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Sewing Machines Stitch Fundamentals

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Sewing Machines Stitch Fundamentals

  1. 1. Presentation By : Kamran Ahmad Khan
  2. 2. The major components of a basic sewing machine include; 1- The casting 2- Lubrication systems 3- Stitch forming systems 4- Feeding systems The speed at which a machine can operate depends on the engineering of machine’s components.
  3. 3. 1- The Casting The machine casting is the metal form that provides the exterior shape to the machine. Shapes of machine can vary according to the type of bed and the sewing function that is to be performed and how piece goods are to be prepared. The casting houses the internal workings that operate the sewing and feeding mechanism.    Gears Shafts Cams The casting determines the bed type and location of the cloth plate. Bed Types        Flat Bed Semi Submerged Raised Bed Post Bed Off-the-arm Bed Cylinder Bed Long Arm Flat Bed
  4. 4. Flat bed Flatbed/ Fully Submerged Bed Types ideal for small parts and where positioning parts to the needle is a "slide" from the tabletop. Semi-Submerged Bed Semi-Submerged Bed Machine for assembly of medium to large parts. Raised Bed Raised Bed Machines where the entire machine is mounted on the top of the table. Used where you need the garment to drape away from the needle for better handling. Post Bed Post bed machine where the needle plate and foot are mounted on a tall post that facilitates sewing in tight spaces like inside sleeve cap, or shoes.
  5. 5. Off-the-Arm Bed Off-the-Arm Bed types facilitate sewing sleeve seams, inseam or out seams on Pant Legs, or other long seams in tight places. Cylinder Bed Cylinder Bed Machines for sewing around the end of Tubular Shapes such as Cuffs, Armholes and Round Neck Openings. Long Arm Flat Bed Long Arm Flat Bed for sewing large objects (Quilts, Upholstery, Flags, Sails, etc.)
  6. 6. 2-Lubrication System   Lubrication factors are the prime factors in maintenance, downtime, efficient operations and long life time of various parts of the machine. The mechanical parts of sewing machine like any other mechanical parts are need to be lubricated (oiled) to reduce friction and keep mechanical parts moving freely. High speed and temperature increase the need for lubrication because of increased friction. There are two types of lubrication systems available. Manual Automatic In the former case oiling is done manually. In these machines no special mechanism for oiling is present. These machines are also called as dry head machines. The conventional sewing machine at homes is also an example in which manually oiling is done.
  7. 7. In automatic oiling systems different parts work in combination with each other to ensure the effective supply of oil to the required parts like;  Oil Pump  Wick Felt Oil Gauge and oil sight window Oil distribution network (oil pipes)   
  8. 8. 3-Stitch Forming System Stitch forming system are the mechanical parts that when correctly synchronized forms stitches, seams and then stitching. Various stitch forming mechanism are:      Thread control devices ( thread guides and thread tensions). Needles Bobbin case, bobbin and hooks Loppers Spreaders Thread Control Devices Thread control devices include thread guides, thread tensions and take-ups which are necessary to provide uniform thread flow. Thread guides Thread guides control the position and movement of thread. Damaged or faulty thread guides can damage sewing thread and cause thread breakage.
  9. 9. Tension Devices Tension devices controls the flow and tension in the thread going to form a stitch. Tension in the thread determines the balance and tightness of a stitch. Tensioning devices consist of a pair of tension disks, a spring and a thumb nut that can be adjusted to control the ease with which thread passes between the disks. Thread take-ups Thread take up control the supply of thread required to form each stitch. It gives extra thread to the needle to form the stitch but takes it away to set the stitch. Needles Needles carry the thread through the fabric so a stitch can be sewn. Hook A hook is a rotating device encompassing the bobbin case that picks up the needle thread loop to form a lock stitch.
  10. 10. Loopers Loopers are available in different shapes respective of their machines. Looper may or may not carry the lower thread in the formation of stitch. As in case of flat lock lopper holds the lower thread but in case of single needle chain stitch it holds the needle thread. Spreader Spreader work in conjunction with a looper to assist in the loop formation. They in fact move the thread but did not carry the thread.
  11. 11. 4-Feeding System The material handling components of machine are also called as the feeding system. For a precise line of stitches to be formed fabric must be moved through the stitch forming area of the machine with accuracy and precision. The feeding system usually consists of the following parts:    The presser foot The throat plate Feeding mechanism The presser foot The presser foot is the upper part of the feeding mechanism. It is mainly responsible for applying pressure and proper holding of the fabric.
  12. 12. The presser foot also controls the amount of pressure as if light fabric is being sewed than more pressure will be implemented however if heavy fabric is being sewed than pressure in the presser foot is lowered to some extent. The throat plate Throat plate is a metal plate that is present directly under the needle. Throat plate has openings for needle and feed dogs. Feed Mechanism Feed mechanism control the direction of fabric movement and the amount of fabric movement for each stitch. Feed mechanism affect stitch length and the rate of travel.
  13. 13. Lock Stitch Machine
  14. 14. Lock Stitch Machine    A lock stitch is the most common mechanical stitch made by a sewing machine. A stitch made on a sewing machine by the interlocking of the upper thread (Needle) and the bobbin thread. Ideally, the lock stitch is formed in the center of the thickness of the material—that is to say: ideally the upper thread catches the lower thread in the middle of the material. The thread tension mechanisms, one for the upper thread and one for the lower thread, prevent either thread from pulling the catching point from out of the middle of the material.
  15. 15. Parts Of Lock Stitch Machine
  16. 16. Stitch Formation Of Lock Stitch Machine
  17. 17. Over Lock Machine
  18. 18. Over Lock Machine     An overlock stitch sews over the edge of one or two pieces of cloth for edging, hemming or seaming. Overlocking is also referred to as “overedging”, “merrowing” or “serging”. An overlock sewing machine differs from a lockstitch sewing machine in that it uses loopers fed by multiple thread cones rather than a bobbin. Loopers serve to create thread loops that pass from the needle thread to the edges of the fabric so that the edges of the fabric are contained within the seam.
  19. 19. Parts Of Over Lock Machine
  20. 20. Stitch Formation Of Over Lock Machine The upper looper is in its rightmost position. The needle begins its move from its lowest position and as it rises, the needle thread loop starts to be formed. In order to pick up the needle thread loop, the lower looper starts to move to the right from its leftmost position.
  21. 21. The needle continues to rise and the lower looper which has picked up the needle thread loop continues its motion to the right. The upper looper starts moving upwards.
  22. 22. The lower looper continues to move to the right, the upper looper picks up the lower looper thread while crossing the lower looper and continues to rise. The needle is approaching its highest point.
  23. 23. The upper looper is at its uppermost position. The needle has already started to descend and enter the triangle formed by upper looper thread. The lower looper has already started to move to the left.
  24. 24. The needle is at its lowest position, the lower looper is at its leftmost position. The upper looper continues to descend further. Repeating this sequence of actions form the seam.
  25. 25. Flat Lock Machine
  26. 26. Flat Lock Machine   Elements in Stitching › Needle › Looper › Spreader Multi Needle Machine can have more than three needles.
  27. 27. Parts Of Flat Lock Machine
  28. 28. Stitch Formation Of Flat Lock Machine
  29. 29. Lower looper scoops needle thread loop and simultaneously upper decorative looper scoops upper decorative thread.
  30. 30. Cloth is fed and only righthand needle is positioned in the outside of decorative thread. Two left-hand needles come down and scoop upper decorative thread.
  31. 31. Needle further come down and scoop lower looper thread. And Two right-hand needles enter in between the respective needle threads.
  32. 32. Needle thread comes off lower looper and needle comes down in its lowest position. Lower looper and upper decorative looper are in the most retracted positions.
  33. 33. 4-Feeding Systems Feeding mechanisms are of 8 types • • • • • • • • Drop Feed Differential feed Needle Feed Adjustable Top Feed Compound Feed Puller Feed Walking Foot Feed Manual Feed (A manual feed is used primarily in freehand embroidery, quilting, and shoe repair.)
  34. 34. Drop Feed When the needle is withdrawn from the material being sewn, a set of “Feed Dogs" is pushed up through slots in the machine surface, then dragged horizontally past the needle. The dogs are serrated to grip the material, and a "presser foot" is used to keep the material in contact with the dogs. At the end of their horizontal motion, the dogs are lowered again and returned to their original position while the needle makes its next pass through the material. While the needle is in the material, there is no feed action.
  35. 35. Differential Feed Differential feed is a variation of drop feed with two independent sets of dogs, one before and one after the needle. By changing their relative motions, these sets of dogs can be used to stretch or compress the material in the vicinity of the needle. This is extremely useful when sewing stretchy material, and overlock machines (heavily used for such materials) frequently have differential feed.
  36. 36. Needle Feed A needle feed, used only in industrial machines, moves the material while the needle is in the material. In fact, the needle may be the primary feeding force. Some implementations of needle feed rock the axis of needle motion back and forth, while other implementations keep the axis vertical while moving it forward and back. In both cases, there is no feed action while the needle is out of the material. Needle feed is often used in conjunction with a modified drop feed, and is very common on industrial two needle machines. Used mainly for Quilting purposes.
  37. 37. Adjustable Top Feed The general arrangements of such feeding systems is that the presser foot is in two sections, one holding the fabric in the position while the needle forms the stitch and other having teeth on lower side and moving in such a way that the top ply is taken along the positively while the needle is out of the material. It can be used on the machines for light weight fabrics with no inter ply shifts.
  38. 38. Unison Feed Unison feed is a combination of feeding mechanisms which provide needle feed in addition to positive top and bottom feeding. It is used for operations on materials that have very low friction coefficients and for operations that are very thick and heavy.
  39. 39. Puller Feed Usually accomplished by feed rollers. Material passes between rolls, between upper roll and bed, or between lower roll and presser foot. Commonly used in association with any other feed system. Generally suitable for straight run or large radius curves.
  40. 40. Walking Foot A walking foot replaces the stationary presser foot with one that moves along with whatever other feed mechanisms the machine already has. As the walking foot moves, it shifts the work piece along with it. It is most useful for sewing heavy materials where needle feed is mechanically inadequate, for spongy or cushioned materials where lifting the foot out of contact with the material helps in the feeding action, and for sewing many layers together where a drop feed will cause the lower layers to shift out of position with the upper layers.

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