Repair, Maintenance, Setting and Replacement of Different Parts of Lock Stitch Machine

Repair, Maintenance, Setting and Replacement of Different Parts of Lock Stitch Machine
Md. Nayimur Rahman
Abdur Rab Serniabat Textile Engineering College, Barisal

The machine which produces stitches by interlacing of threads is called lock stitch machine. This machine produces durable stitches and is very popular in garments industries.
Lock stitch machine
Fig: Lock stitch machine
  • To know about lock stitch machine.
  • To know different parts of the machine.
  • To know about thread path of the machine.
  • To know about the specification of the machine.
  • To know about adjustment points of the machine.
Machine specification:
  • Model No : DDL-5530N
  • Group : lock stitch ( interlacement)
  • Manufacturing company brand: Juki
  • Country of origin: japan
  • Stitch per minute: 1500-5000
  • Needle size: 9,11,14,16,18,20,21
  • Thread per inch: 2.5”
  • Needle per inch: DB*1
  • Needle no-1
  • Seam class: super imposed ,bound,lapped
  • Stitch class: 300
Features of Lock stitch machine :
  1. Stitches are produced by interlocking
  2. Bobbin and bobbin case are present
  3. Threads are supplied from cone.
  4. It has only one needle.
  5. It has different types of feed mechanism
Adjustment points and main parts:
  1. Thread
  2. Tensioner
  3. Needle
  4. Stitch density
  5. Bobbin
  6. Needle bar
  7. Pressure foot
  8. Feed dog
  9. Pressure feed guide
  10. Needle plate
  11. Spindle
  12. Bobbin case
  13. Bobbin
  14. Paddle
  15. Side plate
  16. Machine pulley
  17. Needle
  • For sewing light and heavy fabrics.i.e. all kinds of plain sewing.
Maintenance can be of different types. But following types are important in this aspects.
  • Routine maintenance: Lubrication and regular inspection are the constituents of routine maintenance. Lubrication ensure long life and safe working of all the equipments. Inspection tries to detect faults in equipments so that repairs and replacements may be undertaken at the right time. 
  • Schedule maintenance: This type of maintenance provides for inspection ,overhaul, lubrication and servicing of the machine at predetermined dates. Overhauling of machine, cleaning of all components is normally done on this machine. It involves opening of the machine into its smallest components and carry out lubrication.
The setting of the lock stitch machine is of immense importance. Folding setting points needs to be ensured before running the machine.
  • Stitch density controller: Its controls the no of stitches per inch. Before starting the machine ,stitches per inch is determined by rotating the knob and fixing it at the desired position. 
  • Motor: Motor rpm depicts the speed of the machine. The rpm is controlled by tightening or loosing the belt over machine and motor pulley. 
  • Needle: Needle undergoes accurate setting to ensure proper sewing. Needle is attached by means of a screw which needs to be tightened enough to produce easy sewing. Again the needle size is also important from fabric point of view. 
  • Pressure foot: The type of pressure foot to be used and its proper settting is important, which is ensured by proper attachment with the moor through machine pulley. 
  • Feed dog: It is often found that due to random working the feeed dog is subjected to be loose which may cause accident also.thus the feed dog must be set properly with the screw.
Replacement : 
The replacement is revealed when the relation of equipment is no more remains an economical proposition. A replacement is affected when the equipment is subjected to complete breakage which can not used even after repair or the components has become so obsolete that affects production or it has crossed its expiry date. Replacement can be needle, pressure Foot, feed dog etc undergo frequent replacement.

Precautions : 
Following precautions must be taken when repair, setting maintenance or replacement is carried out in the lock stitch machine.
  1. All repair and maintenance work must be carried out by switching off the machine.
  2. Right tools should be used at right place.
  3. Skilled personnel should be involved for specialized job.
  4. Careful handling of all the components is necessary.
  5. The components should not be too tight or too loose.
Conclusion :
It can also be called plain stitch machine. Here different sizes of needles can be used as per requirements. This machine is mostly used in our garments industries. It has also gives us a basic knowledge on machine maintenance as a whole. The knowledge of this experiment will be very much helpful in our future practical life.


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