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Hi could someone explain how I can go about digitising a large shape. I am interested in using the cnc router to cut replacement windscreens etc for boats. These are often as much as 2 metres long and half a metre wide and shaped rather than just straight so they look straight when bent to fit in the ­frame­ (they are made from acrylic or polycarb)and 2mm-6mm thick

Robin

Hello Robin!

If i am right you want a scanner in order to digitize a shape.
Take a look at this topic here
you might be interested in!!

Hi Mik, that 3D and laser technology is brilliant. I've also looked at photogrammetry, but the technology is beyond me at this time. The 3D laser scanners cost a lot of dosh and the photogrammetry software is £1400. Add to that the cost of a dual core 3Gig computer with 4Gig of ram and we are talking mega bucks. I've got a £15 solid probe and would just like to be able to map a boundary, relatively quickly. I even considered importing a photo and resizing it, but accuracy would be a problem unless there was a simple piece of software that I told it the maximum size of the item and it resized it into a box in Autosketch (Can't manage Autocad too expensive and need a high spec computer to run, tried it at home once and had to go for a cup of tea when ever it needed to refresh)
I can map the boudary manually, using jog and then recording the position manually, but what I really need is a piece of software that will push the probe around and log the positions every 5mm and export to Autosketch or Sheetcam. Should be able to use the switch in the probe to reverse the probe direction and produce a zig zag path around the perimeter, logging the boundary as it goes. I just don't know what technology is out there now.

Robin

I see what you mean.
You want to digitize simple shape nothing too complicated.
I will see what i can find

Robin,
I don't know if i understand what your asking but it sounds like you don't need a scanner but should manually measure your window and then use your cad lines and such to match your measures and shape on the computor. ???

Hi, when I said a simple shape, maybe I should have said a 2D shape. The acrylic has to be cut to within 1mm to fit in the ­frame­s without leaking and they have lots of concave and convex curves which are hard to reproduce in manual cad. I have a digitising probe and would just like to know how to use it. There is a digitising/probe plugin for Mach, but it's just a question of how to. If fact the one for my boat has no straight lines at all, just curves. Cutting rectangles and trapeziums is easy, just draw in cad and process, but the more convoluted shapes take some drawing. These were at the time just manually cut from a template which was made from a ­frame­ template.

Robin

hi call me a loon but my cheap manual solution to your problem would be to set up an aluminum gantry around your window aperture with a thin (.5mm) wire mesh (of around 50x50 mm) ­frame­ work, a window that would allow you to see a direct scale of measurement with a tolerance close to millimeters, then to use a parallel correction lense as used by architects to correct any spherical distortion seen through ordinary lenses.
auto cad 14 run on a pentuim two could easily cope with the manual data
a bit cheaper than a scanner !! you could set up the same scenario with a few laser levels in an array to form a grid on a calibrated gantry
a bit more expensive but still cheaper than a scanner
or hire a scanner.

now you've got me thinking about lasers in a grid array