Firmware 3.5.3 ?  

Re: Firmware 3.5.3 ?

I assume this firmware is for the new filament sensor on the MK3s.

Re: Firmware 3.5.3 ?

3.5.3 Firmware for Prusa i3 MK3S and MK2.5S
@PavelSindler PavelSindler released this 2 days ago · 6 commits to MK3 since this release

This is initial fw version for MK3S and MK2.5S printers. It contains all features from 3.5.2 firmware plus bed level correction range was enlarged to +-100 um. This firmware version is recommended only for single material printers (without MMU2 connected) and should not be used with standard MK3 and MK2.5 printers.

https://github.com/prusa3d/Prusa-Firmware/releases

I have no clue why they'd increase the BLC range and not instead change to use the Marlin 7x7 cal routine. With the 7x7 the BLC isn't needed.

Re: Firmware 3.5.3 ?

I have no clue why they'd increase the BLC range and not instead change to use the Marlin 7x7 cal routine. With the 7x7 the BLC isn't needed.

They said in the Blog that 7 x 7 is not ready for official release because the bed magnets have an effect on the readings that they need to resolve. They also advise anyone running the existing Community 7 x 7 patches beware of increased safety risks.

An increase in BLC range was a popular request in the issue tracking on GitHub before 7 x 7 surfaced and seems to me to be a good interim compromise while they continue to work on professional implementation of 7 x 7.

Re: Firmware 3.5.3 ?

A good compromise would be to modify the interpolation method to something a bit less aggressive and use a full 7x7 BLC table. Front, back, left, right isn't that helpful - each applied to three points, and seemingly interacting with interpolation, is a bit of a quagmire.

It's funny they mention the magnets; that's probably why the 3x3 cal suffers - the interpolation used can't deal with a discontinuity.

Re: Firmware 3.5.3 ?

Actually - thought about the magnets. I can't see why they'd interfere with calibration. The prox detector is AC based (not a Hall sensor), and ignores static fields. And the steel sheet will soak up most if not all the probe energy, leaving none to leak through to the PCB and magnets below it.

And the 7x7 cal is in the Official Marlin Firmware; that's professional enough for me.

Re: Firmware 3.5.3 ?

Actually - thought about the magnets. I can't see why they'd interfere with calibration. The prox detector is AC based (not a Hall sensor), and ignores static fields.

I'll take your word that the probe should ignore static fields (I haven't looked at the datasheet for the probe, and I have no reason to distrust you), but the probe is moving during the leveling process. So, the magnet that is static relative to you watching the process is now dynamic relative to the probe.

That said, AFAICT the 7x7 mesh firmware that I installed doesn't seem to be caring about the location of the magnets and the mesh bed corrections seem to be working better for me. I'm not sure if the magnets are really the problem that Joseph and company thinks they might be.

Granted, this is a sample size of one... They have an entire printer farm for samples... 😉

Re: Firmware 3.5.3 ?

They said in the Blog that 7 x 7 is not ready for official release because the bed magnets have an effect on the readings that they need to resolve. They also advise anyone running the existing Community 7 x 7 patches beware of increased safety risks.

What exactly is the safety risk to using the existing 7 x 7 patch? if the magnets affect the 7x7 that 'feature' is well swamped by the 7x7 results that provide for full plate leveling. (that the 3x3 standard system do not correct even after the use of the left side and right side extra corrections)

Re: Firmware 3.5.3 ?

I'm making all sorts of assumptions about how the sensor works, but I don't think it's Hall effect based (expensive and troublesome in production), so they used some frequency to generate an AC field sensed and used to detect distance. If I read the spec sheet right, the sensor can detect distance 1500 times per second (think conveyor applications sensing cans) , implying the frequency used is a lot faster than 1500 Hz. The Z motion is no where near 1500 Hz, though the instantaneous single step motion may have broadband characteristics, I'm doubtful they'd be detectable by the sensor.

I did some tests using a very strong neodymium magnet under the bed. Indeed the PINDA did see the magnet, but was extremely sensitive to the magnet material location, and seemed to ignore the field the magnet makes. Only when the magnet was physically under the PINDA did the PINDA switch... and it switched regardless of magnet orientation. Not a conclusive test, but I came away thinking the field isn't involved; rather, the permeability of the magnet swamps the permeability of the steel plate. Essentially, the 2mm spec is for metals with a permeability near steel (100-500u), and metals or ceramics with much higher permeability (35,000u) can be detected much farther away.

From Omron: http://www.ia.omron.com/support/guide/41/introduction.html

Detection Principle of Inductive Proximity Sensors
Inductive Proximity Sensors detect magnetic loss due to eddy currents that are generated on a conductive surface by an external magnetic field. An AC magnetic field is generated on the detection coil, and changes in the impedance due to eddy currents generated on a metallic object are detected.
Other methods include Aluminum-detecting Sensors, which detect the phase component of the frequency, and All-metal Sensors, which use a working coil to detect only the changed component of the impedance. There are also Pulse-response Sensors, which generate an eddy current in pulses and detect the time change in the eddy current with the voltage induced in the coil.