Author Topic: Will "S" mesh fix this?  (Read 5104 times)

Offline ABuffington

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Re: Will "S" mesh fix this?
« Reply #15 on: March 24, 2014, 06:01:49 PM »
Part of the key to obtaining the highest tension possible is to have a very clean stretcher with no glue drips on any bars or insertion bars on a bar stretcher.  Sand these down (metal) w/ 600 weight wet and dry sand paper, or carefully remove glue drops from rubber capture bars before attempting S mesh. 

On Newmans you need to make sure you have adequate corner softening to avoid the sharp metal corner where the roller meets the end of the roller. On some Newmans this is an extremely sharp little square corner.  The inside of the channel that the mesh rests on is always problematic since Newmans last a long time and small nicks in the edge are enough to cut fine mesh. There also shouldn't be any dried emulsion bumps, major dents, or dried inks in the channel or on the roller where it rests.  Again 600 wet and dry keeps them very polished and smooth.  First time out you might want a lower grit followed by the 600 wet and dry.

The inside edge of a Newman is quite sharp.  You can fold S mesh under to capture a double layer of mesh.  This helps the tensioned mesh rest on mesh instead of being stretched tightly around the sharp inner edge.  Another trick is to put a flat, bump free layer of masking tape and wrap it around this sharp inside edge of the channel.  Both act like a shock absorber.

To avoid moire run a pencil line along a mesh thread in the long direction of the piece to be stretched so that on the first capture the pencil line is parallel to the channel.  This makes for consistent mesh capture and predictable non moire results. For Shurloc panels the mesh is captured well to avoid this.  In fact from my time studies, the Shurlocs cost no more if you have a stretch table or a manual op.  The time it takes to capture the mesh on a newman costs more in labor than the price of the Shurloc process. (4 captures, 4 softenings all done instantly with 4 clicks of the Shurloc strips. (One other note on Newmans:  Always make sure all rollers turn outward the same amount.  Older tables and sticky rollers can cause one roller to do all the stretching while the other barely moves.  Opposite rollers should always turn the same amount outward.  Keep a rubber mallet handy to assist the table, or bump the pulling clamps with the heel of the hand to help the stretcher out.  Sometimes the manifold can malfunction as well and not send equal air to the cylinders.  When one roller moves outward much more than the other it will curve the thread instead of keeping it straight and this will put a lot of strain on the threads and mesh knuckles.) 

One other key point.  Too often we get in the habit on Newman stretch tables of just flipping the air switch and allowing the last stretch settings to make the stretching faster.  Avoid this with S mesh.  Back the air off 1/3 of the way at least so it goes to 6-9 newtons, then bring up the tension on the warp and weft to desired tensions, just takes a few turns but this helps the mesh stretch a little.  You can also preserve S mesh by dropping the narrow direction of the frame 1-2 newtons from the long direction.  The reason for this is the main print forces are along the long direction, while the narrow width only gets pulled as the squeegee passes.  We textile printers use squeegees within 1.5 inches of the inside of the frame.  Dropping the narrow direction 1-2 newtons helps prevent momentarily high tension that occurs from the squeegee corner to the inside of the frame as it prints.  Eliminates a lot of popping issues on press, especially if you don't round off the corners of your squeegees.

One final trick:  You can stretch this mesh on the bias for specialty halftone techniques like square halftones that run vertically. (This is a Photoshop bitmap technique). Stretch mesh at 22.5 or 61 degree angle.  Affliction uses this technique a lot.  Draw a line along the long direction of the mesh piece, then with a protractor find 22.5 or 61, mark a dot at 22.5 or 61 and on the center mark of the protractor.  Draw another line connecting these dots,  this will be a 22.5 or 61 degree angle biased stretched screen. 

A newsletter we did for this: http://murakamiscreen.com/stretching-s-and-lx-mesh/

OK one more, sorry, I'm gone for a week so I'm putting it all out there now:
We carry another mesh with S designations:  LX Mesh

The main difference is less mesh knuckle, the threads look like they go through one another rather than over and under.  This creates a much smoother surface for the squeegee and also produces a slightly brighter base plate.  The softer outer core of this mesh gives a little to allow better transfer of plastisol.  It was originally designed for water base and discharge.

Al
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com


Offline ABuffington

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Re: Will "S" mesh fix this?
« Reply #16 on: March 24, 2014, 06:07:44 PM »
Hello Chris,

Thanks for the reply.

I know we tested some emulsion awhile back but I think we need to look at a few things there again.

1. Degreasing, use a commercial degreaser.  We have DGR-801 for standard work, for ultra fine details MS-Cleanser will degrease even better. Avoid using dishwashing liquids, most contain lanolin or other chemistry that can leave a residue. 

2. Next is exposure time.  Assuming we have well dried screens, should be real dry where you are, and I remember you had humidity controlled, so I'll assume dry screens.  Then exposure time would be my next area to check.  What emulsion, what time now?
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com

Offline ZooCity

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Re: Will "S" mesh fix this?
« Reply #17 on: March 24, 2014, 06:33:33 PM »
Hey Alan, it's not a degreasing or exposure issue I'm referring to, but one of the emulsion's bridging strength + water resistance. 

The issue is that we have not found an emulsion that will bridge a mesh with this much open area and hold up to a waterbased print run. You wind up with dots having very little thread contact and they will wipe right off on press.  Mark Gervais mentions the same technique you did for printing HSA inks and I agree, it's a great notion and the stencil can definitely resolve the detail but we cannot get it to hold up without delaminating.

I see Mark was using a Murakami pure diazo for this, the AC I think?  Is a pure diazo the solution for that bridging strength or is his choice to use pure diazo more related to supply costs for a large production outfit?  I understand that some of this may be proprietary info if you cannot share no worries.

Offline Nation03

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Re: Will "S" mesh fix this?
« Reply #18 on: March 24, 2014, 06:38:37 PM »
I switched over to static S-Thread frames and even those are a huge difference. I'd like to switch to retensionables at some point in my printing career, but for now, printing manually, these frames are amazing. 150-S is my go to mesh. Holds excellent detail and clears extremely easy which my hands are thankful for.

Offline ABuffington

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Re: Will "S" mesh fix this?
« Reply #19 on: March 27, 2014, 12:13:02 PM »
Hello Chris,

Maybe we should try Aquasol TS.  This is a lower viscosity emulsion designed for fine detailed wb/dc printing. Not meant for low mesh counts.  150 on up.  It is the toughest wb/dc emulsion we sell for fine details and halftones.   Add 8g of diazo per gallon, burn screen for as long as it can stand before it overexposes, post expose in sun or 2X on the exposure unit again, harden with A&B hardener.  Like I mentioned in another post you may want to try some micro grit to texture the mesh for better emulsion bonding.  On our mesh, all meshes above 280 come pre treated.  Give Kevin a call at Forward Printing in Oakland CA, he is really into fine meshes and printing discharge with lots of tones.  He did a 4/C process discharge/WB on 420S for us of 'Trapper Walt' (our salesman) that was excellent. 

Al
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com