Abstract/Background:
Print Quality is a simple term for the complex series of steps and variables that allow the printer to output beautiful images on your substrates. This article is meant to be a starting point to get you thinking about different settings and/or things to check when your print does not look ideal. Providing close-up images of defects in Production images is helpful, but often the Diagnostic Images of Alignment, Nozzle Check, and/or Grey Level Checks are the most useful to help us see what you are seeing and determine what is going on. Note that Print Quality is sometimes confused with Drive Electronics problems, which will be addressed in a separate article.
Symptom(s):
There are a wide variety of symptoms that Print Quality covers. If you have images that are fuzzy, stretched, squished, streaking, missing jagged chunks of nozzles, misaligned, too light, too dark, over-cured/cracking, not fully cured, etc...you have come to the right article! See below for things to check, grouped by scope of defect.
***IMPORTANT*** Always try to replicate the problem to confirm what you are seeing before making any changes. You should NOT do everything listed here at once--try one thing and then do a new test print to compare Print Quality. Document all test print results with dates and pictures.
Potential Solutions/Causes:
If the print defect is only on one printhead,
1. Was the printhead replaced recently? New printheads may need voltage and alignment adjusted. Also, new heads sometimes start printing poorly right out of the box, but can recover over time with enough exercise/printing.
2. Was the voltage multiplier in PrintManager Diagnostic Settings (Voltages Tab) changed? Why? Is one head an outlier/more than ~10% different from the others? Check against historical values, ask PPSI for settings from install if unsure.
3. How does the printhead look in the Alignment and Nozzle Check diagnostic files? Look for X, Y, and Twist Alignment. Check the Printhead offsets for reasonable values.
4. Are there any loose Adjustment Screws, Mount Screws, Springs, or Dovetail locking tabs?
5. Visually inspect the Nozzle Plate for debris or scratches from possible head strikes. Check the edges of the printhead for any ink leaks or ink weeping out of the nozzles.
6. Increase the duration/intensity of Purge via the Web Interface, and do several purges and a Wipe to really prime the printhead. This can drop a lot of ink depending on the duration, so be sure to keep the Drip Tray Drain Pumps enabled during these steps.
7. In order to try and recover a single jetout on a head, a more drastic step beyond automated Purges/Wipes is to do a Manual Wipe with flush, IPA, Ethyl Acetate, or Acetone. Make sure to use a fibreless cloth--PPSI can provide 00-25207 Polyester Clean Room Wipes if needed. If ethyl acetate or acetone is used, an immediate Purge or Spit should be executed to avoid the fluid lingering in the nozzles. This practice is inherently risky because wiping the heads with any material could introduce new contaminants unless extra caution is used. Never put acetone through an SG1024 printhead.
8. To confirm it is not a Drive Electronics issue, try swapping HDC's and/or printhead data cables to see if the print defects follow the head or board or cable. Always have Drive Electronics power OFF when plugging/unplugging cables!
If the print defects are on several printheads in the same color,
1. Are the affected printheads all on the same PCC-E? Try swapping the position of two PCC-E's to see if it follows a certain board.
2. Are the affected heads all adjacent or random? Adjacent heads could have experienced a localized head strike or debris contamination. Random heads could be contaminated ink/ink supply.
3. Are the affected heads all at one end of the printbar? If they are all towards the rear of the printer, it could be a case of ink starvation. Two possible solutions are 1) adjust the angle of the ink supply or even the whole DICEblade to be perfectly level, or 2) increase your Weir Level setpoint on the Settings page of the Web Interface. The minimum Setpoint should be around 52%, and the maximum recommended is about 66%. If you are on the lower end of this range, increase the value by 2% and try printing again. Note that the actual Weir Level % feedback from the float sensor will always be a few % below the setpoint.
If the print defects are on all printheads in a color,
1. Is the ink supply at the correct temperature? Check the Setpoints on the Settings page of the Web Interface. A Heater Distribution Board or Resistive Heating Element could have failed.
3. Does increasing the voltage or temperature significantly (+/- 5% or more on voltage, +/- 2C or more on temp) change the print output? This could be due to a failing Power Supply. Check the output of the HDC Power Supply in the DICEblade's Front-side electrical enclosure (check schematics for PSU name and desired voltage)
4. Are the v-blocks seated correctly on the alignment ball mounts? This could manifest as printbar twist (alignment getting progressively worse from one edge to the other) or degraded print quality from edge to edge.
5. Check the fly height at both ends of the printbar/substrate. Does your system use shims or an operator-controlled height? Is everything being set correctly and consistently?
6. Check that you are using the correct waveform for this color. The waveform should be set by PPSI prior to install and should not be changed unless the type of ink is changed. Feel free to check with us to ensure you have the right one selected. This can be checked in the Print Manager Print Queue Diagnostics Settings Window on the Waveforms tab, or in the Meteor Monitor Configuration file.
If the print defects are not color dependent (occur on all colors at once OR sporadically),
1. Check your Print Offsets for major outliers. Compare to install values and/or Archived configuration files.
2. If the print looks stretched out or skipping, check that the encoder is not slipping on the first shaft of the arched roller assembly (DICEweb/DICEpress) or output shaft (DICEtrax). On DICEwebs and DICEpresses, also check that the Speed Sensor/Cog Tooth Sensor is reading consistently on the last roller in the arched roller assembly for accurate speed feedback.
3. Does the print look like it is not fully cured or sliding around like oil in water? Confirm your Main Cure Lamp (and Pinning Lamps, if applicable) are set to the correct intensities and working as expected.
4. Does the ink in certain colors or color combinations show streaks when printing solid blocks of color? This is usually seen in higher ink laydown applications and is a sign of ink to substrate dyne level incompatibility.
5. Check all your communication cables to and from the HDC's, PCC-E's, and Network Interface Card(s) at the PC.
6. Do you have different workflows for images? Do you have different RIP Configuration files? If the images just seem too light or dark, it could be a matter of ink limits. Check with PPSI if you are not familiar with this process.
General/Other:
1. Confirm the Meteor Config file is correct. Record the Meteor Monitor Revision and report to PPSI.
2. How do the Pump RPM's look in the Pump Info Section on the Home page of the Web Interface? Do they seem higher than other colors, indicating a vacuum leak? Check all Luer fittings and clamps on the ink tubes to the printhead(s) and at the ink supply fittings.
3. Is your ink expired? Check the Manufacture/Expiration Dates printed on the label of the 5L Cube in the Bulk Fill Box/Stand. Inks generally last twelve months/one year from manufacture date, and should always be kept in a climate controlled environment to prevent degradation. This can appear as deviated jets across multiple printheads or the whole printbar.
4. Did you change to a different type of ink? All inks have been tested and validated for specific conditions and substrates and any new ink is not guaranteed to perform well.
5. Are you printing on a new substrate? Different substrates have different surface energy/dyne levels that affect ink wetout.
6. Is there any pre-or post-print treatment (corona, top coat, etc.)? These can affect the surface energy and ink wetout.
7. In addition to the temperature setpoint of the ink supply, some HDC's have built-in heaters and temperature feedback for the printhead (e.g. SG1024). Check in Meteor Monitor (on the Status tab tables on the left) to see the actual jetting temperature of the ink. If it is significantly lower than your ink supply setpoint (more than 2-3 degrees Celsius)
8. Check for abnormal vibrations or disturbances to the machine or environment. Loose bolts in the frame, a fan blowing air directly on the print engine, and even passing trains have had measurable and noticeable impact on print quality.
In summary, the complex topic of Print Quality can be impacted by many different things, and you may even come across new factors not listed here. Please tell us if you do, so we can learn and improve from it as well! During your troubleshooting, stay positive, take notes, be diligent, and always feel free to reach out for help. No one person is a master of all of these topics, and they were accumulated over years of experience.
Additional/Related Information:
Drive Electronics Problems: https://ppsihelp.freshdesk.com/a/solutions/articles/27000075217
Alignment Procedures (Samba and SG1024): https://ppsihelp.freshdesk.com/a/solutions/articles/27000072793
If you have other problems not listed here, or additional questions on how to diagnose/identify these items, feel free to start a new Support Ticket and an Agent will reach out to you shortly! Emailing support@prototypesys.com will automatically create a new Ticket in the Freshdesk system.