Do you think the sled might be reduced to factory size faceplate if these
other things work out?
it all depends on what you are cutting. If you are never cutting anything wider
than one pass of the bit you may get away with it. If you cut out a 4x6 pocket
in a piece, the router would fall into the cut with a small baseplate.
Also, I was considering ducting the cooling air from the motor into a set of
holes in the sled so it could float on air like an air hockey puck and table.
I think this would be a very interesting experiment to try. I would be concerned
about the air escaping through the cuts that you make and ‘crashing’ the sled
down to the workpiece, and the variable height that would result from different
amounts of leakage.
Good thoughts. If I have a vacuum table holding parts in place (including a filling spacer) I don’t imagine there is a terrain will cause problems. I was wondering about the weight and its leverage available to keep the router flat and the bit driven. The float on air is not very distance sensitive as long as there is there is adequate air volume to maintain flow out the edges. The sled is lofted by the psi spread below. I have looked into capturing the vacuum system exhaust to supple this as well. Thanks for the feedback.
I designed a 3d printed cap with a 1/4" center stud for the Rigid router. This allows a cable connection to a U-shaped bracket attached to the router tip and top stud with a bearing on the rotation center. The top part of the U is thin flexible metal and able to accommodate the z axis changes. Looking forward to setting it up.
Extra weight is only added in order to balance the sled flat against the work surface. I’m sure you can find the exact torque specs somewhere to calculate the drive motor’s lifting capability, but really, the only reason the sled is weighted is to lower the CoG and ensure that the chains are as straight and tensioned as needed to keep the sled accurate and flat on the surface.
With a router of 6 kg, I started with 2 bricks, router and sled with 17kg total at 6° angle. Reduced the weight of the bricks now by ~ 3/4 and increased the angel to 10°
Okay, this will probably seem crazy at first but bear with me. What if, instead of using rollers/bearings and a ring/rail to keep the ends of the chain on a point on an arc (which is based on the center of the bit) we instead used linkages? No rollers or anything. My initial concept is a little clunky visually and the physics might not work out in real life once there’s weight on it but imagine two pantograph linkages where the master point is forced to trace a small arc on a circle that makes the other point follow the path we want…
Here’s a quick sketch of the idea:
The points with the black Xs are fixed points that are allowed to pivot, all other points are free pivots. The drawing shows two positions (the black lines and the grey dashed lines). I only drew the right half to keep things simple but you’d need one for each side (they could share the same two fixed points though). The scale here is probably weird and I did not do any math or testing on lengths of linkages but I think you get the idea…
It’s the only way I could think of to mechanically trace a point on an arc without physical access to the actual center of the radius (because that’s a router bit!).
This alleviates costs of bearings, rails, rings, etc. and might prove more accurate since it should eliminate the jerky roller problem. Linkages could be a simple, cheap material and pivot points need not be more complicated than bolts or screws.
Of course this also could be a terrible idea. I might make one to see what it does.
How importand is the distance on the z achse?
I want to make a alu sled.
with proper cone-bearing rails.
i’m plaing to use 20mm Material.
i will post pictures as soon as i started working on it.
My guess is you could simplify the linkage to just a classic 4-bar linkage though.
I tried but my brain couldn’t handle it. Maybe there is a way but as far as I could see all of the arcs that are traced by any point in a 4-bar have a fixed fulcrum at the center of the circle; that won’t work for Maslow because there’s a spinning router bit at the center, and therefor nothing to actually connect to.
My goal was a linkage that could trace an accurate arc without needing to anchor something at the center of the circle/arc…
If this can be improved I’d love to hear more ideas! I will laser cut some adjustable “sticks” here soon and start playing with it. I (regrettably) didn’t label points or lines in my drawing but I do believe that all of the segments between points need to be the same length except for the segment that traces the small arc. If you change the proportions of these segments the resulting arc does weird stuff and is no longer useful for what we are attempting.
Here’s an actual working model of my concept: https://ggbm.at/JW9sxq2A
Note: the sliders allow you to adjust the linkage lengths so you can see that only equal length segments will result in an arc of a circle.
I’d like to build a physical model now to see if the chains always point to the router bit…
pantograph seems way too complicated, ring with bearings seems more logical to me.
It is not always that the most logical idea is the best…
But, I totally agree that a ring and bearing is more logical (to me as well). I also totally agree that this is more complicated in that it has more pieces and certainly looks scarier if you don’t work with linkages often. My goal wasn’t to make something that looks simpler, I was thinking of ways mostly to reduce cost and alleviate the jumpy pulley problem that can be observed in Bar’s videos.
The problem with a pulley on a ring is that the tangential forces that push the pulley to travel along the arc are quite small, frictions and imperfections in the ring and pulley hold the pulley in place until enough tangential force builds up to “scoot” it along, this results in an uneven jerky movement. This can easily be solved with high quality bearings and rings. It can also easily be solved with large-race bearings like Bar shows in his early post. It can also be solved by buying an off-the-shelf CNC machine. Those three solutions all cost more than a linkage system that could be cut from wood for less than $1.
I’m NOT saying it’s the solution, I’m just throwing it out there as an idea. Perhaps it will inspire an even better idea… It’s also completely untested, this might be a terrible idea. Just trying to think out of the box. I think that’s how this open source thing is supposed to work
As for pulleys, would skateboard wheels be a cheap option? A groove could be ground in the plastic to help with tracking…
I don’t know if your linkages work, but it certainly fits in with “outside the box” - and given that not only open source lends itself to those ideas, the entire Maslow was/is kind of “outside the box” - I don’t think anybody else has turned a CNC on it’s side
