When is ink starvation to be expected? (and ways to mitigate?)
Last night I began a print run of a solid, single colour (black) print on white T-Shirts last night. Artwork's a 25x25cm design of a block colour speech bubble with knocked out text, so does admittedly use a good (but hardly extravagant) amount of black ink per print. Turnaround's quite quick for each print, so the machine was almost continuously printing for several hours.
After about 6/7 shirts, I started to notice lines developing in the print on each pass from print head ink starvation (although these were covered up as the print head did its second and third passes). However, after another few shirts, the banding and low ink became noticeable.
Running an ink charge improved things but is obviously wasteful. I started the print run using 1440x720, so on a whim I tried one shirt on 720x720. It was so light (and banding was so obvious) I had to overprint at 1440!
When I first started printing, I was using a pause-after-pass delay of 100ms in Print Pro, later raising it to 500 then 1500ms. This made no noticeable difference to the ink levels, so I can only determine starvation from some other problem is causing this.
Air caps on ink bottles are all open, ink lines are completely clear (I should know... I flushed them last maintenance), the print head's in 100% condition and the dampers are all fine (again, flushed all of them last maintenance). Print head was cleaned before, during and after run, as was capping station and wiper.
As this ink starvation problem verges on the ridiculous - these machines are theoretically supposed to be able to run almost constantly, right? - I'm wondering if there's something else I'm missing. I do realise that after a while ink pressure will drop (hence ink charging making a slight difference) but is there a better way to maintain ink pressure when doing a continuous print run? I was only printing 25 shirts last night - I have another 80 to do today and can ill afford to be sat around running ink charges to keep the ink levels up.
Re: When is ink starvation to be expected? (and ways to mitigate?)
Check your humidity level as well.
I have personally done 125 piece runs with an HM1-C and not had any ink starvation issues. How long has it been since you replaced your capping station and/or dampers?
Re: When is ink starvation to be expected? (and ways to mitigate?)
The humidity level is probably on the low end, but not awful. (I think; the boss STILL hasn't bought a hygrometer although I keep poking him with a big stick!) We do heatpress in the same room so hopefully the moisture coming off the shirts helps a little.
Capping station: about 3/4 months, kept in good nick. Dampers are a bit older but (albeit on visual inspection) seem to be functioning perfectly - we did have some replaced at the same time as our new print head (which was around the same time as the new capping station).
Just started getting banding and lining at 720x720 time for a pit stop!
Re: When is ink starvation to be expected? (and ways to mitigate?)
Are you printing just 100% black? What I do is run 50% cyan, magenta and yellow along with 100% black when I have long runs seems to cover better than 100% black only.
Re: When is ink starvation to be expected? (and ways to mitigate?)
Quote:
Originally Posted by jppurdon
Are you printing just 100% black? What I do is run 50% cyan, magenta and yellow along with 100% black when I have long runs seems to cover better than 100% black only.
I had the same idea as your good self about halfway through the print run had a quick play with colour mixes but unfortunately I didn't have enough time to experiment as it was nearing midnight and the job had to be finished for the next morning (ended up finishing at 1:30am)
I was trying to reduce my black ink consumption, but it seemed from my very quick experiments that mixing up a rich black ala Photoshop just didn't provide satisfactory results. Ended up using K100 C20 for the last thirty shirts or so - but had to do several print head cleans after the first fifty shirts after banding really increased (flippin' thing!)
I'll definitely try a mix of the other inks + K100 when printing solid black next time. Do you print at 720x720 usually?
Re: When is ink starvation to be expected? (and ways to mitigate?)
Quote:
Originally Posted by christopherw
I had the same idea as your good self about halfway through the print run had a quick play with colour mixes but unfortunately I didn't have enough time to experiment as it was nearing midnight and the job had to be finished for the next morning (ended up finishing at 1:30am)
I was trying to reduce my black ink consumption, but it seemed from my very quick experiments that mixing up a rich black ala Photoshop just didn't provide satisfactory results. Ended up using K100 C20 for the last thirty shirts or so - but had to do several print head cleans after the first fifty shirts after banding really increased (flippin' thing!)
I'll definitely try a mix of the other inks + K100 when printing solid black next time. Do you print at 720x720 usually?
It's surprising how much of a difference you'll see between 100K black and a rich black. I wanted to show you this web graphic I found:
All you need is a percentage of C, M, and Y. (100% of each probably won't print well.)
You also have another option -- do you know if your RIP accepts RGB colors? That's how EZ Artist works. If so, just select zero for all the RGB values. That will give you the best looking black.
Re: When is ink starvation to be expected? (and ways to mitigate?)
We're using Print Pro, which afaik is happy with CMYK or RGB colourspaces... Usually work in CMYK out of Photoshop though.
I had so many problems with Photoshop separating black to rich black on export when I first started designing for print! Took me AGES to figure out what was going on.
I'll have to give rgb0,0,0 a try...
Going back to my original question - what's the best way to work around a potential ink starvation issue? Aside from raising the bottles, running ink charges (neither leaving the machine to sit for a while or carrying on straight away seemed to make a big difference). Running several print head cleans seemed to make a bit of a difference however... Is this an indicator that it's a lack of adequate humidity as opposed to ink flow?
Re: When is ink starvation to be expected? (and ways to mitigate?)
Quote:
Originally Posted by christopherw
Going back to my original question - what's the best way to work around a potential ink starvation issue? Aside from raising the bottles, running ink charges (neither leaving the machine to sit for a while or carrying on straight away seemed to make a big difference). Running several print head cleans seemed to make a bit of a difference however... Is this an indicator that it's a lack of adequate humidity as opposed to ink flow?
Well, you don't want to run ink charges. If you have to run ink charges regularly in order to prevent starvation on your HM1, you're raising your ink costs per shirt tremendously.
If running several head cleanings helps your print, this is an indicator that you don't have adequate ink flow. The head cleaning is actually pulling ink through the dampers, and that's why you'll see an immediately good result. I actually think you'll see as much of a difference running 1 head cleaning as 3. Try running a head cleaning in the middle of a job, just as you start to see banding.
The thing to do is troubleshoot why you're getting inadequate ink flow. Maybe a damper filter? The ink lines on the HM1 are fairly narrow, maybe your ink lines have ink settled in them? Check the humidity, too.
Re: When is ink starvation to be expected? (and ways to mitigate?)
Ink lines were the first thing I thought about, so when I did a strip down of the machine last time I cleaned each individual ink line and damper as well as the other serviceable parts! Took me forever, and the syringe flew off the end of a tube several times spraying me with murky semi-cleaning-fluid gunk that was fun.
When I started to have problems last time, I raised the ink bottles slightly (put them on single blocks of that curly polystyrene packing foam inside their springloaded metal holders). Only thing I can think of is that the dampers are slowly dying, so buying eight new ones is a consideration down the line but for the moment not really worth the cost :/ (don't you love that cost-benefit valuation!)
what kind of humidity does your machine sit around in? closed office with heating or air ventilated with through breeze?
Re: When is ink starvation to be expected? (and ways to mitigate?)
Proper humidity levels is one major thing that many users ignore. It is crucial to the proper operation of your D-T-G printer. Here is a repeat of a post I put up last week:
It's that time of year in many parts of the country where it's the cold season and you crank up the heating system to stay warm. The unintended consequence of that heated air is a low to no humidity level in your building. All digital garment printers (make that all inkjet type printers) work best at a humidity level of 40% to 80%.
You WILL have printing problems if you let the humidity level drop too low. This is the time to invest some money (very little) in a hygrometer to measure the humidity in your printer room (digital ones can be found for $10 to $20). And also purchase a humidifier (room size units run from $50 to $100 at Home Depot, Lowes, Sears, etc.). Use both to maintain proper humidity in your work space and you should have a trouble free winter.
This also holds true throughout the year in dry climates such as Arizona with "zero" humidity. Avoid problems - humidify to proper levels.
Re: When is ink starvation to be expected? (and ways to mitigate?)
Quote:
Originally Posted by christopherw
Ink lines were the first thing I thought about, so when I did a strip down of the machine last time I cleaned each individual ink line and damper as well as the other serviceable parts! Took me forever, and the syringe flew off the end of a tube several times spraying me with murky semi-cleaning-fluid gunk that was fun.
When I started to have problems last time, I raised the ink bottles slightly (put them on single blocks of that curly polystyrene packing foam inside their springloaded metal holders). Only thing I can think of is that the dampers are slowly dying, so buying eight new ones is a consideration down the line but for the moment not really worth the cost :/ (don't you love that cost-benefit valuation!)
what kind of humidity does your machine sit around in? closed office with heating or air ventilated with through breeze?
Since Equipment Zone uses cartridges instead of dampers, I can't really speak to whether yours need replacement, but it certainly is something to look at.
We recommend humidity levels of 40-80 percent.
It is better to have your printer in an enclosed area without a breeze or window opened to the outside. That will prevent dust and debris from coming in from outside. Also, if you have a breeze, a fan, or a cooling vent blowing on your printer, you may be drying the print head out with that moving air.
You'll also want to make sure it's in an area that's kept around room temperature for best results.
Re: When is ink starvation to be expected? (and ways to mitigate?)
have to love the irony of the HM1 having a 60mm fan on the left hand side of the case sucking fresh air through the inside Wonder if I should disconnect its power cable when it's not being actively used? (I'm under the impression that fan is to stop ink spray from building up inside the machine as the device prints, but the fan's just on a dumb DC circuit and never stops...)
Re: When is ink starvation to be expected? (and ways to mitigate?)
Quote:
Originally Posted by christopherw
have to love the irony of the HM1 having a 60mm fan on the left hand side of the case sucking fresh air through the inside Wonder if I should disconnect its power cable when it's not being actively used? (I'm under the impression that fan is to stop ink spray from building up inside the machine as the device prints, but the fan's just on a dumb DC circuit and never stops...)
All I can say is that, in our experience with direct-to-garment printers, a vent or air blowing at the printer will cause issues.
Re: When is ink starvation to be expected? (and ways to mitigate?)
That is a very low volume fan. The purpose of which is important. As the printhead moves over the dump station and sprays ink, this ink actually floats around in a mist form. This fan pulls that ink away from the shirt and also away from settling on the encoder wheel. Turn it off if you want, but the reprocussions could be worse.
When is ink starvation to be expected? (and ways to mitigate?) 
time for a pit stop!
had a quick play with colour mixes but unfortunately I didn't have enough time to experiment as it was nearing midnight and the job had to be finished for the next morning (ended up finishing at 1:30am)
Wonder if I should disconnect its power cable when it's not being actively used? (I'm under the impression that fan is to stop ink spray from building up inside the machine as the device prints, but the fan's just on a dumb DC circuit and never stops...)
