Lean Manufacturing: Liberate Your Machining Processes
In today's competitive market, manufacturers are facing demands to keep costs low, improve quality, and reduce turn-around time. Companies, especially small-to medium-sized manufacturers (SMMs), seek ways of increasing capacity without the financial burden of additional capital expenditure. Lean manufacturing offers companies cost-effective solutions that promote efficiency and help them remain competitive among global component manufacturers.
CAM systems are the cornerstone of component manufacturing. They vastly reduce engineering time by automating tool path generation. Tool paths play a big role in a machine's performance because they contain feeds and speeds that directly influence productivity. A poorly generated tool path can easily slow down the entire production even if it is run on the most sophisticated machine tool. Although CAM systems offer a wide variety of tool path strategies, they still remain heavily dependent on their user's (i.e. NC programmer's) judgement and experience.
The problem is that CAM systems are unable to make a calculated judgement about the process efficiency or security and therefore uncritically accept cutting conditions given by NC programmers. NC programmers – feeling the pressure to deliver parts faster – prefer using conventional parameters based on their accumulated experience gained through trial and error type testing over a period of years. Unfortunately, this "one size fits all" approach frequently results in overly conservative tool paths underutilizing the equipment and tooling.
With a digital tool called MACHpro Virtual Machining, it is now possible to remove such inefficiencies within machining processes. Developed at the world-renowned machining research center, Manufacturing Automation Laboratory at the University of British Columbia, MACHpro has the capability to analyze real-world performance of tool paths prior to production regardless of the CAM system used to generate them in the first place. Using this predictive tool, actual metal cutting processes are emulated with sufficient accuracy to achieve a true "virtual machining" system that considers torque, power, vibration, tool stiffness, and geometry and workpiece material properties.
This deep understanding of the metal cutting physics allows engineers to detect machining mishaps such as spindle overload, excessive tool deflection, premature tool wear and chipping early in the planning stage. In addition, machine and cutting tool utilizations can be mapped out to detect unproductive tool path sections, which are then automatically optimized and replaced with the most productive feeds. Feed optimization of tool paths is not a new concept. Some CAM packages already offer volume based feed optimization tools which, however, do not consider the machining physics and therefore cannot predict force, torque and vibration causing them to either overstress or under-utilize the machine or cutting tool.
Optimization of an entire tool path based on metal cutting physics may sound like a daunting task but the process is made fairly straightforward in the software. First, you bring in the tool path generated by a CAM system; define tool dimensions; and select a workpiece material from built-in database. You also define readily available limits, such as maximum spindle torque and power and chip loads recommended by a tool supplier. The software then analyzes the entire machining process and calculates how well target chip and force levels are achieved along the tool path. If it is detected that target levels are not met, for example due to varying cut geometry, the software automatically calculates new feeds to guarantee the highest productivity without exceeding safe limits.
To get most out of the optimization, the software also gives you an option to divide long linear moves with one set feed into multiple smaller segments with varying feeds. This feature acting like an offline adaptive control agent allows you to squeeze excessive cycle time out of the process and make the tool path leaner, faster and better. Once you are satisfied with tool path's performance, you simply export the optimized tool path containing all feed changes with new intermediate tool positions.
Released in the summer of 2011, MACHpro – the culmination of more than 150 person years of research and development – has already been embraced by SMMs. Jason Adams, the lead NC programmer from New World Technologies, BC, Canada, tested the software on several high volume production parts with help from the NRC - Industrial Research Assistance Program.
"Testing was performed on a list of parts all being 4340 37 HRC Rockwell hardness" says Adams. The first part that Adams optimized was a serpentine that resembles a spur gear. Using MACHpro, he determined maximum loading on the tool, a standard length 0.25 diameter carbide 4 flute end mill. This limit was then set to the tool, which was initially programmed at a constant 25 inches per minute (ipm) feed, and the machining process was optimized. New feeds obtained by MACHpro were variable from 25 ipm to 105 ipm, and this resulted in a staggering 32% productivity improvement in the first trial. "The ability to ensure tool load, machine torque/power limits, and chip load is fantastic for a programmer. This software not only increases productivity, but also gives the programmer a more accurate way to simulate program's efficiency without tying up a production machine" concludes Adams.
Long after having entered into an era of information and technology, we are experiencing a paradigm shift in many areas of traditional machining industry. Digital tools aiming at improving operational efficiency are in great demand. For SMMs, one effective way of increasing throughput is to ensure that existing and limited equipment is fully utilized before making larger capital investments. SMMs can greatly benefit from right digital tools that can effectively spot hidden productivity obstacles and eliminate them, like an antivirus program liberating your computer.
Dr. Doruk Merdol, the president of Terranic Systems, has developed a passion for machining under the training and mentorship of a famous metal cutting professor, Yusuf Altintas. Dr. Merdol's main areas of expertise are virtual machining, machine tool vibrations, chatter avoidance, metal cutting mechanics and high performance machining. He is a strong believer of driving innovation by transforming exceptional scientific knowledge to practical software solutions and services that are instrumental for the growth of companies in today's highly competitive manufacturing market.