This is my first post here, so hello everyone. I program and run a large CNC for a stone fabrication shop and had the Idea to make a sled out of one of the bigger pieces of scrap stone/engineered stone we normally throw away. My question is, is it ok to have the sled be symmetrically weighted? Or would I want to mill the sled in such a way that the sled is lighter on the top and heavier on the bottom (like a brick weighted sled)? Also In my browsing the forum it seems that I would want to keep the total weight of the sled under 40-44 lbs. is this correct? I guess I should also ask if this is would be a bad idea before I spend to much time programming and setup time on the machine lol.
Thank you, and any input would be much appreciated.
I think your fine doing this. There are sleds with large sheet steel for the weight. You just want to keep the weight to ~35 lbs. you are trying to have the weight balance when suspended in the center. You may want to wait for more details on the new ring system as this is how you will mount it.
I’ve configured a sled with symmetrical weight using one of the top-mounted linkages. The results were disappointing, accuracy suffered. Having the weight concentrated on the lower side of the sled helps the triangular linkages stay within their optimum positions.
Too, the weight of the sled is a factor especially in the upper center area. The motors are pulling maximum tension in that area, and sled weight adds to the tension.
I’m working on building my sled now. I’d like to use a theatrical stage weight, which I have in abundance. the stage weight is 22#, the router is 10# and the plywood and hardware is maybe 2#. This would be in your 35# vicinity. If I built the sled with the standard bricks, I’d end up around 22#.
How did you come up with your 35# number and why doesn’t the standard build call for more weight?
People are trying different weights on the sled, before we got the chain sag
compensation, heavier sleds were significantly more accurate across most of the
work area (we have found in recent weeks that they suffer in the max speed they
can do in the top areas of the work area, part of the reason the max speed was
recently dropped)
we haven’t had someone do much testing of different sled weights after we got
chain sag compensation, so if you can do some testing of different weights and
angles it would really help.
I think I’ll certainly try different weights, as that’s a pretty easy thing to change.
When you refer to different angles, are you talking about the motor mount points?
no, I was referring to the angle of how far the machine leans back. In theory a
machine closer to vertical will work better (up to the point that the sled
doesn’t have enough force to drive the bit into the wood)
Ok. So 15 degrees seems to be the consensus. Where is the point of diminishing returns closer to vertical? I’m guessing one degree will make or break it.
15 degrees is the default, there was some testing that showed advantages of
going to 10 degrees and possible diminishing returns at 5 degrees. but that was
a long time ago, before the triangulation kits, let along chain sag
compensation.
we do know that bar built a frame that was at 20 degrees and it just didn’t
work.
so I suspect that we are tilted back further than we need to, and that with less
tilt, we may be able to get away with less weight (now that we have chain sag
compensation)