Freesteel Blog » It drags on and on

It drags on and on

Thursday, January 26th, 2006 at 11:27 am Written by:

I am never going to write a const scallop routine again, ever. Most of the glitches are removed now, though I had to do a lot of evening coding during the week of skiing in France when I was dog tired. On two of the evenings I skipped the free wine (which was minging anyway) so I could work late into the evening.

Anyway, it’s starting to take shape, though I’ll no doubt get the usual “Not Fast Enough” complaint that happens in the absence of horrible gouges.

Meanwhile, Martin’s been doing interesting stuff on the web-version and should have that happening eventually. We spent ages getting the drag and zoom right. The server software is now rendering in MESA rather than VTK, which makes the rendering of the triangles into the depth buffer absolutely concrete. All viewing transformations are turned off. We calculate them ourselves to make what we are doing pixel perfect, the right way up (bitmaps put their origin in the top left corner with the Y-axis pointing down, while graphics rendering

We’ve finally given up on our utterly shite mini-machine tool. Workmanship is too awful and we’d need access to a tool-shop where we could constantly remake the bent bits to keep it operational. We kept going back to the University and getting the technician to make pieces for us, but that can’t go on.

We’ll take it down to Bristol to show a friend who works in education, during our expedition to show off Adaptive Roughing software to a prospective vendor (hopefully not making such a hash of the sales pitch as I did elsewhere in the summer). Maybe it will fall off the train on the way, and we can get a new one, possibly from Peatol Machine Tools in Birmingham. Couldn’t be worse.


  • 1. Neel replies at 4th February 2006, 7:34 pm :

    Const scallop routine , is this a combination of constant stepdown in steep areas and constant stepover (offset) in shallow areas? How do the two toolpaths match. What steepness angle do you change from one method to other? Can I have a development version of this strategy to play with and test ?

  • 2. Neel replies at 28th February 2006, 4:48 pm :

    Mastercam latest Maintenance Release (MR1) has introduced similar toolpath strategy called Scallop. It
    Generates 3D passes at a constant distance from each other along the surface of the part, starting from the outside and working in. This toolpath lets the user control the scallop height, allowing for very smooth finishes.

  • 3. Julian Todd replies at 28th February 2006, 5:56 pm :

    You’ll be interested to know that it’s in fact the precise algorithm I wrote! NCG sold Mastercam the code recently, and they’ve embedded it into their product. I’ve never had so much as a note of acknowledgment from anyone for it being any good. Let that be a lesson that nobody cares. Had I known the level of gratitude was going to be like this, I wouldn’t have put so much sweat into it.

    One always writes stuff differently the second (or fourth) time round — I wrote three versions while I was at NCG.

    There’s the chance I’ve gone backwards with this new implementation, making some sort of mistaken assumption. Hard to say at the moment.

  • 4. Neel replies at 28th February 2006, 7:34 pm :

    If thats the case then I guess all the 7 strategies that they have added are from NCG.

  • 5. Julian Todd replies at 28th February 2006, 8:17 pm :

    Yep. All of it is my sweat and code, except the linking of the toolpaths (which Martin did most of) and this core roughing feature (which is kind of an adaptation of the pocket machining by making clearing paths for an overly large area and trimming them to the boundary). I’ve never had so much as a handshake from anyone in Mastercam. Nobody there even knows. It pisses you off if you think about it too much.

  • 6. Neel replies at 1st March 2006, 2:15 pm :

    So what version are you writing now is it ‘Constant offset machining’ or ‘Corner offset machining’.

    Do you actually calculate the constant offsets on the mesh

  • 7. Julian Todd replies at 1st March 2006, 3:34 pm :

    I think it’s “Constant offset machining”. I don’t know what “Corner offset machining” is. There’s no agreed definition to this terminology — the words are usually made up as people write them. That’s why a set of Wikipedia entries on each with detailed definitions would be useful.

  • 8. Neel replies at 1st March 2006, 3:43 pm :

    Corner offset machining is similar to constant offset machining. However with this technique, rather than start from an outside boundary and work in towards the centre, a set of pencil milling passes are created on the features of the part. A tool-path is then calculated over the whole part from those features.

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