So this is a first test of using the height adjustment nut on the bed as an end stop. Based on an idea that @Whosa_whatsis threw out a while back, I decided to see if I could just wire each of the height adjustment nuts (in series) as an end stop.
The nylock nut is a little misleading, because the washer is actually welded to the bottom of it, but it essentially acts as the upper contact point and the current passes through the post from the washer that is under the PCB (it has one of the leads soldered to it). The other lead is soldered to a partial washer that is JB welded to the top of the glass bed so that when the nozzle presses down on the bed it opens the end stop.
I have one of these wired on each of the three height adjustment posts (in series), but the action is not smooth enough to encourage me that it will be repeatable and consistent yet. There’s just too much friction when compressing the springs. As you can see in the video, it actually pressed the whole carriage down some. More importantly, each post compresses a little differently, so there’s no way it would be accurate enough for automatic tram correction (bed leveling via software) at this point.
I am using stainless steel glued to glass so I can use out non contact sensor. A thought you might consider. It’s cheap and you can mount the glass rigid. One of our mic6 cast aluminum beds would work too. It’s so nice to not have to worry about the bed.
Brook
Interesting. Do you mean that the stainless steel is under the glass? That sounds promising. Has anyone had any luck with a capacitive sensor yet?
I am definitely psyched to get to the point where I can quit fiddling with the bed! Even the crude bed tram correction in MatterControl is a huge relief over constantly futzing with the thumbnuts trying to get things perfect.
Gotcha, I was thinking that with a few mm of range in the sensor that a thin piece of glass might allow a positive read on the metal underneath. I’m really attached to printing on glass, but maybe I’ll just have to get over it. We’ll see.
The sensor is awesome. Haven’t had a failed print yet on my metal simple. Liked it so much I ordered another one for the wood simple kit I assembled recently too.
I think the next step would be cutting small holes or etching small indented circles in glass where the sensor would drop and place a piece of thin metal in the openings flush with the glass.
I tried using the back of a mirror but it only sensed it weakly and had to touch. If you had a thick enough metal paint on back it might work with a different sensor. Some have an 8mm sensing distance but I haven’t tested them. We chose 4mm sensors. If you used thin enough glass a metal glued to the bottom might work too. But we are using really thick glass. We are having some really large mic6 1/4" print beds to test on the GOs too. After testing the swing arm switch using a servo, this is a far more elegant solution. I liked printing on glass too but got over it after orbital sanding out the stainless… I like the way it looks.
Brook
Have a closer look on the video…the springs do nothing for height flexibility…the entire structure is warping when you probe - bending the plates. If I apply pressure on my plate it flexes in the springs so I have about 10mm as a safe zone if the hotend goes deep…
@Niclas_Oberg Yes, that’s what I was referring to about the excess friction. The alignment of the posts to the holes in the bed is not great for one thing and the washers and springs trying to move up and down on a threaded post introduces a lot of inconsistency/error as well. I plan to address both of those problems before going further with this. As I said, this is just a proof of concept at this point.
