my canon mg3620 printed pages have random ink smudges not from the document, how do i clean it?

Diagnosis

Random ink smudges, streaks, or "track marks" on the MG3620 are almost always caused by a contaminated bottom plate. This plate is the flat surface the print head glides over as it moves back and forth. Over time, excess ink from the PG-245 and CL-246 cartridges, combined with airborne dust and paper fibers, creates a sludge of ink residue on this surface. When the paper feeds through, the bottom of the page physically drags across this residue, picking up "random" spots of ink that aren't part of your digital image.

You can confirm this is a bottom plate issue if the smudges appear in the same horizontal or vertical location on every page, regardless of the content. If the smudges are only at the very top or bottom of the page, it is likely a roller issue. If the smudges are vertical streaks across the entire page, it is likely a dirty print head nozzle or a leaking cartridge. However, sporadic "blobs" or smears usually point directly to the bottom plate needing a physical purge.

How to Fix It

The MG3620 has a built-in "Bottom Plate Cleaning" utility that uses a specifically folded piece of paper to absorb the ink buildup without requiring you to disassemble the chassis. Follow these precise steps:

1. Power on the printer and ensure no error codes are flashing on the LCD. Remove any remaining paper from the rear tray.
2. Take a single sheet of plain A4 or Letter-sized paper. Fold the sheet in half widthwise (short end to short end), then unfold it to create a center crease.
3. Fold one side of the paper toward the center crease, then unfold it again. You should now have a sheet with three distinct sections and two crease lines.
4. Load this single sheet into the rear tray. The crease ridges must face upward, and the edge of the uncreased half must be facing the far side of the tray. Ensure the paper guides are snug against the sheet to prevent skewing.
5. Open the paper output tray and extend the tray support fully.
6. Press and hold the Stop/Reset button (the red circle with the triangle) until the Alarm lamp flashes once, then release the button immediately.
7. The printer will now perform a series of movements, feeding the folded paper through the mechanism several times to "wipe" the bottom plate. This process takes approximately 1-2 minutes.
8. Once the paper is ejected and the printer returns to its idle state, remove the cleaning sheet and discard it.

If That Didn't Work

• Manual Print Head Cleaning: If smudges persist, the print head itself may be leaking. Open the cover to access the cartridges. Remove the PG-245 and CL-246 cartridges. Use a lint-free cloth dampened with distilled water to gently wipe the gold-colored contact points and the bottom nozzle plate. Do not use rubbing alcohol, as it can dry out the seals.
• Roller Cleaning Cycle: If the smudges are appearing as small dots in a repeating pattern, the feed rollers are dirty. Press the Setup (pliers/screwdriver icon) button, use the plus button to select "Maintenance," and choose "Roller Cleaning." This will rotate the rollers against a blank sheet of paper to remove debris.
• Check for Ink Leaks: Inspect the cartridges for signs of leaking ink around the ventilation holes. If a cartridge is leaking, it will drip onto the bottom plate regardless of how often you clean it. Replace any leaking cartridge immediately to avoid permanent staining of the internal plastic.
• Deep Cleaning Cycle: If the smudges look more like "streaks" of missing color, perform a Deep Cleaning. Go to the Setup menu, navigate to Maintenance, and select "Deep Cleaning." This uses a significant amount of ink to force clogs out of the nozzles.

Heads Up

• Avoid Non-Genuine Ink: Third-party "compatible" cartridges often have improper seal tolerances, leading to ink leaks that cause the very smudging issues you are experiencing.
• Use Correct Paper Weight: Using overly thick cardstock or very thin photo paper in the MG3620 can cause the paper to rub more aggressively against the bottom plate, accelerating ink buildup.
• Prevent Dust Accumulation: If the printer is kept in a dusty environment, the ink on the bottom plate will turn into a thick paste. Keep the printer covered with a dust cloth when not in use.
• Print Regularly: Printing one page of color and black every week prevents ink from drying and cracking in the nozzles, which reduces the likelihood of "ink spray" landing on the internal components.