A drive shaft in a printing or packaging line wears down into grooves within months of continuous work, and every replacement means stopping the whole section. Polyurethane lining restores the shaft geometry and provides a coating that outlasts metal and rubber several times over. Below I explain how shaft lining works, which material to choose by the numbers, how it is mounted and how to order production to your drawing.
What polyurethane shaft lining delivers
Shaft lining with polyurethane means applying a wear-resistant elastomer layer to the working surface of a rotating cylindrical part that transmits rotation. The coating protects the metal from abrasion, corrosion and impact loads, and it also restores precise geometry to a worn shaft without manufacturing a new part.
The effect is immediate on two fronts. First, service life rises sharply: the wear resistance of TIMOL cast polyurethane is 2-5 times higher than standard rubber, so the maintenance interval of the unit is extended. Second, the elastic layer damps vibration and reduces line noise, while improving the shaft’s grip on the conveyed material. The metal under the coating no longer contacts abrasive and moisture directly.
Where lined shafts are used and why they wear out
Lined shafts work wherever the surface of the part is in constant contact with material, a belt or abrasive. These are conveying and pressing rollers, pulling shafts in printing and packaging machines, rolling tracks, shafts in pipe-rolling and woodworking production, and drums in mining and metallurgical lines.
Metal shaft wear arises from several causes at once. Abrasive particles in the material flow grind down the surface, water and aggressive media cause corrosion, and alternating loads lead to metal fatigue and grooving. As soon as the geometry is disturbed, the shaft starts to run out of true, damages the product and overloads the bearings. A bare metal shaft in such conditions has to be re-machined or replaced every quarter.
The polyurethane coating breaks this chain. The elastomer takes the abrasion upon itself, does not corrode and absorbs impacts instead of transmitting them to the structure. The layer is easy to restore by re-casting once it has run out its life, while the metal core stays in service for years.
Polyurethane versus rubber and steel: a comparison by the numbers
In wear resistance polyurethane substantially outperforms rubber, while in weight and corrosion resistance it beats metal. Here are specific reference figures for the materials actually used on shafts.
| Material | Abrasion DIN 53516, mm³ | Working t, °C | Tensile strength, MPa | Hardness | Density, g/cm³ |
|---|---|---|---|---|---|
| TIMOL polyurethane | 38-39 | -60…+100 | 39-87 | 85A-95A | 1.05-1.25 |
| NBR rubber | 80-150 | -30…+100 | 10-25 | 40A-90A | 1.0-1.3 |
| SBR rubber | 100-200 | -40…+80 | 8-20 | 40A-80A | 0.94-1.1 |
| Steel St3/St45 | none (metal) | -40…+500 | 370-700 | 120-250 HB | 7.7-7.9 |
Abrasion under DIN 53516 for polyurethane is 38-39 mm³, whereas for SBR rubber this figure reaches 100-200 mm³ and for NBR 80-150 mm³. That means rubber on a shaft wears out 3-5 times faster under the same conditions. A steel shaft has no DIN abrasion figure in the same sense, because it fails differently, through scoring, corrosion and fatigue, and it weighs 6-7 times more than a polyurethane layer of the same geometry (density 7.7-7.9 versus 1.05-1.25 g/cm³). Metal also does not damp impacts and transmits vibration to the bearings, whereas polyurethane cushions them thanks to its elasticity.
Rubber is cheaper but loses on several counts at once: lower wear resistance, lower tensile strength (8-25 MPa versus 39-87 MPa for polyurethane) and a narrower temperature range for SBR. So for loaded shafts polyurethane offers the best ratio of service life to weight.
How to choose the hardness and thickness of the shaft coating
Hardness is matched to the type of load, and thickness to the shaft diameter and pressing force. The general rule: the higher the pressure and the more precise the geometry required, the harder the polyurethane, and the more delicate the contact with the product, the softer.
TIMOL cast polyurethane is available in the range from 50 Shore A to 70 Shore D, so a single technology covers both soft pressing rollers and hard rolling tracks. For conveying and pulling shafts, the middle zone of 80-95 Shore A is usually chosen, combining grip and abrasion resistance. For high-pressure shafts the Shore D zone is selected.
Engineer’s advice: Do not chase maximum hardness by default. Softer polyurethane grips the belt better and cushions impacts, while an overly hard layer on a thin shaft can delaminate under bending. Before casting, always degrease and prepare the metal surface for an adhesion primer; it is the quality of surface preparation that decides whether the lining lasts its full design life.
Layer thickness is calculated so that it can dissipate friction heat and not overheat in the contact zone. For most conveying shafts a few millimetres is enough, while rolling and heavily loaded sections require more. Optimal values are selected by the plant engineers for the specific unit.
Mounting, adhesion and servicing of a lined shaft
Polyurethane is applied by free casting directly onto the prepared metal core, after which the layer polymerises and forms a monolithic bond with the metal. The free-casting technology accurately reproduces the shaft geometry and avoids air pores in the coating.
The key to durability is surface preparation before casting: removing old coating, degreasing, shot-blasting and applying an adhesion primer. A properly prepared shaft gives a monolithic joint that does not delaminate under bending and alternating load. The finished shaft is balanced to avoid run-out at working speed.
Servicing comes down to visual inspection of the coating and timely re-casting once the layer has run out its life. The metal core is not discarded: it is lined again, and the unit returns to service. This is a fundamental economic advantage over replacing a solid-metal shaft.
How to order shaft lining at the TIMOL plant
You can order shaft lining at the TIMOL plant to a ready drawing, to a technical description or from a dismantled worn shaft as a sample. Production runs by free casting to the specific dimensions, loads and operating conditions of your unit.
The process starts with a consultation, where engineers select the hardness, coating thickness and polyurethane grade for your task. You can review the range of products in the catalogue of polyurethane products, while the technical details of the material and technology are gathered in the reference information section. To get a calculation for your drawing, contact the TIMOL plant. Experience with hundreds of units will help select a solution that extends the shaft’s service life and cuts line downtime.