Browsing by Author "Schreve, K."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Development of a computer assisted gantry system for gaining rapid and accurate calyceal access during percutaneous nephrolithotomy
    (Sociedade Brasileira de Urologia, 2010) Zarrabi, A. D.; Conradie, J. P.; Heyns, C. F.; Scheffer, C.; Schreve, K.
    Purpose: To design a simple, cost-effective system for gaining rapid and accurate calyceal access during percutaneous nephrolithotomy (PCNL). Materials and Methods: The design consists of a low-cost, light-weight, portable mechanical gantry with a needle guiding device. Using C-arm fluoroscopy, two images of the contrast-filled renal collecting system are obtained: at 0-degrees (perpendicular to the kidney) and 20-degrees. These images are relayed to a laptop computer containing the software and graphic user interface for selecting the targeted calyx. The software provides numerical settings for the 3 axes of the gantry, which are used to position the needle guiding device. The needle is advanced through the guide to the depth calculated by the software, thus puncturing the targeted calyx. Testing of the system was performed on 2 target types: 1) radiolucent plastic tubes the approximate size of a renal calyx (5 or 10 mm in diameter, 30 mm in length); and 2) foam-occluded, contrast-filled porcine kidneys. Results: Tests using target type 1 with 10 mm diameter (n = 14) and 5 mm diameter (n = 7) tubes resulted in a 100% targeting success rate, with a mean procedure duration of 10 minutes. Tests using target type 2 (n = 2) were both successful, with accurate puncturing of the selected renal calyx, and a mean procedure duration of 15 minutes. Conclusions: The mechanical gantry system described in this paper is low-cost, portable, light-weight, and simple to set up and operate. C-arm fluoroscopy is limited to two images, thus reducing radiation exposure significantly. Testing of the system showed an extremely high degree of accuracy in gaining precise access to a targeted renal calyx.
  • Thumbnail Image
    Item
    Optical aid for placing composite material (prepregs) in a mould
    (Southern African Institute for Industrial Engineering, 2018-05-31) Van der Westhuizen, J.; Schreve, K.
    ENGLISH ABSTRACT: Increased industrial use of composite materials for manufacturing strong lightweight components stimulates endeavours for more efficient assembly methods. This study attempted to find an optimal method to provide optical aid for the placement of pre-impregnated reinforcing fabric (prepregs). A novel approach to optical assistance for the placement of prepregs was designed to be straightforward and affordable. The developed system meets industry standards for accuracy, and provides the solution at a cost many times less than existing solutions. The findings allow companies in the composite material industry to eliminate prepreg layup errors at an affordable price.
  • Thumbnail Image
    Item
    Three dimensional printing in the South African industrial environment
    (Southern African Institute for Industrial Engineering, 2008-05) Dimitrov, D.; Schreve, K.; De Beer, N.; Christiane, P.
    ENGLISH ABSTRACT: The current development of the rapid prototyping industry in South Africa is characterised by the strong dominance and fast growth in sales of three dimensional printers. Although it reflects the international trend, it seems that the industrial community lacks a clear appreciation of the real strength of this technology, especially with respect to the large variety of devices available today on the market. This paper surveys the current state and capabilities of three dimensional printing (3DP). Based on its technical background – the ink-jet printing known from the printer and plotter industry – a classification structure is developed and proposed. Different printing techniques and process concepts, together with their advantages and limitations, are described and analysed. Typical examples from three completely different application areas – manufacturing, medicine, and architecture – are presented and discussed. Some basic considerations for an informed selection of the right technology for a particular application are then presented.
  • Thumbnail Image
    Item
    A user interface for a seven degree of freedom surgical robot
    (South African Institution of Mechanical Engineering, 2013) Heunis, J. S.; Scheffer, C.; Schreve, K.
    This paper presents the design of a joystick-type user interface for the master-slave control of a seven degree of freedom (DOF) minimally invasive surgical robot. The joystick is a seven DOF all revolute articulated arm. The electronic design implements AS5040 magnetic rotary encoders for the joystick’s position and orientation tracking. The control system required the mathematical modelling of the joystick and robot using the Denavit- Hartenberg convention. Testing demonstrates the intuitiveness of the joystick control.