Polyester mesh lifetime with aluminium frames

[Susana]

Hello to everyone!

I am new in here. I have started screen printing recently and there are a few things that I am still quite lost. I have been trying to find for several days the polyester mesh lifetime. I know it depends on the amount of prints, but could it be possible that the mesh losses tension just by being attached to the frame?? A friends of mine told me that it losses around 2-3 N per month in storage... does it mean that I need to re-strech all my meshes every half a year even when I am not using them?

I would appreciate some light on this topic, as I am a bit lost

Thank you so much in advance!!

[Chuggins]

Hi Susana,

Quick piece about mesh:

Mesh is woven threads overlapping each other. The place where it overlaps is called the knuckle. Within this knuckle there is friction/tension as the threads press onto each other. When you put the mesh under tension (stretching a screen or retensioning) you increase this tension/friction. This is the state at which you will receive a screen from any supplier. There will be some natural slow release of tension over time.

However this is not a static state (yay static frame puns), you can cause changes in this tension. As you print, each stroke "massages" the knuckle, releasing the tension. This releasing of the friction, lowers the tension of the screen. This is why you see screen tension drop over time as it sits - but it will only drop so far - until you print. Thats when the stored tension in the knuckles gets released. This will continue until some "equilibrium" is established. At a certain point the mesh just cant relax anymore and you see some stability... until you increase the tension - this is where retensionable frames come in. This becomes another topic about work hardening of mesh with retensionable frames.

But as to your question about longevity of mesh. You will not continually loose tension on a static screen as it sits in storage. The more you print with a screen, the more you can see tension diminish, but it is a case of diminishing returns. Directly after creation of a screen, it can be at 27n (example), by the time it gets to you it can have relaxed to 22-24n of tension. After your first couple of jobs it will relax further - there are a few variables here. After your 5th or 7th job, you will not be able to record any tension loss.

Part of why there are so many "low tension" screens in the market, is due to them being a commodity item. Printers want to buy the cheapest screen possible and vendors compete to create the cheapest one they can. This directly equates to cheap mesh, cheap frames, and lower tension levels.

Let me know what questions you have about what I wrote and I will dive into it.

[Susana]

Hi Chuggins,

Thank you thank you thank you so much for your super fast reply. You made me possible to understand how it works. The only remaining queston I have is when this lost of tension (in a static state, without using the screen) lasts. I mean, I know that after manufacturing, the mesh losses like 10-15% of the tension and it stabilizes in the next 162 h (at least the ones we are getting). Does the mesh get this "equilibrium" if it is not used? Or does it need to be used in order to "massage" the knuckle and release tension?

Thank you again!!

[Chuggins]

Mesh, under tension, will relax to the point where the tension - is not enough - to move the threads around. At a certain point the mesh is "stable". This can be 3-10 days later depending on the method used to stretch the frame.

Once you start to put pressure on the mesh - either with a pressure washer, coating and drying the screen (this is small but measurable), or (the big one) printing shirts - You will continue to see tension drop until another state of equilibrium is achieved. The time frame for that is highly variable.