How to Install the PF Encoder Scale Disk (Uninet DTF 1000 / L1800 Style) Without Damaging It

Question

I recently ordered a replacement PF Encoder Scale (SKU: PPO-EP-L18-PFScale) for my Uninet DTF 1000 printer and want to be sure I install it correctly. The PF encoder disk has two different sides:

• Side A: Completely flat and smooth.

• Side B: Has raised bumps/texture and the encoder grating (fine lines) on it.

Which way should it face when installed on the shaft?
Should the side with the bumps and encoder lines (Side B) face inwards toward the printer motor, or outwards toward the screw head? I want to avoid installing it backwards and potentially damaging the grating against the sensor or the chassis.

Answer

Let's break down the orientation and installation so you can mount the PF encoder scale disk confidently and safely.

1. Short Answer: Which Side Faces Where?

To keep it simple:

• The sticky side on the core of the encoder disk must face the rod/shaft so it can adhere properly.

• That means:

  • The smooth/flat side of the disk should face toward the printer/motor side (inwards).

  • The grooved/rough side with the bumps and grating should be facing you, i.e., outwards, toward the screw head or open side.

So, in your wording:

Side B (the side with bumps and grating) should face OUTWARDS, away from the motor and toward you/screw head.
The inner side (with the adhesive) sticks to the shaft, and the smooth side is toward the printer, while the rough/grated side is toward you.

This orientation ensures the encoder sensor "reads" the grating correctly and avoids scraping or pinching the most delicate surface against the wrong part of the chassis.

2. What the PF Encoder Scale Disk Does

The PF (Paper Feed) encoder scale disk is responsible for telling the printer how far and how fast the paper feed mechanism is moving. It works together with an optical sensor:

• The disk has fine lines (the encoder grating) that pass through a slot in the sensor.

• As the shaft turns, the sensor sees those lines as light/dark transitions.

• The printer's mainboard counts those transitions to know how many steps the feed motor has moved.

If the disk is installed backwards, off-center, or rubbing against something, the printer may:

• Feed paper inconsistently,

• Throw feed-related errors (skips, misalignment),

• Or in some cases, refuse to run a job properly.

Getting the orientation right is important not just for avoiding damage, but also for maintaining accurate paper feed and consistent print quality.

3. Why the Rough/Grating Side Should Face Outwards

On most L1800-style engines (which Uninet DTF 1000 is based on), the encoder system is designed so that:

• The shaft side is where the disk physically attaches (sticky or press-fit).

• The sensor side is positioned where it can "see" the grating clearly without the disk rubbing against the frame.

When the grooved/rough side with the encoder lines faces outwards:

1. The adhesive surface on the inner core sits cleanly on the metal shaft.

2. The sensor is placed at a fixed gap so it can read the grating on the outward-facing side.

3. The disk's textured surface is exposed where it can be read, while the smooth inner face sits closer to the motor and shaft, where it won't scrape on anything.

If you were to flip it:

• The grating might face the motor/chassis, where clearance is tighter.

• There's a higher risk of the disk scraping, bending, or getting contaminated by grease or dust from the motor side.

• The sensor alignment may be off, causing feed errors or intermittent readings.

So the outward-facing, grooved side is not only correct-it's also the safest for long-term reliability.

4. Step-by-Step Installation Tips

Here's a more detailed installation process to help avoid issues:

Step 1 - Power Down and Access the PF Shaft

1. Turn the printer off and unplug it from power.

2. Open the covers needed to access the PF encoder shaft area (where the original disk was).

3. If the old disk is still on, carefully note its position and orientation before removal.

Step 2 - Clean the Shaft

1. Gently remove any remaining disk or residue from the shaft.

2. Use a lint-free cloth with isopropyl alcohol (no water-based cleaners) to clean the shaft surface where the disk will sit.

3. Let it dry completely. Any oil or residue will weaken the adhesive and can cause wobble.

Step 3 - Identify the Sticky Core Side

1. On your new PF Encoder Scale disk (SKU: PPO-EP-L18-PFScale), locate the sticky/adhesive side on the inner core.

2. This is the side that should face the rod/shaft.

Step 4 - Orient the Disk

• Hold the disk so that:

  • The sticky core faces toward the shaft.

  • The smooth, flat face is toward the printer/motor.

  • The grooved, rough side with the encoder grating is facing toward you, outward.

Think of it as:

Shaft → adhesive core → smooth side → disk thickness → rough/grating side visible on the outside.

Step 5 - Mount the Disk

1. Align the disk so it sits perpendicular to the shaft (not tilted).

2. Gently press the sticky core onto the shaft, ensuring it's centered.

3. Do not press on the outer edge or flex the disk; hold near the core area to avoid bending.

4. Rotate the shaft slowly by hand to make sure:

   • The disk spins true (no wobble),

   • The disk does not scrape against any nearby plastic or metal.

Step 6 - Align With the Sensor

1. Verify that the encoder sensor is positioned so the grating passes through its slot.

2. The sensor should have a small, even gap on either side of the disk-no rubbing.

3. If the printer allows, you can manually move the mechanism to ensure the sensor and disk stay aligned through the full motion.

Step 7 - Test the Printer

1. Reassemble the covers.

2. Plug the printer back in and power it on.

3. Run:

   • A paper feed test, and

   • A nozzle check or alignment pattern.

4. Look for any paper feed errors, skew, or false jams. If the disk is installed correctly and the sensor is clean, the feed should be smooth and predictable.

5. Handling and Protection Tips

To protect your new PF encoder disk:

• Avoid touching the encoder grating with your fingers. Skin oils can interfere with the sensor.

• If the disk gets dusty, gently blow off dust or use a very soft brush-do not scrub.

• Keep liquids and cleaners away from the grating surface.

• If you ever need to remove it again, pull gently from the core area and avoid bending the disc.

About Our Support and Repair Options

Handling components like encoder disks is inherently hands-on, and tiny alignment differences can affect performance. Because of that, we're not able to provide one-on-one remote troubleshooting, live guidance, or detailed repair support for individual printers. Instead, we offer in-person evaluation and repair through our local diagnostic facility, which you can learn more about on our printer repair service page (https://bchtechnologies.com/printer-repair-service). Due to strong demand, work is scheduled strictly on a first-come, first-served basis, and it may take a few weeks after drop-off before your printer reaches the bench. We can work on full printers or targeted components, with clear instructions on how to proceed-but we also recognize that our service pricing isn't always the lowest on the market.

For many users, especially those comfortable opening the machine, self-help is a very practical route. A great resource is our YouTube channel homepage (https://youtube.com/@bchtechnologies). Use the search icon next to "About" on the right side of the menu bar and type in keywords like "PF encoder," "L1800 disk," or "DTF feed issues." I receive dozens of questions every day asking if a particular video exists, and after nine years of making content, I can't always recall each one from memory. The YouTube search function is usually the fastest way to locate exactly what you need, and it may also point you to helpful videos from other channels.

Thank you again for your question, your trust, and your support of BCH Technologies. I hope this explanation gives you the confidence to install your PF encoder scale disk correctly and keep your Uninet DTF 1000 running smoothly.