Warp Knitted Fabrics Construction

Yordan Kyosev

• Publisher: CRC Press
• Year: 2019
• Print ISBN: 9781498780162
• eBook ISBN: 9780429532689
• Topic: Technology & Engineering
• Subtopic: Industrial Engineering
• Index: Technology & Engineering

The aim of this book is to provide the background of the warp knitting patterning with a large amount of simulated 3D images of the structures, corresponding to the modern available tools for this. The warp knitted structures can have very complex architectures and very limited understanding exists on how they are built. The pattern book will allow

Part I

Fundamentals of warp knitting

1

Warp knitting process fundamentals

1.1 Introduction

This chapter provides information about the warp knitting process, limited to the patterning related topics. More details about the knitting process, the working cycle of the machine, different configurations of machine elements and so on can be found in several books such as [4], [24], [26], [18].

1.2 Knitting process and pattern notation

Each warp yarn, used for production of warp knitted fabrics, is formed from a single guide. Several guides are grouped into guide bar, as shown in Figure 1.1. Each guide bar moves around the needles and places the yarn over, between and after or behind these during the production process. The needles, the spaces between them and the guides are numbered, starting from the side, where their pattern drive (cam, chain links, electronic drive) is mounted. Usually, the pattern drive is placed on the right hand side of the machine and the needles, and the guides are numbered from right to the left. For the graphical notation of the warp knitted structures, the complete motion process of the guides is recorded symbolically on paper. For this notation, the person has to assume, that is looking at the needles from the top (Figure 1.1 upper picture), but for simplification, only the needle cross section is drawn as a thick point. For each knitting cycle, one row with points and spaces between these is used.

FIGURE 1.1 Notation principle of the warp knitting pattern.

Let the guide bar have only one yarn on its guide number one (Figure 1.2). During the knitting process, the guide moves between the needles and this motion step is named “swing in”-the needles motion. The gab number, where the first guide of one bar is swinging-in, is used for numerical notation of this motion step; in the case of Figure 1.2, this is the number 3. On the drawing, a short line (or curve) between the dots is drawn.

FIGURE 1.2 Swing in motion step.

After the placing the yarn(s) between the needles the guide bar is moving to left or right in the front of the needles, placing yarn over them - overlapping (Figure 1.3). The overlapping is a shog over one or seldom over two needles. The limitation to one or two needles is based on the need of the yarn length for the loop building process. If yarn is placed over more than two needles, during building of the loops there will be not enough yarn length for more loop heads, legs and underlaps and the yarn will break. In pattern drawing this step is drawn as a small arrow or arc over the point. If no loop has to be built, then the guide bar stays there and does not perform any motion during this step.

FIGURE 1.3 Overlap - the motion of the guide bar placing yarns on the beard side of the needles.

The next step is the swing out - the guides are swinging through the gaps between the needles back. The gap number, where the first guide goes through is used for the numerical notation of the pattern, in the case of the Figure 1.4 this is the number two. On the drawing, this motion is represented by a short line or curve between the points.

FIGURE 1.4 Swing out - move the yarns back between the needles.

Finally, the guide bar moves behind the needles and the guides place their yarns “under” the needles (Figure 1.5). The motion is named underlap. This motion is not limited to one or two needles, because the yarn does not have to build loops on this side, and the required yarn length has to be taken from the beam. The limitation of the underlap motion is determined from the patterning device - it can be often not more than 32 gaps.

FIGURE 1.5 Underlap - place the yarns behind the needles.

After these four steps of the guide bars, the needle bar starts moving all the needles down. Theirs hook have to become closed. Depending on the needle type this happens as follow:

•the bearded needles become pressed during this period;

•the latch of the latch needle rotates, moved from the previous loop;

•the tongue of the compound needle moves and closes the hook.

The new placed yarn piece in this case remains in the needle hook and the previous loop can knock over it. After that, the needle bar moves up and the cycles start again. For each such cycle, the numbers of the swing-in and swing-out positions are notated, separated by m...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Contents
• Foreword
• Preface
• Author
• Symbols
• Part I: Fundamentals of warp knitting
• Part II: Loop based single face structures
• Part III: Single face structures with more structural elements
• Part IV: Structures from double needle bar machines
• Part V: Engineering design
• Bibliography
• Index