Why turtle clamp? Fresh off the printer, the cutout looks like a turtle to me:
Files here:
Intro
Stiffness of the clamps is something that I’ve been keen on improving for a while. I touched on it a bit as part of my I linear rails-ed my Maslow build. 20mm thick clamps seemed like an obvious place to start and gave me a significant improvement, but there was a lot more I wanted to do.
This is what I came up with:
There were a few points I wanted to address:
- No split in the clamp.
- 20mm but minimising Z-travel loss.
- Full compatibility with original Maslow.
No split in the clamp
This is like the main point of it. The split in the clamp has always bothered me for two reasons - as a source of flex, and a source of imprecision. With the 20mm design I came up with for the linear rail build I did my best to minimise flex with a big zig-zag double bolt, and that was ok, but still allowed more flex than I was happy with.
For the linear rail the bigger issue is it messes with the geometry. Tightening and loosening the clamp pulls everything out of square, even if it’s by a very small amount. For anything to do with linear rails that’s a bit of a PITA.
I could run through the many wild and whacky clamping methods I tried, most of which were good at applying force, but only to the point they ripped themselves apart, but it’s not that interesting. The four-clamp, triangle-edged design gives me the clamping force I want, centred, with easy access for adding / removing the router with the Maslow fully built. It even keeps compatibility with the button pusher.
20mm but minimising Z-travel loss
The 20mm thickness combined with no split is what makes it very stiff, but another downside of the design I used in the linear rail build is I lost a chunk of Z-travel. That isn’t a massive deal for me given the bits I personally use, but I wanted to go back and minimise it if possible.
The main focus was the bottom clamp to get the router as low as possible at Z-stop.
From:
you can see that there are cutouts on the Z-stepper arms and little cutouts on the rail arms, for the motors and vacuum plate bolts respectively.
It lets it sit flush to the vaccuum plate:
And gets me to the point of 7-8mm off flat for the bottom of the collet at Z-stop:
Full compatibility with original Maslow
I can’t really show this without teasing the next thing I’m currently in the final stages of refining, but another motivation was wanting it to be standalone (ie a user can just replace the original clamps), but also to work with a linear-bearing-not-linear-rail variation of my linear rail build that minimises extra weight / new parts:
While it looks quite different from the original Maslow 4.1, the important bit to note is it’s using the original linear bearings / plastic risers so the clamps can be used as the only mod to a stock Malsow if wanted.
Build details
Printing the main clamp with 5 layer top and bottom and 5 wall loops, along with 40% adaptive cubic infill gives high stiffness. It can be dialled back to 3 wall loops and 30% adaptive cubic infill (still 5 wall loops) and that saves about 20g a clamp and barely impacts stiffness. The inserts I printed at 100% infill.
It uses m3 slip-nuts / hammerhead nuts / t-nuts - the 2020 profile nuts that turn and grip, combined with 10mm plate washers and 14/16mm cap head bolts (all of which I believe should be widely available everywhere):
Notes:
- It expects 2mm worth of 10mm plate washers, I just used 2 * 1mm adhesive ones.
- Although I say 14mm or 16mm bolts, it should work with anything up to 20mm without fouling on the rotating arms, even if the bolt heads stick out slightly.
- You need to use longer bolts to hold on the posts - I use 25mm with locknuts as it’s a size I use on other projects.
- Everything should be flush when the router is inserted, it’s reasonably tight tolerances so that each insert only needs to slide about half a mm to clamp.
- There is no need to crank it down until you damage it, it holds with a lot of force just from being snug.
I’ll print it and try it in the next day or two, and I have a few tweaks I was going to roll into a 1.2 version soon that I’ll include it as a variant in.