2.7 - Accuracy in design

P2 - Design + making

efficient use of material

• efficient material use take into account - when producing prototype or setting up commercial production line

• waste just be factored into costs of production

• financial and enviromental implications of waste - magnify as scale of production increases

tolerances

the acceptable variation in the size of a product, or part of a product

• usually given s an upper and lower limit

ensuring a high level of accuracy

• required to ensure final predicts are constructed to an agreed standard and perform well

• involves tolerances in production

tolerance levels

usually set within 2 measurements

• e.g. between 5-15mm

• written into the manufacturing specification

importance of tolerance

• determines the accuracy of construction

• varies depending on required performance of a product

• very fine tolerances are less important for textiles than other materials - can be hard otherwise achieve

• knits and fluid fabrics have a lot of give

• can change shape slightly during cutting and handling

variations in tolerances

• finer - in bespoke, made to measure garments = high precision needed for final fit

• low tolerance - for cutting and construction of sections that must fit togtehr successfully

• e.g. skirt waistband

• smaller - sections that need to fit together for visual appreciation

• e.g. applique

• high tolerance - sizing is less important, in soft furnishings like cushions

measuring tools

• more accurate measuring increases the quality

• tools to be used include

  • tape measure, metre ruler, set square, protractor, sewing gauge

pattern layouts

need to be calculates to find the amount of fabric required

• takes into account the most efficient method of cutting out pattern pieces

• commercial patterns includes layouts for different widths, one way designs, and naps

• common widths - 115cm, 140cm, 150cm

template

a pattern used to transfer a design shape onto fabric to ensure accuracy in cutting

matching fabrics

• naps, one way designs, stripes, checks or repeating patterns

• need to be cut in the way that ensures pieces match up

• pattern should be used to good effect

• normally requires extra fabric

seam allowance

• must include seam/hem allowances on any pattern templates

• for domestic patterns = normally 15mm

• slightly smaller seam allowances in large scale commercial production = more economical material use

cutting table

large table/flat surface that allows cutting of pattern pieces more accurately

• can try out different arrangements of pieces to achieve the most economical fit

tailors chalk

a fine piece of chalk or pencil used to mark on one side of fabric

• easily removable marks

• can use tracing paper and a tracing wheel - can leave difficult to remove marks on fabric

tailors tacks

temporary stitches used to mark out seam lines, dark positions or balance marks

• easily removed

• uses double thread

quality control in manufacture

• QC checks at different stages of production

• makes sure products meet agreed standards

• checkpoints can be written into manufacturing specifications

• ensures a logical sequence in the manufacturing process

product inspection

• quicker to check a sample of products as they are made (rather than every product)

• during inspection - samples analysed, adjustments made to rectify problems

• reasons for adjustments can vary

• e.g. fixing faulty equipment, further training of machinists

quality control - the inspection process

• analysis of sample

• feedback

• trace reason for problems

• establish reason for problems

• make adjustments

• products meet agreed standard

datum point

a fixed reference point from which other measurements are calculated

use of measuring aids

• datum points and various measuring tools

• helps ensure accurate markings

• essential to ensure pattern pieces will fit together

use of datum points

• fixed reference point

• e.g. selvage of fabric = a datum point for the direction for eh grain line

• when cutting out patterns must be parallel with grain line

• e.g. centre line of the garment in check fabric - ensuring checks line up

measuring tools - pattern master

a clear plastic ruler with curved and straight edges

• used to draw pattern templates accurately

measuring tools - set squares/protractors

used to measure and draw angles correctly

measuring tools - French curves

used to draw accurate curves

• like armholes and necklines