Warped vacuum press

[jferrari]

Has anyone noticed if their platen is warped (sagging, actually?) 44 x 68 Bienfang, Seal or VacuSeal style press. I thought it should be nice and flat but maybe this is normal. Thanks.    - Jim

[framah]

Could you elaborate on this a bit more?

Exactly where is it sagging?  Is it not sealing tightly around the edge when the vacuum is on?

I think we need more info.

[jferrari]

Thanks, Framah. The platen (heated sheet metal on top) on my press is not perfectly flat. If you hold a straight edge to it, it shows that the center sags down over 3/4 of an inch from the perimeter. The sag is so pronounced that I can see it without the use of a straight edge and this is when the unit is cold. The Drytac style presses use glass for a platen which, I would assume, would be perfectly flat even at temp. I'm wondering if this is normal or if it is an issue. I am having a great deal of trouble with warped foam core board and a sagging platen might be the reason why.   - Jim

[Paul2660]

I used a 48 x 96 Bienfang press for several years. The top metal platen did have some sag but not as much sad 3/4 of an inch more like 1/2 inch to 3/16.   Yours does sound a bit excessive. Have you called Bienfang?  They have excellent customer support even on presses way out of warranty.   You might try sending them some pictures. 

Also if you press a large 3/16's sheet of foam core does it get an excessive curl? 

Bienfang was always very clear to us that they expected the pressed material to be immediately placed under a weighted surface while cooling which on small jobs was easy but not on 4 x 8 sized mounts.

Paul

[jferrari]

Thanks for the reply, Paul. I have not contacted Bienfang yet. I wanted to poll users here first to see if a saggy platen is the norm. I've tried 3/16" and quarter inch and had warping/curling on each. It makes no difference if I immediately weight the pieces or let them cool unweighted. They still end up warped the same amount. About the same amount that the platen sags.   - Jim

[Wayne Fox]

our Bienfang platen “sags”.  I would guess at least ½”.  However, the platen itself seems pretty flexible, and it seems it might flatten against something above it as the vacuum operates. I think the sag is intentional and part of the design.

Our warping issues are directly attributable to the mounting process.  Most customers select foam core and we use a single step board with adhesive already applied for this. I don’t believe the platen is a part of the problem.  Even if we mount upside down, the final print curls upwards (opposite the platen sag in this case).  We have no problem with gator, and we’ve found KoolTack stays much flatter than the single step.  It is in the press for a much shorter period of time.

When we mount on board rather than foam core, we use a Seal laminator.  We have been testing the foam core on the seal, and are still uncomfortable with how much it compresses the board.  We may try moving customers away from the foam core.

[jferrari]

Thanks, Wayne.  You're right, the platen seems somewhat flexible as I can push up on it in the center easily a half inch or more. The vacuum is drawn between the sagging platen (there is nothing above it but foil-faced fiberglass insulation) and the rubber membrane. I have yet to try the KookTack but it is on the short list. I am checking with a supplier for the discontinued 1/4" PSA MightyCore 4 by 8 foot sheets. I've even thought about rolling out the PSA tissue onto regular MightyCore but it starts getting a bit pricey and more labor that I want to exert. The JetMount with PSA works fine for smaller prints but I need something more rigid for the larger ones and can't afford the Gator.

Your curling issues may be related to foam core board being a pretty good insulator and the disparity in temperature from heated side to non-heated. Maybe increase dwell time? Just guessing. Thanks again for your input.    - Jim