Testing Resolution / accuracy , Your results wanted! Z Probe Results
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As you may have already noticed I ordered a Piezo from you right after I posted those results
I was getting decent results until I foolishly decided to have it do a quick calibration before each print like David talked about in his blog. That's when the BL-Touch inconsistency truly bit me. I started getting first layer adhesion problems that shifted from spot to spot on the build plate. I even tried adding in the G29 mesh leveling but I still could get good adhesion at all spots on the bed using PrintBite. Hopefully I can get deviations like other posted in the 0.005 or less range as opposed to my current close to 0.1 range with BL-Touch. BTW the Tevo Little Monster comes with the BL-Touch from the factory and I had hoped it would work well because people at MRRF 2017 seem to like it on their printers. I'm not impressed with it though.
IMO both the BLtouch and IR sensor have their limitations, BL touch is not as accurate as it really needs to be, the notion that if a probe is within 50 microns its good enough is clearly not correct. IR works fine if you have an evenly reflective surface to IR, and on a delta, no effector tilt. In practice neither of these conditions are easy to meet. IR on a cartesian with an evenly reflective surface is a good prospect. Join the piezo revolution guys
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Or you can paint the bottom of the glass black.
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You can but it's still an offset probe though, which can mean nothing or can be a source of frustration. With our Piezo system, and David's new system, the nozzle is the probe, so you swap from buildtak to glass and just hit calibrate/level and print. Sure you might need to babystep 50-100 microns if the surface hardness is quite different, but the only variable is z offset and we are talking 0.1mm between soft and hard surfaces.
I have huge respect for the ir probe, compared to the inductive and capacitative probes it was originally designed to better it was a big step forwards, in almost every way, and is a lovely unit. But times have moved on, especially where deltas are involved, my IR sensor now lives in my parts bin. I like the mod using it indirectly with a rod as the probe but it's still offset in x and y, and a few graphics on your bed surface and your entering height differences at each probing point, which is a tedious workaround.
Leverless high quality microswitches are as accurate and repeatable (slightly better in some cases) than piezo, but that's within one probing run/one deployment, if you test with deploy, probe, stow and repeat you'll see repeatability start to drift.
I've only just started to play with underbed Piezos but so far the sensitivity is amazing. I reckon you could blow on the bed and it would register a trigger, maybe not quite that sensitive but it's very sensitive. This is a plausible solution for deltas and diamond hotends at present.
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interesting, would bed sensing work for cartesan?
I was going to redesign the mount so i do not loose so much z height but the bed might be a better option if i can get it to work.
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Yes it can work. As long as the bed is supported on mounts that can squeeze or bend piezos https://www.thingiverse.com/thing:2446460 then sure it can work, those would need a little redesigning with corner shaped recesses in the top parts, and the mounting screw maybe moved in the lower part to keep the mass over the middle of the piezo, but why not? Good for complex hotends like diamond where mounting options are limited.
The mounts though have to be thick enough to prevent the piezos going above 60 deg C or they behave erratically. So you're still talking 15mm.
I haven't done it myself on a cartesian.
BTW I just tried blowing on the bed of my microdelta and it triggers the z-probe
(and I turned down the sensitivity as it was triggering when anything moved in any direction at first.Just put my jewellery scales on the bed and it registers a trigger at 3-4g of force.
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The only problem I see with underbed sensing is that you need multiple sensors and that the sensitivity may differ depending on where the nozzle will touch the bed. I am currently designing a new mount for my i3 clone that integrates the piezo without loosing too much Z height.
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You'd think that but my experience so far suggests that it isnt a real-world problem. Sure if you had an arrangement of sensors in such a way that pressure on one part of the bed caused cancelling of the sensor outputs, i.e. one sensor was pushed and another pulled in equal measure then yes I could see that being a problem, but this doesn't happen with 3 sensors equally spaced around a circle, I have tapped across the bed in any conceivable problem areas such as the perimeter between two sensors without issue, and it wouldn't happen with 4 sensors placed at the corners of a square.
Perhaps with a 3 point bed mount, with two sensors at corners and the other side with one sensor in the middle of that side, in the same arrangement as 3 point bed levelling screws, there might be a spot on the bed where this effect comes into play. Someone more mathematically gifted might care to try to work it out, where is Ian/Deckingman when you need him? But I'd be willing to say just a slight tweak to one of the mounts, for example the one supporting the middle of the side of the bed, to make it slightly asymmetrical and it wouldn't be a problem.
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Hmm that is exactly what I have a 200x200 on a 3 point spring mount. I have an easy way to reduce the amount of z height required. I should be done with the flexible filament bowden extruder today and will begin playing around with a new x carriage that has the piezo integrated.
Later when i can afford a couple more sensors i will work on a solution for cartesan bed mounts unless you want to send along a couple more sensors for development purposes
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No free ones available at the moment, but there are some good 'ol fashioned ones that you pay money for now available in the shop.
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Yeah I just bought one from you, waiting on it to arrive
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Hi there, not sure if you still need it, but here are my two cents
Bed probe heights: 0.001 -0.004 -0.006 -0.005 -0.002 -0.001 -0.002 -0.002 -0.001 -0.005 -0.008 -0.002 -0.006 -0.001 -0.004 -0.006 -0.005 -0.006 -0.005 -0.009 -0.006 -0.005 -0.004 -0.004 -0.002 -0.005 -0.005 -0.008 -0.005 -0.004 -0.002 -0.006 -0.008 -0.004 -0.001 -0.001, mean -0.004, deviation from mean 0.002
Bed probe heights: -0.006 -0.004 -0.006 -0.004 -0.005 -0.005 -0.005 -0.005 -0.008 -0.008 -0.006 -0.004 -0.008 -0.008 -0.005 -0.001 -0.001 -0.002 -0.005 -0.009 -0.005 -0.006 -0.008 -0.005 -0.008 -0.005 -0.006 -0.008 -0.008 -0.006 -0.004 -0.002 -0.005 -0.005 -0.009 -0.006, mean -0.006, deviation from mean 0.002
I have a Hypercube CoreXY Evolution, Duet Wifi board and the PrecisionPiezo sensor from DjDemonD
Cheers!
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welcome back ~Russ… Thanks ~Russ!
OK i have been doing the life things but I'm back. ill update charts with the new data real soon...
for now I'm getting back on working on my OSDhttp://rwgresearch.com/open-projects/3d-printing-research/oversize-delta-3d-printer/. time to update the firmware. I'm sure I'm a few revisions behind!
~Russ
