Eric Fisher wrote:
I have not changed the z-offset values. To be honest, I’m a little confused
because I think the setup instructions say that those values usually don’t
need to be changed?
normally they don’t, but they assume that you have just a 3/4 sheet of material
for your spoilboard, if you differ a little from this it’s ok, but you are
double the thickness
If my M4 is horizontal on the concrete floor with 1" of rigid foam (and when
I’m cutting pieces smaller than a whole sheet of plywood, 1/2" of plywood
spoil board on top of the foam) what do the z-offset values need to be? Is it
something that I can easily measure? Should I change the values each project
depending on the height of my spoil board(s)? If I use plywood “washers” for
the anchors do they also need to change if the spoil board height changes?
the steeper the angle of the belts, the more important the Z offset values are.
the z offset is the difference in height between the belt at the anchor and the
belt at the arm (a different offset for each arm since they are different
heights.
being off a few mm isn’t a big deal, so just use a tape measure from the floor
at the anchor, then put the sled next to the edge of your spoilboard area and
measure the height there.
If you raise the anchors to where the belts are near flat when the router is all
the way down, you don’t need to change anything for a difference of an inch or
so.
to go into the math.
the default for the top arm is ~100mm, if you are at the closest corner, say
your belt length is 600mm, your effective belt length is sqrt(600^2-100^2) =
591.6mm the maslow takes this into account
if you are off by 20mm, this is sqrt(600^2-120^2)=587.8mm so your belts are
effectively 4mm shorter than the maslow thinks they are.
if the anchors are near the same height, say 20mm (and z offset is set
correctly) the effective belt length is sqrt(600^2-20^2)=599.7mm and the maslow
takes this into account.
if you are now off 20mm, then the math is sqrt(600^2-40^2)=598.6 an error of
only 1mm shorter than the maslow thinks they are.
I’m actually more worried about the belts catching and becoming dramtically
shorter in effective length than about the math error (which is why I suggest
raising the anchors)
I’m thinking that the foam board is overkill, and I only need to use the sheet
of 1/2" plywood as my spoil board. A couple of times when I first started
using the machine and I was still working out how to set the z-axis I cut thru
the plywood spoil board which is why I started using the foam. Since then I’ve
made a z-axis probe and I’m a little more confident that I won’t screw up the
plunge depth.
it probably is, but it’s cheap insurance against digging your bits into the
concrete.
David Lang
