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Manoj Kabre, Indo-MIM
Machining of metals has always been a challenging task and when dealing with metal injection moulded (MIM) parts, it becomes even tougher. The machining process at Indo- MIM started with operations like drilling, tapping, surface grinding to finish features and tolerances, which were beyond the MIM tolerances. Due to unavailability, most of the prominent operations like turning, drilling, reaming, tapping and surface grinding were being outsourced in the initial years.
Indo-MIM had established in-house machining in 2009 and has so far established many critical operations including:
• CNC turning with close tolerances of up to ±6 microns
• CNC milling — 3rd and 4th axis in machines with pallet changers
• High production single-pass honing with one part every 13 seconds
• High production profile grinding at 15 seconds / parts with ±7 micron tolerance
• Multi-part surface grinding
• Lapping and polishing to achieve flatness of up to 2 microns
• ID grinding with ± 6 micron requirement
The following advantages are helping us to sustain our machining process:
Right machine selection
We have engaged ourselves in an active role in the process of selecting the machines. Our guiding factor for the process has been the method of maximising the machine running time. We opted for VMSs equipped with pallet changers to shorten the time lost in loading and unloading time. Further, we opted for machines which were small, compact, rigid and with low torque spindles since we remove much less material and most of our parts are smaller in size.
Whenever critical tolerances are to be maintained within capability, machines have been fitted with probing systems for auto tool offset corrections.
Even for honing and grinding, we have opted for machines with the facility of parallel loading and unloading of parts, while the operations are carried out in other stations.
Work Holding
Even though we use the general chucking systems and collet systems in our turning centres, we have custom built fixtures for specific parts. Having our own design department doing both the part design and fixture design has helped us decide the optimum clamping systems for highly challenging part requirements. All our milling and surface grinding fixtures are multi part fixtures. Having multi part fixtures has not only helped in increasing the productivity, but has also given us the advantage of full machine bed utilisation irrespective of the part size.
Most of the small batch productions have multiple parts / operations preset in the machine bed, thereby practically zeroing the changeover time.
Cutting Tools
Though we get support from different tooling manufacturers and dealers, we work with the suppliers to achieve the lowest possible ‘per piece rate’. The tool cost alone is not taken into account but the advantage of higher cutting parameters and better material removal rate is also being considered to finalise the optimal tool source for any application. We approach each application with an open mind, giving equal opportunity, be it established players like Iscar, Sandivik, Walter etc., or low cost sources in India who manufacture and supply tools which are less expensive.
Continuous Improvements
Our culture to always work on continuous improvements by conducting kaizen events, identification of improvement projects and tracking them has helped us complete significant improvement projects in optimising the usage of Man, Machine and Methods.
Statistical Process Control
The usage of statistical process control is another tool we have successfully implemented to establish robust and repeatable processes. Statistics have come handy in the study of tool wear pattern and establishing auto offset corrections through program macros. The macro programs have reduced the high variability caused by operator interventions. Processes where very close tolerances need to be achieved have been established in this way and we have derived significant reductions in product scrap levels.
Collaborative approach
As we believe that when bright minds meet, ideas spark out, we approach any challenge with an open mind and discuss it with machine tool suppliers, tool suppliers or work holding sources for optimum solutions. This has not only helped us arrive at getting the solution, but also getting them fast. There have been instances where the outcome of our discussions has become standard options for the machine tool manufacturer later.
With the establishment of our Investment casting facility at Tirupati, we have got into the challenge of machining bigger parts having more material removal. The machining of MIM parts has helped us quickly establish highly critical machining projects for investment casted parts.
All through our machining journey, our primary objective has been and will be low operating cost. With our management willing to invest in suitable machines it is expensive but guarantees lower operating cost in future; it is the corner stone for our rapid growth in the machining process. Starting from three machines in 2009 to currently holding 60 machines in 2014 is a remarkable achievement.
Having established sales offices across the world in addition to having satisfied customers has opened new opportunities of bigger and more challenging machining projects. With the strong fundamentals established along with the past learning, we can confidently say that we are well placed to handle them and succeed.