I think the AxiDraw has a hard time maintaining precise down-force because it's so good at maintaining precise position. Maintaining a precise position requires either precise negative feedback (which the AxiDraw doesn't have) or high rigidity, and the AxiDraw does have (comparatively) high rigidity.
But the BrachioGraph has very little rigidity, so (I infer) most of the weight of the pen-lifting servo is supported by the point of the pen, and almost none of the weight of anything else. So I don't think that will be a problem, as long as your gravity field is constant. But maybe someone who's built one can comment?
But the BrachioGraph has very little rigidity, so (I infer) most of the weight of the pen-lifting servo is supported by the point of the pen, and almost none of the weight of anything else. So I don't think that will be a problem, as long as your gravity field is constant. But maybe someone who's built one can comment?