Setup Time Reduction through SMED

1.1.     An Overview

(Refer my Book on Amazon for details)

The development of new technology, sophisticated high production systems and assembly lines has ushered a new era in manufacturing area. Competition and productivity are two phenomenons intimately associated with this changed scenario. Higher costs of these high technology systems are to be justified with their high rate of productivity and flexibility. Productivity can be enhanced by exercising economy at all levels of the organization thereby controlling the quantity of resource inputs as well as by increasing outputs with the same or reduced levels of inputs. Set-up time is one of the vital parameter used in any manufacturing industry and is a form of necessary input to every machine or workstation (Van Goubergen 2000). Setup time reduction is the process of reducing changeover times (from the last good piece of the previous run to the first good piece of the next run). Since setup activities add no marketable form, fit or function to the end products that’s why these are by definition non-value adding activities (Enns, 2007). Manufacturers need to be more responsive to the dynamic customer demands to maintain their competitive edge over others. For this present challenge of the market, “economical production of smaller lot sizes” is the key strategy to achieve flexible and shorter production lead-times. This is possible only if changeover become quick, efficient and foolproof. In straightforward word, reduction in set-up time is the need of the hour for every manufacturing unit. Shorter set-ups may bring following impacts to any type of production system:

·       Make feasible the production of smaller lots and decline the set-up scrap

·       Set-up labour cost is decreased and make production system flexible

·       Production lead time reduced and boost productivity & utilization factor of assets

·       Reduction in cost of manufacturing

To cope up with today’s cut throat competition in market, manufacturers have to attempt to achieve above productions-parameters. Which ultimately are the pathways to ‘Lean Manufacturing’ concept (Gung and Studel, 1990).

Set-ups: Set-ups are collection of sequence dependent changeover activities that are carried out before starting the production of any product. These are the activities lying in between the production runs of different products. That’s why these not only include activities like changing fixtures, dies and tooling but also constitute cleaning up, inspection, trial-runs, administrative work and idle time etc. During changeovers, from production of one type of product to another on the same machine, various activities are carried out in different time zones with some precedence relationship among them. The whole set-up process is divided into four major phases namely; Mixed phase, Separated phase, Transferred phase and Improved phase respectively. (refer my book on Setup times)

First Phase: Any set-up starts from a Mixed phase in which the work pertaining to the machine for next production run get started, while the previous run is still going on, For example: Preparation for prerequisites (like; tools, parts, sub-assemblies, pre-heating etc.) during manufacturing of present product. In this period external set-ups of next product can be done before its manufacturing gets actually being started.

Second phase: In Separated phase, overlapping of present and next production run ends (or get finished) by completing the manufacturing process of present product. The production of next product has still not started, but its set-up operations have been going on and got clearly separated from previous production run.

Third phase: Starting of Improved phase makes the end of internal set-up activities, which are carried out only when the machine or work station is not running, like off-line activities (Van Goubergen 2001).

End of transferred phase starts the production of next product but no body can have production up to predetermined levels immediately after fresh set-ups.

Fourth phase: It requires some external set-up activities to compensate the shortcomings and imperfections of transferred phase. All such external operations are carried out until and unless the production of next product with required productivity norms is not achieved, during the Improved phase of set-up.

1.2 GENERAL SHORTCOMINGS IN SET-UPS

Every set-up has a basic ‘work content’ which is a combination of sequence of irreducible activities. Time it takes is known as basic set-up time and it interns depends upon the type of product to be manufactured and its production system constraints (Hay, 1987). It is not possible to escape from this time, but in actual practice there are some additional activities which inflate the set-up time because of the following critical reasons:

Lack Of Standardization: For example in case of semi-automatic die casting machine of Bajaj Classic (MG-17), the die is bolted on the bed of the machine with the help of specially designed bolts : When any breakdown of torque wrench occurs, it is reproduced either by manufacturer or brought from machine builder. This specific problem causes long Set-up down times of machine, which is just due to lack of standardization of tooling.

Too Close Tolerances: It can cause extra effort during changeover activities of a machine (Kreipl and Pinedo, 2005). For example; In case of gravity pouring die of Eicher-pistons, the air vents on critical part of die are made with too close tolerance limits of (0.02mm – 0.08 mm) which can be extended up to (0.05 mm – 1.2 mm). Now cleaning of air vents & removing of die coatings from vents & airlines becomes a tiresome job before assembling the die. This causes unwanted set-up effort and time consumption.

Design of Machine: This aspect has a serious impact on Set-up of the machine. Like control- panels of machine (MG-7) are improperly designed. The metal temperature of holding furnace is not displayed on the main panel, where all the controls & displays of timers are located. This causes frequent movement of operator to monitor metal temperature and cooling timers of outer moulds and bottom tool, simultaneously. It leads to extra movements of the operator to do the required set-up of machine.

Measurability: To enhance accuracy during changeover activities and improve their repeatability, it is required to make set-up parameters measurable. For this machine should fit with permanent mounted scales, digital indicators or gauges etc. otherwise set-up time will become uncertain and probably increases.

Lack of Effective Methodology: This causes unnecessary movements or activities, which in turn can make the set-up procedures more complicated. Like existing set-up prescription for MG-9 is not consisting clear picture of distribution of different work-contents to given set-up work force. It also includes number of pre-set values to different variables, which take more attention of Set-up workers. Hence probability to commit mistakes is get increases.

Weaknesses of Management: The shortcomings in Production Planning & Control can disturb badly the set-up time of any machine or line. If we have poor scheduling of production orders or recruitment of unsuitable persons on given set-up activities, then the same changeovers can be enhanced exponentially.

Human Factor: Demotivated worker show lack of interest, dis-satisfaction with given work, which causes ineffective time. This also enhances absenteeism from work (Li, 2003).

1.3 REASONS OF SHORT COMINGS

There are a number of reasons for the above said shortcomings.

·       Less emphasis is being paid to this set-up area and consequently less effort is made at the production planning and scheduling stage, resulting in haphazard way of execution of different orders in the shop floor. For example; Pistons having similarities in dimensions and attributes can be manufactured one after the other. This will contain less number of set-up activities during changeover as due to number of similar parameters (Groover and Zimmer, 1998).

·       Lack of standardized prescription for doing set-ups. It causes unnecessary consumption of time because every person tends to do the set-up in his own way (Generally, which gives comfort to him). But this is mostly on the cost of quality & quantity of end product. It also may causes service breakdowns and downtimes on latter stages of set-ups.

·       There is less awareness about the quantitative techniques to be used to calculate requirements of having shorter changeovers. There is lack of knowledge on the part of concerned persons about the impact and importance of smaller set-ups.

·       Poor level of house keeping and cleanliness. It is needed to implement the 5-S concepts on shop floor, especially in die-repair section of piston foundry.

·       The non-existence of special tool-kit for Set-up fitters causes unwanted and unexpected delay in changeovers. A tool kit having all necessary tools, fixtures and spares managed in specific sequence of their use, is seriously needed to make available the required set-up tooling in time.