Topics created by 3Dreamer

@alankilian said in LIDAR Bed Leveling:

@3Dreamer The sensor being discussed is not a LIDAR sensor, it's a LASER triangulation sensor, so it's nothing special technology-wise.

People use triangulation sensors for bed leveling all the time and it has it's good and bad points.

Hi alankilian,
you are right. I'll quote a paper in order to introduce readers to the differences:

3D ranging technologies generally fall into either position-based (triangulation) or time-based (LIDAR) approaches. Triangulation can provide much higher precision at close to mid-range but degrades quickly with the square of distance. LIDARs can provide reasonable precision over much longer distances but, unlike triangulation, they do not improve in capabilities at short range where precision and speed are critical for many applications such as autonomous rendezvous and docking, guidance and navigation, obstacle avoidance, and inspection.

So let's us speak about those technologies!

@3dreamer

I ended up getting my problems all sorted out. But I had to do several things:

Increase the supports for my bed so that it was closer to level to start with. My bed is a bit over 600 mm x 600 mm and wasn't sufficiently supported, so there was a significant sag in the middle. Now I still have some sag, but my maximum variance across the surface is 0.387 mm. Fix the twist in my gantry. There was a couple degree twist along my y-axis, and due to the location of my BL Touch relative to my nozzle, just a degree resulted in a very significant height error. One degree of twist was over 0.4 mm of height error. I picked a common point on one corner for my z-axis datum, my probe z offset, my bed tilt probing points, and my bed mesh compensation. Performed a high resolution map (21 x 21) at temperature. Modified my macros so that for every print it will do the following:
o Verify that the axes have been homed. If not, home them.
o Verify that the bed has been adjusted for tilt. If not, adjust it, and home z again.
o Turn on bed mesh compensation.

I do not like the commonly accepted approach of using the center of the bed for my z datum. I work in a field where I'm very conscious of how things fail, and I don't want my datum at what is most likely the lowest point on my bed. If, for some reason, I don't turn on bed mesh compensation and I'm zeroed at that point, them I'm likely to run into my bed as I move away from the center and screw up my print head and PEI sheet. So I want my datum at one of the highest points.

Also, I want the corners of my bed tilt and bed mesh to be identical to my datum point, and use the same exact point for measuring the probe's z offset. In this way, it's easy for me to verify that everything is working right. My bed mesh should show zero compensation at that corner, and because I've already corrected the tilt, all four corners of the bed mesh should show almost zero compensation.

It's been a few weeks and several km of filament since I last took a bed mesh map, and my prints are rock-solid every time, now.

@3dreamer

Perhaps you should first determine if the current approaches to the problem of uneven bed surface are inadequate for the majority of users.

You may be trying to solve a problem that is mostly theoretical.

If I were tasked with solving this problem I would focus on the possibility of creating a device which would allow measuring nozzle-to-bed distance in real-time and dispense with the whole array of points approach.

Frederick

@3Dreamer One idea that jumps to mind is to place a section of thin sheet of a sacrificial material (maybe PEI) somewhere on your substrate. It would only need to be the size you need for priming and can be quite thin, maybe even kapton tape would suffice if you substrate allows for the high temperature of the nozzle to get near it.

If the area you need to print is significantly smaller than your substrate you can leave the material there until the print finishes. Otherwise you could place the material tactically so you can remove it while the print is running so that spot can be printed over later.

@3Dreamer Update your firmware. Reporting has been added to many gcodes over time. Though with M303 tuning, the results are made active, and you see the results by sending M307 H[heater number]. If you want to see it as an M307 command, send M500 to save the config-override.g file in sys, open it, and copy out the M307 command.

Ian

Hi @dc42,
is there any chance to see "G5 Bezier curves" implementation in the forthcoming period?
We are almost ready with our experimental slicing software, so it would be nice to test it on our machine ,-)

Thanks you so much for your work!

I've found reducing my Z jerk and acceleration and speed for the duration of probing has helped with repeatability. Perhaps give that a test?

Why not use a set of feeler gauges to check the Z accuracy? Home Z, command the head to Z=0.3 or 0.5 or anything else as long as it is higher than your 0.2mm Zmin limit, and use the feeler gauges to check the accuracy of the gap between the nozzle and the bed.

Yes, I'm currently working with feeler gauges.