Sublimation/heat transfer of graphics on plastics lessons
As there is many requests on the topic on how to sublimate graphics onto skis or snowboards or kiteboards or wakebaords, I decided to collect some know-how here. Iv been getting lot of requests and see a lot of variations from person to person when it comes to sublimation, and this is expected as there are many factors involved. This is why I suggest you do a lot of testing on small pieces of material before you do a final press.
The factors that contribute to differences are,
- Press type: some use pneumatic heated press for sublimation while some others have a vacuum press. In case of vacuum press, the only thing pushing down is a silicone membrane. So when the press is heated and clamped down, there is not a lot of heat sink, it will keep almost constant temperature, and also the press cools down very quickly. As for pneumatic press, there is a lot of heat sink when clamped down, so the press takes time to heat up correctly and also to cool down. So the processes here are different.
- The ink and transfer paper type also play a role on what result you will get. I dont like glossy surface paper, I find the matte one absorbs ink and holds it better.
- The material you press: topsheet or base. Thickness of the material also plays a role.
So in a nutshell, dont assume anything, do your tests for each new material you use, for your setup, till you are happy with results. Your criteria is 2 things. Firstly ho well the ink transfers to the plastic, and secondly if the plastic bounding to epoxy is affected. Bot of there you have to fulfill.
The plastics suitable for sublimation are: All sintered bases, PA nylon topsheets and PBT topsheets.
There are 3 parameters to consider: Each of there plastics have own temperature, press time and cooling time. The temperature is set by the material viscat temperature, and the heating time is also set by the temperature you press at. The cooling time is the time you should allow the plastic to cool before you remove it from press. Please check the spec for your material! Below is my experience and some recommendation on the starting temperatures when you do your tests for various plastics:
Sintered base: about 127-135C and 4-8min with vacuum press. The thicker base the easier it can handle higher temperature without deformation. For pneumatic press it might take bit longer, in case your temperature drops. Be careful with cooling process so the material does not get too wavy.
PA topsheet: 140C for 3-5 min, but 160C for 2min is also ok. I prefer lower temp and lowest amount of time.
PBT topsheet: up to 180C for 1min, but I have done it at 140C for 3-4 min with no problem. Again I use vacuum press, and pneumatic press might be very different.
It is worth noting that thin ptex plastics will be sensitive when pressed near viscat point of 125-130C. Suchas IS6000 0.4/500mm plastic. They will become elastic and can loose the shape and become elastic when take out of the press, soyou have to do testing on how to cool it down and what temperature to use.
I seen that plastics suchas PBT topsheet, ptex base or grinded PA nylon topsheet on the epoxy side, are not so sensitive to sublimation time and temperature, while topsheets or bases that are not grinded or fleece backed, but only corona treated or only flamed, can be sensitive and offer weakened bounding to epoxy after sublimation, so you need to be carefull that you do not overheat the plastic and keep it in the press for longer then needed!
Here are some important lessons so far,
- For vacuum press use 1 or 2 layers of breather fabric to let the air flow evenly.
- When putting the materials into the preheated press, make sure you give the 30sec-1min to achieve same temperature as the press, they will expand, and then you can clamp down the press, otherwise if you clamp it too quickly you might have various issues.
- Materials that are not grinded or fleece backed on the epoxy side can be sensitive, sublimation can affect the bounding to epoxy, so be carefull not to ‘over do it’, press longer then needed at too high temperatures.
- thin ptex base plastic can be sensitive when going from press to cooling, due to the low viscat point and thin structure. It becomes wavy. So be careful with this one. Rather press at 127-130C and be carefull with cooling process.
- If you reuse same parts in the press there might be some ghosting from the previous image, as ink can go thru the plastic onto the press parts. So you can reduce your press time or temperature or even implement materials suchas breather fabric to reduce the ghosting.
- when pressing typically ptex will shring 3-5% and the topsheet will shrink about 2-3%
- when cooling in the same press, be carefull, it can be as the plastic shrinks and expands, the paper does not, so you get an image that is not so sharp or is blurry.