either side of the part that is 40-50mm off-centre. Added to this, we have to mill features that require long-reach tools to overcome interfering features. ETG has overcome these issues with the SC100X2. ETG has also cut the cycle time by almost 50% from 14 minutes to 7.26, but more importantly, the Nakamura-Tome SC100X2 has freed the capacity of two single spindle turning centres and a 4-axis HMC whose capacity we desperately needed. We’ve reclaimed three machines and two employees and massively improved our throughput.
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