Best practice for cleaning Riso GR 3770 drum screens?

[Guest]

A friend and I purchased a GR 3770 a few months back. It's taken the whole summer but my friend finally got it running again (with much help from the fine people in this forum I might add )

Now that we've run a number of test prints with all the drums we have, we've concluded that the drum screens need to be cleaned (or replaced?).

The documentation I have doesnt mention anything about this process. Does this mean we should just be buying new screens, or worse, buy a new drum? It seems a little extreme to have to go that far.

I'm looking for a something like a step by step, best practice for going about this process. Also, what kind of cleaning materials, chemicals are best suited to the job?

Thanks in advance for any advice.

[Brave Hart]

What makes you think that the drum screen needs to be replaced?
Please supply more info regarding your finding.

[alex_nelson]

Hey thanks for inquiring.

We don't think we have to replace the screens necessarily. But we do think they should be cleaned. Basically, they're just clogged with ink -- not entirely -- but it is affecting the print. There are patchy areas of ink coverage that are specific to each individual drum. This leads us to believe it's not a master issue.

I'll upload some photos in the next day or so so you can see exactly what I'm referring to.

Thanks again.

[Brave Hart]

Yes you can clean the silk screen and the drum screen just use normal diesel and leave to dry! But if you have this problem with all your drums, clean your impression roller first it might be caked up with old ink which leads to uneven density on printing.

[alex_nelson]

Thanks a lot!

So just to be clear, normal diesel as in normal diesel fuel?

[joelsa12]

Drum Screens

All you need is something that will cut the ink. Diesel is a little extreme. Pull off the master that is on the drum. Take rubber rejuvinator, or WD-40 on a rag. Rotate the drum and wipe off the whole screen while rotating the drum. Do not press too hard you will dent the drum body. The ink on the inside of the drum tends not to dry (that is if you are not using off brand ink). Put drum back in machine and make a new master. It may take 50 copies to get it inked up.

[m_tarighi]

with gasoil or benzin you can wash and clen it if didnt work replace it

[mikadonovan]

Yes you can clean the silk screen and the drum screen just use normal diesel and leave to dry! But if you have this problem with all your drums, clean your impression roller first it might be caked up with old ink which leads to uneven density on printing.

I agree. Your pressure roller needs to have all the dried ink scraped off first. ( I use a lock blade and gently scape with it to avoid damaging the roller). After that you need to check that your presure adjustments are within specs. Too little will cause problems like you are having, too much may damage the drum body.