Why recondition at all
Routine reconditioning maintains print quality and extends roller life. Experienced pressmen already know this: a properly reconditioned, seasoned roller frequently outperforms a new one, because a new cover has not yet been stress-relieved and is apt to start developing high and low spots.
Quality-conscious printers know from experience that rollers must be in top condition to obtain top quality printing results.
Reconditioning is the intervention that sits between daily wash-up and full recoating. The cover is still sound; what has accumulated on and in it is not.
What the process removes
- Rule cuts, removed while maintaining operating diameter
- Case-hardened ink deposits
- Deep surface contamination that washing will no longer reach
- Surface irregularity, corrected by precision grinding and polishing
Reading hardness: what the durometer is telling you
A durometer measures the hardness of an elastomer on the Shore A scale, and it is the most useful single number you can take off a roller. An increase of two to three hardness points is not critical. Five to six points will create problems on press.
Most authorities recommend rollers in the region of 25–30 durometer for ink form rollers. Over a normal service life a roller may reach 30–35. Improper handling and neglected wash-up can push it to 40 durometer, at which point glazing is not a risk but a certainty.
Signs a roller is ready to come off
- Dried ink visible at the roller ends
- Build-up or cracking at the shoulders and ends
- Abrasion, roughness or unevenness across the face
- A durometer reading more than five points above the new-cover specification
Glazing, and what it does on press
Glazed rollers develop gradually, which is what makes them dangerous — the decline is slow enough that the pressroom adapts to it before anyone measures it. The symptom is faint printed areas.
Glazing is due to an accumulation of a dried ink film, and if not corrected, roller surfaces lose their affinity for ink.
The consequences are skidding, streaking and stripping. A glazed form roller has poor frictional potential, so it turns more slowly than the plate cylinder it contacts — and the resulting speed difference produces skids. Left untended, rollers will crack from the surface ink residue, particularly at the shoulders, where neglected washing leads to progressive destruction of the cover.
What happens in our works
On arrival, every roller is inspected for the condition of the covering — size, cuts, rule marks, cracking and adhesion — and for the integrity of the core. Metal defects are repaired, unless the cost of repair exceeds the value of the roller, in which case we say so rather than doing the work.
- Regrinding, removing the minimum material consistent with adequate clean-up
- High-speed polishing with fine abrasive to the required surface finish
- Shoulder sanding to eliminate dried ink
- Solvent washing to remove polishing dust
- Metal protection with paint and rust inhibitor
- Protective wrapping for shipment
