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Makers Guide| Auto Bed Leveling Device Comparison: Strain Gauge VS BL-Touch

In 3D printing, a leveled bed is a prerequisite for a successful 3D print, so all 3D printing users want the distance between the print nozzle and bed to be uniform throughout the build area. However, it is often tough to attain given the expansion and contraction that takes place during the 3D printing process. Fortunately, there are 3D printers coming with automatic bed leveling function.
For achieving auto bed leveling, most FDM 3D printers use a contactless inductive sensor which is simple to install, operate, and configure. These inductive probes work well with a metal build plate, but build platforms made of other common materials, such as glass, are practically invisible to inductive sensors.
Currently, the most often used and most accurate sensor is BL-Touch, directly from ANTCLABS in South Korea. According to Antclabs, the original manufacturer of the probe, “BLTouch is an auto leveling sensor for 3D printers that can precisely measure the tilt of (sic) bed surface.” This sensor works on any type of bed surface, be it metal, glass, wood, or something else entirely. However, what really caught some attention is that Creality released a new printer CR-6 SE featuring an innovative auto bed leveling device via strain gauge.
In this article, it will be comparison between BL-Touch and strain gauge.
About BL-Touch
BL-Touch is a type of semiconductor hall sensor and is an electronic component for 3D printers. It is an auto leveling sensor for 3D Printers that can precisely measure the tilt of Bed surface. It could work with any kinds of bed materials, such as glasses, woods, metals, and so on.
Main functions and controls of BL-Touch are the same as usual auto bed leveling sensor, consists of RC servo and micro switch. Thus, BL-Touch can be applied on almost every board.
BL-Touch is fulfilled with simple structure and high precision by using progressively designed solenoid and hall sensor. It aims for user convenience and enjoyable printing by adding many smart functions, such as self-test, alarm, alarm release & Touch Switch mode, Blue LED for servo signal indicating and Z-probe (Zmin) Testing.

※ The data above can be varied by assembling shape and other environments.
But assembled with the low quality 3D printer, we just get the value as 0.001~0.05mm. (It was the same BLTouch) Actually, around 0.05 is also not much problem at FDM type 3D printers.
About Strain Gauge
Strain Gauge or Strain Gage was developed in 1938 by Edward E. Simmons and also Arthur C. Ruge. Originally, the tool is just one of the substantial sensing units utilized in the geotechnical area to determine the amount of strain on any framework (Dams, Buildings, Nuclear Plants, Tunnels, etc.). The resistance of a pressure scale varies with applied pressure and, it transforms criteria such as pressure, stress, tension, weight, etc. right into a change in resistance that can be determined later on.
Whenever an external pressure is related to an item, it tends to change its shape and size thereby, modifying its resistance. The anxiety is the internal standing up to ability of an object while a strain is the amount of contortion experienced by it.
A strain gauge works on the principle of electrical conductance and also its reliance on the conductor's geometry. Whenever a conductor is stretched within the limits of its elasticity, it does not damage but, obtains narrower as well as much longer. In a similar way, when it is compressed, it obtains much shorter and also wider, eventually transforming its resistance.