LEATHER - CALCULATION FOR MATERIAL ALLOWANCE PART 1

CALCULATION OF MATERIAL ALLOWANCE (LEATHER)

There are various method to calculate “material allowance” as shoe manufacturer need to predetermine the consumption of upper and linning leather required for a particular design and type of leather.

Whenever we talk about anything which is to be found as required there is always a objective behind it. So, if we are calculating Material allowance what is the objective behind it is

1.     To obtain accuracy due to which cutting results in minimum wastage

2.     Consistency between material types

3.     Consistency between styles and shoe sizes

Why it is important to get an accurate figure?

= as when we are calculating the MATERIAL ALLOWANCE of the upper material which constitute the largest single item in the cost of material thus we calculate for a large amount the single digit inaccurate figure can result is a large amount of loss

= thus, the profit percentage depends on accurate costing

= this also results for the clicker as calculation include the clicker allowance too.

For all these many methods have been developed have a look on it.

SYSTEM AVAILABLE

1.     Marking up

2.     Graphical

3.     RSM

4.     SLM

5.     SATRA Summ

MARKING UP:

       This a very old and simple method of calculation. In this method a cutting department supervisor selects a skin or hide from a bundle of leather depending on the style of article. And according to styles the patters are handed over to the cutting person by using the patterns they traced them on the leather (which can be done on both the side of leather flesh as well as grain side but mainly done on flesh side so there should be no issue of cleaning in this case a percentage is usually added that reflects the amount of wastage at the grain side because many defects cannot be seen on the flesh.) surface which should be done according to the cutting principle and quality requirements. Keeping in mind that the complete pairs should be drawn as far as possible and an allowance is calculated b dividing the are of skin by the number of pairs obtained from mark-up.

As every method has its own advantages and disadvantages let have a look on .

ADVANTAGES:

·       Cutting principles are followed

·       The allowance calculation is justified as done one by one and by the cutters.

·       A very accurate method if the marking person is skilled and the skin of the leather is truly representative.

DISADVANTAGE:

·       The worker should be skilled and trustworthy.

·       Time consuming depending on the style if having a more no of patterns.

·       It may not result in proper result as a rather getting complete pair a cutter can cut more no of vamp and at same skin another cutter can cut more number of quarter.

·       As it is not a particular standard system consisting same step to be performed by everyone thus may result in different results for different individuals.

GRAPHICAL:

As the name itself says something related to the graphs. In this system a complete pattern of one pair of a particular style are traced on the graph sheet is most compact and economical arrangement with the best possible interlocking between the Patterns. Then this is enclosed in the quadrilateral can be rectangle or square depending upon interlocking.

Sometimes the sides of quadrilateral cuts the pattern but it is assumed that the part could be placed in the gaps within the quadrilateral.

After this find the area of the enclosed figure thus which gives the area covered by the pattern traced. After adding a specific percentage to the area gives the allowance for the pair. The percentage depends and very according to the following:

• ·       Material type
• ·       Material quality
• ·       Average pattern area in relation to average material area
• ·       Variation in size and width fitting

ADVANTAGES:

·       Easy to use

·       Keeping the style same results the pattern to be same thus same allowance can be used for different material, quality, and sizes.

·       One time calculation and its permanently recorded

·       Less skill required than marking up method

DISADVANTAGES:

·       It is subjective because the original quadrilateral are could vary significantly depending on the interlocking skill of the assessor.

·       The percentage applied are based on previous cutting history which may reflects uneconomical cutting

·       As sometimes their would be project with different material so an estimate has to be made

·       As a complete pair is traced on together but on leather the vamp is been cut on only but side which does not reflects the usual cutting practice

R.S.M:

           This was the first serious scientific method developed and published in 1922 by W.W.RUSS and F. L. SMALL. In this system you can perfectly define the factors affecting the cutting practice Thus can give a adequate accurate result thus have more advantages than any other method or system.

The factors which affect the cutting results or we can say that the factors which we have to keep in mind while calculating are mentioned below-

I. Pattern Area-

The pattern area is nothing but the net which is covered by the upper pattern when traced including the interlocking waste(first waste). Also called as scale area.

The first waste is actually the space left between the two patterns while interlocking due to their irregular shape.

II. second waste-

This waste is additional to first waste. And it depends on the following factors:

a)     The shape of the skin to be used, because as we know the pattern shape is irregular so it not cover the outline of the skin completely so after proper tracing also their will some are left which cannot be used or as a edge is not usable.

b)     Size of the skin as no of traced patter increases the interlocking waste also decreases and also the edge waste so as the area of the skin increases the waste decreases and vice-versa.

c)     And as usual cutting process the certain pattern should be traced in a fixed area of the skin, the direction should be seen according to the tightness and stretchness of the skin, matching the shade of the two same components  all these reason may destroy the  interlocking arrangement of the pattern

Pattern scale are when added to the second waste the reluctant allowance is called GROSS AREA(G). for calculating G  we have certain formula which also changes as depends on different kinds of leather.

REFERENCE:

FDDI (FOOTWEAR DESIGNING AND DEVELOPMENT INSTITUTE)HANDOUTS

IMAGES

FDDI (FOOTWEAR DESIGNING AND DEVELOPMENT INSTITUTE) HANDOUTS