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  1. #1
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    Generating Machine Toolpaths inc Offsets

    Afternoon folks, I'm wondering if there is someone on this forum who knows a thing or two about CNC or similar machining and could give me some advice as I'm a bit stuck on something.

    Basically I'm trying to generate a dimensioned drawing of a 2D toolpath for a milling cutter of a given diameter from a drawing of a profile I'm planning to mill. I'm using SolidEdge to model the part. I can add a simple offset line to the part, but I'm not sure if a cutting tool simply follows a path, offset by its radius? If it does I'm laughing but I fear it may be more complicated than that!

    I have a manual milling machine and am trying to mill a profile that includes both straight and radius edges. I've worked through how you use a compound table, on a rotary table, on the mills main compound table, to be able to follow a path. Fairly happy with that (I think!). Now I need to know how to generate the path allowing for the tool offset.

    That make any sense, and can anyone advise?
    Lloyd B
    Current: Crendon #54 in build - 427 Side Oiler/Cobrajet Heads/Dual 600cfm Holleys/4 speed toploader/Vintage cast knock on wheels
    Dedion Dax/Clarkson 383 Chevy with roller 4/7 swap cam, AFR195 heads - SOLD

  2. #2
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    If it's a CNC machine then yes it does but you need to tell it to use cutter compensation by the use of code i.e. radius left, radius right If it's heidenhain or by G code G41, G42 if it's Funuc based, that's for straight lines then you go onto G17 etc for curves/radius. Oh and don't forget to take compensatin off at the end.
    Is it just a simple profile your trying to machine?

    Its that long since I programmed anything manually I do everything by CadCam now. I'm a bit rusty and would have to double check.

  3. #3
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    More basic than that. No CNC here sadly Keith! Its a manual Series 1 Bridgeport, fitted with digital readout.

    I can now manually follow any 2D toolpath, as long as its straight lines at any angle or a constant radius so I'm really just trying to understand how I can create a tool path from a drawing.

    Is it literally as simple as a line offset by the tool radius?
    Lloyd B
    Current: Crendon #54 in build - 427 Side Oiler/Cobrajet Heads/Dual 600cfm Holleys/4 speed toploader/Vintage cast knock on wheels
    Dedion Dax/Clarkson 383 Chevy with roller 4/7 swap cam, AFR195 heads - SOLD

  4. #4
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    In a word, Yes. That's exactly what the CNC does when it applies cutter compensation. I used to program an old machine once that didn't have cutter compensation and that's the way we did it. You just need to be careful of the feedrate at the cutting edge going round an arc. Obviously the feedrate at the centre of the cutter through an arc is different to the profile being cut. If you're cutting an external arc the feedrate will need to be faster at the centre of the cutter to get the same feedrate at the cutting edge as you had doing a straight line. Logically because it's further. Conversely you need to slow it down on internal arcs because it's going less distance than the cutting edge. Hope this makes sense.

  5. #5
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    Quote Originally Posted by Lloyd Barnes View Post
    Is it literally as simple as a line offset by the tool radius?
    yes it is and the same to produce a corner radius.

  6. #6
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    Excellent, that's great news, thankyou chaps.
    Lloyd B
    Current: Crendon #54 in build - 427 Side Oiler/Cobrajet Heads/Dual 600cfm Holleys/4 speed toploader/Vintage cast knock on wheels
    Dedion Dax/Clarkson 383 Chevy with roller 4/7 swap cam, AFR195 heads - SOLD

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