'Line' process requires smooth running
Bangkok Post
KANUTE NIRUNTASUKKARUT
This is our penultimate article in our series about selecting continuous improvement initiatives for your manufacturing organisations. Our series is based on the fact that the choice should tie closely with the type of manufacturing processes used in your organisation. We have already covered three process types: "project", "one-off", and "batch".
For "project", the improvement initiatives should focus on the human-resource aspects of your company due to its high leverage on people skills. For "one-off", on the other hand, job planning and scheduling are critical aspects because this process typically is for large, complicated products. Lastly, for "batch", improving flexibility is the key aspect due to the need to maximise the overall utilisation of the production line, while minimising the work-in-process inventory.
This week we will move on to the next process type, which is "line". This is similar to a batch except that the issues of idle production or batch queuing do not exist. A line process means that as work on a task at a particular stage is complete, it must be passed directly to the next stage for processing without waiting for the remaining tasks in the "batch". When it arrives at the next stage, work can and must start immediately on the next process. In order for the flow to be smooth, the times that each task requires on each stage must be of equal length and there should be no movement off the flow production line.
Businesses with line processes generally sell standard products that are sold on price and are typically associated with large customer orders. The level of product change is comparatively low and usually prescribed within a list of options. Product design and quality are determined at the outset to meet the perceived needs of the customer. Examples would be the manufacturing of automobiles, FMCG (fast moving consumer goods), and beer bottling.
To provide low manufacturing costs, the process is dedicated to a predetermined range of products, and is not geared to be flexible outside this range, due to the high costs of change. This provides an opportunity to maintain the necessary quality levels throughout the process. Typically the production volumes are high in order to achieve the high level of utilisation necessary to justify the investment, and the cost structures involved. Output changes are more difficult to arrange, due to the stepped-change nature of capacity changes.
To achieve low manufacturing cost, generally relatively high process capital investment is required. The volumes involved allow schedules of materials and components to be planned with associated buffer stocks to cover the uncertainty of supply. Work-in-process inventory will be low.
Although finished goods will tend to be high, many businesses will only make standard products against customer schedules, or on receipt of an order. Also, makers of products for which many optional extras are offered (for example, automobiles) will tend to have a policy of only making to a specific order. The high areas of cost tend to be in materials, bought-out components and plant overheads, with direct labour a relatively small part of the total.
Since the characteristic of the line process is that the output from each stage moves forward continuously, typically with high production volume, we need to focus on two aspects. The first aspect is to ensure that the production line runs smoothly without hiccups along the line, otherwise the process will cease. The other aspect is to ensure the process produces minimal defects along the way because there is no tolerance for substandard output to be reworked.
There are quite a few well-known techniques or concepts that address these two aspects. They include lean manufacturing, the theory of constraints, and Six Sigma.
Lean manufacturing is a "flow-focused" management philosophy focusing on the reduction of the seven wastes (over-production, waiting time, transport, over-processing, inventory, motion and scrap) in manufactured products. The theory of constraints is a "system-focused" concept that concentrates on the part of the overall process that slows the speed of product through the system. Six Sigma is a "problem-focused" quality management programme that identifies and corrects defects in the company's processes and products. Each of these is very appropriate for a line process and selection should depend on the nature of the most obvious problems in your current condition.
Next week, we will move on the last article in this series, about continuous processes.
