Mhm type spitting screens.

[shirtshack]

Anyone with an mhm machine have experience with this.
Load a screen with white ink, and when the machine floods the print for the first time with flood moving from outside to in, the resistance is enough to pull the screen out of the front pins and eject it.. Happened a few times now, worst case damaged a palet and twisted a print carrage so the bearings need replacing.
The fix for us is to load less ink to start with and to make sure the first few prints have the speed for flood set to 0, and then once it's flowing increase flood speed to 2. it works but if the operator forgets to slow down the flood on the next job, it may spit out the screen again.
I know the cause is cold thick white ink (Ic legacy) and the sesaw action of the print head, using an Acton engineering double squeegee, as it floods does not lift the squeegee clear of the ink so that first flood has the resistance of the ink on both the flood bar and squeegee pushing against the air piston at the back of the screen.
Fixes I can think of,
Always stir and Warm the ink up first,
Change direction of the print stroke so the flood moves from inside to out.
Stop using the action double blade squeegee.
Always remember to slow the flood down until ink is flowing.
Increase air pressure if possible to the rear screen piston so it can withstand the force ( not sure if that's possible)
Any one of the above will probably fix it, but just wounded if anyone else with a mhm had come across similar issues and had a fix

[jsheridan]

The ones I've used had an airlock. It was the lock looking icon on the head key pad, makes a click and psst.. when pressed. With it off.. you can easily push the screen back, locked its very hard to push screen back.

Or the cylinder that actuate the lock could be bad.

[shirtshack]

 On Ours we use that icon to unlock the screens for removal, (you hear the air escape) screen easy to remove.. We put a new screen in but do not push the icon again, I always found that any command on the machine re locks the screens, ie index, print.. but maybe i am mistaken and it is important to re lock the screens with the icon.

[Printficient]

Call me 404-895-1796.  Might I suggest Double bevel squeegees?

[T Shirt Farmer]

Is this happening on the flood or pint stroke? Metal flood bar? What s the PSI for screen cylinders I think it is supposed to be around 6 Bar. something is wrong on my press there is no way in hell the screen is moving from pins on a flood stroke, happened mistakenly once on a print stroke but with a dry screen that had no ink.

[shirtshack]

between 6 and 7 bar being fed to the machine due to compressor tank, 7 bar max an kicks in to refil when it hits 6 bar.
metal flood bar,
one way to test is to try to remove a screen while they are still locked, it takes more force but i can remove a screen without first unlocking it, sometimes i do if i forget to hit the icon and on on the opposite side of the machine.

[T Shirt Farmer]

On my S type there is a separate regulator for screen lock air feed, I think the E type it under the plastic dome on top of the machine. The screen lock automatically turns on once any flood or print control has been activated.

[tonypep]

Call me 404-895-1796. Might I suggest Double bevel squeegees?

OMG You did not just say that...........Classic Sonny!

[Printficient]

Call me 404-895-1796. Might I suggest Double bevel squeegees?

OMG You did not just say that...........Classic Sonny!

Yeppers.

[shirtshack]

The regulator on the xtype is behind the front panel, I did take a look at it but it seems it only regulates the pressure when the screens are unlocked so it controls how much resistance you get when removing the screens not how much pressure actually locks the screens which I assume is the full pressure supplied through the main regulator air inlet on the base.

[T Shirt Farmer]

I did take a look at it but it seems it only regulates the pressure when the screens are unlocked so it controls how much resistance you get when removing the screens not how much pressure actually locks the screens which I assume is the full pressure supplied through the main regulator air inlet on the base.

this does not seem correct to me, call Rodney