Optimising Metal Working Process

Combination tooling: This is a favourite approach of many companies in large volume production. Combination tools certainly lead to cycle time reduction on VMCs and HMCs. There are a few problems that arise. Cutting speed is compromised to increase the tool life of that tool which has the shortest tool life. All tools do not wear the same amount at the same time. This is an issue especially in solid carbide tools while resharpening. Chips from one tool can clog into an adjoining tool. Since cutting parameters cannot be optimized for all the tools, chip breaking can be an issue. Spindle Power increases and the same needs to be checked. Roughing with a combination tool is acceptable but not finishing because the finish is affected when another cutting edge leaves or enters a cut.

Introducing LCA: LCA or Low Cost Automation aids are often used to improve productivity especially where assembly operations are concerned. Certainly this boosts productivity and motivates the workmen. Another advantage is that this knowhow is retained in-house. To design LCAs needs investment in training of personnel. It needs a strong 5S, Kaizen and enabling culture in the organization.

Optimising the cutting tool and parameters: Selection of the correct cutting tool and optimizing the cutting parameters is crucial to reducing cycle time and increasing tool life. Companies have invested in higher cost tooling and using higher cutting parameters and reduced the per piece cost because of higher utilization of the power and capacity of the machine and reducing the cycle time. Monitoring the spindle load and ensuring that it is optimally utilized is an approach used by many companies. This approach needs strong data collection to validate the results and periodic monitoring.

Using CAM programming: Companies have also studied the tool path and reduced the air cutting travel, thereby the spindle is cutting metal rater than cutting air. Sometimes due to lack of discipline and special causes that take place manual changes are made in the program and optimized cycle times are diluted.

Improved Fixtures and use of Accessories: Some companies have taken the approach of redesigning fixtures to accommodate family of parts. Others have modified fixtures to reduce setups. Some others have added 4^th Axis or additional axis on their machine to reduce multiple clamping and setups.

Deburring: Deburring is a troublesome process in most companies. Several approaches have been used including developing special tools to deburr on the CNC machine itself, to using different media to deburr. This needs extensive trials to validate the process including customer acceptance.

Use of DOE and ANOVA: For optimizing cutting parameters Companies have used ANOVA and DOE extensively with encouraging results. This however needs good in-house understanding of the process variables and the technique.

Better Asset Utilization

Utilisation of Generator Sets: Due to power outages in our country Companies have had to use in-house generated power. In most cases where the machine shop is large, several generators feed into a grid. An IT based solution has helped companies to optimally use generators based on variable load.

Reducing power consumption: Most machines have several motors for auxiliary functions, eg. coolant pump, chip conveyor, hydraulic power pack, etc. An innovative approach was to replace these motors by mechanical linkage driven by the main motor and thereby reduce power consumption. This approach may not work in all applications but companies have used one motor between two machines, eg. one coolant pump between two machines. The only problem is if the pump fails both machines would stop at the same time.

Refurbishing and upgradation of old machines: Reconditioning of old machines is an old story. In some cases especially in very large sized old machines, which are mechanically very robust Companies have not only refurbished but considerably upgraded them with latest features. While this works where the company is competent to carry out the work and the cost of a new machine is extremely high, it may not be advisable in many cases as technology has evolved and this would just lead to a compromise solution.

Design standardization: This is a route several companies have taken to improve the productivity in their design department where resources are generally a constraint. This approach needs a disciplined and a system based culture in the organisation.

Nesting: Improved nesting in powder coating, painting and heat treatment processes has led to significant increase in asset utilization and therefore productivity. This needs a deep study to understand the effect of higher nesting and validation of results in the longer term.

Layout and flow improvement in machine shop and assembly: Several companies have used this approach to improve productivity. Line balancing is a challenge but can be overcome.

Minor and idling losses: Several companies have looked at minor and idling losses in their machine shop and assembly areas. Small reductions and elimination of these losses have resulted in a cumulative reduction which is quite significant.

Productivity through quality

Process variable optimization: Heat treatment distortions can be reduced by optimizing various parameters such as temperature, soaking time, quenching time etc. This is an approach some companies have adopted to reduce rejections on thin walled parts.

Poka Yoke: Poka Yoke is a common approach adopted by most companies for eliminating rejections. Innovative means are used with low cost sensors, reed switches, motion counters to eliminate rejections.

Dimension changes in drawings: Assembly rework can be considerably reduced by revising the nominal dimensions of mating parts in an assembly after stack up tolerance analysis. The machining process to maintain the nominal dimension was critically assessed. Simply increasing the tolerance is not the correct solution.

Part cleanliness: Component cleanliness is a major issue in several industries. Companies have approached this challenge innovatively by studying chip formation, chip breaker design, chip evacuation, process changes, etc. The approach is to ensure that machining chips do not remain in the part in the first place.

Repeatability of measuring equipment: Often one takes for granted the repeatability of a measuring instrument and looks for reasons elsewhere. Critically and periodically assessing repeatability of measuring instruments has helped some companies to improve quality and hence productivity.

Improper part handling: Companies have found that improved part handling leads to lower rework and rejections. Though this is not new, part design is tweaked from the point of view of ease of handling during the process.

Manufacturing system redesign

Single piece flow: Several companies have adopted single piece flow against batch production to boost productivity. While this certainly improves productivity and drastically reduces in-process inventory, line balancing and reliability of each equipment is very important. Besides reliability of each equipment, the MTTR for each equipment must be very low otherwise there is complete loss of production. There remains a challenge to convert batch processes like heat treatment, washing, etc to a single piece flow.

SPMs to CNC: In moving from SPMs to CNC, companies have overcome the challenge of frequent setup change over using SMED and thereby improved productivity. This needs a disciplined and planned infrastructure to be sustained. The need to do this arose from fluctuations in customer demand and frequent introduction to new products.

Holistic view of the process: While redesigning the manufacturing system, companies have taken a fresh look at the system. Companies have introduced single piece flow, cellular manufacturing, Kanban, SMED, LCAs and innumerable Kaizens. The resulting benefits are huge. Value stream mapping is a commonly used tool to uncover waste in the system. Factory layouts have completely changed as a result. To do this, the management must be forward looking, bold in taking decisions, and take counter measures in advance to foresee disruptions, which to some extent are inevitable at least in the initial phase

The National Productivity Summit 2015 at Gurgaon on 20 -21^st Nov, showcases through its case studies and keynote addresses how teams have significantly improved productivity at their workplace. Various tools have been effectively used by these teams to discover and analyse the hidden losses in their process and find innovative solutions to challenges thrown at them by their customers. This “out of the box” thinking is very important for these companies to continue to be competitive. Participants attending this summit can take away lessons and get motivated to emulate the award winners in their own companies.

Beginning of the last century was an era of traditional craftsmen. Products were costly as they were custom designed and manufactured. Often the middle class at that time could not afford it, e.g. the automobile was owned by noblemen or kings. On Dec 1st 1913, the world changed forever. Henry Ford¹ installed the first moving assembly line for the mass production of an entire automobile. His innovation reduced the time it took to build a car from more than 12 hours to two hours and 30 minutes.

Ford’s Model T, introduced in 1908, was simple, sturdy and relatively inexpensive–but not inexpensive enough for Ford, who was determined to build “motor car[s] for the great multitude.” (“When I’m through,” he said, “about everybody will have one.”) In order to lower the price of his cars, Ford figured, he would just have to find a way to build them more efficiently.

Ford had been trying to increase his factories’ productivity for years. The workers who built his Model N cars (the Model T’s predecessor) arranged the parts in a row on the floor, put the under-construction auto on skids and dragged it down the line as they worked. Later, the streamlining process grew more sophisticated. Ford broke the Model T’s assembly into 84 discrete steps, for example, and trained each of his workers to do just one. He also hired motion-study expert Frederick Taylor to make those jobs even more efficient.

Automation in manufacturing increased and in 1981 Yamazaki Mazak set up a fully unmanned factory at Oguchi, Japan, for machining of castings and components of machine tools. There was huge publicity in the mechanical engineering fraternity since this was the first “lights out” factory where every night the factory operates without lights as no workmen are present. These systems were very complex and maintaining them was not easy for everyone. Such systems are capital intensive and not justifiable in every situation. Small improvements are also not possible and process design disconnects from the workplace.

The pendulum, which swung from one end that of a skilled craftsman at the centre of the manufacturing process at the beginning of the century to a fully automated one with no craftsman, had now swung to the other end. It was soon realized in Japan that a combination of human skills and appropriate automation may be cost effective, easy to maintain and leading to a competitive scenario. In the 90s Toyota Production System, Just-in-time became the buzz word in manufacturing. An offshoot, Gemba Kaizen, which means small improvements at the workplace, brought the synergy of human skills and automation in the form of Low Cost Automation to the Japanese workplace. By definition Low Cost Automation (LCA) means any compact, cheap, simple but very effective manufacturing piece of equipment which is designed and assembled internally by a group of employees at the Gemba using Gemba wisdom.

The key words are cheap, simple, designed and assembled by a group and using Gemba wisdom. By cheap, one means the ROI (return on investment) should be less than a year. Simplicity (Simple) should be in operation, design, flexibility and maintenance. If the LCA is simple then as products change it can be modified, taken apart and reused. LCAs are designed and manufactured on shop floor and the user is actively involved at all stages from design till tryout. It is a group activity and uses the wisdom of the shop floor.

LCAs do not necessarily use hydraulics, electronics, etc. A simple gravity chute to transfer parts from one machine to another is a LCA. A LCA can very well be automatic transfer of information. A simple hand operated trolley using a screw mechanism to load/ unload a component made from left over plumbing parts and a lead screw and nut from an old lathe can become a LCA. Fig1.

In Fig1. The two workmen with the help of their supervisor built this loading mechanism using left over pipes and leadscrew from an old discarded lathe. Their joy in creating something is palpable. The cost was 1/10 of that of an electrical hoist that would have been used. 

Once an organization decides to implement LCA it usually sets up a LCA or Kaizen Group. Members of this group are drawn from the manufacturing personnel who are multiskilled. They are trained using training kits in areas such as pneumatics, logic, PLC, etc. They are exposed to different innovative mechanisms and toys are a wonderful way to educate them. LCA room can be prepared with toys, Kaizen sheets, One point lessons, failed LCAs, hand sketches of proposed LCAs, etc. Fig.2 shows how LCA projects are taken up in the organization.

It is important to note the role of management in LCA. The leadership of the LCA group lies within the group. They decide when to meet, what to do, what resources are required, periodic review etc. Management’s role is limited to deciding, which LCA projects should be taken up, providing resources including training and rewarding when the LCA project is complete and implemented. Management must not be involved during design, manufacture or implementation of LCA.

The need for LCAs arises from the Kaizen events organized by the company. LCAs are designed from rough sketches made at the workplace. Corporate design is too bureaucratic, nor has any priority for carrying out this additional work. Rough sketches can be modified quickly and frequently on the shop floor. It also results in speeding up the LCA as the beneficiary is an active team member and is keen to expedite the project.

Table 1 compares LCA with conventional automated systems. A very important point to be noted; the LCA contributes to competitiveness as the knowhow is retained in-house, whereas a vendor can offer a competitor similar products. Automation often fails because certain considerations are not taken into account. LCA is also a highly motivational tool. Group members take pride in what they have achieved.

Some aspects that need consideration

1. Safety of operator and equipment can never be neglected and is of prime importance.
2. Automation fails if input quality is inconsistent. While designing an automation system, the worst case scenario of input material must be considered. When the user is involved in design as in a LCA, he knows the worst case and will take it into account.
3. There is a tradeoff between flexibility required and cost. If one desires complete flexibility, it may make the automation equipment very complex, costly and difficult to maintain. Often 80:20 rule is applied. Let the automation take care of 80% of product mix.
4. Before doing automation, one must simplify the process and movements. This makes the automation simpler, cost effective and robust.
5. Power failure is an endemic problem in our country. Automation system design must be robust under this situation and a recovery process must be built in.
6. If the automation handles a family of parts, then ease of set up change must be considered.
7. Finally use of automation equipment needs training and the same should not be neglected.

In conclusion quoting an automation champion from Japan, Mr. Shuichi Yoshida, “Manufacturing Technology tends to get more complicated, expensive, impractical and grotesque as design engineers work far from Gemba (users)”

Any automation system must be selected based on its appropriateness. For example a fully automated system is an appropriate solution in a high volume bearing plant, and cannot be designed and implemented by shop floor personnel. Nor can the ROI be one year. However an automated part unloader with manual loading can be a LCA, and more appropriate in batch production at a Tier II automotive component manufacturer. Appropriate automation must be cost competitive based on scale of production. While the words Low Cost Automation catch ones attention, it is not a solution for all automation requirements. It is more meaningful to use Appropriate Automation, which includes LCA.

¹ Reproduced from http://www.history.com/