One Armed Bandit "issues"?

[mimosatexas]

So I have a one armed bandit where the arm/squeegee holder and the linear motion rail in the back are professionally manufactured and the table top was made by me.  Everything "works" but I have a few issues with it that I can't really figure out.  Basically, if I try to print using a basic flood and "pull" print stroke it barely puts down ink.  Adding pressure only causes the arm to flex/twist and the angle/pressure of the squeegee edge becomes inconsistent from front to back.  I end up having to sort of do a "push" stroke with the squeegee where after the flood I flex it back into the flood position and then do the print stroke.  This "works" fine for most prints, but when using thicker inks like white discharge it ends up causing major stuttering due to higher resistance across the longer squeegee.

I am likely going to replace the main arm with a thicker gauge square steel bar to help with the flex/twist issue, but I am wondering if there are other issues with my setup or method.  I am using a 38" triple duro squeegee off a Cameo clamped into the holder and have played with all the angle adjustments on the holder without fixing the issue.  The screens are 46x58, 150T mesh, around 28N. 

Anyone have experience with these that could maybe give me a call or shoot me a pm with ideas?  Thanks!

[Ross_S]

I have some experience with it but you lost me. What substrate are you printing on?  I have never used this machine for apparel only signage and banners.

[mimosatexas]

I print mostly flags on a marine canvas, but have done nylon awning material, all over prints on shirts, posters, signs, etc. The issue happens regardless of substrate. I'll try to get a video during my next run showing the issues more clearly.

[Frog]

Yep, pics or a video can only help.
When I used these in a  past life as a flat-stock printer, they just worked, and I don't remember any issues. Long time ago though, so details on the unit's construction and solidity are not there any more. I don't remember any need for excess pressure as I was usually using enamels, multi-purpose,  and poster type inks which probably were a lot thinner than what you are using.

[Atownsend]

How high is your off contact? I have a old Lawson Geiniette auto that has a absurdly high off contact distance that cannot be changed. It was built when tensions were lower and it just doesn't work well with modern tensions. In order to get good ink transfer, I have to lower the tension to stupid low levels.

[jvanick]

How high is your off contact? I have a old Lawson Geiniette auto that has a absurdly high off contact distance that cannot be changed. It was built when tensions were lower and it just doesn't work well with modern tensions. In order to get good ink transfer, I have to lower the tension to stupid low levels.

couldn't you just build the platen level up?  (maybe a sheet of aluminum or something?)

[mimosatexas]

off contact is only about 1/4 inch (the height of the hinge clamp from the table at the back of the screen).  The screen is not having any issues contacting the substrate across the full length of the blade.

The issue really seems to center around the flex in the arm and the fact that I just cant get the pressure I want out of the thing.  I just cant imagine it was designed to give LESS pressure than I can print manually with the same sized squeegee, which is how I was printing the flags etc prior to setting up the press/table.

the benefits of the concept of the one armed bandit as far as I understood it was even pressure across the length of the squeegee blade due to the center pivot (not happening due to arm twist/flex with anything but the lightest pressure), the ability to apply more pressure due to the mechanics of the lever/fulcrum, the ability to consistently control angle or flood and print strokes due to the design of the head (not happening due to the arm twist/flex), and no more back issues .  Definitely not having back issues, but for lack of a better term, the ability to get a lot of pressure just doesnt seem to be there.  I'm going to replace the arm itself with thicker steel and see what happens, and I'll post some videos when I have another flag job (likely later in the week). 

[Atownsend]

How high is your off contact? I have a old Lawson Geiniette auto that has a absurdly high off contact distance that cannot be changed. It was built when tensions were lower and it just doesn't work well with modern tensions. In order to get good ink transfer, I have to lower the tension to stupid low levels.

couldn't you just build the platen level up?  (maybe a sheet of aluminum or something?)

I was thinking about doing that actually. I'd have to drill a ton of holes and make sure it seals right so we get good vacuum. The only thing is... the screens require a jiffy clamp at the top. Depending on the stroke length / screen size, you calculate & adjust your "screen drop" so you get the right flood. So the jiffy clamp doesn't always land in the same place, it varies with screen size. Its one whacky press... but it is pretty decent for 1 colors once it gets going, esp the thicker stuff like boxes / coroplast. For thinner stock, we have trouble getting enough pressure with the weird flood / pressure adjustments, so we just drop the tension to 1980 levels, which works okay as a workaround. And old vid of it in action is here > https://www.youtube.com/watch?v=0m4Yd2hv9LQ. It really belongs in a museum.

off contact is only about 1/4 inch (the height of the hinge clamp from the table at the back of the screen).  The screen is not having any issues contacting the substrate across the full length of the blade.

The issue really seems to center around the flex in the arm and the fact that I just cant get the pressure I want out of the thing.  I just cant imagine it was designed to give LESS pressure than I can print manually with the same sized squeegee, which is how I was printing the flags etc prior to setting up the press/table.

the benefits of the concept of the one armed bandit as far as I understood it was even pressure across the length of the squeegee blade due to the center pivot (not happening due to arm twist/flex with anything but the lightest pressure), the ability to apply more pressure due to the mechanics of the lever/fulcrum, the ability to consistently control angle or flood and print strokes due to the design of the head (not happening due to the arm twist/flex), and no more back issues .  Definitely not having back issues, but for lack of a better term, the ability to get a lot of pressure just doesnt seem to be there.  I'm going to replace the arm itself with thicker steel and see what happens, and I'll post some videos when I have another flag job (likely later in the week). 

Hopefully the thicker steel fixes it. Maybe the metal is just fatigued? Or just a poor design out of the gate. Definitely take some pics or video! I am super curious. I have never printed with one of these, but have always wanted to. I just don't see them pop up too much on the used sites.

[domineight]

Photos would be helpful. I still run one, or two actually.  Both large format - two meters+. Combination of larger squeegee and low mesh count could cause problems,  I'm assuming 150T isn't a metric count.

If I'm reading it right the main problem is uneven pressure? When applying more pressure to get a clean print the front (closest to you) sees the squeegee practically bent over horizontal while the back of the squeegee looks about right. The answer there is to move the centrepoint of the squeegee carrier toward the back of the image area, so the centrepoint is around 2/3 - 3/4 along the squeegee.  You'd notice the need for this is accentuated when the image area is quite tight in a frame. Sometimes I might need to run an extra little bit of pressure with the palm of my hand on the front of the squeegee if it's really large, the largest I run in these is 1250mm.

For "chatter" or to stop the squeegee crashing into a large open area of mesh just snowplough it. Chuck a wedge or a piece of squeegee rubber into one end of the squeegee clamp so the entire squeegee is offset or tilted. I use an old key that's fallen out of a keyboard,  funnily enough it's the "ctrl" key..

Ive always run a push stroke to print. Habit and how I was taught I suppose. I always print into or toward my lay corner. Thinking about it, I don't think I'd survive pulling the squeegee sideways toward me and maintain control with large format because I do use the palm of my hand on the near end of the squeegee and the other hand operating the arm.