What makes an auto press go out of parallel?

[jvanick]

This is kinda follow on conversation to the Action Engineering LOC gauge discussion, but I feel like it probably deserves it's own place.  I remember the 'hot-rod gauntlet' thread, but I think this might be more general than that as well.

as I see it, there's only several places where the press can go out of parallel, but, if everything's locked down, why is it happening?

- bolts used to adjust the pallet
- pallets warping (hopefully this doesn't happen too often)
- bolts/threaded rods that the screen holders hang from
- the heads moving around?

if the bearings are solid, and all the press is doing is going around in a circle and up and down, how are things slipping out of adjustment?

my press seems to go out of parallel within 2 weeks of levelling everything... sometimes by not too much (less than 1/32"), sometimes more. 

I'm considering replacing all the pallet adjustment bolts with grade8 hardened steal, and trying to find fine thread bolts for that at the same time...  that, plus some judicious use of lock nuts might help?..

where else should we all be looking to try to get the best performance out of our gear?

about 4 years ago now, I built a CNC wood router, literally the support materials are all made out of glued and painted mdf, aluminum 8020 channel extrusions, some angle iron I picked up at Home Depot.  That machine, 4 years later, is still in perfect parallel, and if I put a dial indicator on it, the tolerances are still at .003"... with no adjustments on my part. 

Surely there's gotta be a way to lock our stuff down.

[mk162]

what press are you running?

usually excessive squeegee pressure will knock platens out of level.I would start there.

also spinning your platens by grabbing onto them will do it as well.  I would grab from the underside at the bracket to spin ours.  less leverage on the platen itself, or i spin from the middle top, never a side edge.

there is a difference between platen leveling and press registration.  bearings and so on are related to the registration, not platen leveling.  if your bearing were toast, you wouldn't hold register at all.

[inkman996]

I understand what he is talking about. It is a valid argument. Why if you tighten all the bolts on the hangers, platens and head do they move? You would think with all this steel nothing would be able to move.

But I think things bend and shift after so many prints and hand spinning the carousel. Most of these parts are hanging out in open air with only one side being attached. Unlike on a router table.

 

[tonypep]

Simple geometry tells us that two points make a line and three points make a plane. M&R used to have a four point leveling system but long ago ditched it for a three point. This was largely due to inexperienced individuals trying to level the four point moints. When over torqued in different directions the welds would break rendering that arm useless. In the days before no shirt detectors this was a big problem. So yes, three points due of course make a plane however I've often wondered why the two points are towards the center of the press rather than at the end of the arms where deflection is more likely to occur. Can't speak to the newer presses this may have already changed.

[alan802]

Several of the biggest factors have already been said with excessive pressures being used, especially if one side is stronger than the other, but I think ours goes out because my guy likes to push down on the corner of a pallet to spin the carousel.  I've told him at least 100 times to not spin the press by the pallets but I catch him doing it often.

I've leveled many 3 and 4 point system pallets in my short career, and I'll take the 4 point every time.  I understand the argument for the 3 point, but when done correctly, I've had much better luck with the 4 point.

[IntegrityShirts]

Another thing to consider when you're talking thousandths of an inch, is almost ALL platens are "stuck" to their bracket with a gooey sticky 3M adhesive film.  I have a couple pallets that the adhesive is separating toward the closest attachment point to the center of the press, probably due to only flashing the top half of the pallet with zoned flashing.  Or it could just be pulling away because 90% of the printing and squeegee pressure occurs on the upper half of the pallet.

[ScreenFoo]

One thing that's tripped me up is having spray tack, ink, oil+fuzz etc. on the leveling bolts.  A spray of WD-40 on each one after you loosen them up makes it way easier to tweak them a little.  If it's hard to turn the bolt because of a bunch of crap in the threads, you're pretty much guaranteed to under-torque it.

Sounds like other forces may be at play here though... Have you had someone train you on leveling it, or try to figure out if something's broken?

[jvanick]

I'm on an early 90's (1991?) Javelin

I have not had any formal 'training' on leveling.. however, I do follow the workhorse service/maintenance manual on how to level the screen holders and platens.

I would LOVE to have a tech come out and spend some time with me on getting everything perfectly dialed tho...

I asked before if anybody had a good recommendation of a tech in the illinois/wisconsin area, but I got no replies.

-J

[brandon]

This is just a quick little horror story I once saw. Press operator had a frame laying on the platen and was spinning the press by hand to reg something then started running the press again with frame on it. Holy smokes that press locked up with the platen arm going down and the head up by a lot! Crap it was an ugly sight. Needless to say the press needed a redo of everything after that

[tonypep]

How about a newbie press op standing on the platens so he could clean the top of the machine!

[inkman996]

We used to have someone working here that would actually stack several full cases of shirts on the palettes, and to add to that he would use the in feed and out feed of the dryer as a table to stack heavy stuff on. Fortunately he is no longer here.

[Parker 1]

What about claims from MHM and SRoque not needing to be leveled after install?  Both presses also utilize  "floating Squeegees". 

[alan802]

What about claims from MHM and SRoque not needing to be leveled after install?  Both presses also utilize  "floating Squeegees". 

I've heard it's true.  I don't see how, but I do believe the guys that tell me they've never had to.

[ZooCity]

Great question!  I think all these answers are true.  I really think it's 90% platen bolts walking around.  But, if you think about it, would you rather have to readjust leveling bolts or deal with distorted and torqued out print arms, heads and other welded pcs?  The energy has to go somewhere.

Our manual has 4 point leveling and a slightly different design and bolt setup than the M&R style and it really appears to be superior.  It doesn't get used as much as the auto but, when it does, the platens are getting constantly reefed on from one corner from hand spinning it.  Yet it tends to stay in level much longer and is far easier to adjust when it's out.  I agree that if you didn't know what you were doing, four point leveling system could lead to snapped parts.  Hell, I cracked the cast base of an American print arm off in my early days dicking around trying to level it the wrong way.  But a stronger leveling bolt system probably wouldn't solve the core issue of uneven pressure applied to various areas of the machine.  Again, where does the energy go? 

I believe the MHM system's ability to stay in parallel hinges on the sq and flood bars being mounted "floating" style from a single center point on the print arm and then the platens are mounted in the same fashion, using a single center line of connection on the platen arm?  This makes perfect sense to me- provided the linear motion of the print carriage was in parallel to the platens, the pressure would be even everywhere, at all times, at all points of contact, hence the machine stays in adjustment -it's balanced.   

I think it's the application of uneven pressures on dual chopper style machines that is causing the press/release/press/release cycle that will slowly warp parts and loosen bolts and other connections over time.  A floating style press like described above has no ability to put uneven pressure on outer edges, only the pressure at the center line can be increased or decreased and is then transferred evenly across the both assemblies. 

A partial solution to this for dual chopper presses is the squeegee pressure adjustment where you can set the depth of the choppers once, in parallel, and then raise/lower the air pressure to them but not all presses have that option surprisingly.

Ok, enough playing engineer for today, these posts always get me thinking and nerding out on this....and not doing the work I'm supposed to be doing.

[Screened Gear]

What about claims from MHM and SRoque not needing to be leveled after install?  Both presses also utilize  "floating Squeegees".

I can say that I have 2 years on my press and have not adjusted the pallets once. (10 color MHM e-type) I am not a high production shop so that maybe part of it???

My question to you guys that do level your presses all the time. Why? What is going wrong that you have to level them?