Wanted: QMDI Veterans Sharing Tips

I'm looking for any QMDI tips that you veteren di pressman can share with me. I'm fairly new to the whole print trade being 24 years and only starting in print 2 years ago, but I'm loving working at our little 4 employee shop where I get lots of variety. My boss, a great pressman - trained me on a 2 colour GTO and a wee little Multi.
We got our QMDI Plus less than a year ago, and I got Heidelberg training (super great guys!) when the press was installed. I'm the only one who is trained, so I'd appreciate any help I can get from experienced operators.

Initally there were numerous issues with the press, which didn't all surface at the same time. It was refurbished and had sat for awhile. However, Heidelberg was awesome for fixing stuff while the press was still under warranty. Now for the most part it seems to be running quite well, but I'd like to know how to optimize its(and my) performance.

I've got a bunch of questions, some of which have been discussed elsewhere and on this forum, but if you could give me your experience on a couple of them that'd be fantastic. Some of these things I did get trained on, but as I saw by being trained by 2 Heidelberg guys, some things are a matter of opinion and preference.

1. Ink
We're running the Heidelberg brand Saphira. Our experience is that without enough powder its set off is brutally glue-like. My boss says it's the stickiest ink set off he's seen.. We haven't tried any other inks yet but I'd like to.

2. Black Solids
If it's a large straight black it tends to print weak, if it's rich black it comes out much better. Possibly an ink brand issue? (Our chiller runs around 22.4 deg)

3. Black Plate gets speckly/dirty on non image areas as the run goes on. It starts out clean and gets worse with the run. I'm not sure why the black does this but not the other 3 colours.

4. Powder packs in jar.
It didn't do this in the winter. We have AC. I have rice in the jar. The lines are clear. I'm using old Spray-Rite 250. A couple hundred sheets after stirring and it gets packed again. Any preferences/suggestions on powder?

5. Do you leave ink in the fountains overnight or always clean them out? If you leave it in, do you zero the ink keys?

6. Do you scrap your ink in the trays when you wash up or put it back in the cans?

7. How often do you need to clean your blanket washers? It seems that all 4 don't stay working well long(Our DI has the switches so that I can run blanks, cleaning up the blankets with the paper. I use this feature) I have a hard time knowing how full to fill them with solvent.

8. Cleaning plates manually
If you need to clean a plate by hand is alcohol the best?

9. Do you have a morning maintanance routine? I was taught to clean the laser heads w/alcohol and clean the vacuum cones.

10. MAINTANANCE
(Here's what I've been trained to do, I'd like to hear what you've found is benefitial/necessary)

DAILY
-Clean laser heads with alcohol
-Clean vacuum cones
-Open air valve under feeder (tech 1 said monthly, tech 2 daily)

WEEKLY
-Clean blanket washers
-Clean double sheet detector eye
-Clean delivery (spray down with WD 40, let soak over weekend, oil chains monday)

MONTHLY
-clean yellow pump under feeder
-grease 3/2 valve
-grease 5 cam followers for feeder
-grease the 4 oscillating cams contol panel side
-grease gear on plate cylinder, gripper bars

Non-Tech things I've learned from forums is to
-Blow out the 3 vacuum filter bags under the steps
-Keep gap guards clean

11. Press speed
I was adviced against running over 8000-8500 or so as it wears out quicker. That's fine, if it's running late there can be the temptation to speed it up to save a few minutes

12. What run length is generally max for plate life? Does your black plate wear out the quickest?

13. Any other tips/tricks/suggestions?

Thanks so much, and hopefully this thread can be beneficial to more than just me!

-Korey

 

Korey,

I'll answer each of these in the order you posted them. Forgive me if this is a long post as I am somewhat familiar with the machine and tend to be detailed. LOL

1. In this area things have changed since I have been around the machine. When the machine first came out in 1994, there were very few ink manufacturers who provided inks that work on the machine. Since then nearly every company makes an ink for the QMDI. In my experience no one ink covered everyjob, although you do want to choose an ink that will cover at least 90% of them. In the case of the Saphira brand inks we have tested them on the QMDI and found that one to work the best. While my opinion may be biased I can tell you I have watched many a sheet go through our equipment testing different ink and coating combinations here in our Print Media Center.

2. Build rich blacks when ever you can. Black on it's own does not print well on the QMDI in the case of large solids. This is due to the size of the ink train as well as the characteristics as to how the ink is applied to the blanket in the case of the QMDI. Keep in mind that the ink is pulled out of a thermally etched well in the plate. It is not on top of the plate as you would find in the case of a conventional plate. As a result the ink splitting is somewhat different, causing a mottled effect when printing a solid on the QMDI or any machine of its type. This is what causes not only black to look not as smooth in a large solid but the other colors also.

3. Two factors cause the plate to collect ink in the non-image areas of a QMDI. Too much pressure from the blankets being over packed or paper dust and excess powder. The reason it is commonly seen on the first unit is because this is where your paper starts to bring contaminants in contact with the 1st blanket. Make sure you cut your paper with a sharp knife and if you are running paper through for a second pass make sure you run the powder as low as possible on the first pass.

4. It is recommend to periodically stir the powder in the jar. This is not unusual to happen in any powder system in which no agitators or vibrators are used. It has nothing to do with moisture, but to do with low frequency vibration caused by the press during a run. It packs the powder over time. Stir it in between press loads is the typical recomendation.

5. You can leave the ink in the fountain over night if the ink is the type to do so. Always close the keys when doing so. Personally, I prefer to clean the fountains every night and clean under the ink keys thoroughly to prevent build up on the protective underfoil.

6. Always scrap the ink, putting it back in the cans only opens you up for trash to stick to the plates.

7. I recommend to clean the blanket washers once per week under an 8 hour per day operating environment. This does not mean dumping out the fluid adding a new felt with fluid then sticking it in the press. I mean a full, tear the entire blanket washer down, clean every component including the tray until there is not a spec of ink left in it. If you do this they will work just fine.

8. Alcohol is the best means to wipe down a plate when pre-cleaning large solids before allowing the auto plate washer to come on.

9. Your morning maintenance is correct along with topping off the blanket washers and predampening the plate wash felts before your first burn in the morning.

10. I agree with all of your maintenance list.

11. I run the press at the fastest speed it is capable of producing work at. Typically this is in the 8,500 iph to 9,000 iph range. The machine was designed to run at 10,000.

12. On the first pass 40,000 impressions is not unusual provided the blankets are packed properly. On the second pass the 1st unit will generally start to show signs of wear around 20,000 impression depending on the amount of powder you ran on the 1st pass.

13. There are tons of them. Look through this forum from beginning to end and you don't find anything you are looking for post a question such as the only you already have.

Good luck with your machine!

 

Thanks so much Paul, that was a great response! I fixed up my numbering so now the list should be numerical

RE #4: the powder is getting packed quicker than it takes to run a small lift, but it didn't do this when we got the machine. Since than, I've added rice and have started keeping the jar fairly empty to try and keep things light in there (originally we didn't have AC when we got the machine and I first noticed the problem on a hot humid day). Maybe I'll have to try ditching the rice and filling up the jar with powder tomorrow and see if I have better results.

 

My powder situation seems pretty good now. With AC and a full jar of powder I'm happy

 

RE #2: What do you people do if a customer-supplied file has a large black solid that isn't rich?

 

Make it rich.

 

Is there an easy way to do that?

 

Enfocus pitstop pro, a plugin for acrobat. Or in case of emergency open PDF with Illustrator but that is not the way I like it.

 

That program would be sweet..kinda pricey for my little shop at this point! I might have to talk to my graphic designer about using Illustrator tho