JUKI DDL-8700 Series: A User's Guide

The JUKI DDL-8700 series of industrial sewing machines are renowned for their reliability, speed, and precision, making them a staple in garment manufacturing and tailoring workshops worldwide. Whether you're a seasoned professional or a budding enthusiast, understanding the intricacies of your DDL-8700A, DDL-8700L, or DDL-8700H model is crucial for achieving superior stitch quality and ensuring the longevity of your equipment. This guide will walk you through some of the most common and important operational procedures, from setting the bobbin to fine-tuning the feed timing.

Setting the Bobbin

A correctly set bobbin is fundamental for creating strong, even stitches. The process on the JUKI DDL-8700A-7 is straightforward, but requires attention to detail. Follow these steps:

1. Thread the Bobbin Case: Pass the thread through thread slot A on the bobbin case.
2. Engage the Tension Spring: Pull the thread downwards and towards the right, ensuring it passes under the tension spring. The thread should emerge from notch B.
3. Verify Rotation: Gently pull on the thread. The bobbin should rotate smoothly in the direction indicated by the arrow.

A common pitfall is insufficient tension on the bobbin thread, which can lead to skipped stitches or loose bobbin stitches. Conversely, excessive tension can cause the thread to break. Always test your stitch on a scrap piece of fabric after setting the bobbin.

Understanding the DDL-8700 Variants

JUKI offers several variations of the DDL-8700, each tailored for specific material types and performance needs:

The differences in stitch length and speed highlight the importance of selecting the correct machine for your intended use. For instance, the DDL-8700L is specifically designed for robust performance with heavier materials, necessitating adjustments that cater to thicker threads and fabrics.

Lubrication and Oil Management

Proper lubrication is paramount for the smooth operation and longevity of your JUKI DDL-8700. The machine utilizes an automatic lubrication system that splashes oil to key components.

Oil Pan and Level

• Fill the oil pan (1) with JUKI New Defrix Oil No. 1 up to the HIGH mark (A).
• When the oil level drops below the LOW mark (B), replenish the oil pan.
• Adequate lubrication is indicated by splashing oil visible through the oil sight window when the machine is running.

Adjusting Oil Supply to Face Plate Parts

You can regulate the amount of oil supplied to the thread take-up and needle bar crank by turning the adjust pin (1). Bringing the marker dot (A) closer to the needle bar crank (2) by turning the pin in direction B reduces oil supply, while moving it opposite to the needle bar crank in direction C increases it. It's vital to find the correct oil balance to prevent wear without staining the fabric.

Confirming Oil Splashes in the Hook

The amount of oil splashing onto the hook mechanism is critical for its smooth operation and to prevent seizure. To check:

1. Run the machine idle for approximately three minutes to warm it up.
2. Immediately after stopping, place a confirmation paper under the hook.
3. Confirm the oil surface in the reservoir is between HIGH and LOW marks.
4. The entire confirmation process should take no more than five seconds.

Samples of appropriate oil splashes are provided in the manual. For the DDL-8700A, the ideal splash is around 0.5 mm, while for the DDL-8700H and DDL-8700L, it's around 1 mm. Too little oil can cause the hook to overheat and seize, while too much can lead to oil stains on your work. Adjust the oil amount using the adjustment screw on the hook driving shaft front bushing; turning it in direction A increases oil, while direction B decreases it.

Adjusting Feed Timing (DDL-8700L)

Feed timing ensures that the fabric is advanced correctly with each stitch. Incorrect timing can result in uneven feeding, puckering, or skipped stitches. For the DDL-8700L, this adjustment is made via the feed eccentric cam:

1. Tilt the machine head to access the underside.
2. Loosen screws (2 and 3) on the feed eccentric cam (1).
3. Standard Timing: Adjust so the top surface of the feed dog is flush with the top surface of the throat plate when the feed dog is at its lowest point.
4. Advanced Timing (Direction A): Move the feed eccentric cam in direction A to advance the feed. This is often used to prevent uneven material feed.
5. Delayed Timing (Direction B): Move the feed eccentric cam in direction B to delay the feed. This can increase stitch tightness.
6. After adjustment, ensure screws (2 and 3) are tightened securely. Be cautious not to over-adjust, as this can lead to needle breakage.

It is also important to note that after adjusting the feed dog tilt, the feed dog height may change. Always re-check and adjust the feed dog height if necessary.

Feed Dog Height and Tilt

The height and tilt of the feed dog are crucial for proper fabric feeding. The manual provides specific height ranges for each DDL-8700 model:

To adjust the height, loosen screw (2) on crank (1), move the feed bar up or down, and retighten screw (2). Ensure sufficient clamping pressure to prevent slippage.

The tilt of the feed dog can be adjusted to prevent puckering (front up) or uneven feed (front down). For the DDL-8700H, a specific forward tilt is standard. When adjusting tilt, always re-check the feed dog height.

Needle-to-Hook Relationship

The precise timing between the needle and the hook is critical for forming stitches correctly. Incorrect timing leads to skipped stitches or needle damage.

Adjusting Needle Bar Height

1. Turn the handwheel to bring the needle bar to its lowest point.
2. Loosen set screw (1).
3. Align the marker line (A or C, depending on needle type) on the needle bar (2) with the bottom end of the needle bar lower bushing (3).
4. Tighten set screw (1).

Adjusting Hook Position

1. Loosen the three hook set screws.
2. Turn the handwheel and align the marker line on the ascending needle bar (2) with the bottom end of the needle bar lower bushing (3).
3. Align the hook blade point (5) with the center of the needle (4).
4. Maintain a clearance of 0.04 mm to 0.1 mm between the needle and the hook (0.06 to 0.17 mm for DDL-8700H/L).
5. Securely tighten the hook set screws.

The specified clearance is a vital parameter. Too little clearance risks damaging the hook blade, while too much can cause stitch skipping.

Other Important Adjustments

• Presser Foot Pressure: Adjust the pressure to suit your fabric. Too much pressure can damage delicate fabrics, while too little can cause uneven feeding. The standard range is typically between 29-32 mm.
• Presser Foot Lift: The knee lifter typically provides a 10 mm lift. This can be adjusted up to 13 mm using the knee lifter adjust screw (1). Ensure the needle bar does not hit the presser foot at its lowest position after adjustment.
• Thread Tension: Needle thread tension is adjusted by turning the tension nut (1) clockwise to increase and counter-clockwise to decrease. Bobbin thread tension is adjusted with screw (2) on the bobbin case, clockwise to increase and counter-clockwise to decrease. Fine-tuning both tensions is key to achieving a balanced stitch.
• Thread Take-Up Spring: Adjust the stroke and pressure of the thread take-up spring by loosening set screws and turning tension posts. This affects how much thread is pulled up with each stitch, influencing stitch formation, especially with different thread types.

Regular maintenance, proper lubrication, and understanding these key adjustments will ensure your JUKI DDL-8700 series machine continues to deliver high-quality results for years to come.

Frequently Asked Questions (FAQs)

• Q: My JUKI DDL-8700 is skipping stitches. What could be the cause?
  A: Skipped stitches are often caused by an incorrect needle-to-hook relationship, a bent or dull needle, incorrect bobbin tension, or improper threading. Double-check these elements first.
• Q: How often should I lubricate my machine?
  A: Regularly check the oil level in the oil pan. Top it up as needed. Ensure you can see oil splashing during operation. A routine check before each use is recommended.
• Q: Can I use a different type of oil in my JUKI machine?
  A: It is strongly recommended to use only JUKI New Defrix Oil No. 1 or an equivalent high-quality sewing machine oil specified for industrial machines. Using the wrong oil can damage the lubrication system and the machine.
• Q: What is the purpose of adjusting the feed timing?
  A: Adjusting feed timing ensures the fabric is moved correctly under the needle for each stitch. Advancing the timing can help with heavy materials, while delaying it can create tighter stitches. Correct timing prevents puckering and uneven feeding.
• Q: My machine is making a loud noise. What should I do?
  A: A loud noise could indicate a lack of lubrication, loose parts, or an issue with the motor or belt. Check lubrication levels, ensure all screws are tight, and inspect the belt for wear or proper tension. If the noise persists, professional servicing may be required.