Following @Scorch and @donkjr steps, here is my clamp for k40 (made a couple of weeks ago)
Uses 20x20 slot rails, 20x40x1.5 and 15x20x1.5 alu profiles and some printed parts. I’ve loosely designed at http://a360.co/2n5biCB
Have to say I’m very happy with my build, Green printed parts are jigs of 1.5, 2 and 3mm to be put between the columns and the rails, so can adjust focus in a predictable way.
Cons are that I’ve lost a bit of cutting area in as Y motor is poorly placed on K40.
If anyone have access to 15x15 rails could gain some space. Anyways, I’ve got a nice 300x200 cutting area.
You beat me to the build :). Very very nice work and design ideas.
Couple of questions, 6 actually :):
1). How are the spring shafts in the clamps connected to the upper angle frame, threaded rivet?
2). Does the unit sit freely in the compartment or bolted?
3).Can you point us to the parts sources for rails.
4). How does the rear clamp work and slide forward and back then lock. Do they slide in the rail and then lock with the wing nut? Any concerns about it binding if the left and right sides are moved relative to each other?
5). I like the toggle clamp in your CAD design do you have a source for them. I suspect they will interfere with the gantry? i.e to tall?
6). Are the columns fixed height or adjustable if so how do they adjust?
Some notes: I used a dremmel with cutting wheel to cut away the exhaust port until it was even with the back gantry frame that will buy you enough space for the rear clamp to keep some area.
1). Have no threads! The plastic nut has an slot to insert a M5 hex head bolt from the bottom, whose thread end I’ve cut away. The same nut is made to slot into the rail, providing enough stiffness and squareness, and have a inner M3 nut trap to fix the part to the column.
The bottom rails are screwed to the k40 case. Had hard times measuring to get them square and well placed. Used M4 T-Nuts to screw from the bottom outside the case with M4 bolts. The holes made to the case are 5mm, so have some air to perfectly align.
It uses the top wing nuts to screw tight to the lower rail. As the threaded shaft have that printed guides to the nuts (blue glue locked to the shaft, 3rd pic) and are M4 (rail holes are 4.8mm) it allows some twist (10~15º) But the whole clamp part is strong enough, no bendings so far.
Well they were fine, but as they are printed and have no barrel nuts in my store, made barrel nuts myself with some 8mm Alu tube, drill and thread. The first try to tight the thread went off Anyway, flynuts or knobs are ok
As you can see, I did some printed supplements (black top of columns) to perfectly reach the focus height (82~83mm) for engraving. Trying to solve the T/2 problem I made that fixed height jigs (green, 2nd pic). If you have to cut 3mm MDF, then loosen flynuts, take away the clamp, insert the jigs on the bottom of the columns, screw again.
I’ve updated the CAD file, the 40x20 profile is bolted to the rear of the column with rail nuts.
Notes:
I’ve cutted my exhaust thing also (the black rubber rim is a must if you have to save all your fingers ). I will do again as maybe not enough if insert the bottom jigs. If no jigs used, the rear clamp goes perfectly below that.
An improvement to the upper profile is to cut out a couple of thumb holes, so you can push the lower profile without harming your nails.
@Jorge_Robles I think that @Russ_Rsty3914_None is saying that we could put wheels that ride on the extrusions to make the columns move easier. I considered that but I think it takes up to much space.
@Jorge_Robles I liked your idea of using the extrusion because the movement side to side is constrained and it is simpler to lock from the top. The extrusion also affords more stiffening options if needed.
I modified my design to do something similar:
1). The design still allows independent vertical adjustment and locking of each corner.
2). A separate locking knob(s) lock each columns sliding position.
3). Mounts to floor with 2 brackets and thumbscrews for easy removal.
…
All the parts/materials except the 1/4" jack screws and the knobs are off the shelf from home stores, Mcmaster and http://servocity.com
…
I also plan to use spacers to adjust for 1/2T but haven’t added that yet as I am trying to do it without removing the clamp.
Umm… cannot figure how are these working. I mean, one of the objectives is to get the material clamped. Using these… the material goes lying on the top? Or contrary, that ones pushes the material down compensating the columns out of focus?
I was thinking on it, but ended using the spacers. One minute task.
Another solution could be having (on my build) knobs on the rear fixing bolts, loosing the upper clamp and insert spacers there, but seems more difficult to do.
For adjusting the focus, could you have a separate rail between the top & the bottom (spring loaded rail) that you can push down with a threaded bolt? This would allow you to adjust the focus height in whatever increments you need.
@Yuusuf_Sallahuddin_Y Nice! Have to find a place to put them without losing clamping space. Also you will have a limit off focus. But instead screws I should use calibrated spacers
@Jorge_Robles you insert spacer in the hole and slide to the left. The lower part of the spacer pushes the surface of the material down.
The keyhole slot can also be put in the top frame.
Different size spacers push material down different distances.
Works very similar to @Yuusuf_Sallahuddin_Y adjustable upper plate.
@donkjr I figured you wouldn’t have built yet, with your tinkering style I’d imagined you want to get the build “just right” before you starting putting any tools to materials
Nice work @Jorge_Robles ! I really like this clamping mechanism as well and am in the process of building my own. I found some 2" springs and 2" Chicago screws (see photo below) at Home Depot and as the springs sit on the big head of the screw, it eliminates the need for the bottom plate. It looks like it will work really well. With minimal effort, the design could even be modified to be laser cut and glued. All you’d need in parts is a sheet of 3 mm MDF, 4 springs and 4 Chicago screws. Really inexpensive!
@Yuusuf_Sallahuddin_Y Don’s an engineer through and through. I understand his affliction very well as I, too, am one. This need for design engineers to “understand” often trumps the “doing” and tends to become more pronounced as we age. Gotta love @donkjr for his passion!
@Ulf_Stahmer I have to say everything @donkjr does is extremely useful to the rest of us, so his affliction is a welcomed one. I find myself designing things more often than making them too, usually due to a lack of resources (hate waiting for
parts in the mail so I usually procrastinate on ordering them) or getting side-tracked with new ideas that I can’t wait to design.
@Yuusuf_Sallahuddin_Y leather and so requires hard mesh below. Clamps cannot tension enough to keep that straight.
Also, the mesh should be rigid enough. I’ve tried with some light metallic mesh and bends upon tightening.
Anyway, flynuts or knobs are ok 
