Pattern Area measurement: Manual method – Part 5
…Continued from Part-4
8. SLM: Scientific Leather Measurement was introduced to the shoe industry in early 1950s. It contain two separate components for allowance calculation i.e Pattern assessment and leather assessment.
This system will not use old records. Its own records of usages and areas of waste were established scientifically. The system will consider the ‘shoe size’ variable which helps for all individual cutting jobs. SLM involves the use of PLANIMETER ( Ex. Centiplan machine) to measure the patterns and first waste.
(Centiplan machine uses an electronic measuring system to determine the area of a pattern, including first waste i.e interlocking wastage. Place one pattern on the working surface of the machine and move the calculating head across the pattern. The machine automatically produces a mirror image of 2nd pattern and gives an instant read-out of the area of 2 patterns with interlocking waste.)
The system, therefore is in two parts:
- Pattern assessment
- Leather assessment
- Pattern assessment: This counts the: –
a) Interlocking wastage between patterns.
b) The wastage between different patterns.
c) The waste around the perimeter of the skin
This gives an allowance per pair assuming that the leather is 100% usable.
- Leather assessment: The final pattern allowance is influenced by “leather coefficient”. This leather co-efficient is established by combining by two parameters a) Cutting co-efficient” and b) Discrepancy co-efficient.
The cutting co-efficient is the amount of usable leather and of the total area of the skin (in %ge). The discrepancy co-efficient is the difference between the tanner’s quoted measure and the actual area measure. For example, assume there is a difference of 5 % between tanner quoted and actual area. In this case, pattern allowances increased by 5%.
SLM also consider the shoe size. An amount 5.3 % is considered between sizes.
In this system each pattern in the shoe set is measured separately. The pattern is drawn carefully on the paper and then “blocked off” by drawing straight line connecting highest points on the pattern perimeter. This gross area is measured and then the most economical interlocks are chosen and drawn into position. The interlocking pattern must be kept parallel or at 180o to the original. The area of interlocks falling within the gross area are measured, plus any shared wastage and a proportion of this area subtracted from the gross area. The result is known as the “Slim area” and this is used as basis for allowance calculation.
Slim area of all the components required to make one shoe and are added to get total slim area. Total slim area represents the area of leather necessary to cut all the upper components for one shoe. This in increased by a percentage based on the type of material (upper 10%, lining 7%). This is again increased by a percentage allowance (known as basic put-up) based on the number of pattern in one shoe, using table of allowance. A further percentage increased by an edge waste allowance, is obtained from the edge waste sheet and equivalence area sheet by selecting the foremost pattern known as the inner pattern and adding the slim area value of smallest pattern from edge sheet against the appropriate skin size.
The figure is doubled to find the allowances for 1 pair of model size upper assuming a leather coefficient of 100. Then added allowance for leather coefficient. Further percentage are added to allow for different shoe sizes and fittings.
SLM is a very successful system and widely adopted in shoe industry worldwide. It has been adapted and modified by individual companies to suit their particular needs. There is also a system for assessing the cutting value of the leather in use. Computer programs are written to make this part quicker and easier. SLM was sold as a commercial package designed to provide clickers with a leather saving bonus. Clickers were paid a proportion of the value of the material they saved. It is widely used, although often heavily modified.
a) The leather assessment components of the system is generally recognized as most accurate of all systems.
b) It has wide application possibilities covering most styles and materials.
c) Eliminates difficulties due to varying shoe size.
d) Improved material utilization giving substantial savings to management.
e) Has a scientific base and does not depend on past records.
a) Time consuming patterns assessment system.
b) Does not take into consideration adequately pattern or skin shape.
c) killed pattern and leather assessors required.
d) Bonus paid on individuals job “savings”, means a cutter can lose more leather than he saves and still receive some overall bonus.
e) Overall maintenance cost of the system greatly increased.