Coding BricsCAD to drive a Lego Mindstorms plotter?

Joe Dunfee
Joe Dunfee
in Printing and Plotting
I don't know how likely I am to pursue this.  But, let me throw out the idea, and see if I can perhaps get some advice.  The goal is to create some code inside of BricsCAD, perhaps using VBA, that will drive a polargraph type of machine. This will allow me to plot the large patterns I need.

One type of machine I am considering is a polargraph. These work by placing two motors on the top of a vertical writing area.  Then, the motors have a spool on them that winds out some cord that goes to the actual writing head.  By varying the length of the two cords, the pen is moved around. The results tend to wiggle around a bit, so this is not a high precision plotting device.  But, it is a way to make large drawings with minimal equipment. Here is a link to one in motion, and a forum.

There is another idea, that I think is more precise, is called a CoreXY. it would seem to be easily scalable to a very large size. It, can be very simply made, though it does require a horizontal beam.
Another person made one, with additional rigid elements.

Either of the above might also have their pen head, swapped out with a laser diode, and might actually be able to cut my rip-stop nylon for the kite.

In my case, I have a Lego Mindstorms, which includes a bluetooth interface and a pair of motors that have encoders. I can send commands via bluetooth, to the motors, to turn each motor a specific amount.  As a variation on the design of the typical polargraph, the motors will be mounted in the same group as the pen holder, which also has the Mindstorms controller.  I could also adapt it to the CoreXY design also.

My motivation to make the above, is that I am in the process of creating some patterns for a large inflatable figure to be part of a Christmas kite display. So, I need a way to enlarge the patterns I am creating in BricsCAD. The Christmas star will be the kite at the top.  Then, hanging from the kite line will be one of the Wise Men on a camel.  They are comparable to the fan inflated figures people put on their front yard during the holidays. However, rather that be inflated with a fan, it is inflated just by the wind, like a wind sock.

Now, the hardware is the easy part for me.  And while there are Mindstorms based polargraph, none of the creators have shared their code, or even given any indication that their system can import any vector based art.

So,  since I work in Bricscad  I am wondering about the process of reading all the vector information about the drawing I have, and putting it out as commands I send to the Minstorms over bluetooth.  I think I can handle the process of transferring the vector end points into the G-code like command I will need to send to the motors.  But, I am vague about how I extract the vector information from the drawing.

Any advice?

Comments

  • Richard Webb
    Richard Webb
    Inkscape seems to be the most popular vector-to-gcode application; the current release includes the gcodetools extension. It imports DXF files so you can use all of your usual BricsCAD tools and then pass the result through Inkscape to get to gcode.

    Haven't used it myself -- my gcodey stuff has all been via STL export and 3D printing but this looks like a good starting point.

    Be cautious about mounting a cutting laser in a home-brew system. Lots of potential for Bad Things to happen.

    Longer term, if this turns out to be more than a one-off project for the holidays, you may want to look at building a system around one of the Mightyboard clones rather than the Mindstorms system. The Mightyboard clones are only 8-bitters but they are setup with multiple stepper drivers and I/O and can handle Core XY geometries.
  • Joe Dunfee
    Joe Dunfee
     I went to the Minstorms, partially because I have it, and because I will probably release this to the public, so others can replicate it easily.

    I do like the idea of just creating a Gcode driver.  So, I could use Inkscape to make the Gcode file. Then, my driver software just loads the Gcode.  That will make the program much more generic.   As it was, I was puzzling over how I was going to get text converted into vectors.  But, Inkscape to Gcode eliminates that issue.

    -Joe
  • Hans De Backer
    Hans De Backer
    In case you want to generate Gcode 'directly', without the need for Inkscape, you may want to have a look at this lisp code written by Chris Radek: Realize.lsp
    Supports converting LINE, CIRCLE, POLYLINE and POINT entities to RS-274 GCODE

This discussion has been closed.