How It Works
3-ZONES IN A CHAMBER – WHY?
WHY ONLY FROM DPS?
It is important to start with the 2nd question first: Deneka Printing Systems, Inc. owns multiple patents covering the 3-Zone Chamber. (Others cannot legally produce it.)
Why 3 Zones in a Chamber?
Introduction: A doctor blade chamber must do two fundamental things or it is essentially worthless: 1 – Must fill every cell with every revolution completely, with no air left entrained in the cell, and do this at nearly every speed. 2 – Must meter the surface of the anilox/gravure roll very precisely. Not doing these two steps will leave uncertainty and variable results as a constant concern. The design of the 3-Zone chamber achieves both goals.
The cavity of the 3-Zone chamber has 3 separate areas doing 3 separate tasks, beginning with the 1st Zone:
Supply channel:
This is where ink/coating enters by means of the output from a pump. This zone is kept completely full by pump flow rate and, thereby, introduces the ink to the engraved surface of the anilox/gravure roll. The turning motion of the roll carries ink into the 2nd Zone:
Pressure Flat:
As the fluid is forced into and across the Pressure Flat, it goes from a tumbling motion in the Supply Zone to a linear motion across the flat. At this time three things happen: the Pressure Flat clearance decreases; the fluid approaches the centerline of the hydraulic pressure as the fluid stream increases; it spikes at the centerline, after which the pressure returns to normal/ambient. While the pressure is increasing, velocity of the fluid also increases and can actually move faster than the surface speed of the roll surface. The hydraulic spike forces ink into the cell with real pressure, pushing any air out of the cell. The increasing fluid speed gives the air a “preferred path” to move forward into the 3rd Zone.
Exhaust Zone:
The Exhaust Zone is kept about ½ full. The “free head space” in this channel forces air out of the exhaust port and back to atmosphere at the tank.
As line speed increases the hydraulic pressure generated across the Pressure Flat also increases. This is also the case if viscosity of the fluid is higher. Therefore, there is constant positive force causing the air in the cells to be fully forced regardless of the line speed. The pressure rising with speed more than compensates for reduced dwell time in the chamber. This has been demonstrated at 3500 fpm. This translates to consistent color density across very wide speed ranges. In fact, this remains true up to the fastest trial speed ever run – 3,500 fpm. The nice thing about the fluidic performance is that it will always work – in fact it, can’t not work because that is the way God made the world. The 3- Zone cavity works because it takes advantage of the principles of fluid dynamics and puts it to your advantage: high quality, consistent ink density.
Roll Surface Metering:
Moving on the 2nd fundamental requirement. The pressure necessary to fill cells is dealt with in the center of chamber cavity, meaning there is no significant ink pressure pushing against the blades themselves. This allows the blades to operate very well indeed at ¼ to 1/3 pressure exerted by nearly every other chamber in the world. ????
Only enough pressure to “slightly” flex the blades sealing the containment blade and give the metering blade enough pressure to meter just at the tip of the blade. No need to “roll” or “knuckle” the blade to get a nice, sweet metered surface. As a direct consequence, doctor blades last longer and the threat of “score lines” is removed. We use about 0.25#/inch – 0.33# of blade length at operating speeds. Industry norms are 1.5 – 3.0#/inch of blade length – much higher.
We use precision die springs to develop the pressure in an extremely stable way with no fluctuations, such as occur with air cylinders. This explains why it is really possible to get a week (24/7) of blade life even at speeds of 1500 – 2000 fpm when using normal range cell patterns of 500 – 900 lpi (lines per inch).
These characteristics coupled with effective end seals (which are adjustable) and very tight machining tolerances, yields the top performing chamber in the game. The correct applied science, executed with competence, makes this straight forward. And that is what we do and why it works.
Questions about this or other pages on the site? We do have REAL answers not smoke.
Concerned about choices of chamber materials, surface corrosion barriers etc., please give us a call.
We can help you make the right decision – the best choice and best value for your application.
