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Where Did One of My White Ink Channels Go?

 Why is My DTG Ink Channel Not Working?

It is frustrating when something that has been working well for a while suddenly decides to cease functioning for no apparent reason. However, there is always a reason, weather we understand it or not.

Our office is a typical bee-hive of activity. Projects are juggled constantly and our mPower DTG printer does not always get the attention it should. Sometimes we run continual test prints evaluating new Firebird ink formulas, sometimes we run prints to evaluate new Firebird PT (pretreatment) formulations and many times it just sits waiting for someone to spend time with. Sounds typical of many DTG printing devices.

This sporadic printing activity is typically the root of many daily headaches. One in particular that I see and hear about is the dropping out of a white ink channel(s). Although each DTG machine may vary from company to company or model to model, the overall concept is the same. Deliver ink from the source to the print heads and produce awesome looking t-shirts that help pay for the machine and make your business grow. Sounds simple enough.

But when the printer is not performing as it should, a simple process can turn into a major frustration. Many users may run a simple head clean or two to get the channel printing again. Hopefully, this is the only fix you need. However, when head cleans are not solving your problem, it is time to dig in deeper.

The Most Common Reasons for a Channel Drop Out

One of the most common reasons for a channel to drop out suddenly is when air is introduced into the print lines. When the air in the lines is minimal, a head clean or two can resolve this. When multiple heads cleans do not seem to help, the air problem is a little deeper than just bubbles in the lines.

anajet-mpower-dampers1Having been around DTG printers for quite some time (AnaJet in particular), I have a good sense of what components could attribute to the problem. In many printers, the first place to look would be the dampers. In most DTG printers, the ink lines go from the source to a damper dedicated to each color. The line connected to the damper should have an “o-ring” on it so that when the brass nut around the ink line screws onto the damper, the o-ring blocks air from entering the system. Checking these connections and the condition of the o-rings maybe one solution to resolving an air leak.

However, not so in my case. I had to dig even deeper.
nva-screw-locations1The AnaJet mPower series DTG printers incorporate a re-circulation system for the white ink lines to help prevent settling of the TiO2 in the white ink. The white ink channels use a slightly different needle valve assembly than do the CMYK channels. Over time, I have found that white ink builds up inside this valve and is the root cause of one of my  white ink channels dropping out. The good news is, this is actually a simple fix. The only tools I will need is a phillips screwdriver and possibly an old tooth brush.

The first thing to do is power down the mPower printer. Pop open the hood and locate which channel is not printing (there is only two…so it’s one or the other). The 1 st white channel (or inside channel) was the problem in my case. Remove the ink cartridge from this location. There is a small PCB just above the area that I need to work in. This PCB is easily removed by gently lifting up on the sides, one at a time and the board will pop free. I did not find the need to disconnect anything from this board. I was able to just rotate it out of the way.

Using a phillips screwdriver, remove the two silver color screws that hold the needle valve assembly (NVA) in place. One is at the bottom left corner the other is at the upper right. The entire block is now free and can be pulled away from its mounting location. On the same side of the NVA are two more black phillips screw heads. Removing these will open up the NVA. Use caution to not lose the small hex nuts on the back side of these two screws.

With the NVA now open, it was apparent that white ink had built up on the bottom portion of the inside valve area. Using an old tooth brush, I simply brushed away the ink deposits and wiped this half of the assembly with a clean cloth. I took the other half of the assembly to the sink and thoroughly rinsed all of the components and then wiped them down with a clean cloth prior to re-assembling the two halves.

After re-assembling and re-mounting the NVA, I ran two head cleans and my white was completely back to where I had expected it to be.

Understanding the root cause of my problem and being able to fix it simply had me back up and running in no time. I will now implement a monthly inspection of the NVA as preventative maintenance.

In our next instalment, we’ll talk about other preventative maintenance procedures needed for an enjoyable summer vacation.