BLTouch V3.1 Auto Bed Leveling Sensor for Perfect First Print Layers

The BLTouch V3.1

BLTouch by Antclabs is an auto bed leveling sensor that can precisely measure the tilt of the bed surface. It has been around for quite some time now, and the V3.1 is its latest version. BLTouch is a very popular upgrade on open-source 3D printers similar to Ender 3 and CR-10. It will improve your print quality with flawless first layers even on an unleveled or warped bed. This article will explain the process of bed leveling, including the questions like what is auto bed leveling and the working of a BLTouch, and who should buy it?

What is Bed leveling?

A 3D printer’s nozzle can move in the flat XY plane. When we level the bed, our job is to get it parallel to that plane. The more level your bed is the better prints that you get off it. This is because the printing plane and the nozzle are at the same height. 3D printing bed leveling is a crucial step when you first put up your 3D printer or even good as regular maintenance.

How to Manually Level the Bed Surface?

Many budget 3D printers will come with physical knobs to level the bed yourself. For manually leveling the bed, you’ll need to check the distance between the nozzle, and the bed remains constant at all four corners. Some 3D printers have an auto homing option. The printer head will move around five points by itself. All you have to do is set the height at each corner. If you don’t have that option, you’ll have to disable the stepper motors and manually move the printhead. Move the head through each corner and set the initial height. A piece of paper is usually used for this. You keep the paper under a particular corner and keep raising the bed until the nozzle drags against the paper.

We then use calibration squares to fine-tune our first layer. These are a set of five squares (four at each corner and one in the middle) that are printed to check the bed leveling. The goal is to get smooth and consistent squares at each corner. Keep printing, reviewing, and tuning your bed until you get all squares correct. If the middle square is off every time, then you have a warped bed. Five calibration squares are printed at each corner and the centre of the bed. You can download the .stl files by clicking (here).

Calibration squares printed..

What is Auto Bed Leveling(ABL)?

No amount of manual leveling can fix a warped bed. This is where ABL is useful. In ABL, the movement of the printer will be altered to match the slope of the bed instead of the user manually adjusting the bed to be parallel. A proximity sensor is required to use ABL. A high-end printer like the Prusa MK3 does not come with any type of manual bed adjustment. It has an attached bed. It has an inductive sensor attached next to its extruder assembly. The nozzle comes down and toches the bed surface at nine different points. The inductive sensor (PINDA probe) measures the height at each of these points and comes up with a 3D representation of the bed surface. While printing, the firmware will use this data to adjust the position of the nozzle as it moves across the bed. It makes small adjustments to the Z-axis to ensure that the nozzle is always a perfect distance away from the bed.

Auto Bed Leveling Using a BLTouch

Unlike the PINDA probe on the MK3, the BLTouch is a mechanical sensor. Attached is the same fashion as the PINDA probe, the BLTouch uses its pushpin to touch the bed at different points and measures the height for that point. The BLTouch is very accurate with a standard deviation of the outputs less than 0.01. This is thanks to the Hall sensor that it uses. Hall effect sensors detect external magnetic fields. BLTouch can work on any bed material, unlike the inductive, or optical sensors which work only on selected materials. You’ll need to change your firmware settings once you connect a BLTouch to your printer board.

BLTouch attached on a extruder head

Working of BLTouch

Inside the pushpin, there is a little magnet on the top, which is near to the hall effect sensor of the PCB. Under the strip labeled “Smart” there are a bunch of copper windings that make up the solenoid. Based on the polarity of the solenoid, the magnet along with the pushpin gets pulled or pushed away. So when the pin is extended and it touches the bed, being pushed up, and passes the Hall effect sensor, it detects the height and changes the polarity of the solenoid to pull up the pin. This method is much more reliable than the inductive, capacitive, or optical sensors used for ABL. Even when compared to other mechanical sensors like a standard micro switch, the process of BLTouch is far more complex, accurate, and reliable than it so a comparison between them is pointless.

PCB with QR code and a pushpin

What is New With the BLTouch V3.1?

V3.1 is the latest version of the BLTouch. The major change in this is that from this generation onwards, the BLTouch will only work on 32-bit boards. There were far too many issues with BLTouch working on 8-bit boards. For instance, on 8-bit boards, there were no physical ports to plug-in accessories, so for fitting a BLTouch, you had to spend additional money on a pin27 expansion board. Additionally, there is limited memory space on the 8-bit boards. Thus you couldn’t have all features selected at once. The 32-bit boards have rectified this issue as they come with additional I/O ports and also have ample memory space. The BLTouch V3.1 also has some additional features like self-test alarm, touch switch mode, and alarm release, etc.

Summing Up the BLTouch V3.1

There are plenty of BLTouch clones in the market. Counterfeit products are lower in quality, and nowhere as reliable as the real ones. Many times these fake products are faulty out of the box. Thus don’t waste your money on these instead buy an original BLTouch from one of their verified sellers. One way to check a genuine BLTouch is that original ones have a QR code on the PCB behind them. If you already have a 32-bit board, avoid buying bundles that offer pin27 boards. Only the 1.5-meter extension cable will be OK. You’ll have to print the mount yourself.

Overall the BLTouch is an excellent product that will give you a perfect first layer on any bed surface. It is reliable and consistent with its results. It is a definite must-buy for someone who wants to add ABL capabilities to their printer. A genuine BLTouch will cost somewhere around $45, with the appropriate length extension cable.

Image credits: The Manual bed leveling images are taken from HobbyHoarder. The BLTouch images are taken from the Amazon product page.

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