Sewing Machine Feed Mechanism
Md. Rubel Miah
Department of Textile Engineering
World University of Bangladesh
Feed mechanisms is the basic motion of needles, loopers and bobbins, the material being sewn must move so that each cycle of needle motion involves a different part of the material. This motion is known as feed mechanism. For general categories, there are: drop feed, needle feed, Differential bottom feed mechanism, puller, Unisom feed mechanism, Adjustable top feed mechanism. Besides these general categories, there are also uncommon feed mechanisms used in specific applications like edge joining fur, making seams on caps, and blind stitching.
- To advance the fabric in the feeding zone of the sewing machine.
- To decide the length of individual stitch (spm)
- Appropriate feed mechanism is sleeted to confirm case in sewing
- Operation & to avoid different sewing faults.
- Drop feed mechanism.
- Differential bottom feed mechanism.
- Adjustable top feed mechanism.
- Needle feed mechanism.
- Unisom feed mechanism.
- Puller feed m mechanism.
- The simplest feed system of sewing of sewing machine still commonest.
- Also known as regular feed.
- Main components of drop feed mechanism are.
(b) Feed dog.
(c) Presser foot
|Fig: Drop feed mechanism|
- When two plies fabrics are sewn- lower ply moves forward by the help of feed dog but foot. So two plies of fabric can not move forward at the same speed. As a result lower ply is more fed than upper ply. This is called ply shifting/differential feeding pucker/feeding pucker. Sometimes roping is occurred during making of hem for ply shifting.
- It pitch of stitch s pitch of feeding dog same then fabric may be damaged for repeating contact of feed dog teeth & fabric at the same place.
- Silk less of the operator.
- Needle manual technique such that, stitch length & pitch of feed dog should not be equal.
- Modification of drop feed system.
- In the feed mechanism the feed dog consists of 2 section one at back & one at front of the needle.
- Mechanism of each section of feed dog is like the drop feed system. But the speed of each part can be adjusted separately.
- Extensively used for stretchy materials.
|Fig: Differential bottom feed mechanism|
- When the speed of the front feed dog is higher than the back feed dog. “ The bottom ply is pulled by the back feed dog but this will over come by the greater speed of the front feed dog. So less possibility of shifting”.
- When the speed of the front feed dog is less “ we get lacy effect because the feeding speed in grater than the delivery speed”.
- Stretching & gathering of fabric can be done by this system.
- In general arrangement the presser foot is in two section.
- One holding the fabric in position while the needle form the stitch and the other having length on the lower side & moving or waking in such a w ay that the top ply is taken along, positively while needle is out of the materials.
- In sewing machine, the feed mechanism can be used with both drop feed & differential bottom feed.
- Combination of adjustable feed & differential bottom feed can make top ply gathering or the gathering of bottom ply.
|With drop system.|
|With differential bottom feed.|
Fig: Adjustable top feed system.
04. Needle Feed System Mechanism:
- Another name of needle feed mechanism is “Compound feed”.
- Needle itself moves forwards & backward.
- Needle penetrates the fabric enters into the note of the feed dog & for the advance movement of 1 stitch length of fabric feed dog & needle pass the fame distance at the same time.
- Then needle rise up & moves to form the next stitch with one step advance.
- Practically useful in bulky sewing situation such as when quilting through the fabric. wadding & for slapping fabrics
- For the change of stitch length, setting of bath needle & feed dog should be changed.
|Fig: Needle feed mechanism.|
- AKA “walking foot system because the presser foot has two independently driven section; the holding & the holding & the feeding feet.
- Mode by combination of needle feed & positive top & bottom feed.
- In this system one presser foot is inside the other presser foot & gives movement at different times.
- The inside presser foot & needle are driven at the same time toward the same direction.
- No possibility of ply shifting.
- Suitable for sewing stitch fabric & for bulk seam in heavy weight materials.
- Normally not so used unless special case.
|Fig: Unison feed.|
- Modification of drop feed system.
- A pair of roller used.
- These rollers give a pulling motion on the fabric behind the presser foot.
- Top roller is generally driven by machine whitest the lower one moves due to control & presser of the top roller .
- The surface speed of puller roller is slightly higher then the feed dog speed to presser ply shifting roping.
- Useful in multi needle machine specially for W/B making.
|Fig: Puller Feed mechanism|