ADVANCED MACHINE-TIMING TECHNIQUES
..to achieve the stitch you want.
This example uses non-typical canvas-making materials which, in turn, requires some non-standard Timing Settings of your sewing machine. We hope that this article helps you to fine-tune and time your machine; and not to be afraid to deviate from standard timing guidelines.
Background: Our polycarbonate machine had set for three or more weeks, seemingly untouched, after successfully sewing a polycarbonate sailboat project. It had sewn the project quite flawlessly.
Day One: You can imagine my disgust when I began to sew another polycarb project, only to discover that the machine can’t seem to make a stitch! Knowing that the last project used black thread and this project calls for white thread, I knew the tensions would be different. What did he say? Yes, it is true. Black thread and black fabrics can contain carbon for coloring. They behave differently when sewn. For example, white Dacron or Polyester sheets will wrinkle easier than black. After an hour or two of adjusting tension, the machine was no better than before I started.
Day two: Two hours of check, check, and re-check of the timing. Perfect! Upper and lower shafts are good. Hook timing is perfect. Hook Distance is at minimum gap. Bobbin Opener timing is exact. Bobbin tension is spot-on. Upper thread tension is beautiful while sewing test-swatches. Foot pressure is medium pressure. Take up spring is medium tension. Walk Balance is perfect at 1mm high outside. The feed dog peaks are cresting at 1mm. So, why won’t this thing sew? I teach sewing machine repair. I know when a machine is in perfect timing!
Day three: Another couple of hours of pure frustration. When you reach this boiling point of frustration and anger, it is time to STOP! Start making a mental list of what is different about this job compared to the last? What is the machine doing that it didn’t do before? What has changed since the last time the machine was used?
Day Four: Six hours later, the machine was sewing great again! So what differences did we find? What changes had occurred? How was this job different than the last successful sewing project?
In this scenario, even though I had sworn that the machine had not been touched since the last time, many things came to light.
Machine Changes since last run: machine was used in the Sewing Machine Repair Class and was re-timed perfectly. Every setting was exactly as it should be, according to the manufacturer. The machine was freshly oiled. I found the large ‘U’ steel bobbins and replaced the smaller ‘M’ bobbins for the next project, making sure everything was as the ‘factory’ intended.
Differences in the fabric, thread, materials this project: Using Tenara HTR2500 in white, instead of black. Sewing double-fold Facing (4 layers) onto polycarbonate, rather than the typical 3 layers of Sunbrella-only
New sewing machine Issues: The biggest problem was the machine was skipping stitches, missing An entire chain of stitches. Secondly, we saw bird-nesting of thread underneath when beginning a stitch or while sewing in reverse. The third issue was that the material was Flagging badly. Flagging is when the material raises up as the needle is rising. This flagging of the material also pulls the thread up with it and causes the loop to disappear. No loop, no stitch!
Finding The Solution
Knowing that Timing Adjustments are normally set to center, medium, or dead-to-the-marks, it makes you wonder why there is much more adjustment remaining? Examples of non-standard adjustments are: looser or tighter, retarded or advanced, higher or lower, left or right, closer or farther. Starting with a perfectly timed and adjusted machine, let’s see how we fixed the sewing issues…
DOWN-PRESSURE for FLAGGING: The first thing I needed to address was the flagging: The owner’s manual suggests a ‘light to medium’ down-pressure setting to the Presser Foot. In the case of polycarbonate, I have maximum down-pressure applied to the Presser Foot. Originally, the coil spring could not overcome the lifting of the Polycarb. It only stopped lifting when I had reached the maximum down-pressure on the foot. Eliminating flagging should be a big step toward eliminating skipped stitches as it stops the thread from pulling up and tacking away the loop.
SCARF HEIGHT for a BIGGER LOOP: Normally, the hook-point is set to the middle of the scarf. To create a larger loop in the thread for the hook to catch, I raised the Needle Bar higher so that the hook-point passed the at the bottom of the scarf, just above the needle hole. This stopped the chain of missed stitches, leaving only a missed-stitch now and then. We’re getting closer!
HOOK TO NEEDLE DISTANCE for SKIPPED STITCHES: Normally, the tip of the hook is set just in front of the needle with a small gap between them. To ensure the tip of the hook had the highest possible chance to catch the loop, I moved the hook point to a minimum clearance (closer to the needle). In fact, most modern machines have a ‘needle guard’ which is a protrusion along the outer bobbin assemble that keeps the needle from deflecting to the right. When setting a minimum clearance, the needle-guard will be 0 to 1mm from touching the tip of the needle on each cycle.
TAKE UP SPRING for a BETTER LOOP: The Take-Up Spring may need to have the tension lessened so that it does not pull the thread prematurely; thus, removing the loop.
BOBBIN TENSION for BIRD NESTING: An average bobbin tension sometimes allows excess thread in the system. A little added tension helps bobbin thread flow more evenly, especially in the case of backlash in the bobbin.
HOOK TO NEEDLE TIMING for SKIPPED STITCHES: This adjustment is the biggest improvement and the real solution! When a mechanical driven machine is timed, it is not under power; meaning the motor is not running. However, when a machine is placed into motion by the use of the motor, sometimes your perfectly timed machine isn’t performing as well as it did when you cycled it by hand. Many factors come into play when a machine is under power such as: centrifugal force, inertia, torque, and tolerances. All of the previous adjustments improved the skipped-stitch problem but, it did not eliminate it completely. To ensure that the loop could form to it’s fullest extent before the hook arrives to grab it, we decided to retard the Hook Timing. This, along with all of the other adjustments we had done, was the final phase of the solution!
For the first time in twelve years, we can actually sew 60mil polycarbonate at full machine speed without thread breakage, without thread fray, without skipped stitches! The bottom line is that sewing machines have ‘starting places’ for timing and tensions. Don’t be afraid to move away from those starting points when necessary.
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