Appearance
A manufacturer of gravure printing cylinders (stainless steel, 8 in dia x 60 in face, 0.125 in wall) used e-beam drilling to produce 50 million cells of 0.005 in diameter at 20-degree angle, 200 cells/inch density. E-beam drilled at 2000 holes/second (0.0005 s/hole), total drilling time 7 hours. Cells inspected by microscopy at 0.1% sample (50 000 cells), acceptance criterion < 0.1% blocked.
Permeable Gravure Cylinder Drilling
Permeable gravure and anilox cylinders use electron beam (e-beam) drilling to create arrays of microscopic through-holes. The cylinder is a thin metal shell (stainless steel or nickel, 0.050-0.250 in wall thickness, typically electroformed or spun) that is mounted over a perforated inner support tube. The e-beam drilling system uses a pulsed electron beam (50-200 kV, 1-10 mA, pulse duration 1-100 microseconds) focused to a 0.002-0.010 in diameter spot. The beam is pulsed at 500-5000 Hz, and the cylinder is rotated and translated under the beam to produce the cell array.
The drilling parameters are: beam current 2-8 mA, pulse width 10-50 microseconds, repetition rate 1000-3000 Hz, and the cylinder rotation speed is synchronised with the beam pulse rate to produce the desired cell spacing (200 cells per inch = 0.005 in centre-to-centre spacing). The cell diameter is 0.003-0.008 in (typically 0.005 in for publication gravure), and the cell depth is equal to the shell wall thickness (0.050-0.250 in), giving an aspect ratio of 10:1 to 50:1. The cell angle (the angle of the hole axis relative to the cylinder surface) is 20-90 degrees (20-30 degrees for high-ink-release-volume packaging gravure, 90 degrees for fine-screen anilox rolls). The e-beam drilling process produces a hole with a slight taper (the entry is 0.001-0.002 in larger than the exit), which is desirable for ink release. The drilled cylinder is then electropolished (removing 0.0002-0.0005 in from all surfaces) to remove the e-beam recast layer and to improve the ink flow characteristics. The permeable cylinder eliminates the need for an ink pan and doctor blade, reducing ink waste and simplifying the printing press design.
E-Beam Drilling vs Laser Drilling Comparison
The following table compares e-beam drilling to laser micro-drilling for permeable ink cell production.
| Parameter | E-Beam Drilling | Pulsed Laser Drilling |
|---|---|---|
| Drilling rate | 500-5000 holes/s | 100-1000 holes/s |
| Cell diameter range | 0.003-0.008 in | 0.002-0.006 in |
| Aspect ratio capability | Up to 50:1 | Up to 20:1 |
| Hole taper (entry vs exit) | 0.001-0.002 in | 0.0005-0.001 in |
| Heat-affected zone | 0.0001-0.0005 in | 0.0005-0.002 in |
| Recast layer thickness | 0.0001-0.0005 in | 0.0005-0.001 in |
| Operating cost per cylinder | Moderate | Low-moderate |
| Equipment capital cost | Very high | High |
| Shell material suitability | Steel, nickel, copper | Steel, nickel, polymer |
Cell Geometry Parameters for Different Printing Applications
The cell geometry is tailored to the printing application, as shown in the table below.
| Application | Cell diameter (in) | Cell angle | Density (cells/in) | Aspect ratio | Ink release volume |
|---|---|---|---|---|---|
| Publication gravure | 0.005 | 20-30 deg | 200 | 25:1 | High |
| Packaging gravure | 0.006-0.008 | 20-25 deg | 150-175 | 15:1-20:1 | Very high |
| Fine anilox rolls | 0.003-0.004 | 90 deg | 300-400 | 10:1-15:1 | Low |
| Wide-format flexo | 0.004-0.005 | 30-45 deg | 200-250 | 20:1-30:1 | Medium |
| Specialty coating | 0.006-0.010 | 60-90 deg | 100-150 | 8:1-12:1 | Low-medium |
FAQ
What is the advantage of an internal ink reservoir in a permeable cylinder?
The internal ink reservoir eliminates the need for an external ink pan and doctor blade assembly, reducing ink waste by 30-50% and simplifying the printing press design. The ink is supplied to the internal chamber at low pressure (1-5 psi) and flows through the permeable cells by capillary action and surface tension. This closed system also reduces solvent evaporation from the ink, improving environmental compliance and reducing ink odour in the pressroom.
Why is a 20-degree cell angle preferred for high-volume gravure printing?
A 20-degree cell angle (relative to the cylinder surface) produces a longer flow path through the shell wall, which increases the ink release volume per revolution. The shallower angle also creates a larger entry opening on the internal surface of the shell, allowing more ink to enter the cell from the internal reservoir. For publication gravure, where high-speed (up to 3000 ft/min) printing of large solid areas requires maximum ink delivery, the 20-degree angle provides approximately 40% more ink volume than a 45-degree angle at the same cell diameter.
How is the cell array inspected for quality?
The cell array is inspected by automated microscopic imaging at a sampling rate of 0.1% of the total cells (typically 50 000 cells inspected per cylinder). The inspection system measures each sampled cell for diameter, roundness, and the absence of blockage. The acceptance criterion is less than 0.1% blocked cells and less than 1% of cells outside the diameter tolerance of +/-0.0005 in. Cells that are blocked are recorded by position, and the cylinder may be re-drilled in localised areas if the blockage exceeds the acceptance threshold.
What causes cells to become blocked during e-beam drilling?
Cells become blocked when molten metal from the e-beam drilling process re-solidifies inside the hole before being ejected. This occurs most frequently at high drilling rates (above 3000 holes/s) or when the beam power is insufficient to fully penetrate the shell wall in a single pulse. Blockages are also more common at shallow cell angles (20-25 degrees) because the longer flow path increases the probability of molten metal re-solidifying before it exits the hole.
How does electropolishing improve the e-beam drilled cylinder performance?
Electropolishing removes 0.0002-0.0005 in of material from all surfaces of the drilled cylinder, including the internal surfaces of the cells. This removes the e-beam recast layer (a heat-affected zone of re-solidified metal that has a rough, irregular surface that impedes ink flow). The electropolished surface has a smooth, passive finish (Ra 0.1-0.2 microns) that improves the capillary flow of ink through the cells and reduces the tendency for ink to dry and block the cells during press stops.
Data are based on published research and industry experience as of 2026.