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Thread: Help! Any other low (no) budget CNC lathe CAM users here?

  1. #1
    Join Date
    Apr 2004
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    Default Help! Any other low (no) budget CNC lathe CAM users here?

    I have a fairly easy job for my little homemade CNC lathe conversion this weekend but the .dxf/gcode conversion is killing me. I'm trying to use what I already have until I can find and learn a cheap or free program down the road a bit.

    The project is turning an ID curve in aluminum; ie: the flared inlet on a model engine venturi. The basic hole is already bored a few thou undersize. I used TurboCAD to draw a simple bezier curve, offset that line 5 times, .005". and the other 4 @ .020". I trimmed the cut lines and connected them with short line segments. I then drew lead-in and out lines. 1st 4 cuts @ .020", finish cut @ .005"

    I used AceConverter to do the .dxf/gcode conversion but apparently it uses the order the entities were drawn to establish the cutting order which of course is backwards. I went back and put all 15 line segments on their own separate layer and set each one in the proper order in Ace. It put them in the right order but most of them start on the wrong end of the cut.

    Obviously I'm using the wrong tools for the job but cannot afford to buy much of anything right now. Anybody know of a free/cheap bare-bones program that will let me assign the proper cutting order? Doesn't need to be fancy at all, just able to edit the order of cutting and which end to start from.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  2. #2
    Join Date
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    Grand Blanc Michigan
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    How complex is your part? I recently did some manual g-coding just to see how hard it was. Hard enough, but not impossible. I used my 2-D CAD program as an aid.
    First, I drew a symbol, a circle with center crosshairs, the diameter of the endmill I would use. I copied and placed these symbols at strategic places on my CAD drawing. I then "connected the dots", the centers of the symbols, to define my toolpath. Placing the cursor on the center of the symbol I wrote down the coordinates, in the order that I wanted the cut to be made.
    I then typed the coordinates and added the g-code commands into a text file that was sent to the CNC system.

    This is fresh in my mind because the process will appear, along with illustrations and photos, as well as my experiences with a CNC program in my column, The Mechatronist, in the Summer 2011 issue of Digital Machinist magazine.
    Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
    ~Practitioner of the Electromechanical Arts~

  3. #3
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    Thanks Wes; I've done a few successful turning & facing cuts via hand coding but this has a semi-elliptical curve made up of a gazillion little line segments. Too much for me to hand code for sure.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  4. #4
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    Easiest cheap/free way I can think of is to find a way to get the CAD program to dump out a list of the points for the curve and then use Excel to massage it into G-code. I used to generate code to mill log spirals this way and it's actually not that bad.

  5. #5
    Join Date
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    Mach3 has some built in conversational lathe wizards that you can use to put together a lot of simple code. Works pretty well.

    Since you have turbocad but the turbocam add on and use that to create your code.

  6. #6
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    Clearwater,FL USA
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    You could always see if LazyTurn will work for you as well. I think it downloads for free of the Mach3 website.

    It does and it was pretty easy to figure out.
    http://machsupport.com/downloads.php

  7. #7
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    Does your CNC only recognize straight line segments or can it process arcs as well?

    Gene

  8. #8
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    I'm using TurboCNC and yes, it does arcs....in its own way.

    Regnar, I looked at LazyTurn but it requires Mach, right? I have very limited PC power in the shop and don't have anything powerful enough for Mach right now. Hopefully that will change before too long. I know I'm limiting myself by not running Mach but it's not an option at the moment.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  9. #9
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    Download the trial version of CamBam. It has no functional limits except for the maximum number of gcode lines which is around 500 or so. Then download my plugin script called Spiral Polygone. It also has no time limit.

    It can produce hyperbolic curves with a spiral toolpath that CamBam can cut. Since it creates one long polyline the cut order is determined by which end of the line is the start. That is easily set in CamBam.

    Spiral Polygone is here:

    http://ixian.ca/server/SpiralPollyGone_v24.vbs

    Example:



    This was generated using the defaults in my script with the exception of setting the ID to 20, the Z to 20 and selecting item 3: Inverse parabolic as the curve.

    This becomes the toolpath. It took all of 60 seconds to do. You will of course have to learn how CamBam works but it is worth the time and the price is right.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  10. #10
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    Thanks Evan, sorry 'bout the slow response. I gave up temporarily on software & CNC expeditions because I had to get the parts finished by this morning. I ended up modifying a previously made form tool and finished the parts last night. Old school to the rescue!

    Thanks for the CamBam tip; I didn't realize it could be used on a trial basis up to 500 lines of code. I looked into it last night but it says it needs a MS .net version which allegedly won't work with my shop pc's W2000 OS. It was getting late and my brain was too numb to risk doing anything risky. I dusted off an old Dell laptop this morning that has XP and will try later & see if I can get it to load CamBam successfully.

    In looking at it, I can see I have a long way to go in learning this stuff. My DOS 2.5D CNC router experience is pretty lame compared to modern software.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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