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Autoleveling on 3D printers: 9 myths and 12 sensors tested!

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There are many options for a 3D printer's bed sensor and even more misconceptions about what they can and should do. So after a ton of testing with a custom-built precision test apparatus (TM), 9 myths about these sensors have been examined - and we got a ton of data about how precise each one can be! 🛒 M8, 2mm inductive sensor (5V) http://s.click.aliexpress.com/e/UnYVZFe 🛒 M12, 4mm inductive sensor http://s.click.aliexpress.com/e/e6QJqn6 🛒 M16, 8mm inductive sensor http://s.click.aliexpress.com/e/fuVJu3F 🛒 M16, adjustable distance capacitive sensor http://s.click.aliexpress.com/e/YfIQFie 🛒 M16, 20mm capacitive sensor http://s.click.aliexpress.com/e/ujEuvZf 🛒 David Crocker's IR sensor http://www.escher3d.com/ 🛒 SHARP analog sensor http://s.click.aliexpress.com/e/mEMnaQF 🛒 Microswiches http://s.click.aliexpress.com/e/2z3Njm2 🛒 BLTouch http://geni.us/BLTouch 💙 Buying items through my affiliate links gives the channel a small kickback without adding any extra costs for you! All details and more links at https://toms3d.org/support-me/ Amazon (international) http://geni.us/bKkJuy Aliexpress http://s.click.aliexpress.com/e/iMB6emu Matterhackers https://www.matterhackers.com/?rcode=TSAN86 eBay (international) http://geni.us/eSOtG iGo3D http://go.toms3d.org/iGo3D 🎥 All my video and editing gear https://toms3d.org/my-gear 👐 https://www.patreon.com/toms3dp Certain elements may not be included in the CC-BY-AS license, e.g. third-party images and music. Trademarks are property of their respective owners. Polygon background created by Starline - Freepik.com Standard deviation graph by Jeremy Kemp under CC-BY 2.5
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Text Comments (644)
Werner Boden (23 hours ago)
It is a nice video and I learned something, but I my expectation was, you would have tested more different types. Besides, most printers use an optical sensor, which block the light. For bed leveling, it is often the touch sensor, which you did quicly glance over. I kinda missed the hal sensor and the piezoelectric sensor.
BigEnderTroll Zockt (10 days ago)
bist du deutsch?
Eric N (16 days ago)
So, I've been thinking about these results, and I don't believe they can be conclusive for which sensor is actually best for "bed leveling" since that involves sensing at several different places on the bed. This test setup, though certainly useful and helpful, may not be telling the whole story since it continuously tests only one spot on the big aluminum block. A better more conclusive test would test how accurately each sensor can sense the actual flatness of a bed; i.e., at multiple points. Since an aluminum bed, for instance, may not be perfectly uniform across its entirety with respect to its inductive properties, would an inductive sensor actually perform worse than or only as good as a physical touch/contact type sensor in an actual "leveling" application?
Joshua Bryant (27 days ago)
I thought you needed an PNP sensor? (at least for a ender 3) Can you use either and set the high/low trigger in marlin firmware? Also, what voltage divider did you use?
ZZP Zing Pheonix (1 month ago)
So what the best for practical use? All that for no practical results. ............ PRUSA Knows how to work it.
Maikel van Gorkom (1 month ago)
2 years further, are there newer sensors on the market that do a better job, or is this video still relevant?
My Generation (1 month ago)
Great video. My only question is which sensor is best for the Anet A8 with a 3mm glass over an aluminum bed?
Pipee Papofckgug (1 month ago)
"Prusa has the smallest and shortest of them all" - ouh, burn. :D
gizmoguyar (1 month ago)
I want to address something I've been seeing floating around the internet regarding the inductive/capacitive probes. People keep saying you need a 12 V to 5V voltage divider on the output. This is partially wrong, and may, in fact, introduce more errors in your bed leveling. The sensors do absolutely need to be run from 12 volts to achieve their rated specs, but if you are careful to buy an NPN type sensor, you can simply plug the output directly into the Ramps input pin. This sensors are what is called "open collector drain" output. It means that it doesn't provide an output voltage when trigged, rather it pulls the signal provided to it to ground. The Arduino/Ramps board has internal 20 kohm pull up resistors on all of its pins (enabled in Configurations.h). This pull up provides 5 volts to the output pin of the sensor, when the sensor triggers, it pulls that 5 volt signal to ground. If you use a voltage divider, you might reduce the 5 volts enough to cause unreliable switching in the Arduino. PNP type = needs voltage divider. NPN type = do not use voltage divider.
vagabound1010 (1 month ago)
Incredible experimental design, helped me so much in making an informed choice. Earned my subscription and then some!
Dharani Sharma (1 month ago)
Which sensor should I use for pcb heatbed and glass combo
ST NT (2 months ago)
Very very informative, thank you.
Nova Leary (2 months ago)
Which one should I use for my Ender 3? I have a 2.2mm glass bed on the printer
Rok Dok (2 months ago)
HELP !!! my new 3D printing (A10M geeetech) does't work petty well.. the Y sensor stop to work but the sensor is not broken I'm sure.. no problem on the cables.. but.. where is the problem ??
sagar makhija (2 months ago)
What about altrasonic sensor
Pascal Garcia (2 months ago)
Thanks for your videos. I have experienced difficulties with sensors. After a few consecutive prints, the levelling of the bed was not accurate, but was accurate again the day after. I now make the levelling when the bed is hot, but the problem still exists. I believe that the sensor close to the bed and the head warms up little by little, and the temperature of the sensor may have some effect of the measurement.
Iggy Norant (2 months ago)
It would be interesting to see how piezo and stress gauge sensors fair.
Matthias Hansen (2 months ago)
Thanks for your work! But one question: Is it possible, that a electical heatbed can get a bad influence on these probes? For e.g. eletric magnetic behaviours? On your test is a "perfect" metal block without heatbed wires etc.
Noah Plum (2 months ago)
9:53 "alumininium"
Noah Plum (2 months ago)
+jrok96 look at how many n's are in it
jrok96 (2 months ago)
ok good so you agree ? alu -mi- num some of these wierdos from that irrelevant continent across the pond pronounce it Alu mini um and it drives me nuts
Cnc Machinery (2 months ago)
You measured mostly repeatability, and mostly ignored system accuracy due to heating/cooling. Excellent video, great charts. Should have had an external digital DTI measure the setups actual position, logging, and dwelled (paused) after contact on the probe. Then the DTI log would show where the moving piece actually was at probe contact, vs the start position when all was cold. Likewise, the triggering circuit for probe hit is critical. I did a lot of work on this, 8 years ago, on testing for lathe spindle index sensors, and we proved conclusively that sensors will give very fuzzy signals, that vary with temp/speed/luck. A sharp triggering circuit, and a sensor tuned to give a crisp response, will be about 100x more accurate on a range of speeds vs a typical probe "hit". I also saw that optical sensors will repeat to about 2 microns, with very simple basic cheap sensors.
Bruno Antunes (3 months ago)
What a great video!
HHHarry09 (3 months ago)
Would you mind sharing the sketch/code?
Nicholas Brown (3 months ago)
Why only 5 volt? Are they powered by USB? Since most USB ports are 5 volts? Great video! But you didn't show us stepper motors that have all this stuff built in. Is this just a cheaper method using an external sensor?
Peter Brown (3 months ago)
Hello Tom, I wonder if you can help me with a couple of queries. I have bought a LJ12A3-4-Z/BY inductive sensor. It is the 12mm diameter version as I did not have room to fit the larger 18mm version. The problem is that the detection distance is halved to just 4mm. I was wondering if I could power the sensor directly from the power supply and possibly fit either a voltage regulator or resistor voltage divider to reduce the signal back at the board? I also have some 0.1mm stainless steel foil that I am intending to place under the 2mm glass. Will this increase the ability for the sensor to pick up the magnetic field? One last point, do you know if it is possible to devise a method of using a k type thermocouple instead instead of a thermistor? I know that a thermistor decreases voltage as it heats and a thermocouple works in the opposite direction but i would like to use a PID to control hot end temperature as it better controls better without overrun once heating temperature is achieved.
backyardbasher (3 months ago)
Hello Peter, this being a year old video chances are Thomas does not answer questions anymore. The inductive sensor has 3 wires, +V , -V and Signal , +V can be anything from 6-36V DC , the Signal wire is either OC or CC referenced to -V (ground) depending on what status the Sensor is in. I dont know what Printer you want to add it too but if it's a printer with a micro switch on the Z axis then you should run the Inductive Sensor through an Optocoupler and then hook it up to the wires where the micro switch were. Depending on what Optocoupler you use you can run it and the Inductive Sensor off the 24V Printer PSU without and kind of drop down regulator.
Zoltan Korossy (3 months ago)
The BLTouch manual specifically states the sensor must be run vertically. Since your test rig is horizontal, the results are suspect. It would be good to rerun the BLTouch test with it held vertically.
Poptart McJelly (3 months ago)
what about ultrasonic sensors?
Florian Stelter (3 months ago)
Filip Paryż (3 months ago)
Please test the HallOn v3 from GMZ :D
guuuuustaf (3 months ago)
If I have a capacitive sensor. and a aluminium bed. what is the best height the sensor should be at? Somebody must know. have searched. cant find any good answers. =) thank you.
Michael Gara (3 months ago)
So, would I be correct is assuming the LJ12A3-4-Z/BX is incredibly accurate and the 1 to get, at a fraction of the cost of some of the others?
keytree69 (4 months ago)
Another one to try is the piezo force sensor. Mount it in your bed support or (as I did) in your hot-end mount on the carriage and it registers contact of the nozzle to the bed. Zero probe offsets in X, Y and Z, change nozzle and all you have to do is run the auto-level. Super convenient. Precision Piezo do a good rig.
Rob Jones (4 months ago)
Hello Tom. May I first congratulate you on your clear, informative videos and have now subscribed to you. I am new to 3D printing and Arduino world in general. I have just bought the Ender 3 and having watched various autolevelling videos also purchased the BLtouch sensor. I have added the bootloader to the Ender 3 and now want to download the relevant sketch to control the BLtouch. Can you direct me to any video/information that will help as I am a little confused with what I have seen so far. Many Thanks. Rob
God Slayer (4 months ago)
The M16, 20mm capacitive sensor links shows inductive sensors.
rallekralle11 (4 months ago)
may be a bit late, but someone might see this and find it useful. copper tape can be used on the bottom of glass beds, and an inductive sensor will work in my experience.
David Stafford (4 months ago)
So much work and planning to make this. Great job!
Smoogalers! InYourFace (4 months ago)
would it be possible to use the z end stop as an auto level, for example moving the z end stop to the extrude instead of the side and have auto level turned on in firmware
christopher michaels (4 months ago)
When I look at your sheet and go to buy one I noticed that your links are not named at your data sheet. Could you please rename them correspondingly and provide a link for the PINDA
SchwettyBawls (4 months ago)
I know this video is over a year old at this point so I hope this is still relevant. He tested all of these sensors horizontally. The BLTouch specifically states NOT to use it that way. It needs to be hung vertically as it would be mounted on a printer. I've used a mechanical switch with manual leveling, a mechanical switch that flips up with a servo, capacitive sensors, inductive sensors, glass beds, PEI sheets, Zebra Plate from PRINTinZ, aluminum beds, and even tool steel beds. I've tried a total of 15 different sensors and 11 different beds in my few years of 3D printing. NONE of them were as accurate as simply using the BLTouch. When it is installed correctly, it just works flawlessly. Best of all it doesn't care one bit what surface you have, it will work on anything. I think it deserves a re-test.
tompo1975 (4 months ago)
So.... which one is the best? More accurate, reliable and worth to buy? Great video but without conclusion is quite useless, still have no idea what to buy as an upgrade to my printer :/
Matthew Gooch (5 months ago)
Incredibly thorough, concise review! Keep up the great work
Darius Steele (5 months ago)
I would love to see this video updated to include Ultrasonic sensors, and name brand inductance sensors like those made by Osram up to say 16mm sensing distance. That being said, this video is so helpful. Thank you for making it.
Mustafa Delimus (5 months ago)
pls, extruders Compare we wait for it like mk10,titan,direct ,compare only direct & bowden :( thanks sir.
Vladmir Putin (5 months ago)
The only reason I moved from an inductive sensor to David Crocker's IR sensor is because of the bed. If the thickness of the bed varies, or there are holes in it to reduce weight, the induction sensor will trigger at a different height to more/less material being on the bed in one location.
Making Cooking Fixing (5 months ago)
So, there is no clear winner? I was hoping that the BLtouch was. But like others mentioned, you tested it horizontally and BLTouch clearly says that readings will be inaccurate that way.
Bast König (6 months ago)
Hi - did you plan to test the Touch MI (hotends.fr) and again the bl Touch 2.0 ? regards!
Damjanhd (6 months ago)
there is great inductive sensor which works on 5V and it is cheap, a blue on ebay
Allan Madsen (6 months ago)
You are talking about 50µm (0.05 millimeters) If your 3d printer i high end maby and i say may your 3d printer has a tolerens of 0.1mm , maby better with out belts, and using ball spindels. 0.05 millimeters is just so unreal.
Allan Madsen (6 months ago)
Maby use a better spindel.
WumNet (6 months ago)
Mal ne Frage...Kann ich mein Bed ohne Glassplatte leveln, danach zum ersten Mal den Sensor einbauen und dann wieder die Platte aufs Heatbed drauf machen? Oder muss ich irgendetwas verstellen nachdem ich die Platte wieder drauf habe? LG
moestrei (2 months ago)
Nein, nix verstellen.
Bob Davis (7 months ago)
What a great video. This is one of the BEST Tom. Great job!!!!!
MrRedstone (7 months ago)
I got a 8mm "orange" inductive sensor. It detects from 5mm away at 5V, perfect for my mirror covered bed. Too bad I have deviation between the Z homing distance and the probing distance. Then nozzle homes about 1mm lower than it actually prints at. Same with endstop, that's not the sensor's fault.
HappyandAtheist (7 months ago)
what is the TH3D EZABL V3.1 Sensor please inductive ?
Dustin Lehmann (7 months ago)
What Type of Filament and color are those printed parts for the test rig?
tecknick (7 months ago)
Hmm, as detailed your video was, and I consider myself as a reasonably intelligent bloke, I still haven't determined which sensor is the best. Apart from the two that were obviosly way out on the last chart you showed, all the rest performed similarly. So, be brave, which one would YOU choose to use regularly?
Munky332 (8 months ago)
Here's a question, with the inductive sensor, does the voltage range matter? ie does the sensor (say, a 6-36v sensor) work the same at 6v, as it does at 36v?
JurgenIntemann (8 months ago)
Hi, great video's.
gymkhanadog (8 months ago)
Almost 2 years later now and I still adore my BLTouch. Even if it statistically or scientifically isn't the most accurate out there, as you say, it's 'more than good enough'. It's so rare to have a calibration fail.
ZeroPointAlpha (8 months ago)
Any chances of doing a review of Piezo-electric sensors? Been reading up on them, but most of the hype I've found seems to come from people who work for the company selling commercial versions, so getting third-party reviews would be interesting.
ProfessorM. (8 months ago)
you didnt check magnetic hall effect sensors? or are the inductions one just that?
pugofstardock (8 months ago)
Great vid. Any plans on doing this with piezo sensors?
Info Mario Reus (8 months ago)
hy all, i have a bltouch on ramps 1.4, i have a isue that the right side of the bed is always lower as the left side, any explication?
Angel Nieves (9 months ago)
Do you think magnetic beds will affect the accuracy of the inductive sensors and all of your results?
Vega 128 (9 months ago)
1 question i my print bed is a repurpased mirror so what sensor shuld i get
BigCooter.com (9 months ago)
Assuming the data collected is accurate, in order to make probe comparisons, large tolerances must be added to inductive probes that include the build plate tolerance stack for non-conductive top sheets (adhesive, PEI, etc...) . Also the BL Touch is intended to operate vertically, more friction is introduced horizontally. Once all this is considered and included, the BL Touch will compare MUCH better, if not the best. Also, if tossing on a thick G10 build plate for printing Nylon ... only the BL Touch or a micro switch can accommodate that, without having to change the probe z offset value.
Ricardo Molina (9 months ago)
Presents a magnet high sensor
MAUI MANGULABNAN (9 months ago)
so which would you recommend for an Anet a8 with glass?
Thomas (9 months ago)
I never thought about using such sensors for measuring the bed level. At work I use mostly inductive ones but just for checking if there is an object or not. When I saw your video about the Prusa i3MK3 and its autoleveling I had doubts about the precision, but your video here has told me better. Thank you.
Mostafa Mohamed (10 months ago)
Is there better sensors out there ? Link them if yes
Bill-D IT (10 months ago)
Hi Tom, it would be nice if you could post just the data so that we can read it more readily.
OhFishyFish (10 months ago)
Technically speaking the whole process shouldn't even be called "auto levelling" as the printer doesn't make anything more level after probing. It just compensated with stepper motor movements for the uneven bed.
runs the sensor 42 times. That's the anwser, well done :)
MisterFixIt1952 (10 months ago)
Lots of great information which in the end was overwhelmingly confusing. Your scripted, rapid fire delivery, in the end just left me confused and without a clear direction as to which sensor I should use. There was no wrap up or recommendation as to which sensor was the best one to use. It seems that you were trying to keep the video as short as possible rather than delivering useable information. I just want a good sensor at a descent price and I still don't know which one to use.
ackthbbft (10 months ago)
So which one was the winner?? I need decent bed leveling desperately, I just can't get a truly flat surface on my CR-10, even after trying multiple mirror tiles.
Scott Baker (11 months ago)
Has anyone -thought about- tried using polarized light to detect variations in print bed height?
loopingcooper (11 months ago)
Hello. Where can we read the results please? I am very interested by mecanical switch results (with and without lever) As I understand, at 7:24; mecanical without lever is more precise than BLTouch ? cool!!
Apple Cultists! (11 months ago)
LOL, I just eyeball it and it works well.
Roberto Brenes (11 months ago)
what board is he using?
Brian Ipsen (11 months ago)
I wonder how the HallON compares to some of these other sensors....
Bill Schwanitz (11 months ago)
If you ever re-run this test I'd love to see the piezo sensors be included. I'm about to give one a try myself but curious to see your experience vs mine/others
treefrogjoness (11 months ago)
I am looking for someone who has a custom configuration.h file that they are already using, and configured for the BLTouch Sensor, and SKYNET3D that they could put a link in for dropbox or somewhere for my CooCheer 3d Printer. The file needs to be configured for an Anet board with LCD 12864 graphic display. Print Bed Size configuration is W 220 L 270 H 230 mm. If someone would put a link in a reply, I would appreciate it. I'm sure there are other people who could use the file also.
Δημήτρης (11 months ago)
Well i am sure that this aswer had been said again in this video but what the heck!! 2mm thick glass will work on Roko sensor(inductive) prety well, i have not run a perfect test as your's offcourse but it works.
Bela-Botond Bandi (11 months ago)
Any chance to give me an idea, how to set up autoleveling in smoothieware, how to level the bed and what gcode should I put in start/end code? I have a 18mm capacitance proximity sensor on hotend carriage.
jesondag (1 year ago)
FYI, you tested the BLTouch in the wrong orientation. I tested mine thoroughly at multiple homing speeds and standard deviation was 0.01mm with the occasional one that that was +/- 0.02mm, on all but really fast homing speeds. I now do a two step homing with it, once at 1500mm/m, and then a slow home at 100mm/m from ~2mm of the bed.
RandomNoobs (1 year ago)
i guess the biggest one is the best and most expensive one, lets see
EdCranium (1 year ago)
Some time ago I built a DIY heated bed to my Printrbot Simple Metal. In order to get the sensor to detect the bed through the glass, I had to put a sheet of 1 mm galvanised steel sheet under it. But now, the sensor almost touches the surface of 3mm thick borosilicate glass. Not really useable. I could not find borosilicate glass less than 3 mm thick. I read that plain glass can withstand a certain amount of heating and cooling as long as it happens slowly. But how slowly? I decided that glass of the type used in picture frames was cheap enough for an experiment and I bought a couple of 200mm square glass frames from a bargain store. This glass, being only 1.5 mm works reliably with the built-in heating setting (I did not have to make the glass heat more slowly) though I must warn that, since I only use PLA, this setup has never been tested above 60c! Also, borosilicate glass can withstand some downward pressure (when things go slightly wrong) - but picture frame glass cracks immediately. I lost both in the experiment, but have had 6 perfect prints off the third, with one coat of Magigoo on the glass.
Jens Cocquyt (1 year ago)
conclusion use a microswitch
Inspironator (1 year ago)
I wish your test apparatus also used a layer of glass, typically found on CR-10x's. If the sensor needs to be too close to the glass so as to interfere with prints during printing, then that is a fail. Please account for sensing distance to the detected object.
pugofstardock (1 year ago)
recommended this vid a lot of times to people. Is an updaten with piezos planed?
Zoonosis (1 year ago)
Hi can anyone help on a question I have? I want to buy the anet a8 3D printer, and I was asking what sensors would work on it, if any. I don't think any of the sensors will work as it requires manual straightening , but can anyone help? Is there any other ways of making the bed straightening automatic on that printer?
bob f (1 year ago)
If you have marlin 1.1.7 installed, enable mesh bed leveling... no need for extra expense of these.
DarkDekieon (1 year ago)
I would like to know how accurate the different tounch sensors were to each other? The BLTouch, the microswitch with the lever and without?
Sir Haugen (1 year ago)
So what you are saying is that the only sensor who can "see" the glass bed is capacitive, but is not reliable?
Technocrat (1 year ago)
It's really helped.
Christopher Ellis (1 year ago)
Dude, you are my 3D Printing Super Hero... Love your passion for the 3D printing. I'm in the Vegas Area and they are always talking about probing, especially with Area51 so close. Lol
Joe Keaveney (1 year ago)
Hi Tom, just came across this video while I'm building my i3 clone, great videos! Do you know if there are any 12mm sensors longer than 50mm? My sensor doesn't go close enough to the print surface so doesn't detect the print bed. Would really like to get the printer working, going to watch your clone prusa series now!
Joe (1 year ago)
what voltage divider did you use on the inductive 6-36v sensor? The one you built in your first video about inductive sensors? (15kohm & 10kohm)?
Gary McKinnon (1 year ago)
I'm wondering if copper sheet might work better than aluminium foil for inductive sensors on a glass bed.
Gary McKinnon (1 year ago)
Good review, thanks.
Asger Vestbjerg (1 year ago)
Thanks for sharing 😀👍
Climbers137 (1 year ago)
your music is so good!
Mike Feldmeier (1 year ago)
From the BLTouch website: BLTouch must be installed perpendicular to the ground. If BLTouch push-pin can't be perpendicular to the ground, BLTouch will out put wrong signal.

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