MHM platen deflection and other issues

[ZooCity]

Following this and the thread it split off with great interest right now. 

I hate deflection, with a passion.  It's one thing I don't ever want to have to explain to my press ops or really deal with.  It's a real demon with even coverage/penetration and of course the issue is exacerbated with large image areas and process work.  Any new press should be devoid of it, in my opinion. I agree that any machine will have some small degree of front/back deflection but I feel like it should be absolutely minimal even at very high stroke pressures.

I also agree that side/side deflection would be a parallel or setup issue by nature with a self leveling print head, unless maybe we're talking about really wide, oversized prints. 

Could be mistaken but I think the new S-type and X-type heads both have the chopper depth adjustments, one on each side of the carriage? 

On the MHMs, one feature I like is that you can stroke from the inside of the press out.  Has anyone found this to be of benefit for dealing with deflection and also the inherent issue with passing the blade over shirt collars loaded onto the press?  The shirt collars onto the platens cause extra deflection and fuel the need for pressure.  I always thought that printing from outside in would be exponentially better.  The ultimate, ideal in my mind would be stroking from outside in and the stroke slows down slightly just before hitting into the collar.

Last of, MHMs have peel.  Could peel adjustment be playing into a need for high pressure and this cascading down into deflection problems?

I have zero experience on MHM machines but far too much with flexy older series 1 M&R machines and those machines, pain though they are when it comes to deflection, teach you so much on how to minimize and work with it. 

[T Shirt Farmer]

MHM has 1 single wheel you turn to increase or decrease squeegee height... no peel function on MHM

[blue moon]

I just checked, when pushing hard we have a deflection of slightly more than a 1/16th of an inch. Is that what everybody else is seeing?

pierre

[Screened Gear]

Ok I just went and checked my press. This deflection thing is driving me nuts. I haven't seen any effects from it and now everyone is talking about it.

This is what I did. I took a ruler and put it up against the front of the screen where the pallet tip is. I am printing at about 3.5 bars. There is, like Pierre said, about a 1/16 deflection when the squeegee comes down. Now That make me think. Where is this deflection coming from. Well I then looked at the pallet arm. There does not seam to be any movement there. The MHM pallets have to connection points. These are small bars that the pallet attaches to. What it is is the pallet is bending from that point. So just the tip is bending. Makes sense. Is that what others are seeing. There really is a easy fix if it bothers you. Just add one more block to the tend of the pallet. This will take away that pivot point and the pallet will be more solid. Kind of what one guy I know does with his 20" pallets from Action that bend a ton at the ends. He puts a piece of Laminate flooring between the pallet and the pallet support at the end.

I have to say I have not seen any effect from this. I print alot of butt registration and have no issues. I guess maybe Extreme sees it more since he is doing larger prints. I don't know. I wonder if other presses see this? Does the Srough do that same thing since it has honeycomb pallets???

[Binkspot]

Just throwing this out there but if you are at 7 bar on one head and 2-3 on the others when printing on the one with the higher pressure it will deflect more. Then print on the lower pressure ones deflect less. Depending how much it deflects on the high one could throw reg out in theory, distorting the image. Printing within 1 bar (14psi) of each other should clear this up.

[ZooCity]

MHM has 1 single wheel you turn to increase or decrease squeegee height... no peel function on MHM

from my recent quotes for both X-type and S-types:

"Individual screen lift/lower, with screen peel."

Maybe this is a newer feature?  I don't see why peel wouldn't be incorporated in any heads up/down machine.

[blue moon]

Just throwing this out there but if you are at 7 bar on one head and 2-3 on the others when printing on the one with the higher pressure it will deflect more. Then print on the lower pressure ones deflect less. Depending how much it deflects on the high one could throw reg out in theory, distorting the image. Printing within 1 bar (14psi) of each other should clear this up.

Brian as a guy that installs presses, what have you seen? Is 1/16th a lot? What is normal? Are there any that do not flex at all?

pierre

[ZooCity]

Just throwing this out there but if you are at 7 bar on one head and 2-3 on the others when printing on the one with the higher pressure it will deflect more. Then print on the lower pressure ones deflect less. Depending how much it deflects on the high one could throw reg out in theory, distorting the image. Printing within 1 bar (14psi) of each other should clear this up.

This is how it goes on the old series 1 machines like our Gauntlet.  Sonny helped teach me this.  After a lot of work with deflection my conclusion is that some is OK but if any is present then the key is to deflect the same amount on all heads.  Otherwise yes, no reg or worse, inconsistent reg.  To make it really work you logically must have very similar mesh/tension/blade/angle/speed/ink rheology in addition to similar pressure.

This limits what you can do with the machine, near zero deflection is preferred as you can really adjust all of the above just right for it's ink and place in the art.

So if the deflection is not so extreme as to cause coverage or penetration issues than it's no problem provided you can run each job as I outlined above.  If that won't fly for your shop then deflection won't fly either. 

[Extreme Screen Prints]

We keep are base at 5 and top colors at 4, if we go less it can throw reg off by elongation. Jon watch the rod that comes up from the bottom and the support arm, at first I thought it was the pallets and we did add a solid block of channel under our pallets to take up for that gap and no dice. Still deflection. I say this is a problem because trying to train employees about variables is tough, when I use to print I could easily work around stuff like this but asking your employees to is few and far between. I am not saying it causes registration issues but I am saying it makes certain jobs a pain. When you spend 100,000 on a press there should be no deflection. If the Sroque can do it then MHM should have a fix for it. I have shown both MHM techs and they tell me I print with to much pressure. I then ask them to tell me how to print with less and get the results I get with my process. There answer is we are not printers. Trust me I have tried everything to not have deflection. I will also say that the etype pressure is different than the Stype or 4000, 3 bars on the etype is equivalent to 5 on the Stype. My thought on this is you can lower then height of the blade more on the etype but on the stype and 4000 you are limited by the mechanics of the chopper setup, you could have 200 pounds of pressure driving a squeegee but if the blade doesn't go down far enough than it doesn't matter. By putting rubber on the pallets you will gain some height and that should help a lot.

[Extreme Screen Prints]

Just throwing this out there but if you are at 7 bar on one head and 2-3 on the others when printing on the one with the higher pressure it will deflect more. Then print on the lower pressure ones deflect less. Depending how much it deflects on the high one could throw reg out in theory, distorting the image. Printing within 1 bar (14psi) of each other should clear this up.

This is how it goes on the old series 1 machines like our Gauntlet.  Sonny helped teach me this.  After a lot of work with deflection my conclusion is that some is OK but if any is present then the key is to deflect the same amount on all heads.  Otherwise yes, no reg or worse, inconsistent reg.  To make it really work you logically must have very similar mesh/tension/blade/angle/speed/ink rheology in addition to similar pressure.

This limits what you can do with the machine, near zero deflection is preferred as you can really adjust all of the above just right for it's ink and place in the art.

So if the deflection is not so extreme as to cause coverage or penetration issues than it's no problem provided you can run each job as I outlined above.  If that won't fly for your shop then deflection won't fly either.

Zoo you just summed up my thoughts exactly, it throws to many variables and we already as printers deal with enough variables.

[ZooCity]

Man, I can't stop posting on this one.

Jon, if it's the platen material itself flexing, you're correct, easier fix there.  Just support the platen material or use more rigid material.  OEM honeycomb on that press should have been strong enough to avoid this.  If it wasn't/isn't then there is a design flaw regarding the bracket/arm support in my opinion and this is what I'm deeply interested in as we are looking very hard at an MHM machine but I won't tolerate defection as an inherent design flaw. 

We solved a big chunk of the worst of our deflection woes by swapping out the older M&R brackets on our press, which were very short, with full length brackets which support the tooling plate along the entire length of the platen.  Big difference there. 

[ZooCity]

I say this is a problem because trying to train employees about variables is tough, when I use to print I could easily work around stuff like this but asking your employees to is few and far between. I am not saying it causes registration issues but I am saying it makes certain jobs a pain. When you spend 100,000 on a press there should be no deflection. 

And you just summed up mine!  My crew can understand some of this, nearly all of it in fact, but then they ask "so why did anyone build the machine this way" and I can only shrug. 

[ZooCity]

I feel like the acceptable amount of deflection is relative to your off contact. 

ex/ Our plastisol o.c. is 5/32" off the platen's top to screen, or ≈0.16".    So 1/16", or ≈0.06" is 37.5% of our overall off contact.  On Jon or Pierre's E type, we would have a situation that varies in off contact from front to back by 37.5%. 

[ebscreen]

Extreme,  what durometer of squeegee and angle are you using for your DC ubase? Your results speak
for themselves but there are plenty of ways to skin a cat or whatever. We can completely penetrate most
fabrics with 3 bars or so and discharge white on a 230 mesh. All about duro/angle/speed.

Deflection has not, to my knowledge, given us any issues on our S-Type.

The S-Roque's are essentially a MHM 3000/4000 as far as I can tell, in terms of platen support and drive.
Lot of similarities there really, which likely means it's a good machine.

Fact is, ANY machine without cast arms that are like a foot in diameter, CH3's included, are going to exhibit
platen deflection if you are printing with serious pressure. The cost to overcome what many deem a minor issue
is what keeps manufacturers from eliminating this issue, I'm sure.

I will say this, a pallet support system that is closer to acute, with the furthest outward support as close to
the pallet tip as possible, will be a hell of a lot stronger than a more obtuse triangle as seen on American made machines.
That's simple geometry.

[Binkspot]

I honestly could not say whats too much. I would have to say as little as possible or not enough to deflect the pallet or head to the point of distorting the image. I think it has to do more with the printer then the machine.

I will say this much, I have been to plenty of shops where they print plastisol like discharge, mash the ink through the screen instead of shearing it running 70-80 psi. You can actually watch the head and or pallet arm move. I can usually show them by tweaking other things they can get a better print with less pressure.

My old Jav and Olympian it would be next to impossible to deflect anything. On our current press I can not go over 40 psi (3 bar +/-) without popping a squeegee. This has had a few consequences, first we had to learn how to print just about everything between 15-35 psi, second I have to step down a mesh size and double stroke on every discharge job in order to get good penetration. The best improvement we have found is that red white and blue squeegee, I have no idea what it is just that it kicks ass.

I have had the pleasure of printing on a press like Zoo's and its just like he said if your not carful there is all kinds of deflection.

I am not saying its not possible but MHM has that nice support rod under each pallet arm, just can't believe that would deflect. But like Jon said where the pallet pivots makes the difference.