The Gantt Progress Chart
BY WALLACE CLARK
Purpose of the progress chart
The purpose of the Gantt Progress Chart is to show what progress is being made in the execution of a plan or program.
One of the fundamental principles of management was formulated by Gantt when he said: “The authority to issue an order involves the responsibility to see that it is executed.” It is obvious, therefore, that when an executive, i.e., anyone who has control over others, has Issued instructions that certain things are to be done, his next step is to provide a mechanism which will at all times keep him advised as to whether or not his orders are being carried out and, if the progress is not satisfactory, will tell him the reason why. The Gantt Progress Chart gives this information clearly and concisely and since the facts are presented in the relation to time, the chart induces action.
Some executives look back over their records at the end of a given period of time, possibly a year or a month, compare actual accomplishment with what they believed was possible, and conclude that the performance was either good or bad. It is the wise executive, however, it goes carefully over conditions at the beginning of any period, studies the tendencies, and decides then what performance will be satisfactory. This is his plan or schedule. Should there be, later on, a marked change in conditions which it was not possible for him to foresee, he will, of course make necessary alterations in the schedule.
In this way the executive relieves himself of the necessity of analyzing records every time a new figure is received, comparing it with other figures and deciding whether it is good or bad. Usually in the rush of business, comparison of this kind is likely to be done hastily, and the decision is up to be unwise. However, where the executive determines before hand what will be satisfactory to him, he is almost sure to study the matter thoroughly and to secure all the expert advice and accurate information available.
After the schedule is worked out, a comparison of accomplishment with the plan becomes Marili a clerical task; the executive’s time is saved and he is left free to study the tendencies and take the action indicated by the records.
The Value of the Gantt Progress Chart
In this phase of an executive’s work the Gantt Progress Chart is of Inestimable value. It’s used makes a definite plan necessary and presents that plan so clearly that it can be readily understood in detail and as a whole by the executive’s associates and subordinates. It compares the performance with the plan both as to time and amounts, and makes it possible for the executive to foresee future happenings with considerable accuracy. It shows what part of the work has been done in accordance with the schedule and emphasizes the reasons why performance has fallen short of the plan, fixing responsibility for its success or failure.
Usually it is not necessary for the higher executive to follow on progress charts all the details of the work being done under his direction, but he does wish to follow the progress of the work as a whole, which may be done by following key operations, typical items, or totals. If the progress made on one of these subdivisions of the work is satisfactory, he will pay a little attention to it, but if another part of the work is behind schedule, he will call for the detail charts in the hand of one of his subordinates. From these records he can see what particular items are being delayed and the reasons. He can then concentrate his efforts on that particular problem and, because of his broader authority and greater resourcefulness, may overcome difficulties which to his subordinates are insurmountable.
Saving Time for the Executive
This method makes it unnecessary for the general manager of a manufacturing plant, for instance, to wade through volumes of reports or to go the rounds of his superintendents or foremen in an attempt to find out what work is not progressing satisfactorily. His subordinates are likely to minimize the importance of some delays and on other items not to realize the effect a short delay will have on other work. Gantt charts emphasize the fact that time is the most important element in production – they bring to the attention of the general manager the things which are most urgent and hold his attention until he takes action and sees the results.
The progress chart also enables the general manager to know whether or not he will be able to live up to whatever promises of delivery he has made, for He knows that a reputation for keeping promises is one of the most valuable assets of any organization. Of course, the ability to make quick deliveries will frequently secure an order which would otherwise be lost, but quick deliveries depend entirely on the volume of work ahead. If a customer is continuously promise quick deliveries by a certain plant and much later deliveries by its competitors, the reputation of that plant will be injured rather than enhanced, for the customer is likely to conclude either that the poor quality of the product prevents the plant from securing orders or that another customer’s orders are being set aside for his. One impression is as detrimental as the other, for the customer knows that if another customer’s work is being set aside for his, it is probable that his work will be set aside for the next insistent customer.
It is clear, therefore, that a reputation for deliveries must be founded on the ability to live up to whatever promises are made. If a promise of a delivery is to be kept, all the work in a plant must be planned so accurately that, when a new order is received, it is possible to tell almost to a day when the work will be completed. The Gantt Progress Chart enables the manager to keep before him all the promises he has made, to concentrate his attention on overcoming obstacles and avoiding delays, and when it is impossible to live up to a promise, it enables him to give the customer advance notice of the fact.
Drawing the Progress Chart
Angles opening to the right and to the left indicate respectively when the work is to be begun and completed. The amount of work scheduled is shown by a figure at the left of the space and the amount to be done to date by a figure at the right of the space; light lines represent work done during any period of time and heavy lines the amount done to date, as explained in Figures 1, 2, 3 in Chapter I.
If work is done in a period of time for which no work was scheduled, it is shown by a figure in the middle of the space, for instance:
When the amount of work done is more than is scheduled, the light line is drawn across the space more than once, thus:
These lines are built up from the bottom to emphasize the fact that they belong to the heavy line below them. If no work was done in a period for which some was scheduled a Z (for zero) is placed in the middle of the space, thus:
A chart will look crowded if more than three light lines are drawn, so when the number of lines exceeds three, the figure is shown thus: (This indicates that the work done was seven times as great as the amount scheduled.)
Manufacturing in Order
In a plant which manufactures only on orders from its customers or its own sales organization, a promise of delivery is usually made on each order and each must be watched to see that the promise is kept. The Progress Chart of Crank Handles (Figure 24) was drawn in a plant where all orders were charted. The angle which opens to the right indicates the date on which the material was to be issued from stores; the figures indicate the dates on which the various operations are to be begun, that is, on the first line of the chart, 1 indicates that the first operation was to be begun on January 19, operation No. 2 on the 21st, etc.; the angle which opens to the left indicates the date on which the parts were to be shipped, the heavy line shows what operations have been done, and the letters under the lines indicate the reasons for delay.
The V indicates that this chart was reproduced on March 3. If the work had proceeded exactly according to schedule, the heavy lines would all end under that date except for those orders which were due to be completed before that date. However, the work had not made the expected progress; the third order on the sheet was a week behind schedule, the fifth about 2 weeks behind, the sixth 2 weeks ahead, and the seventh 10 days behind time.
From this chart the manager could see at a glance which orders were behind schedule. On the fifth order on the sheet, for instance, he could see that the eleventh operaion had been begun but not finished, and the R showed that the delay was caused by repairs. Reference to the shop order told the manager what that operation was and the department in which it was being done. Over the telephone he found out in detail from the foreman the repairs needed and the probably date when that operation would be finished. The chart showed how much more time would be needed for the remaining operations, so that the manager could take whatever action he deemed wise to rush the work and he could advise his customers as to the probable date of delivery.
In a plant where articles are manufactured continuously, the Progress Chart is, of course, somewhat different from that used in a plant which manufactures on order. The chart of Links Manufactured on Schedule (Figure 25) illustrates this.
On the first type of link, No. 467-BT it was found that the normal usage based on sales for the last two years with more weight given to recent months was 10,000 per month. The broken lines were the first ones entered on the chart; it was found that about 16,000 finished links were in stock, and accordingly a broken line was drawn through the first month and 60 per cent of the second month. It was also found that manufacturing orders were in the shop for 10,000 additional links, so a broken line was drawn through an amount of space representing 2.6 months, that is 1.6 months for the links in stock, which, of course, had been covered by past orders, and 1 month for the uncompleted orders. An inventory showed that there were in the storeroom 30,000 forgings besides the 26,000 links in process or in finished stock. Accordingly, a line was drawn through 5.6 months to represent 56,000 forgings and links.
During the month of June, 7,000 links were sold and a light line was, therefore, drawn through 70 per cent of the space, with a cumulative line of the same length. Also 12,000 links were received in stock, so a light line was drawn through 120 percent of the June space and a heavy line of equal length was added to the broken line. During the same month orders were placed for 27,500 links because the management had decided to build up a 4 months’ stock and after that to manufacture each month an amount equal to the sales of the previous month. No forgings were received that month so a Z was entered in the space.
During July and August, sales fell below the normal usage with the result that at the end of August, when the chart was reproduced, the difference between the cumulative line representing sales and the line representing receipts into stock showed the amount of links in stock, namely about 3 1/2 months’ supply. During August manufacturing orders had been entered which would bring into finished stock during September another month’s supply. It was evident, therefore, that there would be a 4 months’ supply on hand sometime in September, and accordingly no further manufacturing orders were placed. It was also evident that there were sufficient forgings on hand so that no further purchase orders were necessary.
On the next type of link, No. 1297-BP, the normal usage was 4,000 per month. When the chart was made up June 1, 5 months’ supply was already in stock with manufacturing orders placed for 15,000 more and forgings on hand sufficient to last up to October of the following year. The chart made it clear that it was unnecessary to place additional orders for the manufacture of links or for forgings.
At times a series of delays occur which interfere seriously with production, but it is difficult to get a comprehensive understanding of the situation from a table of figures and still more difficult to explain it to someone who is not familiar with the details.
During the latter part of the Great War, the Director of Arsenals considered the recuperators or recoil mechanisms, for the 75mm. field guns the most important work in American arsenals. There had been a number of delays on this work with various explanations given and finally the director asked to have the progress shown on a Gantt chart. Figure 26 shows the progress made during a certain week on the framework of the recuperator, usually called the “brake,” and compares that progress with the schedules.
A large machine shop had been erected and machine tools installed to manufacture these recuperators at the rate of 4 per day. The chart shows that on the first operation 5 wer done on Monday and Tuesday, 4 on Wednesday, and none the remainder of the week. The production for the week was, therefore, 2 1/2 out of 6 days. Going through the various operations it was evident at a glance that the principal delays were occuring on operations 4A and 5, planing, and on A6 and A7, reaming, and that on the remaining operations little or nothing was being done. This chart focused the attention of the management on those operations and made apparent to everyone concerned the relative importance of this delay.
The work of an office is usually more difficult to measure than that of a shop, but it can be done in nearly all cases. Office departments usually have a few things around which their other work revolves; in an advertising department, for instance, they have several individuals whose duty it is to get out the circular letters. It is easy to decide on a daily task of a certain number of letters. Another group in this same department may be answering inquiries, and since no one knows in advance how many inquiries will be received each day, no one can say how many should be answered. However, it is most important to have those inquiries handled promptly, so the real task of this group of people is to answer each day all the inquiries received. Their daily task is then expressed in numbers of inquiries received.
The daily tak in most office departments can be expressed in one of these two ways, i.e., b a definite quantity per day or by the amount of work received each day. Of course, it is impossible to get out at closing time, say, 5 o’clock, work which is not received until 10 minutes before 5, but the day for receiving work may be regarded as ending at 3 o’clock or possibly at noon, while the day for finishing work may not end until 5 o’clock.
In a purchasing department, for instance, the task may be to send out requests for quotations or purchase orders by 5 o’clock, covering all requisitions received up to 3 o’clock. The task of a stenographic department would be to transcribe before closing time all letters dictated before 4 o’clock. The filing department’s task would be to get into their proper places in the files all papers secured from the various office deparments at 9 o’clock that morning.
In order to get things done on time in an office, a department head or office manager must be kept advised continually and promptly as to whether or not those under his control are doing their work on time. It is also his duty to maintain a definite standard of quality in the work turned out, but that is not quite so difficult as to keep the work up to date. A Progress Chrt such as is illustrated in Figure 27 keeps an office manager accurately and promptly advised as to the status of work under his charge and enables him to give whatever assistance may be necessary to those behind schedule.