Denim Garment Construction: Spreading, Cutting, & Sewing
Spreading
Before marking and cutting, the denim fabric must be spread on the cutting table. All rolls must be from the same fabric dye lot. The plies of fabric are placed exactly on top of each other. Care is taken to mark defects and piece ends.
Denim rolls are very heavy and are oftentimes handled one at a time with a forklift. Because there is a major issue of shade variation from one dye lot of fabric, most manufacturers try to group the rolls from the same dye lot together. Stackable pallet racks facilitate such storage and allow a large number of similar rolls to be delivered to the cutting room at one time.
A supervisor or lead person in the cutting room will typically roll out the assigned marker on the cutting table. The marker will be checked to ensure that it is appropriate for the fabric being used, that all of the pattern pieces are included for the sizes designated in the cut order. The table will then be marked with the appropriate splice marks, and notation will be made of any variation of ply height from one section to the next.
Because of the weight of denim rolls, most are loaded onto a spreading machine using a forklift, a hoist, or two people. The operator spreads the fabric according to the length of the combined sections in the marker. Roller bearings on the machine allow the roll of fabric to move freely. The operator secures the fabric at one end and then allows the weight of the fabric to turn the roll and feed off the necessary fabric. This is possible with denim because there is little stretch in the fabric. The spreader will adjust the spreader cart to maintain an even edge of fabric onto the near side of the spread and watch for fabric defects as the fabric lays onto the table. Each end of each ply of fabric should be cut squarely and accurately to avoid wasting fabric or to avoid having garments with incorrect piece length.
With directional fabric which has a face side, the company may choose to spread all of the fabric with the face side up. This requires the spreader to walk the length of the table without laying down fabric for each ply. The total height of a spread, the total number of ply, is determined by the cutting process used. Whenever the spreader finds a defect in the fabric, it must be cut out. Some of the flaws or joints are pre-marked by the fabric mill. To ensure that all garment pieces are complete, the spreader must use designated splice marks to determine where the fabric can be cut and restarted.
Once the appropriate number of ply has been laid on the table, the paper marker will be rolled out and positioned to provide the cutter with an outline of each pattern piece. It is quite common to have multiple sections in a marker, each of which contains all of the pieces to make a designated number of garments for a particular size. Because equal quantities are not needed in all sizes, different sections may require a different number of ply. The appropriate paper marker should be cut to fit on each section to avoid distortion in the pattern pieces.
Cutting
Once the fabric is laid for cutting, the marker is positioned to provide the cutter with an outline of each pattern piece. The markers are arranged to allow for maximum usage of the fabric, with as little waste as possible. It is common for a marker to have several sections, each of which contains all of the pieces needed to make a designated number of garments in a particular size.
The cutting process on denim requires considerable force because of the density of the fabric. Consequently, there is a limited number of ply that can be cut regardless of whether the fabric is cut manually or with a computer-controlled cutter. The cutter must guide the knife through the fabric following the lines drawn on the marker laid on the top of the spread. Unfortunately, the more efficiently the pattern pieces are laid into a marker, the more difficult the cutter’s task becomes. There are, of course, some areas where cutting accuracy is more important than others because of multiple pieces that must fit together.
In addition to these areas, the cutter must pay particular attention to notches and corners. Shade mark parts is required because of the mentioned shading issues and the fact that a garment has pieces sent to many departments and then returned for assembly. Most manufacturers adhere a special sticker to each garment piece that denotes the size, bundle, and ply number of the garment. These stickers may be applied to all pattern pieces or just major body pieces. The numbering system makes the cutting room aware of missing pieces early in the process as well as giving the sewing operator a checking mechanism to ensure that bundles have not been mismatched or have one or more ply out of the proper rotation within the bundle. Once the fabric is cut, control tickets are placed on each bundle of parts to aid in process control tracking as well as matching the appropriate parts. The bundle parts operation is where individual pattern pieces are tied into bundles and sent to the appropriate department where sewing begins.
Sewing
The assembly of denim fabric into jeans is a fairly complicated process. After cutting, the parts are marked for shade and then sewn into jeans. The heavy weights of most denim fabric and the fabric’s rigidity mean that heavy-duty sewing machines must be used.
Now that cutting is complete, the process continues with assembling the jeans components. Denim jeans are made of many components including:
Pockets
Special sewing techniques are used including bar tacking for special pockets and added strength. There are two basic types of pockets: patch pockets and hung pockets. The patch pockets have the edges turned under, this is called a hem pocket. To finish the top of the pocket, the material is run through a folder and stitched parallel to the folded edge. The number of rows of stitching and the color of the thread are often considered a style feature. When sewn by manually sliding the material into the folder, the operator must carefully control how much fabric is fed into the folder. It is typical to sew the pockets, still connected by the thread, into a box and then clip and stack them apart. The use of an automatic machine reduces the skill level of the attending person to that of a loader and will normally include the stacking function.
Decorative stitch pockets are both a tedious and important task. Many jeans manufacturers consider pocket stitching to be a trademark. Some companies even carry it to the point of sewing two rows of stitching with two passes of a single needle machine rather than using a two-needle machine in one pass. Typically the pockets are stitched after hem pockets to ensure the placement of the stitching relative to the finished edge. When trademark definition and capital expenditure allows, the use of a programmable sewing machine greatly reduces the skill required and makes reproducing the exact contour of many different designs possible. The machine is equipped with a clamp that moves the pocket under the sewing needle, therefore only requiring a loader rather than a skilled operator. A lockstitch will normally be used to prevent the entire design from raveling out if one stitch is broken.
The set patch pocket is very similar whether the pocket is set to the back panel of the garment or to a sub-assembly as done when attaching the watch pocket to the front pocket facing. The operator must fold the edges of the pocket under and then accurately follow the designated contour of the pocket. Depending on the style features, this may be done with a single needle or double needle lockstitch. To increase flexibility, the operator may use a double needle machine but remove one needle for the appropriate single needle styles.
Marking a pocket outline with chalk is one of many methods used to ensure proper pocket placement. The difficulty of this operation, and the lack of skilled operators, have forced many companies to spend the money on automatic pocket setters. These computer, or CAM-controlled machines, require special attachments for each style and therefore limit the variety of pocket shapes offered.
Hung pockets are pieces of fabric either the same as the garment or some less expensive pocketing material that are attached to the pant at a seam and form a bag or pocket when finished. When a different material is used the customary practice is to sew a piece of the body fabric, a facing, onto a portion of the pocket that will show in the finished garment.
Set pocket facings is the operation that attaches the facing to the pocket back. Labels or decorative items may be attached to either piece before they are sewn together.
Staystitch labels is an operation that exactly positions the labels that will be sewn into the garment during a subsequent operation. Prepositioning one or more labels in this manner frequently makes the subsequent operation, such as set band, which is done from the opposite side of the garment less difficult and reduces quality problems.
Once all preliminary operations are done to a hung pocket, it goes to a close pocket bag where several of the edges are closed often after folding the fabric to eliminate having to sew one side. This operation is typically done with a safety stitch seam in order to increase the durability of the pocket.
Before the pocket is sewn to the pants it must be turned right side out. This turn pockets operation utilizes a pointed rod or dowel to shape the corners and fold the seam in the proper direction.
The closed pocket bags are then attached to the garment in the set from pocket operation. A single needle lockstitch is often used because of the unusual curves which are used as style features on the pockets. This operator has a significant impact on the final look of the finished garment, especially the consistency from the left side to the right side. To improve the efficiency of this job and to allow the operator to follow the same curve line for a number of garments, all of the left fronts in a bundle will be sewn, and then all the rights.
Yoke
A regular style feature of blue jeans is to have a yoke or riser attached to the lower panel of the jean back. In addition to appearance, this panel can add some functionality to the shape of the garment when cut in the appropriate direction of the fabric. Set back riser is performed with an off the arm felling machine which utilizes a double folder to turn both ply to the inside with the resultant interlocking seam.
The double-needle chain stitch machine with an extended arm allows for easier positioning of the parts and creates a very durable seam with a little stretch. Because the same type of seam is used to fell seat seam, this plant chose to have the same operator perform both sews.
The thickness of the fabric when the two risers are sewn together requires extra care on the part of the operator. One method of closing the outseam of pants is to sew them with a single-needle stitch. While not extremely common in jeans, this method does allow for easier alterations.
Front & Back Leg Panels
To maintain the integrity of the fabric in the seam during wear and washing, it is necessary to overedge the panels before they are seamed together. By performing this operation after the seat seam is joined, the operator must pick up and dispose of fewer panels. The back panels are then ready for assembly. The same method is used to overedge the front panels before the fronts and backs are joined.
Zipper
Set zipper to fly is a small parts operation that joins the edge of the zipper tape to the inside piece of the front panel. Some plants use a zipper that is already cut to length, while others use zipper tape from a continuous roll and then chop it apart. A double-needle chain stitch is used to provide extra durability and some give or stretch in the finished fly. Set fly to front and edgestitch is a two-step operation utilizing the same single needle lockstitch machine. The operator stitches the fly assembly with a zipper attached to the front and then creases the seam with the back edge of the snips to ensure that the underlying plys of fabric fall in the appropriate direction.
The seam is then edge-stitched, a very narrow topstitch to hold the seam in place and for reinforcement. Once the fronts are joined a specialty machine is used to bartack fly. This stitch forms a very strong reinforcement, performing very closely located zig-zags with several lengthwise stitches. Exact positioning is required to eliminate any puckers at the front of the garment and to provide the intended support.
Once the inseam is joined together, it is reinforced by the topstitch inseam operation. One of the more difficult parts of this job is to get the underlying seam to lay in the proper direction, especially at the crotch seam. A single needle lockstitch, while uncommon for jeans, would allow for easier alterations of a garment. If the stitch should break, it will not unravel. The operator will then use an edge guide to maintain a consistent seam margin down the side of the pant.
Waistband
Bust side seam with a hand iron is an operation that spreads open the two-ply of fabric down to the stitch line. This ensures that the seam will be evenly distributed in the bottom hem of the leg. The set waistband operation attaches a folded band to the completed pair of pants. The band is cut from the marker and is long enough to encircle the finished circumference of the pant plus enough to tuck into the end of each band.
The operator then inserts the band into a folder that turns the lower edges of the band to the inside, creating a finished edge inside and out. The operation is performed with a multi-needle chain stitch machine. The operator must tuck the ends of the band inside after the fold is created by the folder and before the end of the band is positioned at the needle. At the trailing end of the band, the operator must also tuck the ends before the edge of the garment goes under the sewing machine foot. Using a cylinder bed machine makes it easier to sew the circular top of the pant. The operator should take care to keep the hung pockets from being caught in the seam.
Waistband Product Label
Once the waistband is set, the set waist label can tie the stitch line into that of the waistband set machine. The label must be set in an exact position and is considered a trademark by most companies.
Belt Loops
Belt loops are often cut in the spread of cloth in order to ensure the color match of the finished fabric. Care must be taken to keep all the loop strips together and matched up with the same lot of pants. The ends of the strips are overlapped as they are fed into the folder for making belt loops. The double-needle lockstitch machine is set in a cover stitch configuration to form a decorative stitch on the top and protect the raw edges on the bottom. Pressing the continuous chain may aid the automatic machine in measuring the loops and detecting the overlap joints so that the joints will be cut out and not go onto a pant. Setting belt loops is normally a difficult task because of folding the short ends and holding them in an exact position during the sewing. An automatic loop setter reduces the difficulty of that task to simply being able to position the garment band in the proper location for the loop. The machine will cut the loop to the proper length, fold the ends under and then sew both ends of the loop. The machine may have a red dot light to aid in positioning. The position of the stitches on the loop must match the style features of the garment. The bar tack machine will be set to the proper length and number of stitches as noted in the garment specifications.
Buttonhole
Once the waistband is complete the buttonhole is sewn into the end of the band. This particular sewing machine is computer-controlled to set the length of the buttonhole and the number of stitches. These specifications will be determined by the size of the button to be used on the finished jean. The operator simply positions the pant onto a guide on the machine bed and activates the machine to complete the sew thus reducing the skill required. The sew time is long enough to allow the operator to grasp the next garment.
Rivets
Reinforcement of the front pockets has developed into a marketing tool. Many of the rivets are custom-produced for a jeans manufacturer even when more commonly available rivets are used, the placement is dictated by the spec sheet and may be used as a style feature. The rivet can be set with a motor-driven machine where the rivets are fed from a hopper and the operator simply activates the machine. The placement of the rivets may be guided through the use of a red dot pointer. The other extreme of this operation is when the operator loads the rivets into the magnetic holding dye and then forces the rivet pieces together using a leg pressing motion.
Cap
Set metal cap button is very similar to the rivet operation. Jeans typically do not have a sewn-on button but have a pointed metal stud that is forced through the fabric and then a cap with a shank is forced down over the stud. In most cases, the operator will use an edge guide to position the garment. Some manufacturing plants mark the placement of the button through the buttonhole and then use a red dot light to accurately position the pant. Any quality problem at this operation will require the replacement of the waistband and all subsequent attachments such as loops and labels.
The metal caps are decorative and are frequently part of the trademark of the manufacturer. The press machine normally has both the studs and the caps fed automatically to the work position through a track. In some cases, the size or design of the cap or mechanical failure does not facilitate automatic feeding of the parts and the operator must position one or more parts by hand. This significantly increases the time required for the job but not necessarily the skill required. Trim and inspect pants is next performed to detect any defects in the fabric or the sewing of the garment.
When garments are to be washed, the function is typically performed before going to the laundry because any open seams will ravel during the wash process and render the garment unusable. There will typically be an after wash inspection as well to prevent defective garments from going to the customer. The inspector will trim any excessive threads left by the sewing machines as well as determine the department or person that should make the necessary repairs. The button jeans operation is a fairly arduous task because of the thickness of the four-ply of fabric in the waistband and the inflexibility of the metal button shank. This stiffness is more contentious if the pants are buttoned before washing. A wire loop pulling device is a major improvement to the process.
