Pressing 3D Laminates and Blow outs
There are many different tips and tricks to pressing. Often I am asked for formulas however I often find that each company may require different settings based upon the material they are pressing, the profiles, glue type, stage height and so on. One common issue that all companies have or will eventually face are blow outs. During the press cycle you can hear a blow out occur by a pop and a hissing sound. After retrieving the tray from the press you will typically find that dreaded hole and all the parts did not form properly because the press lost its seal.
Blow outs are typically caused by either too high of a heat versus too low heat. You can tell them apart because blowouts by too low heat are more like tears and blow outs by too much heat are typically circles or tear shaped holes that seem uniform.
Keep in mind that raising or lowering the temperature alone may not solve a cold or hot spot issue. Imagine if you raise the temp but get heat issues but lower the temp and get lack of forming.... Other issues may be at play such as having too short of a preheat. If your preheat is too short then it may be possible that the heat did not have time to soak or penetrate the entire thickness of the 3D Laminate.
There are different scenarios where cold spots can form such as using thicker films in a 16 mil to 20 mil where the heat has not soaked all the way through the thickness of the product. Imagine if you are using a very dark color like a Wenge which is almost black and it conducts or absorbs the heat more rapidly however you get cold spots blow outs. Then when you raise the heat you get hot blow outs. The solution to this type of problem can be to do a longer preheat but keeping the temp low enough so that you do not over heat any one particular area of the material. You may also want to use heat strips to ensure you are getting heat distributed uniformly in the press.
With membranes on a Shaw Almex, Wemhoner or Italpress for example you may experience less blowouts because the membrane is the source of pressure and that pressure keeps the blowout from occuring. With an Italpresse with no membrane (for example) that inflates the vinyl to the upper platen you get a balloon where the center of the material is touching the platen and heating up very rapidly however the outer portions may not be heating as rapidly and you can actually experience cold spot blow outs towards the outer perimeter of the press. There are two solutions for this type of problem. The first is to have a longer preheat but at a lower temperature so that you get all the material uniformly pliable but not one portion of the film is so hot that it is weakened. There are some machines in which you can reduce the inflation time and then preheat part of the time with it inflated and then preheat part of the time while its not infated. You may need to contact your machine supplier to ensure that your particular model has this option.
Another scenario with blow outs can be caused by utilizing the Eco Jig pin system manufactured by Dackor. This pin system is an affordable alternative to automatic systems (although not as efficient as an auto system). In the Eco Jig system you must ensure that the pins are pushed under far enough so as not to create a penetration point for the vinyl to hit. By pushing the pins under further it creates an even distribution of pressing at the bottoms of the doors and will stop blowing out under this situation.
In summary, there are many variables which can cause blowouts based upon settings.
Step 1: Determine if are having cold or hot blow outs
Step 2: If raising or lowering temp does not help then try working with your preheat
Step 3: If the above does not work email your settings, machine details and problems you are having to firstname.lastname@example.org
I hope that this article was helpful, be sure to contact us for further assistance.
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