Architecture for Direct Model-to-Part CNC Manufacturing
In the traditional paradigm for Computer Numerical Control (CNC) machining, tool paths are programmed offline from the CNC machine using the Computer-Aided Design (CAD) model of the workpiece. The program is downloaded to the CNC controller and the part is then machined. Since a CAD model does not exist inside the CNC controller, it is unaware of the part to be machined and cannot predict or prevent errors. Not only is this paradigm labor intensive, it can lead to catastrophic damage if there are errors during machining. This paper presents a new concept for CNC machine control whereby a CAD model of the workpiece exists inside the controller and the tool positions are generated in real-time by the controller using the computer’s graphics hardware without human intervention. The new concept was implemented on an experimental lathe machine specifically designed to machine complicated ornamental wood workpieces with a personal computer. An example workpiece was machined and measured using a 3D camera. The measured data was registered to the CAD model to evaluate machining accuracy.
A New Paradigm for Woodworking with NC Machines
We present a paradigm that makes the exibility of NC machining available to the non-technical woodworker. In this context, general-purpose CAD software and manufacturing systems are not appropriate due to prohibitive complexity and cost. We propose a machine architecture and suite of software tools that together oer a cost-eective and simple way of realizing art in wood. Designs can be tested in a 3D simulation before being realized. As a proof-of-concept of the new paradigm, we show a prototype NC milling lathe, a design tool for the special case of Islamic star patterns, and a decorative piece designed and cut using the system.
Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
Abstract Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1–1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.