Types of Sewing Machines and Their Functions

Introduction:
Sewing is the process of stitch formation involving needle and thread. Sewing machines are textile machinery employed to stitch fabric or other material together with thread. Sewing machines were invented during the first industrial revolution to decrease the amount of manual sewing work performed in clothing companies.

The efficiency and quality of a particular sewing operation depends directly on selecting the proper sewing machine and accessories. It is important to be familiar with the technical characteristics of various sewing machines, in order to decide what kind of machine is adequate for a particular operation, or which operation will be performed in the best manner on a particular sewing machine.

Industrial sewing machines differentiate themselves from home sewing machines by varieties of bed and feed type, computerized functions and the possibility of integrating the work aids. While the bed types of sewing machines are important for optimized handling, the feed types enable uncompromised quality, computerization eliminates non-value-added elements and work aids de-skill the operation. Complete automation in sewing is limited due to difficulty in handling the limp dimensionally unstable material in 3D space. The cyclic sewing machines and sewing automats are primarily batch processes and concentrate on effective utilization of operators by deploying a lower person-to-machine ratio.

Classification of Sewing Machines:
Sewing machines are normally considered general working and from the perspective of its technical features sewing machines could be classified as shown in Figure-1.

1. Basic sewing machines comprise machines that sew with a lock stitch and multi-thread chain stitch. These are mainly intended for attaching garment components that are not exposed to high amounts of loads during wear using a lock stitch. Garment components that undergo higher load during wear require basic sewing machines that utilize multi-thread chain stitch.
2. Special sewing machines are proposed for specific technological operations and they can be categorized by (i) function, such as machines for pocket piping, sewing zips, knitted fabrics, etc. and (ii) stitch class and types except 301 and 401 stitch types, with blind stitch, zigzag stitch, for attaching pocket bags, etc.
3. Sewing automata are sophisticated specialized machines. The key features of these kinds of machines are its capability to perform automatic sewing when the fabric is positioned and the machine is actuated, cut the thread after sewing, release the fabric, etc.
4. Sewing systems are under advanced sewing machines. They have all the features of sewing automata and facilitate the automatic performances of two or more sub-operations.
5. Numerical-controlled sewing machines are machines where the fabric is guided automatically as in the case of sewing automata and sewing systems, but which follows a predetermined seam contour line. The numerical data are stored in the memory of a computer.
6. Robotic sewing systems have a multifunctional manipulator, where reprogramming and designing possibilities can be enabled for easy sewing.

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Sewing Machines Classification Based on Its Bed Type:
Sewing machines are mainly classified based on the bed type. The machine bed is the lower part of the machine and feed dog and loopers are positioned beneath it. The difference in bed types is attributed to the way the fabric moves with respect to the bed while being sewed. Table-1 shows the various kinds of machine beds along with their uses.

The major bed type categories are the horizontal and vertical bed. The categories are based on the plane of the fabric sewing. The different types under each category are given in Figure 2. Some sewing machines are made in more than one bed types based on the production requirements.

The bed of a sewing machine is that part of the sewing machine on (or against) which the fabric rests while it is being sewn. The classification of sewing machines bed types or shape types is done based on the manner in which the fabric falls, behaves and travels with respect to the bed during the course of sewing, to enable easier movement of materials around the machine.

Table-1: Sewing machine classification based on its bed type

Sewing Machine	Picture	Features and Applications	Stitch Type
Flat-bed machine		A vast working space permits a wide range of sewing applications and is utilized for all types of flat sewing work.	Lock and chain stitch
Raised bed machine		The machine bed is in the form of a pedestal which helps in assembling of presewn parts. This is specifically used for attachment of accessories and special attachments.	Lock and chain stitch
Post bed machine		It has a raised working machine bed and is used for stitching of three dimensional products such as shoes and bags.	Lock and chain stitch
Cylinder bed machine		It has a horizontal arm-shaped bed as well as increased working height. It is most suited for sewing tubular components like sleeves, cuffs and trouser legs, and can also be utilized for button sewing and bar tacking.	Lock and chain stitch
Side bed machine or feed off the arm sewing machine		These are dedicated for edge sewing and requires a lesser working space	Chain and over-edge stitch

Classification of Sewing Machines Based on Machine Type:
The sewing machine classification based on the machine type is given in Table-2.

Table-2: Classification of sewing machine based on machine type

Different Feed Types in Industrial Sewing Machines:
Feed system, feed types and feed mechanisms are interchangeably used terminologies in different literature. The universally used feed system in sewing machines for fashion and commodity apparel manufacture is called drop oscillation feed or simply the drop feed from the bottom, which accounts for more than 90% of sewing machines installed in factories. The machine parts responsible for feeding from the bottom are drop oscillating feed dog and belt, while parts responsible for feeding from the top are needle, puller, rotary presser foot, walking (oscillating) toothed presser foot and belt. There are various feed types of sewing machine, they are given below.

Drop feed (bottom feed) sewing machine:
The three sewing machine parts that together constitute the drop-feed mechanism are presser foot, throat plate and feed dog. In a drop-feed system, the feed dog feeds the fabric from the bottom while the needle is up (Figure-3). As only the bottom ply is in contact with the teeth of the feed dog and the top ply is expected to slide (along with the bottom ply) below the presser foot with negligible friction, there is no positive binding force between both the plies.

Depending on the surface characteristics of fabric, the drop-feed system is subjected to severe inter-ply slippage (for slippery fabric or fabrics with very low frictional value) or negligible inter-ply slippage (for very high surface frictional value).

When the needle is up and stitch tightening is taking place, the feed dog is also up and the fabric is being supported from the top by the presser foot and at the bottom by the feed dog; therefore, there is no possibility of fabric being bulged by the tension of sewing thread, and drop feed is considered universally as the most suitable for sewing lightweight fabrics.

When two or more thicknesses of fabrics are being sewn, regardless of whether they are separate fabrics or folded sections of the same fabrics, the problem arises that friction between the bottom ply and the feed dog is greater than that between intervening plies. The tendency of the lower ply satisfactorily moving ahead with the feed dog and the upper ply being retarded by the presser foot is known as inter-ply shift, differential feeding pucker or just feeding pucker.

Needle feed (compound feed) sewing machine:
A compound feed is the combined simultaneous feed action of a needle feed and drop oscillation feed and is useful for sewing with a low inter-ply frictional co-efficient. In a compound feed system, the needle and feed dog together feed the fabric while the needle is down and inside the fabric (Figure-4). The needle moves in the direction of the stitch in a pendulum action (the tip of the needle is actually moving in an arc). As the fabric is transported by the feed dog from the bottom while needle is inside the fabric, there is controlled inter-ply slippage. As the needle movement arc length is small (0.083 inches for 12 SPI) and the fabric layer thickness being sewn is also negligible, the resultant inter-ply slippage is negligible to be noticed in sewn material.

However, when the needle is up and stitch tightening is taking place, the feed dog is down and fabric is not being supported from the bottom by the feed dog, and therefore there is a possibility of fabric being bulged/buckled by the tension of sewing thread in case there is not enough stiffness in the fabric plies. Although compound feed can control inter-ply slippage in thick material sewing (car seat cover, shoes, upholstery, luggage, etc.), it cannot be used for lightweight fabrics.

Compound feed is used to eliminate inter-ply slippage in multiple-ply sewing of thick materials, negotiating the corner of acute-angle-shaped components while top stitching at the edges. Generally double-needle lockstitch machines have a needlefeed system.

Unison feed sewing machine:
The feed dog, needle and presser foot all move together to feed the fabric while the needle has penetrated inside the fabric plies. The presser foot is split into two parts; one part has teeth beneath and moves in direction of feed while the other part moves only up and down and holds the fabric in between feed strokes, that is during stitch formation (Figure-5). Unison feed is used for sewing multiple plies of thick materials like tarpaulin fabric, polyvinyl chloride (PVC) and leather. It helps to do consistent sewing over cross-over seams of all types of thick materials without pitch errors (no stitch gathering or stitch elongation). It is used for sewing car seat covers, luggage, furniture using leather, PVC or other spongy thick fabrics, particularly in piping and binding-tape attachment processes.

Differential drop feed sewing machine:
Here two feed dogs are arranged in a series differential position in which the feed dog lengths follow one another in a straight line, one behind the needle and another in front of the needle (Figure-6). The rear feed dog (away from the operator) is called the main feed dog while the front feed dog (closer to the operator) is called the differential feed dog. When the differential feed dog takes longer or faster strokes than the main feed dog, the fabric will receive a linear compression force, and vice versa. The amount of feed by two feed dogs can be independently adjusted. Generally all overlock and/or cover stitch sewing machines have a differential feed system. In all areas where fabric is prone to stretch during sewing (diagonal and curved edges), differential feed ensures forced compression of fabric, which counterbalances the stretch and ensures correct shape and size of the seam.

Variable top and bottom feed:
One feeding foot at top and one feed dog below the throat plate feed the fabric plies together. The bottom of the feeding foot has a toothed surface. Feeding takes place while the needle is outside the fabric plies. Here, the top feed and bottom feed amounts can be independently adjusted to create inter-ply slackness or tension in the fabric being sewn. The presser foot is in two sections, one holding the fabric in position while the stitch is being formed and the other having teeth on the lower side and moving or walking in such a way that the top ply is taken along positively while the needle is out of the material (Figure-7). Positive control of the top ply allows for adjustments so that the fabric plies will either be fed through exactly together or, if required, the top ply is gathered into the bottom ply.

The feeding foot works before the needle to create a gather in the top ply, for example giving fullness while sleeve setting in the armhole of a blazer, and works behind the needle to create smooth seams, for example centring the back seam of blazer. The feed difference that can be created between top and bottom ply at best create fullness but cannot create visible gathers in one ply.

Variable top and bottom differential feed:
One feeding foot at the top and two feed dogs (like differential feed) below the throat plate feed the fabric plies together. The bottom of the feeding foot has teeth underneath. Feeding takes place while the needle is outside the fabric plies (Figure-8). This mechanism enables sewing two plies with the top ply gathering while the bottom ply remains flat. Here the feed difference that can be created between the top and bottom plies at the best creates visible gathers in one ply. This feed system is available with an overedging machine; a long panel join in skirts with a smooth flat seam without inter-ply slippage is possible, as well as a waistline join in a dress with a bottom ply gathered and sewn with a smaller bodice block.

Bottom feed and alternating drop feed:
One feeding foot at top and one feed dog below the throat plate moves in synchronization to feed the fabric plies together. The bottom of the feeding foot has teeth beneath. Feeding takes place while the needle is outside the fabric plies. The presser moves up and down alternatively with the feeding foot. This feed system is used for difficult-to-feed materials and multilayered portions of medium and heavyweight material like synthetic leather products, vinyl coating products, leather products, rubber clothing and sponge clothing, with great precision. There is no irregular feed pitch due to positive feeding from both top and bottom plies.

X-feed sewing machine:
X-feed from Typical Corporation is characterized by needle feed and alternating drop feed. The feed dog is split into two independent feed dogs; the central one has a needle hole and acts like a needle feed, and the side one acts like a drop feed. During the first half of stitch length, the needle enters the material and also through the hole of the central feed dog (which is in ‘up’) and transports the fabric just like the compound feed mechanism; the side feed dog is below the throat plate level (Figure-9(a) and (b)).

When the needle is leaving the material and going up, the central feed dog goes down and the side feed dog comes up and transports the material in the sewing direction just like the drop-feed mechanism. As the side feed dog is transporting the material in the sewing direction, the thread take-up lever is pulling the thread, an effect that stretches the stitch like on a puller machine. Due to the alternating movement of both feed dogs, material transport is continuous and calm in comparison to the intermittent feeding of drop feeding.

The X-feed claims to sew with 35% lower thread tension, which results in a flatter and pucker-free seam appearance, and the occurrence of ply slippage is also significantly lower in X-feed than in drop feed.

Special Types of Sewing Machines:

Overlock machine:
It sews over the edge of the fabric plies for edge neatening, hemming or seaming. Generally, an overlock machine called a ‘sergers’ (Figure 10) will trim the fabric edges during sewing using cutters. The addition of automated cutters ensures these machines to produce a finished seam easily and quickly.

It uses a bottom thread known as a looper thread fed by larger size cones compared to smaller size bobbins in the case of lock stitch machines. The loopers provide thread loops that pass from the needle thread to the fabric edges thereby raw edges are enclosed within the seam. Overlock sewing machines are normally run at high speeds, from 1000 to 9000 rpm.

Single needle lock stitch machine:
These kinds of sewing machines are generally used for sewing fabric, leather, etc. particularly one that uses two threads such as an upper and a lower thread. Figure 11 shows the single needle lock stitch machine. The one side of the needle has the eye and a sharp tip while the other side is attached to a needle bar that moves up and down to form a stitch. The arm also secures a presser foot which presses the fabric while sewing. The needle penetrates into the fabric from the top, to bring the needle thread through the fabric to the bottom to form a stitch.

The needle thread in a spool is threaded through the thread guides, tensioning mechanism and into the sewing needle eye. The bottom thread (bobbin thread) is wound onto the small package called a bobbin before sewing and is secured inside a bobbin case. For stitch formation, the needle brings the needle thread loop to the bottom of the fabric where a small hook on the bobbin case catches it. As the bobbin hook rotates, it takes the needle thread around the bobbin to produce a stitch and then the take-up lever takes back the extra loop of top thread to tighten the stitch. As the needle is out of action of fabric, the feed dog comes above the throat plate, and pushes or moves the fabric up against the presser foot for next stitch.

Double needle lock stitch machine:
This machine (Figure 12) is similar to a single needle lock stitch machine; however, here all items have two sets, that is, two sets of bobbin case, tensioner, take up lever, thread guides, spool pin, needle holders, etc. In this machine, the bobbin case is fixed compared to a removable one in the case of a single needle lock stitch machine. It has a synchronous tooth belt for driving, a knob-type stitch regulator and a plunger pump for lubricating. These kinds of machines are suitable for stitching shirts, uniforms, jeans, overcoats or similar clothing.

Cyclic sewing machines:
Cyclic sewing machines complete the sewing work in a short automatic cycle thus the name cycle, cyclic or automatic. In these machines, the needle moves only up and down to form the stitch, and the clamp feed moves the fabric horizontally (x-axis) or vertically (y-axis), creating the required shape. The movement of the clamp is controlled by a cam-follower mechanism or electronics. In an electronic machine, the movement of the cam is controlled by a microprocessor, and thus a different pattern and/or shape of tacks can be sewn easily by changing the program in the microprocessor.

Button-sewing machines:
A button sewing machine (Figure 13) is used to sew the button in the garment without damaging it. Various types of buttons like a button with two
holes, four holes or shank could be sewn on this machine by making simple adjustments. These are either single chain-stitch (107 type) or lockstitch (304 type) machine heads where the fabric is placed over the cloth clamp and button is placed in the button clamp. Once the operator starts the machine the button clamp comes down and touches the cloth clamp; the button and cloth clamp together moves horizontally and vertically as per cam-follower or microprocessor movement and at the end of the cycle the thread is cut and the empty button clamp move up to the original position for sewing the next button.

Button with thread shank can be created by placing a spacing finger over the button during sewing (Figure-9), for shank button the button is clamped on its side and the needle passes alternately into the garment and then into the hole in the shank and into the garment.

Buttonhole machines:
Buttonhole machines are used for creating buttonholes in the garment and to finish the edges. A buttonhole machine as shown in Figure 14. Buttonhole-sewing machines have either lockstitch zigzag (304 type) or double chainstitch zigzag (404) machine head where the fabric is placed over the cloth clamp. Once the operator starts the machine, the fabric-holding frame comes down and grips the fabric against the clamp and movement of the clamp starts. A buttonhole is formed by a series of zigzag stitches with varying degrees of needle throw-in synchronization with xey axis clamp movement. The hole in the buttonhole is created by slashing / cutting fabric either after sewing or before sewing. In an ordinary straight buttonhole (shirts and blouses), once the sewing cycle is complete the knife comes down to slash the center of the buttonhole e called the cut-after mechanism. In knitwear, often buttonholes get distorted after washing; the appearance can be improved by doing stay stitching around the proposed cut area at the beginning of the sewing cycle. A stay stitch acts as reinforcement and stiffens the area around the cut.

Buttonhole Sewing Machine Types:
The buttonhole sewing machines are categorized based on the following:
1. Stitch type such as lock stitch or chain stitch machines
2. Size and shape of the buttonhole
3. Method of creating buttonholes

1. Button hole cut before stitch – The button hole is cut first and then finished with stitches. The stitches radiate from the center to the outer edge of the buttonhole. It gives a neat appearance as the sewing thread covers raw edges of the hole effectively.
2. Button hole cut after stitch – As the name indicates, the buttonhole edges are finished first and then slashed. It is created by a continuous line of sewing around the end and then the hole is cut subsequently.

4. Presence or absence of gimp

Blind stitch sewing machine:
A blind stitch machine (Figure 15) is used for hem stitching in a knitted fabric since the hem stitch is too small in the right side of the garment and is invisible. In a few circumstances, the machine could be set to skip a stitch that is to pick up the fabric on alternate stitches only. But this type reduces the stability of the stitches.

The sewing needle utilized for this machine is a curved one because it does not pierce through the fabric fully, but partially. Based on the application and type of fabric, the blind stitch can be grouped into two types; for fine fabric producing long and narrow stitches and for heavy fabric with short and wide stitches.

Pattern-tacking machines:
Pattern-tacking machines have a lock stitch zigzag (304 type) machine head where the fabric is placed over the cloth clamp. The machine sews a pre-determined number of stitches in a particular shape or pattern using a combination of lockstitch and zigzag. The most common shape for cam-follower-driven machines is a small ‘bar’ or ‘I’, used to reinforce stress points like pocket openings and zip openings; thus the name of these machines was ‘bar-tacking machines’. The microprocessor-controlled machine can create any shape and therefore the name of the machine changed to the more generic pattern-tacking machine. Figure-16 shows sewing of a cross-tacking in a pattern-sewing machine. The cost of these machines depends on the maximum size of the tack and corresponding clamp size. Machines are available from approximately 6 cm2 to 4 m2 stitch area.

Feed off arm sewing machine:
A feed-off-arm bed is a cylindrical sewing machine frame that permits joining of two opposite edges of a flat-shaped fabric to create a hollow cylindrical-shaped item. It is used to stitch a tubular seam of narrow width on the edge of shirts and trousers (Figure 17). It is particularly utilized for sewing a lapped seam which has to be closed such that the garment panels become a tube-like structure. These machines are common for sewing outside leg seams in jeans where the lap felled seam is used.

Bar tack sewing machine:
The bar tacking sewing machine shown in Figure 18 is used for sewing dense tack around the open end of the buttonhole. These machines are used to make more tight stitches across the point to be reinforced and then sew covering stitches at a right angle over the first stitches.

The applications of the bar tack machine in the garment industry are given below.

• Closing of buttonhole end.
• Reinforcing the ends of pocket opening.
• Sewing on belt loops.

Classification of Computerized Sewing Machines:
Computerized sewing machines have small monitor displays for easier operation. A computer is used to control several different motors – precisely move the needle bar, the tensioning discs, the feed dog and other sewing machine parts. The computer controls all these fine controls, so it is possible to produce hundreds of various stitches. With the motor, the computer controls the right speed to move the needle bar up and down from side to side in a particular stitch pattern. We have published a complete article on computerized sewing machine. You can read below:

References:

1. Apparel Manufacturing Technology by T. Karthik, P. Ganesan, and D. Gopalakrishnan
2. Garment Manufacturing Technology by Rajkishore Nayak and Rajiv Padhye
3. Design of Clothing Manufacturing Processes: A Systematic Approach to Planning, Scheduling and Control
   Edited by Jelka Geršak
4. Apparel Machinery and Equipments by R.Rathinamoorthy and R. Surjit