Printing presses and paper making machines are built around large rollers and drums. Every roller in a printing press or paper machine needs a through-bore for heating, cooling, or weight reduction. Some of these rollers are the largest components I have ever drilled in the industrial roller category.
I have drilled rollers for newspaper printing presses, commercial sheet-fed presses, and paper mill drying sections. The materials range from chilled cast iron to hardened steel to rubber-covered rollers with steel cores. Many of the principles from industrial roller deep hole drilling apply here, but the scale and material variety are greater.
Printing Press Roller Drilling
Printing press rollers transfer ink from the plate to the paper. The rollers must maintain a consistent temperature to control ink viscosity. Many printing press rollers have a heating or cooling system that circulates fluid through the bore.
For a typical printing press roller core:
| Parameter | Value |
|---|---|
| Roller length | 1-3 meters |
| Bore diameter | 40-100mm |
| Wall thickness | 8-20mm |
| Material | Ductile iron or steel |
| Cutting speed | 70-90 m/min |
| Feed rate | 0.10-0.18 mm/rev |
| Coolant pressure | 400-800 psi |
The roller wall thickness varies by application. Printing press rollers that carry ink need a thicker wall for rigidity. Rollers that only guide the paper web can have thinner walls.
Chilled cast iron is common in printing press rollers because of its wear resistance and thermal properties. It drills well with carbide tooling at standard parameters. The main issue with chilled iron is the hard surface layer. Some cast iron rollers have a chill depth of 5-10mm that is significantly harder than the core material.
For chilled cast iron rollers, I reduce the cutting speed by 20% for the first 10mm of the bore to get through the hard layer, then increase to standard parameters for the rest of the hole.
Heated Roller Design
Heated rollers in printing and paper machinery circulate hot oil through the bore to maintain the roller surface at a specific temperature. The heat transfer depends on the bore surface finish and the oil flow rate.
For a heated roller with thermal oil circulation:
| Bore Finish | Heat Transfer Coefficient | Relative Performance |
|---|---|---|
| Ra 3.2 um | 85% | Baseline |
| Ra 1.6 um | 100% | Reference |
| Ra 0.8 um | 108% | +8% improvement |
I target Ra 1.6um for most heated printing rollers. The improvement from Ra 1.6um to Ra 0.8um is marginal and does not justify the additional processing time.
The oil flow rate through the bore is also important. For a 60mm bore in a 2-meter roller, I have seen flow rates of 50-150 L/min depending on the heating system. The bore must be smooth enough to avoid turbulent flow, which reduces heat transfer efficiency.
Paper Machine Drying Cylinders
Paper machine drying cylinders are large drums that the paper web contacts as it dries. These cylinders are typically 1.5-2 meters in diameter and 3-6 meters long. They are heated with steam through a rotary joint at one end.
The deep hole drilling work on drying cylinders is the bore through the cylinder journals. The journals are the shaft ends that support the cylinder and carry the steam into the cylinder interior.
For a drying cylinder journal bore:
| Parameter | Value |
|---|---|
| Journal length | 500-1500mm |
| Bore diameter | 50-150mm |
| Material | Cast iron or fabricated steel |
| Cutting speed | 60-80 m/min |
| Feed rate | 0.08-0.16 mm/rev |
| Straightness spec | 0.3mm over journal length |
The journal bore must align with the cylinder centerline. If the bore is off-center, the cylinder wobbles as it rotates, causing uneven drying and paper web breaks. I check the alignment by indicating the cylinder OD while rotating and comparing it to the journal bore centerline.
Rubber-Covered Roller Cores
Many printing and paper rollers have an elastomer or polyurethane cover bonded to a steel core. The steel core is drilled before the rubber cover is applied. The drilling must be done carefully because the core is relatively thin-walled compared to solid steel rollers.
I have drilled steel cores for rubber-covered rollers where the core wall thickness was only 6-10mm. The straightness requirement is still important because the rubber cover follows the core geometry. A core that is 0.5mm out of straight produces a rubber roller that has 0.5mm of runout, which causes uneven pressure in the nip.
For rubber roller cores:
| Core OD | Bore ID | Wall Thickness | Max Straightness Error |
|---|---|---|---|
| 80mm | 60mm | 10mm | 0.3mm |
| 100mm | 80mm | 10mm | 0.3mm |
| 120mm | 100mm | 10mm | 0.3mm |
The 10mm wall thickness is common across many roller sizes. The drilling parameters are similar to standard long shaft work but with lighter clamping to avoid distorting the thin-walled core.
Lubrication and Cooling Bores
Some printing press components have small-diameter bores for lubrication distribution. These bores deliver oil to bearings and gears inside the press. The bores are typically 3-10mm diameter through 200-500mm of material.
Lubrication bores are drilled with gun drills at high coolant pressure. The main challenge is chip evacuation in small-diameter holes. A 4mm lubrication bore through 300mm of steel has a 75:1 L/D ratio, which demands 1500+ psi coolant pressure to clear the chips.
Key Takeaways
- Printing press rollers in chilled cast iron require 20% speed reduction through the 5-10mm hard surface layer
- Heated roller bores at Ra 1.6um provide optimal heat transfer without the cost of finer finishes
- Paper machine drying cylinder journals must align within 0.3mm of the cylinder centerline
- Rubber-covered roller cores with 10mm wall thickness need light clamping to avoid distortion during drilling
- Small lubrication bores at 75:1 L/D ratio require 1500+ psi coolant pressure for chip evacuation