Deevo wrote:
Yup http worked. That’s a great diagram, looks I will do a 12’x8’ box on my
garage floor for my anchor points if it can fit. That seems to have more
green area on your diagram. So your saying if you go more than 2 lines from
the green error you get more inaccuracies. I am not sure exactly what you
mean when you are referring to the stress when you get into the yellow, like
there is too much or too little tension on the belts in those areas to keep
the router in an accurate position?
The green areas are where the belts and arms are able to keep lined up. when you
get into the yellow areas, the arms hit the uprights, and so the belts aren’t in
line. As a result, instead of a straight line between the center of the bit and
the anchor, you have a triangle with one short side being the arm, the other
short side being the belt, and the long side (which is shorter than the sum of
the other two sides) being the effective length.
because the distance ends up being shorter than they should be with that much
belt out, the tension in the belts will be higher. This will cause things to
flex (belt, arms, frame, etc)
There is a little table above the diagram that shows what the effect is when you
think you have 1000mm between the anchor and the center of the bit for different
angles (the bands on the diagram are 1 degree of error per band)
angle effective length
1 999.98
2 999.921
3 999.822
4 999.684
5 999.507
6 999.29
7 999.034
8 998.738
9 998.403
10 998.029
so when you hit the first band, you are only off by 0.02mm, not enough to notice
the second band you are off by 0.08mm, still not enough to notice
but at the third band, you are not off by 0.18mm, much more error, but probably
not enough to notice
at the fourth band, you are off by 0.3mm, which is right about the desired
accuracy of the maslow
etc.
when belts are shorter, the error is more significant than when the belts are
longer. so as you go into the top left corner (where the error is in the long
belts to the top right and bottom left anchors) the error will be less than this
table shows
but as you go to the center of the left side, the errors are probably going to
be higher than this table shows
as always, your milage may vary, and how sensitive you are to errors will depend
on what you are cutting
and most important of all, an error in the frame dimensions (calibration) may
produce far more error than a few bands into the yellow
I hope this helps explain things.
David Lang