Effects of Mould Surface Roughness on Press Forming Process of Polymer Coated Paperboard

Abstract In paperboard press forming the forming forces are transmitted on the formed substrate by controlling the sliding of the blank with a blank holding force. A set value of the force and the friction between the tool surfaces and processed material define the force transferred on the formed substrate. Mould surface roughness is one of the main factors affecting the magnitude of friction and maximum usable press force. A series of surface roughness measurements was made to investigate the surface roughness in different areas of two different blank holders to determine a sufficient quality for the tool surfaces. Also the static friction coefficients of formed substrates were determined and the friction force distribution was investigated. The results show that the effect of mould temperature on friction force can be reduced significantly by mould surface polishing, while making the press-forming process more predictable and easier to adjust due to reduced variation. Hence, the polishing of mould surfaces can be recommended.