Inserting mesh into roller frames

[Rockers]

So I recently came across this this thread on the M&R forum called Mesh Manufacturer Choice.
There is a comment by Bill Hood which reads "Studies have shown that with the proper mesh insertion into the T-slots, this small variation in difference between warp and weft can easily be resolved. The instructions for Newman Roller Frames takes this into accord by having the X and Y rollers set at different positions prior to inserting the mesh. When the rollers are turned and the mesh is tensioned, the mesh is equalized."
So unless I have not read and watched the instructions on how to insert mesh into a roller frame correctly I don't know where having the X and Y rollers at different positions is coming from.
Maybe someone can enlighten me please.

[mooseman]

I am going way out on a limb here.....remessing screens is not difficult, and over technofiled or some high brow word like that.
There are a couple of simple things you should pay attention to that will bring consistant success.

get the mesh grain, (warp and weft)  running parallel / perpendicular to the rollers, mesh comes off rolls from the suppliers the edges are printed with the mesh data this goes to the side rollers. Get the mesh in parallel, if you are off the tension will energize the threads unevenly failing the overloaded bias threads.

soften the corners properly, this takes some skill to get it even and consistant more tecqunique here just like getting the grain in properly.

check your frames for burrs dried emulsion etc that will put stress points on the mesh threads. Overloading even a few threads creates a high stress point due to uneven tension distribution causing those threads to fail giving you the classic running rip in the mesh.

lastly don't get caught up in the micro tech BS that some of the gurus throw around. Terms like "studies have shown" should be a dead give away the issue is a labratory professor issue and most likely completely dissassociated with the real ink world we work in everyday.

mooseman




the weft properly soften corners, use a tension meter.

[Rockers]

Well I'm unsinnig Roller Frames now for a few years and never had any major issues, that's why I was wondering about having the x and y rollers in different positions before inserting the mesh as mentioned by Bill Hood. Don't know where he got that from, especially as he refers to the instructions from Stretchdevices.

[jsheridan]

Warp and weft.. I always forget which way is what.. I guess that's an indication that it doesn't really matter that much.
It has to do with the longer threads and shorter threads, I.e a 23x31 roller frame. The long threads (31) will pull more so the idea behind this is that if you offset the end rollers in more, it will take up the extra slack in the long threads vs the short (23) rollers.

In the end it's all wishy washy and not a big deal.

what's most important is to get the mesh square in the frame before you insert the locking strips.

[bimmridder]

Warp is the length, weft is the width. But who cares?! It may have mad a difference years ago, before most people here were printing. Back in the day, it did make a difference. All of the advances is mesh has made it's a non issue. And I'd bet my left one, if you asked Mr Newman himself, he'd also tell you not to expect all four rollers to turn the same amount anyway.   

[ZooCity]

what's most important is to get the mesh square in the frame before you insert the locking strips.

+1 for that. 

[ScreenFoo]

The weft threads elongate less, those that run across the length of the bolt tube--this is the direction you want parallel to the long roller.  The warp threads are those concentric to the tube you pull from--these should be parallel to the short roller.

As I understand it, the weft threads are under more tension when the mesh is woven and heat set, so they elongate less under tension.  By aligning these threads to span the larger distance, the elongation distance stays similar to the larger elongation of the warp across the shorter span, keeping your mesh openings square.

Perhaps NRM is manufactured differently from Hitech, PeCap, or Murakami mesh and doesn't require this.

[ZooCity]

The weft threads elongate less, those that run across the length of the bolt tube--this is the direction you want parallel to the long roller.  The warp threads are those concentric to the tube you pull from--these should be parallel to the short roller.

As I understand it, the weft threads are under more tension when the mesh is woven and heat set, so they elongate less under tension.  By aligning these threads to span the larger distance, the elongation distance stays similar to the larger elongation of the weft across the shorter span, keeping your mesh openings square.

Perhaps NRM is manufactured differently from Hitech, PeCap, or Murakami mesh and doesn't require this.

You know, I've read older lit that says this same thing but is it relevant still?  And what about the welded LX mesh?

I also hear that tpi is actually different in either direction!  TMI man, T.M.I.....I think we got enough to think about as it is.

[ScreenFoo]

Hah, didn't write that out right anyway--edited for longer elongation of warp, not weft. 
I haven't used 'welded' mesh, so I have no help for you there.
Anyway, if it's too much information, you can always ignore it--just trying to help with a good starting point that took me years to find info on.

What Rockers was referencing is getting extremely precise about it--actually stretching and work hardening a screen, measuring the difference in elongation, and indexing the rollers so they are evenly rotated at work hardening is a heck of a lot more work and more scientific than what I was talking about.  Aligning the threads properly is as easy as getting the right width of mesh.   

The reason I mention it is that I used to deal with rollers that were mixed, i.e. 2 screens with the warp the long way, 3 the short way.   The shop was totally committed to never retensioning, so once those screens were cycled fifteen or twenty times, the advantage of those properly aligned quickly became obvious. 

[ZooCity]

Well I meant that to be at least half sarcastic of course.  I'm all about balanced screens, it does make a difference.  And, you may have to put on the thinking cap and do a lot of that hard work up front setting up your standard but, once done, you never worry about. 

I bet that the issue of warp v. weft elongation you are referring to is exacerbated with the more rectangular frames like 25x36.  Sometimes I feel lucky we use the oddball 25x30 size, it's nearly square and very easy to balance.  I got a static 25x36 in for a flag printing job yesterday and it was very well made, yet the tension varies by nearly 5 n/cm length to width.