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Why aren't people using prusa jam detection sensors?

Posted by Power3DPrinting 
Why aren't people using prusa jam detection sensors?
April 10, 2020 11:29PM
I keep finding some of these modules here and there and for the price, it's not terrible value for what it offers. Any ideas why not every printer and its mother is getting sold and modded with one of these prusa sensors but almost every prusa mk3 has these sensors working?

[www.aliexpress.com]
Re: Why aren't people using prusa jam detection sensors?
April 11, 2020 12:17AM
Even Prusa stopped using those as they where unreliable!

MK3S does not have that sensor.

It uses an optical switch with an interrupter
see [manual.prusa3d.com]
Re: Why aren't people using prusa jam detection sensors?
April 11, 2020 02:09AM
We tried a laser sensor too, but there are some filaments that it just doesn't work with. We found it more reliable to use the filament to turn a shaft and measure the motion magnetically, so we made this [duet3d.dozuki.com]. As with the laser monitor, the firmware correlates measured extrusion with commanded extrusion so it doesn't only detect complete jams.

Edited 1 time(s). Last edit at 04/11/2020 02:11AM by dc42.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Why aren't people using prusa jam detection sensors?
April 11, 2020 03:59AM
Quote
dc42
We tried a laser sensor too, but there are some filaments that it just doesn't work with. We found it more reliable to use the filament to turn a shaft and measure the motion magnetically, so we made this [duet3d.dozuki.com]. As with the laser monitor, the firmware correlates measured extrusion with commanded extrusion so it doesn't only detect complete jams.

I integrated a radially magnetized torus (9X4, 5 pole pairs) in my extruder idler. It triggers a digital HALL sensor. Does the job although the mm of filament per pulse is around 7mm. Quite coarse compared to yours.
Note this kind of magnet is hard to find. Got it from a clock.
Magnets are better than optical solutions that are more bulky and more likely to get dirty.

I realized that to restart a print is not that great. So it is fine to detect a jam, not just end of spool like a simple switch.


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: Why aren't people using prusa jam detection sensors?
April 11, 2020 12:35PM
Oh, okay Dust, I did not realize they stopped using the sensors, I get how the optical switch works but what is an interrupter?

Good to know DC42, the magnetic sensor looks really cool but maybe out of my budget for all the printers I intend to upgrade, still probably worth testing out, do you think it has marlin support for RAMPS?

MKSA I understand HAL effect sensors are great for driving motors, never throught to use one as a jam detector but makes sense one could be used in the same way as the duet's magnetic sensor. While not being able to detect filament runout reliably is unfortunate and I'm not sure why, I can always use a limit switch to detect run out and in theory the printer can reverse calculate to back up 7mm? Just not particularly sure what to order in regards to a HAL effect sensor and magnets.

I appreciate the good information from all of you, looks like I have a lot of testing to do
Re: Why aren't people using prusa jam detection sensors?
April 11, 2020 08:42PM
Quote
Power3DPrinting
...
MKSA I understand HAL effect sensors are great for driving motors, never throught to use one as a jam detector but makes sense one could be used in the same way as the duet's magnetic sensor. While not being able to detect filament runout reliably is unfortunate and I'm not sure why, .....



??? It IS reliable, the point is that it takes a few cm to detect the jam !

There is not that many pulse per turn due to the magnet I use.The availability for a hobbyist of this kind of multi pole magnets is the issue here. It is possible to make toothed wheel (like used in car ABS) etc...
Plenty of different approaches, but more complex.
DC42 magnetic sensor is more sophisticated, it is the same used for servo.

I don't think Marlin can handle my or DC42 sensor.

Hal sensor are not used to drive motor BTW.

The point is that to resume a print is not that easy to get good result. Try it.

Micro switch will just detect the end of spool. It is like running out of gas. Plan in advance. The slicer gives you the amount needed and you can weight the spool !

.


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: Why aren't people using prusa jam detection sensors?
April 11, 2020 11:21PM
Okay ha, well that is good to hear it is reliable, I got the wrong idea from what was said, my bad

It is unfortunate there is no marlin support so I will sideline this project for now.

Spool weighing has always been unreliable to the exact gram left in a spool or even within 50-80 grams, ideally the runout sensor gives a 20-30mm running low on gas alarm so the printer can take a pitstop for refuel to go with your analogy. I had some success pausing my printer to do multi-color printing so I am not sure if it works the same way.

I appreciate the help you guys gave, hopefully one of these days filament jam sensors become more accessible
kr_
Re: Why aren't people using prusa jam detection sensors?
May 18, 2020 06:15PM
Maybe they don't use them because most printers never experience jamming problems?
It hasn't happened yet on my home built printer, after years and many spools. The worst was hearing a missed step from time to time while using Filaflex or printing the first layer too close from the bed.
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