I'm actually surprised we don't get more threads about trapping. It's something that needs to be done and done right, but can be difficult. I think it maybe have to do with the less experienced people don't deal with trapping and those who deal with it are to the point where they have it down. And I guess some don't deal with it at all.

I'd rather let the printer deal with it because he knows the tolerances he needs to have to get the registration right.

Wide format doesn't use traps.
Vinyl cutting does. Sometimes.

In the case of black, most traps can be handled as simply as overprinting the stroke or the type. But unless you know what you're doing and what your printer expects, trapping can live uip to its' name.

I overide all client traps period. I do the trapping. We don't charge for it anymore anyhow. It's not worth the risk it getting on press and some silly trap or wrong overprint or ko causes a $1,000,000.00 press and $30 and hour pressmen come to a screaching halt. Show your boss this thread.

Let the printer do the trapping.

I work in Prepress and we never use the client's traps.

yep, I learned this the hard way. A couple years ago when I first got into sending files to the printer myself, I thought It'd save money to do the trapping myself, and one of the objects ended up dropping out of the file, so I had to pay for another proof. Most printers don't charge for it anyways, and they prefer to do it.

Save yourself the headache and tell your boss you're better off leaving it to those actually RIPing it.

I've personally never done anything with traps. Nor would I know how. In the unlikely event that a printer asked me to do all my own traps, I would have to give myself a crash course, but I've just never needed to do that.

If any printer asks you to trap your own work, find another printer. And that's coming from a printer.

I work at a printshop. I would never use the client's trap either. I do have a hard time understanding it too because every application is different, all projects are printed differently on different presses etc. But the ONLY way I know that it's right is after I RIP it and view on the RIP computer. Sometimes I grab my pressman and ask him if that's enough trap because I don't even know how some of the presses with handle certain registration.
If it's not right, I go back to the Mac, try to fix it, send it over again, view it....sometimes I have to go back and forth until it's right.
Sounds like your print shop is just making up for lost time because they don't have someone that's that experienced about it either. And you have to be pretty darn good.
Just explain to your boss that all of your assignments are different, all of the printer's presses are different, and you would have to know how much to trap on each part of each project each time and won't even know that their RIP process would do it correctly. It's just in no way economical.
Do you even know for fact that your printer would accept your trapping or do they just automatically charge for that?
Sorry, but unless those designs change, there's no other way!

Speaking of trapping, does anybody know any good resources to learn more about trapping. Books, websites, classes?

Back in the early 90's Agfa put out a great little booklet called "Digital Color Prepress". To this day I still refer to it as it was one of the clearest references out on the subject. I have vol 1 & 2. It was a freebie handed out by their reps.

I tried to see if they had a link for the booklet, but I don't know if they still put it out there. Anyway, I scanned the 3 pages on trapping and stuck them in a pdf.
Feel free to download it.

AGFA_trapping.pdf [2.5MB]

yoink! thanks viki that will be most useful.

Don't trap yourself

There are basically two ways to output for Commercial Printing. One involves a RIP (Raster Image Processing) which basically means that information is translated from one language to something that an output device understands. As far as I know, most of these RIP's have trapping available. Whether it is used properly is another story.

The second way is to print Separations to the output device. The trapping had to be done on the files in most cases. If you use a printer that has one of these old school ways....find another printer.

With some files needing a trap you could drive a truck through and others being ruined if they are trapped at all, you should always leave trapping up the the printer.