Troubleshooting White Ink Circulation Issues in DTF Printers

Question:

For DTF printers, I have added a circulation pump of white ink pipes with a timer on it to get opened & closed automatically. One of the white ink dampers is not filling, the second is working well. Is it related to the circulation motor operating too quickly? What is the best speed for the white ink circulation motor? For this reason, I am afraid the return pipe doesn't hold enough pressure, which could also lead to an imbalance. To fix it, I put a two-channel splitter as close as possible to the return pipe, just before the white ink tank to regulate priming pressure better. In L805 printers, however, there isn't a lot of space on top of the carriage to comfortably fit a large splitter as in L1800. Could you assist? I will add photos and a sketch of my setup.

Answer:

To answer your question, you are using a diaphragm pump that needs a secondary tank to work properly. Your setup does not have to have such a big tank as in your picture. Instead, a more compact solution (for example: https://bchtechnologies.com/products/secondary-tank-for-dtf-printhead-3-mm-od-1?_pos=1&_sid=0309e5e18&_ss=r) to dispense the DTF ink would be appropriate. A secondary tank is still recommended even if you get a peristaltic pump to help maintain steady ink flow.)

Figuring Out What Went Wrong With the Dampers

The problem you’re discussing — one damper fills while the other stays empty — could be caused by several things:

Pump Speed and Flow Rate

Your particular printer model and tubing configuration will determine the ideal speed of your white ink circulation pump, for small DTF printers such as the L805, A flow rate of 30-50mL per minute is typically considered safe.

If the pump speed is too fast, it may result in unstable ink pressure, which can cause ink flow on neighboring dampers to fluctuate. You can try decreasing the flow rate to see if that levels out the dampers.

Bleeding Off Pipe Pressure

You are correct that the return pipe does not hold enough pressure. The return pipe, which supplies ink from the cartridge to the pen nib, acts like a pressure release system. The flow doesn't work correctly if the circuit doesn't have proper resistance.

Stabilize pressure to the tank and this can be done with a two-channel nozzle splitter. There's no room for a more prominent splitter in smaller printers like the L805.

Another way is using a smaller in-line pressure regulator or a check valve which should avoid excessive RSVP suction on one damper from the return flow.

Dampers and Normal Operation

Under normal operating conditions, the dampers are half full. This is perfectly normal if you take them off for inspection and see that they are only half full.

One damper may be complete and the other completely empty, indicating that the flow must be balanced from left to right.

Possible Fixes

Pump speed should be reduced to prevent system over pumping.

Ink flow can be managed by using a secondary tank.

Make sure you have as much resistance as possible in ink supply and return paths, a check valve or a smaller splitter could prove helpful in the L805.

Check and clean the ink lines to see if any blocks affect either side.

Final Thoughts

Since printer problems are hands-on, resolving these issues can sometimes get messy. We cannot perform remote troubleshooting, suggestions, or assist with printer repairs. That said, we do provide in-person evaluation and repair of printers at our local diagnostic facility (https://bchtechnologies.com/printer-repair-service); this is limited on a first-in, first-out basis to how many printers we are at the time, so there may be a wait until we can get your printer in. Depending on what goes wrong with the print head or the printer, we will guide you on your route. We can help repair the printer or the print head itself. However, we recognize that our repair prices may not be the cheapest. If you plan on doing your repairs, we suggest browsing online resources as we can't keep up with the changes. Some good troubleshooting videos on YouTube are available to help with test procedures. You can use the search icon next to "About" from our BCH Technologies YouTube channel (https://youtube.com/@bchtechnologies). We have over nine years of video content, so the most effective way to hone in on something relevant to you is to use the search function on YouTube.

You still deserve my appreciation for taking the time to write this and for your support. Thank you for your continued support and for working with BCH Technologies.