Ok, so the basic principle is the similar.I think I understand now what you’re saying.
With regard to the last drawing, I would suggest swapping the on/off position as now the levers stick out a lot. This limits the size of parts if you would clamp on the x-axes as the handle sticks out and could potentially run into the z-axes of your SM. That’s why I went wit the spirals and separate handle. Ofcourse, in this scenario you can also use a removable handle.
The CAM advance is limited, so you need to be able to position the the device close to the stock and like have it on a rail or multiple holes to screw it down with. I did consider this, but again preferred different sizes of spiral because: mechanically simpeler and no real assembly needed. And if something breaks, very easy to just print a new one. Using shim stock was my first idea as well. I even printed like a small rectangular “plate” with a hole in the middle with different distance to each side so I could use that as “universal” shim stock. But I figured that would get lost anyway and it’s visually easier to guess what size of spiral I need
As mentioned in my the previous post, for non square stock, a curved shim piece which is flat at one end could be used . Similar to what’s in your picture.
So my first design was actually more similar to that! However, I tried to simplify it and put ease of use above pure clamping force. (which is ok for the projects I have in mind)
Finally, if you also want to easily align your pieces you would need more than just the corner fence (like the other dogs) and the (corner) fences covering more than one hole that are on my todo-list. Otherwise, I think the force of the clamps could easily push it out of alignment.
So not saying that your proposal isn’t good. My first version was much more similar to yours! Just wanted to give you insights as to why I made my version and the reasoning behind it. In a nutshell, simplicity, ease of use, and not a really big deal if one of the parts broke because they are simple and easy to reprint.
I totally understand where you are coming from . The CAM is use is “LOCKED” at the end of the turn based on mechanical design, although in both our cases friction is used. The advantage of a CAM LOCK is that it can not undo itself from vibration.
For simple hold in place for laser your spirals are ideal. Quick and easy. Mine is geared more for CNC milling.
A locking cam design and a spiral cam design are only similar in that they are both cams. There’s a very important difference in the geometry which makes them rather dissimilar. In order for a clamping cam not to self-loosen due to vibration, it needs to have the property that small changes in angle do not decrease the clamping pressure. For a simple point-contact cam, that means that it’s locally circular. “Locally” here is a mathematical usage; it means that the derivative of contact distance with respect to angular cam position is zero.
Therefore a spiral is non-locking everywhere, because its distance changes constantly, and a circle is locking everywhere, because its distance is constant. To make a locking cam, splice together a spiral and a circular arc. You can do this multiple times to get a cam with multiple locking positions. But you can’t make this kind of cam locking in all positions unless it’s a circle. In other words, you can’t get continuous locking positions out of a single cam.
To get continuous clamping positions, use an adjustable parallel. It’s a standard machinist’s setup tool. It’s just a pair of sliding wedges that can be fixed with respect to each other. These can be FDM printed by using an overlap joint with a fixed bolt or two on the bottom and a slot on the top. Use a threaded knob on the top to tighten. This will be taller than the work, but what’s tall is away from the edge where milling clearance really matters.
Thanks for the clarification. The 1/4 turn locking cam is dependent on adjustable shims (parallel) so a quick turn to lock and unlock is all you need. The locking cams would be bolted into the waste board at specific points, so the parallels are absolutely required for any workpiece that is under the locked cam spacing distance. I am 3D printing 6 sets of the parallels (3sets at two different heights.) I need to clamp a workpiece that is 120mm high and the locks are important. I only want to use 3 clamps on the diameter.
time for an update. I’ve been using it for the first time this weekend and thought I would share some updates.
first:
all correct: that’s why the spirals have 2mm long flat areas as well (it’s not perfectly smooth by design to help it lock a tiny bit better. It’s not much, but that was by design
Anyway, conclusion after first cnc job:
They do work. Granted I did a smaller type of job and was not clamping big pieces. They were strong enough for me to break two bits on the piece of wood I had on the table. (that will teach me for forgetting to adjust the z-axis after changing a bit and plunging 7mm deep…)
When the wood is perfectly flat on one side: they work very well. When this isn’t the case (it was rounded on one side and the corner wasn’t perfectly square. It does get a bit troublesome. With a perfectly straight edge (straight on z-axis) it works very well and I can’t pull it loose easily at all.
the new version as per suggestions in this thread with screwholes makes a big difference. When they are screwed down, they work very well in my opinion! I used versions screwed down on each side + some other just for alignment.
So in conclusion, I’m rather pleased so far. I didn’t have anything flying around
And for those curious how I broke the bits:
running boundery at z-height 0. and appareantly a non flat piece of wood on the bed :-
changing the drill bit and running boundeary 20mm above the workpiece but forgetting to reset the z-axis origin and pluning 7mm deep. it lasted for about 4cm and then broke as well.
I’ve sacrificed 3 or 4 bits with those errors myself. You’d think that the run boundary command would automatically back off at least a couple of millimeters…
Looking forward to testing out your clamps - they look like just what the doctor ordered!
Thanks for the feedback.
I have been using them myself for a while now. For larger pieces or if I cut all the way true I usually glue to the board now (painterstape on the board and painters tape on the piece of stock and instant glue to glue them together)
For carving jobs they work perfectly. I do use the screws to secure them in place.
I’ve got my first test running quite nicely. I went straight to the screw versions to ensure that they’d be solidly placed. The other realization I had was that this is a much better solution than the standard clamps for when I need to run the same job multiple times since it can act as a jig to ensure that the pieces are always installed in exactly the same spot and always squared up.
I got some import errors on the cornerdoglarge.stl & cornerdoglarge-hole.stl files downloaded from Thingiverse into the slicer that you might want to check on.
These look awesome especially for rounds. I keep having issues with it. I make the image smaller than the piece but it then hits the clamps…ugh I’m still a beginner but hope to figure this issue out.
(that will teach me for forgetting to adjust the z-axis after changing a bit and plunging 7mm deep…)
I’m still a beginner but hope to figure this issue out.