Glass break on exposure unit

[Logoman]

I have an Exposure unit that I have had for about 1 yr and have broken the Glass 3 times. I have checked screens for burrs or anything that may break the glass as it vacuums down but have found nothing wrong there. I have tried Anieled  (told by Mfr. to use this type) Not sure if that is correct spelling, and Tempered and have broken both types. Any suggestions on glass to put in unit.

[Orion]

I know that lid alignment could be causing this. The fix was to close the lid and loosen the hinge screws. Turn on the vacuum and when the air is fully drawn from the blanket tighten the screws. That was a long time ago on an old Atlas 5-way unit.

[3Deep]

Is the glass breaking in the same place?

[Admiral]

Could possibly be cause by screens that aren't flat as well.

I forget the name of the glass but you really want the most non UV blocking glass.  It might have been low iron but I can't remember.

We had to replace glass 2x over 6 years though.  It stinks.  Luckily we don't use glass any more but if we do, the glass for the Starlight is thicker than the glass for our MSP 3140 so that's a plus.

[mooseman]

three thoughts
1 Look very closely over the entire area where the glass sets into the unit. Something as small as a screww head that is a little too high, a small bit of weld spaltter or a bent frame can cause a huge stress riser and a broken glass.

2 get sone 1/8 in thick rubber sheet , or some coroplast or some sort of cushion and set it ub under the 4 corners of your frame (screen corners) While this will raise the mesh higher off the glass it will not be a problem especially after while the cushions will compress down some. We have had coro plase cushions on our glass for several years.

3 reduce your vacuum amount. All you need is the blanket squeezing down on your overall image area. If your pump an seal is good you could be pulling a near full vacuum . If your screen  looks like Han Solo in the carbon freeze where every detail is sucked down you most likely are imposing way more stress on the glass than you need.

My bet goes with some high spot in the frame where the glass seats. this is not a weak glass issue there is a stress riser there somewhere.
mooseman   

[lancasterprinthouse]

Could possibly be cause by screens that aren't flat as well.

I forget the name of the glass but you really want the most non UV blocking glass.  It might have been low iron but I can't remember.

We had to replace glass 2x over 6 years though.  It stinks.  Luckily we don't use glass any more but if we do, the glass for the Starlight is thicker than the glass for our MSP 3140 so that's a plus.

I agree. I broke my glass twice in a month span. Turned out to be frames that weren’t flat. I have rollers so I just flattened them out and kept an eye on them but a quick fix for statics would be putting a few business cards under the corner that is off the glass so it applies even pressure during vacuum.


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[blue moon]

three thoughts
1 Look very closely over the entire area where the glass sets into the unit. Something as small as a screww head that is a little too high, a small bit of weld spaltter or a bent frame can cause a huge stress riser and a broken glass.

2 get sone 1/8 in thick rubber sheet , or some coroplast or some sort of cushion and set it ub under the 4 corners of your frame (screen corners) While this will raise the mesh higher off the glass it will not be a problem especially after while the cushions will compress down some. We have had coro plase cushions on our glass for several years.

3 reduce your vacuum amount. All you need is the blanket squeezing down on your overall image area. If your pump an seal is good you could be pulling a near full vacuum . If your screen  looks like Han Solo in the carbon freeze where every detail is sucked down you most likely are imposing way more stress on the glass than you need.

My bet goes with some high spot in the frame where the glass seats. this is not a weak glass issue there is a stress riser there somewhere.
mooseman

the top conformity of the blanket is not a good indicator if there is enough pressure. You should look at the image through the glass (from the bulb side) and see if you see the oil slick type of patterns. If the sheen like patterns are visible, you have a good vacuum. (or so I was told by one of the best printers in the world) It has served us well . . .

pierre