What is bed leveling and bed leveling sensor?

What is bed leveling?

Bed leveling is very important for 3D printing successful. If the 3D printer bed is not level when 3D printing, the model 3D printing will be failure or the 3D printed models  have flaws. Manual bed leveling is not easy for 3D printing users,especially for nobs. So, there is a high demand for auto-leveling features in 3D printing.

Auto leveling measures the bed via a touch sensor. The touch sensor probes several points on the bed. It takes these measurements and creates what we call a bed mesh. A bed mesh is a map of the bed that the printer uses to add compensation. This compensation is called “ Z comp” or “ Z offset compensation. Z comp raises or lowers z offset based on bed warp. This helps give you a better print by increasing bed adhesion . Bed warp is caused by the metal plate on the Y axis being warped. They get warped over time of being heated and cooled. Also poor quality Y axis plates lead to warpage from the factory.

What is the BL Touch sensor?

BL Touch is also called 3DTouch. It is an auto leveling sensor that uses plastic tips to measure the hot bed. These tips are fully replaceable. This is nice in case the tip hits a print and breaks it off. This is a weak point on the BL touch. Because the tips are plastic they break quite often. That being said, tips are readily available at the time of writing. The BL Touch is rated for an accuracy of .005mm. Some claim the sensor is even more accurate. But the sensor that was tested in house had an accuracy of .005. The BL touch uses a hall effect sensor to measure the probe distance. This means the probe has to move a considerable distance before the sensor is triggered. What is a hall effect sensor? A sensor of this type sees a change in voltage when a magnetic field is introduced. In the case of the BL touch the plastic probe is fitted with a small magnet. This magnet moves upward as the probe is pressed into the bed. The semiconductor then senses the magnet's influence on the current and triggers. The printer then notes the Z height at which the probe triggered. It then writes it to the bed mesh and moves to the next point for probing. The BL touch has a stowed 0mm length and a 4mm deployed length. This is important because the probe needs to be able to deploy before the nozzle touches the bed. This restricts some of the mounting positions for the BL touch.BL touch is found very cheap online ranging from $13 to $ 45 usd.

BL Touch Pros :

1. Probes are replaceable in the event of a print collision.
2. BL Touches are cheap compared to other leveling sensors.
3. Accurate up to .005 even though some manufacturers claim .003 .
4. BL Touch uses a 3 pin and 2 pin connector design that fits some other printers.5. BL Touch version smart uses an optical sensor instead of a hall effect sensor. This decreases the probe time with faster activation.

6. Plastic tip can break, saving the print from failure due to collision.
7. Thicker mounting ears offer better protection than the Cr in the event of a collision.

BL Touch Cons :

1. Probe has a less accurate sensor that can be manipulated by outside sources. Magnets Electrical interference

2. There are many versions of the sensor that are discontinued but there is a possibility that the cheaper dealers are using these older versions.

3. Possibility of buying an imitation BL Touch.
4. Large probe movement before sensor activation. This means slightly longer probing times and large increase in total mesh time.

5. 4mm Deployed length limits mounting options.

What is a CR Touch?

The CR Touch is another type of leveling sensor. The CR Touch uses a metal tip probing the bed the same way as the Bl touch. CR Touch has an accuracy of 0.005mm the same as the BL Touch. Some of the sensors I have tested have shown better accuracy at 0.002 and 0.001. The sensor style for the CR Touch is an optical sensor. This sensor style is optimal for one of the fastest probing times. What is an optical sensor? An optical sensor uses a small laser beam to measure movement. The sensor is triggered when the probe blocks the beam from the receiver thus the sensor is triggered. This sensor type is typically found on garage doors. When you break the laser the door stop is triggered and the door reverses. These sensors are most accurate because it only requires small movement to trigger the sensor. Unlike the hall effect sensor the optical sensor is not disturbed by magnets or electrical interference. The CR Touch is an OEM (Original Equipment manufacturer) part from creality. You can find these sensors on some of their printers in stock form. Ender 3 s1 pro , Ender 5 s1 pro, Ender 3 s1 just to name a few. CR touches feature a 0mm stored length and a 6mm deployed length. This is better for placement allowing you to mount the CR farther from the nozzle. This is crucial for custom builds such as Voron or those of you who make their own mounts. CR Touches are around a $30 to 45$ price range.

CR Touch Pros :

1. Better Optical sensor for faster probing times and less activation length.
2. 6mm Deployed length allows better mounting options for custom printers.
3. Cr touches are OEM equipment and can be found on several creality printers.
4. Metal tip will not break like the plastic of the Bl.

CR Touch Cons :

1. Price Cr touches are more expensive than their Bl touch counterparts.
2. Metal tips can bend and knock over prints.
3. Metal tips are non replaceable.
4. The mounting ears are not as thick as that of the Bl touch and typically break when a collision happens.

5. The Cr touch uses a 5 pin connector. This means it only works with boards that have the available Cr touch plug in. Most common Cr touch boards are Creality’s 4.2.2 board and the 4.2.7 board found in most of the Ender 3 series. This limits options for non Creality printers.

What sensor is the best?

Both sensors do the same job but which one is better? This is more a question for the use and printer it is being attached to. The Bl touch is the cheaper of the two sensors and has more board availability. That being said the Cr touch offers faster probing and more options for mounting for custom built printers. Cr touch is also more genuine than the Bl touch because the Bl is often cloned. You can buy both sensors through creality with similar price tags. $40 per sensor kit at the time of writing. If you are trying to cheap out and just need a simple sensor the Bl touch is the best for the job. However if you are using a custom built printer or you would like faster probing the Cr is the best fit.

FAQS

Q: What is required to add a touch sensor?

A: Most touch sensors come with a kit for install which includes a mount and wiring as well as aguide. Some applications might need a longer wiring harness. A firmware upgrade is required to use the touch sensor no matter what sensor you buy.

Q: What firmware should I use?

A: Depending on what board you are using gives you options. Most firmware is fitted to the user so don't be afraid to try several. Any firmware that works for the Bl touch works for the Cr touch.

Q: Can I keep my Z stop?

A: No you must remove it as the touch sensor now acts as the z stop. Removing means unplugging from the board and removing the sensor from the printer.

Q: I am using klipper . Can I use the touch sensors?

A: Yes you can, you just have to modify your Printer.cfg file and add in the Bl touch config.

Q: How do I check the accuracy of my touch sensor?

A: If using marlin you will need to connect your printer to a pc and use cura to send gcode.The M48 gcode will check accuracy and report back a standard deviation. If using klipper you will use your console in mainsail/fluidd and use the PROBE_ACCURACY command.

Q: How much longer does the Bl probe for than the Cr?

A: Milliseconds but over a total mesh it can add up to 15 seconds or more. This is depending on how big your mesh is as standard mesh is a 5x5 probed mesh.End Result? Cr touch is a high quality sensor with faster probing and OEM part design. But it comes with the OEM part price. The Bl touch does the same job for less price for the hobbyist user. With more board availability and lower price point I think the Bl touch is a winner for our hobbyist printer. The Cr touch is more for the production side with faster probing times and more accurate measuring sensor. At the end of the day the choice is yours. Whether it is the Cr touch or the Bl-touch you'll be glad to have an auto leveling sensor by your side.