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Regular / Plain / Hi-speed Lockstitch Sewing Machine

Hi-Speed Lockstitch Sewing Machine

A hi-speed lockstitch sewing machine is the best common mechanical system stitch made by the sewing machine. The term  of single needle stitching often found on dress shirt labels, referering to lockstitch machine. The height of needle from its lowest position of upward stroke when the hook point reach at the center line of needle.

Feature of Lockstitch Machine

  • Most common machine for woven garments
  • More secured sewing
  • No of needle:1 or 2
  • SPM:1500-5500
  • Stitch Density is variable, max. stitch length 5mm
  • Different types of feed mechanism (Puller Feed, Top AND bottom Feed etc.)
  • Automatic bobbin winder and thread trimmer present in some of the versions.
  • Daily Maintenance:
  • Single needle Lockstitch machine
  • Double needle Lockstitch machine 

Hi-Speed Lockstitch Sewing Machine Maintenance

Done by : Operators

Supervised by: Maintenance Personnel

Criteria:

Needle Replacement: Check whether the needle of hi-speed lockstitch sewing machine is bent or blunt or not. If it is bent or blunt change the needle and install it under the supervision of maintenance personnel.

Rotary hook: Clean the tail of thread of hi-speed lockstitch sewing machine dust and lint in the rotary hook and bobbin case.

Lubrication:Lubricate the lockstitch sewing machine parts where necessary.

Time required: 10 minutes.

Cleaning the bobbin case and other possible parts: Clean the lint, loose thread and other dirt from the shuttle of bobbin and bobbin case. Besides the table and other parts which cannot effect the setting must be cleaned.

Required time: 5 minutes.

Lockstitch Machine Weekly Maintenance:

Done by : Maintenance Personnel

Supervised by: Maintenance Manager

Criteria:

Needle – Hook point timing: Check whether the needle of lockstitch – hook point timing is correct or not. If there lies miss-timing then adjust it.

The check points are

  1. Needle – hook point clearance
  • At the same time the distance between the hook point and the top end of the needle eye.

Required time: 10 minute.

The clearance between bobbin case holder and bobbin case holder bracket: Check the clearance between the bobbin case and bobbin case holder bracket (1-1.5mm). Make sure that the hook will not touch bobbin case holder bracket of lockstitch mc.

Required time:5 minutes.

Presser foot pressure: Check whether the pressure of presser foot of lockstitch is proper or not. If not adjust it by adjusting the distance between the bottom washer and top of pressure bar guide bracket. And the bottom of work clamp must be kept parallel to the top of the work.

Required time: 5 minutes

Thread take-up amount: Check the amount of the thread take-up stroke, clearance between needle thread and thread take-up lever guide (.5-1 mm). Make sure that it is not more than necessary.

Required time: 5 minutes

Needle & bobbin thread tension adjustment: Check whether the standard operating range of thread take-up spring of lockstitch mc is accurate or not (6-8 mm). The tension at appropriate operating range must be checked.

Required time: 5minute.

Needle installation: It must be remembered during needle installation of lockstitch  mc that the long groove of the needle is on the left and tightened with the needle clamping screw. Adjust the needle clearance and lift amount.

Required time: 2 or 3 minute.

Stitch Length:  Check whether the lockstitch length is appropriate or not. If not , push the reverse feed  lever halfway down, turn the dial until desired number align the pin at top and release the reverse feed lever. It is remembered that the number, the longer the stitch length will be and the reverse sewing device is the automatic-resetting type.

Required time: 2 or 3 minute.

Needle Bar height:  It is remembered that when the needle bar is in its lowest position the reference line on the must be at the lower end of the containing the needle bar. If it is not so, remove the needle plate, loosen the needle bar connecting stud clamping screw and adjust by raising or lowering the needle bar.

Required time: 10 minute.

Adjstment of Pressure on the material (fabric): The pressure on the material during sewing must be as weak as possible, but strong enough so that the material does not slip. Adjust the pressure through loosing the adjustment nut.

Required time: 5 minute.

Feed Dog Height: The standard height of the feed dog for sewing thin material is 0.8 mm, and for medium material is 1.00 mm and for thick material is 1.2 mm (when the stitch length is set to the maximum).

Adjust the feed dog height by loosening the screw when the feed dog is above the needle plate surface and move the feed lifting arm up and down.

Required time: 5 minute.

Feed dog angle: in order to prevent puckering, material from slipping the feed dog is to be raised or lowered downward at standard angle.

When the feed dog angle has been adjusted, check to confirm that the height of feed dog has not changed.

Required time: 5 minute.

Presser foot height: The standard height of the presser foot is 6 mm when the presser foot is raised with presser foot lifter lever. To adjust the presser foot height, loosen the nut of the adjustment screw and then the presser foot adjustment screw so that no pressure will be applied to the presser foot, then loosen the set screw and adjust the presser foot height by raising or lowering the presser bar.

Required time: 5 minute.

Lockstitch Machine Monthly Maintenance

Oil replacement and other interrelated checks:

  1. Check lubricant or oil whether that is to replace.
  2. Check bush leakage, oil seal leakage or age, vibration of oil and the flow of oil pump more or less than setting.
  • Check rubber cushion seats, four corners of machine tool groove on which oil pan stands.

Required time: 10 minute.

Rotary hook of plain sewing machine: Check rotary hook wear whether it is need to replace.

Required time: 10 minute.

Presser foot canal: check hi-speed lockstitch sewing machine canal wear. If necessary replace it.

Required time: 10 minute for lockstitch machine.

About Engr. Kh. Mashiur Rahman

He is Garment Automation Technologist and Editor in Chief of Autogarment. He is certified Echotech Garment CAD Professional-China, Aptech-India, NCC-UK and B.Sc. in CIS- London Metropolitan University, M.Sc. in ICT-UITS. He is working as a Successful Digital Marketer and Search Engine Specialist in RMG sector during 2005 to till now. Contact him- apparelsoftware@gmail.com

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