Sublimation stress!!!!!!!

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Allianceskis
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Joined: Tue Dec 11, 2012 11:12 pm

Sublimation stress!!!!!!!

Post by Allianceskis »

https://i.imgsafe.org/f8bf3df082.jpg

https://i.imgsafe.org/f8ce280ab2.jpg

https://i.imgsafe.org/f8d1668956.jpg

https://i.imgsafe.org/f8d1c74eab.jpg

My sublimation press keeps doing this in the transfer process, i can't figure out why as i have had perfect results with the exact same settings. can high levels of humidity have an effect on the process as it was raining this day.

Any info on this would be hugely appreciated as its quite a costly thing to keep getting wrong.

Cheers
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chrismp
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Location: Vienna, Austria

Post by chrismp »

What type of sublimation press do you have? I sometimes have the same problem with certain types of topsheets and I think it comes from my vacuum press not being able to create full pressure quick enough. The topsheet then starts to contract under the heat and wrinkles form that cannot be flattened out again by the press.
Allianceskis
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Joined: Tue Dec 11, 2012 11:12 pm

Post by Allianceskis »

The sublimation press i have consists of;

5 air rams 300m apart pressing a steel bed
9mm fibre cement sheet
silicon heat blanket
5mm aluminium sheet

graphics and top sheet

5mm silicon blanket
18mm mdf
steel frame again

The air rams are ran at 90psi and apply quite a lot of pressure

i run the heat blanket at 155 celsius for 9 minutes.

What sort of time frame/heat do you run with?

I've just purchased a 25mm ceramic fibre blanket to put on top of the silicon blanket to hopefully take up the rest of the minor discrepencies.

Fingers crossed haha
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chrismp
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Location: Vienna, Austria

Post by chrismp »

That sounds like you need a second hard surface (i.e. thin aluminum sheet, maybe 1-2mm thick) on top of your silicone blanket. The wrinkles from material contraction can become quite strong and indent the soft silicone blanket in some spots.

I usually press at 155C for 5 minutes with white PBT topsheet. However, you should always do some small test pieces with different temps and times to see what works best.
mikic1
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Joined: Tue Nov 15, 2011 11:51 am
Location: sweden

Post by mikic1 »

I use a vacuum press for sublimation. I run thru 3 presses until I designed a one that works well.

Setup,

--silicone membrane/blanke
--2 layers of breather 150gms fabric
--sub paper
--sub topsheet
--2mm aluminium sheet
--silicone heating blanket
--isolation
--ABS sheet for vacuum seal
--MDF table

I found that
1) Not having a breather between final silicone membrane and the graphics can keep trapped air and give similar result that you have
2) Vacuuming too fast does not allow the air to escape and the topsheet to expand at the temperature and makes same wrinkles as you have
3) I press at 135C and 1 atm, for 4-5 min, then cool to 105C before I take it out.

I think you should try, less pressure, and less temperature, a breather fabric and also dont ramp the pressure too fast (so the materials can expand and reach the right temp.
Also the silicone expands a lot at this temp., so it will create wrinkles.
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chrismp
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Location: Vienna, Austria

Post by chrismp »

@mikic: what material do you use as insulation under the heat blanket?
mikic1
Posts: 183
Joined: Tue Nov 15, 2011 11:51 am
Location: sweden

Post by mikic1 »

Hi, I found this one in a local store, its some kind of mineral board (promatect L), used to fireproof buildings. It works well for vacuum press, I dont think it will work in pneumatic press, it will crack.

http://www.beijerbygg.se/store/privat/b ... -1200x2500

it has a very low thermal coeff. 0,087 W/mK
mammuth
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Location: somewhere in the alps

Post by mammuth »

Maybe something like that could be used in a pneumatic press:

http://www.flumroc.ch/produkte/bauprodu ... denplatte/
Tom
Allianceskis
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Joined: Tue Dec 11, 2012 11:12 pm

Post by Allianceskis »

i use 9mm fibre cement board which is glued to 18mm mdd sheet thats attached to the steel frame.
i think it may be down to what chrismp said with the top sheet being able to wrinkle when the silicon blanket gets warm and deforms ill try with a aluminium sheet o top of it to try and maintain two flat surfaces.
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