PolargraphSD: Building the machine

Select the surface you’re going to build on. Here’s mine. It’s slightly sloped.

You can see it bears the scars of draw. Get used to this. I taped a sacrificial sheet of card onto it – and it makes for a nice smooth cushioned surface to draw on too. Smoother lines and a better impression.

Stick your motor brackets on in the top corners.  As much as you can, make sure they’re level horizontally.  Slot two little cactuses into each plate.  The motors themselves mount on these things.

Mark up your board. 

  • Draw the top edge of your notional machine – this is a straight line directly in between your motor axes.
  • Draw the sides of your notional machine.  These are vertical lines that form a tangent on the inside radius of your sprockets.  Just look at the pic
  • Draw a parallel line marking where the top edge of your sheet of paper will go.  This is 120mm from the top edge on my machine.  If you have a wider machine (wider than about 800mm) then you might need to move this down proportionally.
  • Mark a point in the centre of the second line.  This is your home point and is the “magic” point that you’ll use to calibrate your machine before each drawing.   In reality it doesn’t matter where it is on the machine, as long as you can measure it’s position accurately.  I prefer to have it off the page though, so that it doesn’t get covered when I stick the sheet of paper up, and so that dropping the pen by accident doesn’t ruin my fresh sheet of paper.

Now, wield your tape measure and note down:

  • The width of your machine – distance between the two edges.  Remember the edges are the lines that run from the inside perimeter of your sprockets, NOT the physical edges of your board.
  • The height of your machine – distance from the top edge to the floor.
  • The home point position – distance from the top edge to the home point.  This’ll probably be 120mm.


2 thoughts on “PolargraphSD: Building the machine

  1. hi,
    i have built a polargraph on a 3d printer.. i am using your software and firmware to drive it .. BUt i am getting a strange error… the drawing is getting made in a tapered way.. wider on the top and narrower on the bottom… what is it that i am doing wrong???

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