#Lean Manufacturing processes focuses in driving out as much waste as possible. You can never eliminate waste (as in 100%) because waste will always be inherited in processes, even if you invest in new technology , then you can use that technology to drive out more waste.
#SixSigma refers to process variation reduction, meaning… get your process stable enough so it repeats within the variation as tight as possible, closest to the mid limit value, given a set manufacturing process.
As a Manufacturing Engineer, you would ask yourself, how would you implement these principles into a machining process?
I will give you an example of one of the many CNC milling processes that I have worked on, quite recently. I had various shapes into 30 something pocket features with various open and tight tolerance bands, these pockets are equidistant spaced into a ring component…..I won’t go into the details of these features, or the work holdings as per NDA and also this is not the subject now, but you get the idea. It isn’t anything special, normal milling – roughing and finishing.
I have tried different tools for the roughing stage, and I found the “XXXX” roughing end mills to give the best results so far, combined with the shrink fit tool holder Given the tool’s 6 cutting flutes you remove material faster than using a 4 flutes and also the “tool’s core” is stronger. In roughing it’s important to remove the material in a certain sequence to eliminate any potential residual stress, and also generate tool paths in such a way that cutting forces are directed axial and radial in order to lower tool vibrations and also to use the entire cutting flute length in the areas were the workpiece have thin metal so the tool wears evenly through the process.
For the finishing stage I have used the Duo-Lock XXXXX Grade XXXX, mainly for the 11 flutes and the tool’s adapter shank for the safe lock system that also allowed to integrate the Haimer Safe-Lock with cool jets shrink fit tool holder — preventing tool’s pull out . The tool path for the finishing stage is just simple radial engage as it gave the highest tool life, and lowest cycle time.
-Now, this stage can best explain the difference between #SixSigma and #Lean-: To ensure, highest tolerance and to eliminate thermal drift, the tool is recalibrated radially and axially by semi finishing a feature with two parallel faces. The distance between the two face is measured by either a probing cycle that updates the radial tool’s wear and the tool’s length wear, or actually do manual checks and updated the tool’s wear, manually – given the CNC machine capabilities. This actually adds extra cycle time given that the tool is recalibrated for each component, but given the tool’s 11 flutes, this is only being done once. So there is required balance between #Lean and #SixSigma in order to achieve a stable process.
I do believe that certain principles as #SixSigma and #Lean are useful in a machine shop environment, and given the machine’s shop capabilities can be applied to a given level.
I hope you can use this example to improve your process, and eliminate waste as much as possible.
Adrian Hainarosie C.A.D. Mechanical Designer & C.A.M. Programming C.N.C. Manufacturing. 