Cut­ting sys­tem for paper machine cloth­ing with con­trol, dri­ve tech­nol­o­gy and vision appli­ca­tion from Beckhoff

Machines for the pro­duc­tion of paper are divid­ed into sev­er­al sec­tions, each requir­ing a spe­cial con­vey­or belts the so-called paper machine cloth­ing. These are belts, some of which are sev­er­al meters wide and made of high-tech tex­tiles with dif­fer­ent prop­er­ties. The paper pulp is trans­port­ed through the paper machine on them. Due to dif­fer­ent machine types and paper for­mats, these cloth­ings, which are made of high-tech tex­tiles, are sup­plied in cus­tomer-spe­cif­ic for­mats. How­ev­er, on the weav­ing machines used to pro­duce the cloth­ings the width can only be rough­ly adjust­ed. There­fore, after pro­duc­tion, a cut­ting process is required to cut the fab­ric to the desired width. For this cut­ting process, new mobile cut­ting machines were devel­oped and put into oper­a­tion in coop­er­a­tion with Hille Engi­neer­ing for a pro­duc­er of paper machine clothing.

For the cut­ting process, the cloth­ing is stretched with the help of two cal­en­ders. The cut­ting machines are posi­tioned and aligned on both sides of the cloth­ing. The cal­en­ders now move the cloth­ing through the machine until the belt has run through once com­plete­ly. The tex­tile is clamped in the machine between an ultra­son­ic head and a cut­ting wheel. The ultra­son­ic exci­ta­tion caus­es the mate­r­i­al to be cut and the edge is slight­ly melt­ed by the heat gen­er­at­ed simul­ta­ne­ous­ly. This seals the edge and pre­vents it from fraying.

When mov­ing the very large-for­mat cov­er­ings, there are always slight changes in posi­tion orthog­o­nal to the direc­tion of move­ment. To com­pen­sate for these move­ments and ensure a con­sis­tent width of the cloth­ing, both cut­ting machines must fol­low these changes. For this pur­pose, each of the machines is equipped with a vision sys­tem. 

The ultra­son­ic head and cam­era are mount­ed on two inde­pen­dent­ly mov­ing axes. Col­ored threads which are insert­ed into the fab­ric at reg­u­lar inter­vals in the direc­tion of move­ment makea changes in their posi­tion detectable by the cam­era. The devi­a­tion from the tar­get posi­tion is trans­mit­ted to the cut­ting axis so that an adjust­ment can be made. 

Hille Engi­neer­ing was respon­si­ble for the mechan­i­cal design and man­u­fac­tur­ing in this project. The con­trol, dri­ve tech­nol­o­gy and image pro­cess­ing of the cut­ting sys­tems were imple­ment­ed by Qual­i­ty Automa­tion com­plete­ly with com­po­nents from Beck­hoff. PLC and Motion Con­trol have long been part of the Beck­hoff prod­uct port­fo­lio, but with Twin­CAT Vision the option of image pro­cess­ing is now also inte­grat­ed on a uni­form con­trol plat­form. This not only sim­pli­fies the con­fig­u­ra­tion of the sys­tem, but also enables cam­era-based con­trol and syn­chro­niza­tion in real time. In this way, the posi­tion data acquired by the cam­era on the machine is processed by the motion con­trol in the same PLC cycle and the posi­tion of the axes is adjust­ed with­out laten­cy. The com­pre­hen­sive library also enables the solu­tion of com­plex require­ments in the area of geom­e­try con­trol or sur­face analy­sis. All cam­eras with ‑GigE–Vision inter­face can be con­nect­ed to the con­troller. Only the appro­pri­ate dri­ver must be installed on the Beck­hoff Indus­tri­al PC. A cam­era and optics from Matrix Vision, both in dust- and vibra­tion-proof design, are used on the machines.