Sandwich Sled Design

Kicking around a design for a new sled. This is a very early draft with many missing pieces but I figured I should go ahead and start a thread since the feedback on this forum has been helpful for some of my other designs.

Main goals:

  • Add some structure to help make a more rigid, flat base regardless of material
  • Sturdier ring support
    • Mine are bent. The sandwich design will give the supports two points of contact making them much easier to keep in place.
  • Parametric max height
    • I don’t use most of the travel of my meticulous Z, I would like to be able to adjust this design to target a specific router/bit combination.
  • Try to reuse parts/dimensions from the meticulous Z. I’d like to reuse my hardware unless there’s a good reason not to.

I’m thinking of using half inch wood for the tower then quarter inch to form the sandwich.

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Devil’s advocate (I’m always very happy to be proved wrong, it means I learned something)
How are you supporting the ring and having it still be adjustable?
where are weights?

you have two 1/4" think disks and the frame between them. Is this really any lighter than a 3/4" disk? is any extra stiffness going to matter? has anyone reported problems with the sled warping?

The tower can be only as wide as the side supports and 9 to 9.5 inches high. I built mine like that out of 3/4 ply, but you could do it out of 1/2. I pocket jigged the 3/4 ply to hold it together. 1/2 might be difficult to secure that way, so a glued slot might be best for the thinner pieces. You do not need 300 mm linear bearing rails for a z axis. 200-250 is plenty.

The ring won’t be as adjustable. I’m hoping to get it close enough that the support will have a fixed hole and the adjustability will all be in the slots on the ring. If you need something different print or cut a new support. Since the ring adjustment only cares about the CG on one dimension I may try to brute force an estimate based on the volume and material.

For weights this should have roughly the same space as the meticulous Z to add them. That part of the top could be left off for bricks whatever people find. I have a few lead ingots that might fit inside the sandwich as is though I would really love to cast these to fit that corner perfectly. I have sand, an old frying pan, and a fire pit. I just haven’t built up the nerve to give it a shot yet.

Will the new base be lighter? I’m not worried about that yet. It might be lighter just looking at the overall volume of wood but even if it doesn’t I’m OK with a little extra weight below the ring.

My sled (3/4 plywood) is warped and it rocks a few mm side to side, not sure if anyone else has had the issue. I want to use an HDPE base but I’m afraid of using the thinner materials and having the same problem come back.

As for the connections there will be box joints all over the place and I plan on using glue/nail gun for most of the assembly except for a few serviceable parts like the base plate and ring supports. Not sure what I want to do for the tower yet, I need to sort out all those intersections first.

The problem with this is that it depends on the router that you use (weight and

David Lang

Filling in more parts. The ring supports should be replaceable so in the worst case scenario I just cut or print several and use trial and error to find the correct one.

Now things are getting weird. I’ve built a Z axis for a target of 40mm travel. I want to sacrifice visibility and the ease of changing bits to have a sled that’s as short as possible. I need to do some work with the upper window to make an opening big enough for manually setting the z height. Changing bits I’m OK with doing through the bottom of the sled; this is how I did it for awhile anyways.

I also came up with the idea of using the vertical structure as skids to help prevent the sled from getting caught in holes. This will allow a thinner base material with little compromise to its ability to get over lager bumps. I’m not happy with the pattern of vertical supports or how they interact with the ring supports. Finding a clean solution for that is going to be the most difficult part I think.

It’s finally coming together!

The initial version will require some 3d printed parts. I would like to have a wood only option but I have to wrap this up for my sanity.

A grid structure will support the base. This should stay rigid and is easy to calculate intersections.

I’m giving up on ramps all the way around. Dealing with the weights and dust tube is really hard and raising them will mess with the center of gravity. If the ramp ever gets hit the cut is probably compromised anyways and getting caught moving down won’t rip the Maslow motors off.

The ring supports (not yet designed) will only be bolted to the top. They won’t interact with the support structure or base. I think this will be acceptable since I’ll be able to build them very short and stout due to the raised platform.

What’s left:

  • Manually space supports
    • I don’t need that much so close to the 1/2" parts
    • I also need to avoid the SK bracket under the platform
  • Design ring mounts