High accuracy automated scalloping of decorative lace
thesisposted on 19.12.2013, 11:27 by Philip Bamforth
Decorative lace production has been highly mechanised since the 19th century. Modern lace is manufactured on CNC Jacquard and Raschel looms, little technological development has occurred since the early 1980's. Decorative lace is knitted in webs as much as 3.8m wide containing may smaller lace breadths. The lace breadths must be separated from the main web ready for garment manufacture. The separation process for decorative lace is traditionally carried out using scissors or a guided knife system. The development of a machine vision guided laser cutting system at Loughborough University in the 1990's demonstrated that an economical fully automatic cutting system could replace the slow and expensive traditional methods. Marketing of the laser cutting system has identified some weaknesses in the quality of the cut-edge for some markets that require higher quality lace. The vision-guided laser cutting system utilises a continuous wave (CW) laser. Incorrect positioning of the laser causes melting to the lace edge which can be detected by a rough texture. A high accuracy pulsed laser-cutting solution for lace is demonstrated in this thesis. The lace is cut by applying a short pulse of laser energy directly onto individual threads that connect the lace breadth to the waste material. An edge directed algorithm that utilises a transmissive illumination method locates the position of the cutting point on the threads. The transmissive illumination method highlights lace density as well as position. The density information facilitates the accurate location of the lace-cutting path. A 3D transient finite difference thermal model of the cutting process has been developed to aid in the optimisation of the laser process. Deficiencies in the existing CW process have been highlighted with the model. Optimum processing parameters have been calculated with the model for the pulsed process. Fully automatic, vision guided, pulsed laser cutting of lace has been demonstrated on a low speed system. The lace produced on the pulsed laser system has been shown to have a significant improvement in edge quality over lace produced using the CW process. The edge quality approaches that of traditionally cut lace.
- Mechanical, Electrical and Manufacturing Engineering