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

Its been 4 years, will be cool to see a redo with current offerings

I think you did the BLTOUCH a disservice, Tom. While the other sensors perform equally well in any position, such as your horizontal position in the test fixture, the BLTOUCH is designed to work vertically. When put in the horizontal position, the sensor pin and magnet must overcome the additional friction of sliding along the bore of the guiding hole. This can lead to inconsistent measurements due to friction and grabbing. I consistently get average variation in readings around 0.015 mm

This was awesome. Finally a proper comparsion between the different sensor types. Thanks a lot for your effort!

Thank you for this comparison! We just doing the same for a customer and we were asked this question very often as we do a lot of printer customizing.

Thank you very much for this very interesting & informative video!! I love those technical contributions.

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.

Incredibly thorough, concise review! Keep up the great work

That test machine was brilliant! I built an i3 clone following your guide and this sort of thing is really great for developing upgrades. Thanks for being so thoughtful in the design and execution of the testing.

This was awesome. I love these technical kinds of videos. Thanks for the info, Tom!

Clear, concise, metrologically accurate and empirically awesome. Legend.

Very informative video that highlights the differences in sensor types. Just what I was looking for to help decide what sensors to look at.

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.

I think one of the things you have to remember is that the BLTouch is an all-in-one solution for bed leveling; it won’t interfere with your nozzle at all because of its retraction. That retraction most likely adds a significant wobble.

Especially good description of what standard deviation means in this situation. Gut gemacht!

Invaluable advice and comparisons Tom. Massive appreciation mate.

This is amazing! Finally a useful application of the scientific method to get some hard data. It is so much more convincing than people's opinions. Love your videos!

Wow Tom that was a very in depth video and very well put together as usual. Thanks!

So much work and planning to make this. Great job!

Really cool video! The idea of applying statistics touched base, true engineering style, trial and error!

How are you only at 67K subscribers? Your videos are so good and the editing lighting etc is amazing! I wish you lots of success Thomas. I really enjoy every single video that you make.

Perfect, new video right as I get home from work. Amazing content

Guden Thomas, wie immer: Sehr Informativ und Professionell! Ich danke dir für all deine Super Videos zum Thema, diese brachten mich in die Welt des 3D-Drucks! Weiter so, alles Gute und schöne Grüße aus dem Hessen, Otter

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.

Tom. You pretty much nailed this one....also you mentioned that capacitive sensors are thrown off by humidity...they are actually the instrument they use to sense humidity.

What a great video. This is one of the BEST Tom. Great job!!!!!

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.

Is this going to be the sensor version of Fillaween? ... Sensorween?

Your work is excellent. Thanks for the video, it's going to be very useful for my graduation project.

Very happy with David Crocker's differential IR sensor and a sheet of Printbite.

I have not seen any video like this one, wow! super informative! keep it up man

This is the kind of video I subscribed for. Great content!

Incredible experimental design, helped me so much in making an informed choice. Earned my subscription and then some!

This is exactly what I was looking for, thank you!

Great video. I really enjoyed the scientific real world tests. More like this please

Thanks for your video, now I can comfortably purchase an induction sensor with the knowledge I will likely have to give up my glass bed. I appreciate all the testing you did!

Great Video - seriously stellar quality and effort clearly went into this. The pinned top comment is exactly the question one is left wondering. Great job!

good video.... I like the effort you actually put into this, I really did have ever these questions

Great video Tom it was really informative.

So comprehensive comparison! Thanks

Well done! Great information and nice experimental set-up!

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

Ormerod represent! Seeing DC42s revised IR sensor made my day!

Awesome video, thank you for sharing, great engineering skills too!

Nicely done! Thorough as always. I learned stuff.

Really great channel Tom. Keep up the good work!

If the tests were conducted as in the video , what do you make of Antcap's instructions regarding how the BLTouch must be mounted ? The manufacturer's website for the BLTouch clearly states this: if the sensor is mounted horizontally it WILL give wrong results. They don't equivocate. It is a crystal clear stipulation. It is underlined even . Would you care to comment ?

brillant breakdown, very rich in useful info.

Very, very nice testing here! Thanks Thomas! I've been using a little microswitch (with lever) on a metal strip moved by a servo. It's working flawlessly for years now. (all metal printer, no 3d printed parts) Nice to see that this turns out to be a precise way indeed :-)

Thanks Thomas, you have helped me figure out why I am getting inconsistent results with my 8mm capacitive sensor. Time to go and get BL Touch instead. :/

High quality content episode, as always ! it s a plaisure to follow you thomas

Good video. I have thought about switching to inductive sensor but now I just think I can keep the microswitch without the lever.

AWESOME. I don't know how you find the time, but I would to live next door to you. Thank you for your hard work!

Fantastic work, excellent video, thanks!

Very good testing ... Great Job

I have a unique idea for a sensor that might work better than any of these. I know it works much better than a Microswitch for sure at least....when I built it initially I didn't know what use it may be, but now it is all quite clear! Thank you Thomas! You inspire me!

This is awesome! Also fun fact: I use an aluminum mk3 heatbed with a 3/32 inch (2.38 mm) sheet of glass AND blue tape. The 8 mm inductive sensor triggers just fine for me thankfully.

I'm surprised/impressed to see how accurate the no-lever microswitch was. (And pleased to see the 6~36v 4mm sensor is good, 'cos I have one ordered :)

pretty rigorous tests. Thanks Thomas!

Very helpful video , thanks!

I liked this video a lot, I simply wish the sensor I use (David Crockers IR Sensor) had a slightly deeper/more in depth review. I am given more confidence to continue using it, however, will no longer calibrate it with the heated bed on. That is a variable I had not even thought twice of! I simply set the bed for 55° for my PolyMax PLA and calibrated it when it was done heating right before the print...Thank You for that!

Very informative, thats exactly the content I prefere. Some more mythbusteresque explosions would be neat.

I feel like I've been in a time capsule. I got an early MakerBot CNC (#180) in 2009-ish, and was printing 3mm ABS on a raft on Kapton tape, using a .37mm layer height and no fans or heated beds. I woke up in 2021 receiving a Prusa Mini+ that prints directly on a magnetically attached and heated bed, using 50 micron layer height if I so desire, and supporting PLA, PETG and a plethora of other materials out of the box. In the old times, I tried using an optical mouse sensor for auto-leveling using focus. It actually worked with the sensor 1 mm from the bed, but I wanted something more like 10mm from the bed and never got the optics to work correctly. The idea was that the optical mouse sensor not only sensed the height, but also could read markings on the bed, or a printed sheet attached to it both for calibration precision and for communicating what to print. I never got to finish this project, but it seems like it still might be worth while: the inductive SuperPINDA doesn't even provide much headroom. Does anybody here have experience using optical focusing for Z height calibration?

Tom, you really should continue wit the Myth-busting line. I have been experimenting with sensors I have to say that your conclusions corroborate my experience 100%. Given mechanical switches with lever , although less precise than inductive, can be used with borosilicate glass, I will stick to those. Awesome video, congrats.

Very good synthesis

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.

another great video, thanks Tom.

This was a great summary! For once, a youtube video that has more information than I actually need :-) (btw, the links for the inductive/capacitive sensors are all pointing to the same model)

Wow, how informative video it is... I should applause.

Inductive always!! Its like a engine position sensor :)

Thanks Thomas! very helpful

Outstanding work!

Very very informative, thank you.

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.

Informative as always. I use a LJ12A-4-Z/BY with an LM7805 VR on the output this gives a steady 5 volt trigger signal. If you increase the input voltage does it does it strengthen the sensing distance.

I've just discovered your channel and love the friendly sound of your voice. I want to do a few small projects and I was weighing paying for prints vs buying my own printer. I found the new matter mod-t for 299 but wondered was there something better for beginners that maybe will help them as they transition to an intermediate level of skill without going a lot higher ( +$200 US) in price. In any case, I enjoy your videos. Thank you.

always enjoy your videos, also enjoying the new seinci videos, make more with those too please!! Bryan, Canada

Hi Thomas, your videos are great!, thank you

Cool comparison. I was looking for a sensor to measure distance for my research project. So this helped me to understand the basics of the sensors. Thank you for that. Also is it possible to have the part list for your test setup? It will be really useful.

I have Omkon SN04-N inductive sensor. I use glass bed and have one layer of aluminum tape ON TOP of the glass where the sensor probes. It works pretty well :)

Excellent review and presentation Tom!! Very well done! I have a 6-7 mm glass on top of an aluminum bed. Which sensor should i use?

When I was working on the auto-alignment at Type A Machines, I was very surprised at the unsolvable nature of the auto-alignment problem. There's essentially no way to get the desired flatness when combining the standard deviation of the sensor, with the rated flatness of aluminum, and the thermal expansion when heating to over 80C. You could conceivably do it with steel, but that has other challenges from the weight and cost of facing. Glass is really the only material we could find with below +/- 50 um flatness and dimensional stability when heated (we even managed to find some with +/- 0.3 um). Really the solution is to crowd source some magnetic glass, minimum order is 5 tons and works with induction.

Should've tested 3D touch as well, for example from the famous clone manufacturer Trianglelab.

Very good video! Useful, interesting and professional. Glad I subscribed to your channel.

great video! cool rig, shows the power of rapid prototyping. been thinking about Auto leveling, I have a delta that uses pressure pads, would be great to see how well it stacks up, down side is Auto leveling is tapping printer head into the bed every time.

love the video. can you publish the accuracy finding?

one thing you're missing are FSRs, force sensing resistors. i use them on my delta which has a glass bed over an aluminum heat spreader. they seem to be very repeatable but only above 0.13mm deviation, any less than that and smoothieware's autocalibration gets upset

+Thomas Sanladerer Great video! Aluminum tape definitely works though! I have used it multiple times, amd we also use it reliably at our Makerspace. There are different types of aluminum tape however. It looks like you are using the "metalized" type that is similar to Mylar. That stuff will not work. You need actual aluminum tape. The metalized type isn't very conductive. Actual Aluminum tape is basically just like aluminum foil with an adhesive backing. The only thing you have to watch out for is the adhesive. Alot of aluminum tape has a low temp adhesive and will start peeling up at around 50°C, but you can find some that has a high temp adhesive which is what we use under our PEI at the Maker Space.

Awesome test! Very methodical tests. I have the cap sense and have noticed the heat issues. I think I'll switch to inductive. I would like to try a glass bed over the aluminum lower plate. I wonder if the the longer range inductive sensor would be practical at detecting the aluminum glass combo.

Super Übersicht. Danke! Ich weiss jetzt, warum mein kapazitiver Sensor so eine Streuung hatte. Benutze zur Zeit den PiBot Sensor, der auf optischer Reflektion wie der Sharp basiert. Bisher mit sehr gutem Erfolg.

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.

Great info, thanks Tom. I recently installed David Crocker’s IR sensor on my Prusa i3 box frame, which uses a 3mm glass bed and a red Mk2 PCB heated bed, inked black with a permanent marker in the sensor probing areas. After watching your video, I tweaked Marlin so that G30 would output the trigger height to 3 decimal places (1 micron resolution). I turned on my printer and made 46 measurements with G30 and got an s.d. of 1.4 microns. I noticed a trend in the data, presumably due to temperature drift somewhere in the system (probably the steppers warming up my crappy M5 threaded rods so the trigger point appeared to get lower with time). So I did another 34 measurements and the s.d. was 0.8 microns, but still with an obvious trend. I think these numbers are an order of magnitude better than you got with glass. Maybe it matters what is behind the glass? I should also mention there was a thin layer of glue stick on the bed under the probing area from the last print. Also I have slightly modded my sensor board to increase the trigger height from about 2.7 mm to 3.2 mm by tweaking the angle of the outer LED using a hot-air rework station. This is so that it would clear the bulldog clips I use to hold the glass down so I could still retain my full 200x200 build area.

Thanks a lot for that Video. Now all makes sense.

Perfect timing Thomas!!! I've been looking into upgrading my whole X carraige on my cheap I3 clone, with a new E3D V6 and titan. I was planning to use an inductive sensor with foil tape, I didnt even know about those optical sensors! my cheap chinese hotend and extruder are crapping out on me after a few years, I think i probably deformed the teflon liner trying to print either PET or nylon and there's a huge amount of internal resistance. I was printing some makergeeks PLA rated for 210-220 at 240C and only 12 mm/s, any faster or colder and the extruder skips like mad. I also dont think that it was actually 240C and my thermistor is probably going bad too

for my scratch built reprap delta we used a simple conductive type, running 1 wire to the nozzle, and another to the aluminium bed, reeally simple and easy, and no need to worry about effector tilt

i use inductive 4mm and the bed is made from 2 sheets of glass (3mm) and graph foil (0.2mm) in between and works great.

Hello Tom thanks for these instructive videos, in industry we use sensor with one µm resolution from baumer (MY-COM G75P/S35L) I get one on an old equipment, and plan to use it on my 3D printer in progress ; my main issue is to manage the way to lift this system not to hit the bed or printed object while extruding. Hope this will help. Pierre

awesome video! could you make a video going over the Auto leveling types? like which method is more accurate and the differences between auto leveling a delta vs. a core XY or Cartesian printers.

Great, informative videos. Thank you. I was wondering if you tested the BLTouch horizontally or vertically? I think that its accuracy is affected by gravity and would benefit from a vertical test. I agree that it is a good alternative for glass probing.

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