Fabric
yield estimates are an attempt to account for these components of
material utilization. More detailed and accurate itemization of
production processes in the estimate gives more accuracy. Less detail
and more averaging leads to less reliable estimates (a common approach,
for example, is making a sample size estimate marker and adding an
average percentage to the yield to account for all the other
components). Estimates are often done at three stages in the style
development process.
A design estimate may be made early in the
design phase to determine if the style can be produced profitably. This
is the least accurate "ballpark" estimate because the final
determination of patterning, fit, and fabric cuttable width and quality
may still be in development.
Once a style has been adopted as
part of a line a fabric purchase estimate is needed. Accuracy here is
very important since 25-40% of the cost of manufacturing will be spent
using this "yards per garment" number. Most of the components of
production yield are nearly in their final form, so good estimate
numbers are possible
That is, the pattern is close to final fit
approval and the fabric source/cuttable width/quality are available. The
fabric quality, in the form of an inspection report from the mill, can
be converted into an anticipated damage percentage that will be cut out
in spreading (more on this later). While a significant percentage of
sales numbers are still missing, if any at all are available, past
season's sales percentages by size are available for a similar style and
are a sound basis for yield estimate calculations
The final
estimated yield is made going into production in the form of a cut plan.
The cut plan can be made for a single order or for the entire season's
production on the style. Production markers are made to cut the
quantities sold in each size. They reflect the verified cuttable width
of the fabric. The historic or calculated damage cut out percentage is
added to the marker yield, as is the historic or standardized marker
section overlap allowance.
When final production units and
yardage used are recorded, this actual yield is compared to the design,
fabric purchase, and cut plan estimates to calculate the percent error
at each stage. Tracking estimate error allows gain/loss calculations and
the opportunity to identify improvements in the process.
Let's examine the methods available to estimate fabric yield and which are best applied to each type of program.
Duplicate
the production process. I worked for a children's wear screen printing
firm that sold only a few basic styles, in a fixed ratio, in a limited
number of fabrics, year after year.
Nearly all the components of
production yield were known and only the screen printing varied. We made
full sets of ratio production markers for fabric purchase estimates and
were very accurate in our estimates of final production usage. Due to
the simplicity of the patterns this was cost effective and could be done
within our design and production time schedule. Design estimates were
not needed as our production history provided the ballpark yields
needed. Cut plans were made on an order by order basis but not for the
season, since the fabric purchase estimates were very accurate. This was
an unusual situation as most companies cannot afford the time or cost
of fitting, grading, or production marking early in the production
cycle.
Use Graded patterns for estimate markers. Graded patterns
usually offer a more accurate way to estimate yield than using the
sample size pattern.
For example, look at an 8-18 size range with a sample size 10.
size 8 10 12 14 16 18
% of Production 8 17 25 25 17 8 = 100%
Sales Ratio 1 2 3 3 2 1
Using
a size 12-14 combination in the estimate marker has two advantages: 1)
these sizes represent 50% of production, and 2) they fall in the middle
of the size range and so they more accurately represent the yield of the
10-16 and 8-18 size combination production markers. To this "marker
yard per garment" yield can be added allowances for damage, overlap,
etc. For Local and CMT programs, the improved accuracy of the fabric
purchase estimate usually justifies the time and expense of grading. For
Package programs, the main question is how much work is going to be
done on patterning, if any, for the sake of evaluating bids and
negotiating fabric costs. The simple answer on this is - patterning is
worth it! More on this later.
Use sample size patterns for
estimate markers and average the other components of production. This is
one of the most common procedures but has serious limitations. In the
above 8-18 example the sample size 10 represents only 17% of production
and the marker layout does not represent the 12-14, 10-16, or 8-18
pattern arrangements. An average percentage can be added to the size 10
estimate marker to compensate for this discrepancy but there will be a
significant error in this averaging from fabric to fabric and style to
style, even within a body type. An additional source of error is that
most sales numbers do not occur in a convenient 1-2-3-3-2-1 ratio, as in
this example. For Local/CMT/Package programs, marking a sample size
pattern and adding a lumped average percentage (representing grading,
damages, etc.) at any stage of estimating yield leads to a high error
rate that can be avoided.
Estimate yield using a similar style
from a previous season that has a known production yield. Without a
pattern, the accuracy of the estimate gets even more erratic. Small
patterning differences can cause larger than expected yield variances. A
review of 17 styles of women's 5-pocket jeans all marked at 61.5"
showed final production yields from 1.11 to 1.32 yards per garment - a
19% difference! Trying to mathematically convert the yield of a similar
style marked at one width (e.g. 62") to a new style at a different width
(e.g. 54") will skew the results further. With Package programs the R/M
that chooses not to develop a patterned estimate is vulnerable to
overcharges on fabric. A company recently approached me saying that by
evaluating bids based on similar styles their average negotiated fabric
cost was 15% high.NNNNN is
a new offering to the apparel industry that accurately estimates fabric
yield by itemizing all the components of production into its
calculation. The accuracy of the results depends on the quality of the
data entered. If the seven components of final production consumption,
listed above, are used with a sample size estimate marker the results
can be accurate to within one percent of the actual final production
consumption. If a "block" or non-final-fit pattern is used and averages
are itemized for each of the other components the error can be held to
under five percent, on the average. The fabric purchase estimate for
Local/CMT/Package programs will fall within a 1-5% error depending on
the accuracy of the data input. The software also includes a conversion
program in which the damage cut out percentage is calculated by
inputting a fabric inspection report; a useful tool since inspection
reports are readily available from fabric mills and damage cut out
percentages vary widely.
Using the infant's wear example below in
the size range Small-5XL with a sample size Medium estimate marker, it
becomes easier to see how this process is better than the others.
Size S M L XL 2XL 3XL 4XL 5XL
% of Production 6 9 18 19 16 15 11 6 = 100%
Pattern Grade % 9 0 8 17 26 35 42 48
Using
any simple combination of graded sizes, much less the sample size, in
an estimate marker will not adequately represent the pattern grade or
the distribution of production within the size range. With Estmarktm,
each percentage of pattern grade and unit distribution within the size
range is used in the calculation, so there is no averaging. The
resulting estimated yield can only be improved on by making a full set
of production markers.
NNNNN is a tool for
Retailers/Manufacturers/Import Brokers/Contractors to achieve a
fact-based partnership. The calculated yield is as accurate as it can be
using the best data available at the time. If any of the items in the
calculation change (e.g., fabric width/quality or patterning), the
itemized process provides the fact-based recalculation format for any
yield adjustment
No comments:
Post a Comment