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

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  • 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
    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~

    Comment


    • #3
      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

      Comment


      • #4
        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.

        Comment


        • #5
          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.

          Comment


          • #6
            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

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

              Gene

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              • #8
                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

                Comment


                • #9
                  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: Click Here

                  Comment


                  • #10
                    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

                    Comment


                    • #11
                      Just in case you wonder why I called the program Spiral Pollygone,

                      This is the reason.


                      The Perils of Pretty Miss Polly Nomial...

                      Once upon a time (1/t), pretty little Polly Nomial was walking across a
                      field of vectors, when she came to the edge of a singular sparse matrix.

                      Now Polly was convergent, and her mother had made it an absolute condition
                      that she must never enter such an array without her brackets on. Polly,
                      however, who had changed her variables that morning and was feeling
                      particularly badly behaved, ignored this condition on the grounds that it
                      was insufficient, and made her way amongst the complex elements.

                      Rows and columns enveloped her on all sides. Tangents approached her
                      surface. She became tensor and tensor. Quite suddenly, three branches of a
                      hyperbola toched her at a single point. She oscillated violently, lost all
                      sense of directrix and went completely divergent. As she reached the turning
                      point, she tripped over a square root which was protruding from the Erf and
                      plunged headlong down a steep gradient. When she was differentiated once
                      more, she found herself apparently alone, in a non-Euclidean space.

                      She was being watched, however. That smooth operator, Curly Pi, was lurking
                      inner product. As his eyes devoured her curvilinear coordinates, a singular
                      expression crossed his face. Was she still convergent he wondered? He
                      decided to integrate improperly at once.

                      Hearing a vulgar fraction behind her, Polly turned round and saw Curly Pi
                      approaching with his power series extrapolated. She could see at once, by his
                      degenerate conic and his dissipative terms, that he was bent on no good.

                      "Eureka," she gasped.

                      "Ho, Ho!" he said. "What a symmetric little polynomial you are. I can see
                      that you are bubbling over with secs."

                      Polly began to fear that something was not ordered.

                      "Calm yourself, my dear," said our suave operator, "your fears are purely imaginary."

                      "I, I," she thought. "Perhaps he's homogenous then."
                      "What order are you?" the brute demanded.
                      "Seventeen," replied Polly.
                      Curly leered. "I suppose you've never been operated on yet?" he asked.
                      "Of course not," Polly cried indignantly. "I'm absolutely convergent."
                      "Come, come," said Curly. "Lets go off to a decimal place I know and I'll
                      take you to the limit."

                      "Never," gasped Polly.

                      "EXCHLF!" he swore, using the vilest oath he knew. His patience was gone.

                      Coshing her over the coeffiecient with a log until she was powerless, Curly
                      removed her discontinuities. He stared at her significant bits and began
                      smoothing her points of inflexion. Poor Polly. All was up. She felt him
                      tending to her asymptotic limit. Her convergence would soon be gone forever.

                      There was no mercy, for Curly was a Heavyside operator. He integrated by
                      parts. He intergrated by partial fractions. The complex beast even did a
                      contour integration. What an indignity! To be multiply connected on her
                      first integration! Curly went on operating until he was absolutely
                      orthogonal.

                      When Polly got home that evening, her mother noticed that she had been
                      truncated in several places. It was too late to differentiate now. As time
                      went by, Polly increased monotonically. Finally, she generated a small but
                      pathological function which left surds all over the place until she was
                      driven to diffraction.

                      The moral of this story is: If you want to keep your expressions convergent,
                      never allow them a single degree of freedom.
                      Free software for calculating bolt circles and similar: Click Here

                      Comment


                      • #12
                        LOL, that was funny.
                        Maybe I should have my head examined....

                        Igor

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                        • #13
                          That was so funny, I'm fractally speechless!
                          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

                          Comment


                          • #14
                            I learned some stuff ' bout my lathe CAM issues so I thought I'd add it here in case someone as tight as me (not very likely) stumbles onto this thread someday.

                            I found this software http://www.cad2gcode.com/ and think it'll do what I need. It's so simple, even I can understand it and will buy it when I get paid for my most recent job. The lathe portion is only $29.95 and the whole thing (mill, plasma and other apps) is only $49.95. I'm going to get the whole thing since the mill part of my rig needs some help too.

                            I watched a couple of his tutorial videos and the solution to my order-of-cuts issue hit me like a ton of bricks. I offset the curve as before in TurboCAD and added all the connecting & clearance lines, selected "Join Polyline" and clicked each entity in the order I wanted them to cut, hit "Finish Polyline" then save-as R12 .dxf, converted to gcode in ACEConverter and VOILA! All the moves were perfect and in the proper order. I haven't made chips yet but the gcode simulator version looks perfect.

                            This trick will get me by until I buy the package but I'm really looking forward to all the CAD work his (Robert Adams) programs will save me.
                            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

                            Comment


                            • #15
                              Have a look at this.

                              http://www.cncsimple.com/

                              Not saying it will work as i have never gone into it but it's free and that's a decent place to start.
                              .

                              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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