1 / 36

Automatic Generation of 3D Machining Surfaces With Tool Compensation From Graylevel Image Models

Automatic Generation of 3D Machining Surfaces With Tool Compensation From Graylevel Image Models. Theodor BORANGIU, borangiu@cimr.pub.ro Anamaria DOGAR, dogar@cimr.pub.ro Alexandru DUMITRACHE, alexdu@easynet.ro. Summary. Height Map images Modelling the machining surface and tool shape

leala
Download Presentation

Automatic Generation of 3D Machining Surfaces With Tool Compensation From Graylevel Image Models

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Automatic Generation of 3D Machining Surfaces With Tool Compensation From Graylevel Image Models Theodor BORANGIU, borangiu@cimr.pub.ro Anamaria DOGAR, dogar@cimr.pub.ro Alexandru DUMITRACHE, alexdu@easynet.ro

  2. Summary Height Map images Modelling the machining surface and tool shape Performing tool compensation Generating roughing and finishing toolpaths Error analysis Future plans

  3. Height Map Images

  4. Obtaining Height Map Images 3D Model in POV-Ray Height Map Model

  5. Obtaining Height Map Images Remove light sources Remove material textures Use an ortographic camera Apply a pigment with brightness proportional to the distance from the camera plane: farthest point: pure black (brightness 0)‏ closest point: pure white (brightness 1)‏

  6. 2.5D Surface Modelling Pixel graylevel at (i,j) encodes surface height at (x,y)‏ Pixel-to-millimeter ratio: x = R i y = R j Minimum Z of the surface: black pixel Maximum Z of the surface: white pixel Graylevel value: 8-bit integer: low precision, low storage space 16-bit integer: good precision Floating point: best precision, high storage space

  7. Simplest Case: 2 Dimensions Part model: • Tool model: • Tool compensation:

  8. Simplest Case: 2 Dimensions • Offsetting is done by image dilation • For efficiency, only contour pixels need to be processed • Tool path is generated by extracting the contour • By image erosion we obtain the machined shape

  9. Tool Shape Modelling Conic Mill Round End Mill Bull End Mill

  10. Tool Compensation Objective: Generating gouge-free tool paths Idea: For each (x,y) position, find the maximum depth at which the end mill can go down without cutting extra material Algorithm: Graysale image dilation Image: Surface model Structural element: Tool model

  11. Tool Compensation Result A surface on which tool's end point can move safely

  12. Advantages Gouge-free tool paths for many tool shapes Immediate generation of basic roughing and finishing tool paths Simple implementation, no need for complex 3D geometry computations

  13. Disadvantages High computation time (Example: image 1000x1000 pixels, tool 50x50 pixels, running time: 11 seconds on a Pentium 4-M 2.00 GHz)‏ High storage space for the image model Compromise between precision and speed!

  14. Increasing Speed It is not always necessary to compute the entire surface The algorithm can be parallelized

  15. The Software

  16. Software Features Grayscale model support Tool shape editor Roughing toolpath generation Finishing toolpath generation ISO CNC (G-Code) output

  17. Tool Shape Editor

  18. Tool Shape Editor Predefined tool shapes: spherical end mill conical end mill flat end mill bull end mill User defined tool shapes

  19. Roughing • Each roughing stage is performed at constant Z level • At a given Z level, selecting the region where the cutter should clean up is an image thresholding operation • For flat endmill cutters we use 2D offset compensation

  20. Roughing

  21. Finishing – First Method • In XY plane, the tool moves parallel with either one axis or an arbitrary direction • The tool moves on the “safe surface” • There is no need to compute the whole “safe surface”

  22. Finishing – Second Method • Tool paths are at constant Z levels • Because of the tool shape, we cannot use 2D compensation any more • The whole surface needs to be computed!

  23. Finishing - Combined

  24. Semi-Finishing

  25. Finishing

  26. Error Analysis • A tool can be too big to machine the fine details • At first, we can use a bigger tool to machine surfaces without fine details, and then a smaller tool to machine only the small details • We can simulate one cutting operation and see what could not be machined

  27. Final Touch

  28. ISO CNC Output Toolpaths are made of linear segments and circular arcs Succesive segments may be approximated with circular arcs Toolpath optimization: reduce the time for moving the head without cutting M03 G0 X80 Y7.75 G1 Z-40 F100 G1 X65.5 G0 Z0 G0 X71.75 Y10.75 G1 Z-40 F100 G1 X80 G1 Y13.75 G1 X73 G1 Y16.75 G1 X80 G1 Y19.75 G1 X73.25 G0 Z0 M05

  29. Sample Workpiece

  30. Technical Data Dimensions: Material: Cutters used: Image size: Roughing: Semifinishing: Finishing: Final Touch: 100 x 50 x 20 mm Wood: Beech (Fagus)‏ Flat 5mm, Round 6mm and 3mm 1000 x 500 379 instructions, 22 minutes, 200 mm/min 2034 instructions, 36 minutes, 200 mm/min 7131 instructions, 53 minutes, 400 mm/min 88 instructions, 1 minute, 300 mm/min

  31. Other Example:Semifinished Workpiece

  32. Other Algorithms Used Contour Detection: Moore Neighbourhood Search Simplifying Polylines: Douglas – Peucker Generating Discrete Line Segments: Bresenham

  33. Future Plans:Collision Detection The whole tool shape can be modelled, including the tool holder, to check if a tool path will cause a collision with the workpiece At every moment the amount of material can be computed; this is useful to check if the maximum allowed cutting depth of a tool is not exceeded.

  34. Future Plans:Better Milling Strategies Roughing example

  35. Future Plans:CNC Simulator Input: a file with RS274 G-Code Realtime 3D Simulation for CNC Mill Engine based on height map images Collision detection Possibility of exporting animations

  36. Thank You!

More Related