A method is described for the compensation of errors associated with tool path generation, particularly during five-axis high-speed machining (HSM). Information on machine tool performance and its dynamic features is used to calculate possible errors and convenient modifications of the NC program, thereby avoiding errors when parts are actually being machined. This 'preprocess method' by means of postprocessing with NC software is presented. The errors dealt with are mainly servo lag errors, but the explored approach can support most systematic errors associated with machine tool performance. These are briefly summarized. Research so far has largely been aimed at the implementation of compensation routines in the CNC controller and at corrections in real time. The problem is that most applications are only available for three-axis milling. The presented approach (compensation before machining by using software routines in a specially designed postprocessor) is based on a fuzzy logic expert system. The benefits can be summarized as data reduction, data improvement, precontrol of feed, and improved component accuracy. The applied procedure is also convenient for implementation in an industrial environment by retrofitting existing equipment. The suggested method provides improved control over machine dynamics, permitting high-speed machining centres to maintain a maximum or near-maximum feed rate despite axis reversals and tool path changes, even at corners. Two categories of results are presented, namely the management of NC data related to expected performance of the machine tool and improvements of the machine tool performance in terms of productivity and accuracy of the machined test components.

This thesis deals with the machining method milling and the forces affecting the tool during a milling operation. A survey of different tool geometries and conditions of the tool engagement during a machining process is presented. The general cutting theory and the equations used to estimate the load are explored. For practical use this simplified approach may be enough but when a more precise calculation of the load condition are required, i.e for process control or research when the varying chip thickness must be taken into consideration, the general theory is not adequate.

As a result of the research work an accurate mathematical model and a computer software has been developed at the Division of Production Engineering. The model calculates the cutting forces acting on the tool during one revolution. The stepsize is one degree. The forces are expressed according to a coordinate system with its origin in the center of the tool. In order to evaluate the software the calculated values have been compared with real forces recorded during machining. The reliability of the equipment and of the developed model has been verified.

Different ways for further development of the software have also been investigated. These developments are based on tool life studies made at the Division. One of the applications presented in the thesis is related to the working material. Equations for calculation of the material parameters needed are developed and the structure for a new computer software for the calculations is shown. The presented results can simplify the development of adaptive control modules and improve process planning routines associated with numerical programming of machine tools.

Avhandlingen behandlar bearbetningsmetoden fräsning och de krafter som påverkar ett fräsverktyg under en fräsoperation. En redogörelse av olika verktygsgeometrier och de ingreppsförhållanden som råder under en bearbetningsoperation genomgås. Den allmänna skärteorin och de ekvationer som utnyttjas vid överslagsberäkningar av verktygets belastningar har sammanställts. När en mer exakt beräkning av skärkraften är krävs, exempelvis vid processtyrning eller forskningsarbete när hänsyn till den varierande spåntjockleken måste tas, är den allmänna skärteorin otillräcklig.

För noggrannare beräkningar av verktygets belastningsförhållande har en matematisk modell och en programvara utvecklats vilken presenteras i avhandlingen. Modellen bestämmer de olika skärkrafterna på ett fräsverktyg under ett varvs rotation. Steglängden är en grad och krafterna uttrycks i ett fast koordinatsystem relaterat till verktygets centrum. Programvarans funktion jämförs med verkliga skärkrafter insamlade med en skärkraftsmätningsutrustning. Utrustningens och programvarans tillförlitlighet har analyserats och verifierats.

Olika möjligheter till vidareutveckling av programvaran har också undersökts. Dessa baseras på utslitningsstudier genomförda vid institutionen. En av de applikationer som visas i avhandlingen är relaterad till arbetsmaterialet. Ekvationer för bestämning av nödvändiga materialdata har utvecklats och strukturen för en ny programvara presenteras. De erhållna resultaten kan förenkla en utveckling av adaptiva styrmoduler och underlätta beredningsrutiner vid generering av NC-program för verktygsmaskiner.