Cleaning Problem Summary 1 Captop Lower Tube _ Ink Supply Problems (Part 1) ARTJET 2026

1_1. Industrial Heads (Konica, Ricoh, etc.)

• Air is injected to push ink downward out of the head, and the head is then wiped with a cloth.

1_2. Epson-Series Heads (Small UV Printers)

• The Captop rises up from below the head and seals against it.
• With the seal in place, the motor pump runs and draws ink out.
• Ink flow path: Damper → through the head → Captop → Captop lower tube → motor pump yellow tube → waste ink tank
• After pumping, the wiper automatically cleans the underside of the head to complete the cleaning cycle.
• If ink cannot be drawn out through the motor pump into the waste ink tank, there is no way to clean the head.

• The photo below shows the ink flow path from the main ink bottle to the waste ink tank. Every section must be fully sealed for the motor pump to run and move ink into the waste tank.

• When viewed from the front of the printer, the Captop is the part labeled #1 that seals the underside of the head.

1_1. Rigid Tube

• This tube runs from the main ink bottle, through the cable carrier, and connects to the underside of the head carriage board.
• It is made from a hard material that doesn’t compress when pressed — resistant to friction and wear during X-axis movement.
• Connecting a rigid tube directly to the damper may seem fine at first, but air will seep in over time.
• Since air infiltration causes ink supply problems, rigid tubes should never be connected directly to the damper.

1_2. Flexible Tube

• The final ink tube connecting to the damper must always be flexible.
• Its soft material creates a tight fit when inserted into the damper — once in, it resists being pulled out.
• This tight connection is what prevents air from entering over time.

• In the early days of selling UV printers in 2020, we replaced the Captop lower tube with a standard flexible ink tube.
• But inkload (pumping), which had been working fine, repeatedly failed afterward.
• Tightening with a cable tie would fix it temporarily — only for the problem to return. At the time, we couldn’t identify the cause.
• Much later, while replacing consumables on 8 used machines, we discovered that the Captop lower tube has a smaller diameter than a standard flexible ink tube.
• That’s when we remembered what the Chinese manufacturer had once asked — “Aren’t you going to order the Captop lower tubes?”

• Click here to watch a video showing how rigid, flexible, and Captop lower tubes feel when connected.
• The Captop lower tube must always use the dedicated smaller-diameter flexible tube.

• “When I pour alcohol on the Captop and run inkload (pumping), the alcohol comes out — but no ink does.”
• There are usually three causes:
• The tube connected to the damper is loose and pulling in air
• The Captop and print head are slightly misaligned
• The Captop lower tube has loosened and air is entering
• After checking the damper connection and replacing the Captop without success, a loose Captop lower tube is the most likely cause.

1_1. How to Inspect

• Detach the Captop and pull the lower tube by hand — if it separates easily, air is entering.
• The tube should resist being pulled out — that is the normal condition.
• A tube that comes off easily should ideally be replaced, but if the dedicated tube is unavailable, cutting off the end and reconnecting it will also work.
• Don’t assume it’s fine just because it doesn’t pull out with moderate force — always confirm it holds firm even when slightly stretched.
• Overlooking this point often leads to hours of checking other components before the Captop lower tube is finally replaced and the problem is resolved.

• Waste ink line is blocked or kinked
• Peristaltic pump yellow tube has shrunk or torn (the yellow tube is a consumable)
• Captop lower tube is torn or its connection has loosened (covered in this article)
• Captop itself is defective
• The metal frame protecting the print head is damaged, preventing the Captop rubber from sealing against the head
• Head and Captop are misaligned
• Damper connection is faulty (always use flexible tubing, and verify the connection)
• Ink line is pinched somewhere, causing an air leak
• Ink has hardened inside the ink line, blocking supply