Automatic Manual bed leveling needed

I put together my first 3d printer and find bed leveling time consuming and, because of dual motor Z axis, frequent. I do not want auto-leveling that builds a mesh as I do not want Z axis to move within each layer as it would slow it down and introduce inaccuracy.

What I'm looking for is for the printer to measure distance to the bed (using some distance sensor, switch etc) at all four corners and tell me how much I need to adjust each corner using a thumb screw holding the hotbed (in mm - I can translate it to turns myself). My controller board based on ATMega is currently running Marlin firmware. Any suggestions are welcome as I don't have any previous experience with 3d printing.

thanks, Bob

Edited 1 time(s). Last edit at 04/10/2017 02:06PM by newbob.

The reason your printer has autoleveling is because the bed is not flat, and the machine can't maintain the level setting from one print to the next. That's how they can sell the machine so cheaply. If you want to throw a little $ at it, you can fix those problems which would eliminate the need for autoleveling or even anything more than rare manual leveling. Specifically, you have to make sure the frame is rigid, especially the portion that supports the Y axis guide rails, and use a flat plate (cast aluminum tooling plate works) on 3 leveling screws that actually level it without bending it. Finally, connect the Z axis screws with a belt and drive them with a single motor. The X axis will never tilt again, and the bed will stay level.

My previous printer build (see the link, below, in my sig) hasn't needed leveling since the last time I took it apart to make some mods, at least 6 months ago. My most recent build was leveled once about a month ago and I haven't had to touch it since, even after transporting the machine laying on its back (it's sort of big) in my car. This stuff works...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Hi newbob,

As DD points out, ABL is sometimes (or often) used as a correction for badly made printers. Having said that, ABL is only one reason for having automatic Z height detection. Errors caused by having something trapped between the bed or heater and the build surface, change of thickness of build surface or change of nozzle all introduce errors. As well as these, airly small differences in the thickness of the first layer can also influence the adhesion of the first layer.

For all of these reasons, a nozzle contact type of automatic Z height setting is well worthwhile and the Piezo disc type is a very good contender for best in class here. Look at [forums.reprap.org] for more information.

Mike

Reprapfirmware can use a probe to give you a diagram of your bed flatness. Quite useful for having a visual aid to bed levelling, otherwise there is none. Trying to build a flat bed does help alleviate some of the problems though.

As much as Digital Dentist hates it, some form of automated bed levelling is needed otherwise 3D printers will never come out of the dark ages, either fully automated or a screen popup telling you to alter a thumbscrew on the bed.....

Do you real want auto level?

As I understand it -- auto level maps the bed then
sends Z corrections on each layer to make it flat

Do you want the Z axis moving up and down (backlash)
to make not so nice layers?

Is it too hard to get a feeler gage and set bed level every so often?

My printer is Cartesian and I only want Z to move from layer to layer. What I want is a way to (automatically) verify that bed is level before each print and preferably tell me which corner is offset and by how much. Per @Origamib recommendation I'll try switching firmware to Repetier and see how it goes.

Doesn't some of the firmwares print the probing offsets into the console when doing the auto leveling? So you could just run the autoleveling procedure as normal and see from the console logs if your bed is tilted and which way. Maybe put removable sensor if you are doing the leveling rarely.

Quote
Juggeli
Doesn't some of the firmwares print the probing offsets into the console when doing the auto leveling? So you could just run the autoleveling procedure as normal and see from the console logs if your bed is tilted and which way. Maybe put removable sensor if you are doing the leveling rarely.

You mean like thus?



You hover the mouse over the probe point you are interested in to see the coordinates.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42

Quote
Juggeli
Doesn't some of the firmwares print the probing offsets into the console when doing the auto leveling? So you could just run the autoleveling procedure as normal and see from the console logs if your bed is tilted and which way. Maybe put removable sensor if you are doing the leveling rarely.

You mean like thus?

...

You hover the mouse over the probe point you are interested in to see the coordinates.

Yep i'm using Duet Wifi myself...

But i think that i did see in Tom's stream that also Marlin prints out the probe results to console when doing the autolevel routine. You'd of course need to hook up a PC to the printer to see the results.

@42 that's really neat. I don't expect an 8 bit board to do that...maybe through oktaprint (I have to look into that one)

@Juggelli, thanks for the suggestion. I have not tried ABL yet but perhaps I should before switching to repetier (which I read it's no longer open source) and maybe try tweaking ABL code to output results to LCD.

Quote
newbob
My printer is Cartesian and I only want Z to move from layer to layer. What I want is a way to (automatically) verify that bed is level before each print and preferably tell me which corner is offset and by how much. Per @Origamib recommendation I'll try switching firmware to Repetier and see how it goes.

Isn't that what printing a skirt is partially for??

A different approach is to use a dedicated Gcode file along the lines of:-
: code to use probe to report height at 4 corners.
G28 X Y :home x and Y
G92 X0 Y0 Z0 : set positions to zero
G0 X20 Y20 :go to 1st position
G28 Z :home Z
G92 Z0 : set Z to Zero
G0 X160 Y20 Z2 : go to 2nd position raising probe
G28 Z : home Z
M114 :report position 2
G0 X160 Y160 Z2 : go to 3rd position raising probe
G28 Z : home Z
M114 :report position 3
G0 X20 Y160 Z2 : go to 4th position raising probe
G28 Z : home Z
M114 :report position 4

This should report the z heights relative to the 1st position in your host program.
Include getting the bed and hot end to temp before starting this.
You will still have to measure/set the height offset to the nozzle in your slicer.
You should also rerun it after any changes as position 1 can be affected by the others. Obviously the positions need to be set to what works for you.
Im not an expert and haven't tried this but hopefully you will get the idea.

What the OP is asking for is for the machine to measure the bed position and then predict the change in position based on turning the leveling screws. The problem with that is it will vary with the initial conditions because it is nonlinear. If the bed started rigid and flat (and stayed that way), and the support structure were rigid, and the bed was on three leveling screws, not four, you'd have half a chance at making it work. With a thin flexible bed, a flexible support structure, and four "leveling" screws, you can't make any such predictions. Every time you turn one screw the bed and support structure distort.

If you had the sort of structure and bed that would allow the bed level to be predicted based on turning the screws, you wouldn't need the predictive stuff because you'd only set the bed level once and it would stay that way.

The only real value in a pretty, brightly colored display of the bed shape is if you recognize what it is telling you- that your bed/printer sucks and you need to fix it.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

If I can put my interpretation of what newbob said (and I apologise if I am wrong) it is not a matter of predicting the change but of measuring the error directly above each thumbscrew. This is only meaningful with a three point system as the_digital_dentist said - trying to adjust four or more points can result in a build surface that may be level but not flat.
I think further, in asking for that feature in the printer rather than in an attached computer, he is asking for a command accessible through the standard 4 line LCD display/knob setup which allowed something like "Report bed level" which would measure the error directly above each of the adjusting screws.
For example:
select quick settings
select Report Bed Level
LCD displays P1 0.00mm, P2 0.12mm, P3 -0.07mm

That would neither be a sign that the printer had been built poorly, nor an indication of bad feeler gauge training but merely a sensible check before starting a print.

Mike

Edited 1 time(s). Last edit at 04/13/2017 12:07PM by leadinglights.

Quote
the_digital_dentist
The only real value in a pretty, brightly colored display of the bed shape is if you recognize what it is telling you- that your bed/printer sucks and you need to fix it.

No, the real value in the height map display is that it tells you how it sucks and by how much, so that you know which screws to adjust. And when working out how much adjustment to make, it's easier to look up the height error at a point by putting the mouse over one of the dots in the diagram than it is to work out which entry in a table is the correct one.

You can rotate and tilt the view. Here's a side view of the same height map:



From this angle you can see that the main issues is severe X tilt, which is easily corrected using the adjusting screw, and there is some sort of anomaly at high X mid Y that needs to be investigated.

Edited 4 time(s). Last edit at 04/13/2017 02:03PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Fixing the real problem isn't very difficult or expensive. All it takes is understanding what's going on and why, and having a desire to do something about it.

Or if you prefer, you can play whack-a-mole with the 4 "leveling" screws and generate lots of pretty colored graphs that you can rotate in 3D and kid yourself that you ARE doing something about it.

The difference between the two approaches is that if you fix the actual problem, you won't have to keep releveling the bed. A colored graph that you can rotate in 3D, while an impressive piece of programming, isn't necessary if your printer maintains the level settings from one print to the next. But what do I know? I just build 3D printers that rarely require releveling. Maybe people prefer to look at colorful 3D graphs and don't mind looking at them over and over and over again.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Heat up bed
Home Z
set Z home position
adjust Z switch

Move extruder to point A
use feeler gage adjust bed
Move extruder to point B
use feeler gage adjust bed
Move extruder to point C
use feeler gage adjust bed

Done

or
sensors, sensor calibration
Hundred of lines of code
measurement plots
measurement interpretation

Execute auto level measure
measurement plots
measurement interpretation
adjust bed

Execute auto level measure
measurement plots
measurement interpretation
adjust bed

Execute auto level measure
measurement plots
measurement interpretation
adjust bed

The definition of insanity doing the same thing over and over expecting a different outcome

What's next ----- Lane departure alarm, auto parallel park, auto braking, auto back seat nag?

Read posting by cozmicray
Throw eyes heavenwards in perplexity and exasperation

Read posting by cozmicray
Throw eyes heavenwards in perplexity and exasperation

Read posting by cozmicray
Throw eyes heavenwards in perplexity and exasperation

Read posting by cozmicray
Throw eyes heavenwards in perplexity and exasperation

Read posting by cozmicray
Throw eyes heavenwards in perplexity and exasperation

Read posting by cozmicray
Throw eyes heavenwards in perplexity and exasperation

or

Dont read posting by cozmicray

The definition of insanity doing the same thing over and over expecting a different outcome

Mike

Quote
the_digital_dentist
Fixing the real problem isn't very difficult or expensive. All it takes is understanding what's going on and why, and having a desire to do something about it.

Or if you prefer, you can play whack-a-mole with the 4 "leveling" screws and generate lots of pretty colored graphs that you can rotate in 3D and kid yourself that you ARE doing something about it.

The difference between the two approaches is that if you fix the actual problem, you won't have to keep releveling the bed. A colored graph that you can rotate in 3D, while an impressive piece of programming, isn't necessary if your printer maintains the level settings from one print to the next. But what do I know? I just build 3D printers that rarely require releveling. Maybe people prefer to look at colorful 3D graphs and don't mind looking at them over and over and over again.

DD, I've seen from your previous posts that your attitude is "My printer doesn't have X, therefore X is not worth having". Why else would you think that moving the SD card between your printer and your PC every time you want to print something new is cool? I try to avoid criticising technology that I have never tried.

Your mention of the problem you get with 4 levelling screws (which almost everybody knows is a bad idea) has no connection with what we are discussing.

Sure, you can design an expensive printer and build it right - as you have done, and I have done with my precision Kossel - and it should only need to be levelled once. And I can scan the bed and look at the height map to check that it is still level whenever I want to. But the printer that produced the height map in my earlier posts in this thread was built from an inexpensive kit. Sadly it doesn't have a rigid frame, so when I move the machine the bed levelling changes. Fixing it would be expensive - I'd have to build a new printer from scratch. It's my backup printer, used only for testing firmware in Cartesian and CoreXY modes and for printing when my precision Kossel is out of action, so it's not worth replacing. Usually I just let the bed compensation do its stuff, but when I posted that height map yesterday, I realised how badly off it was. So a few minutes work adjusting 2 of the 3 bed support screws and running a few more scans gave me this:



I can see immediately from this that the bed is flat and level enough to use even without bed compensation.

Edited 3 time(s). Last edit at 04/14/2017 03:31AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

In theory step skipping could be an issue but so far I have no evidence of it therefore any effort to 'fix' it would be a waste of time and money. Automated bed calibration on the other hand would save me time and increase quality of the prints.

@42 I like the heat map visualization a lot.
@cozmicray - I use a precision dial right now but I feel it could be almost fully automated...well if my bed had three lead screws with servo motors than it could be fully automated but that's probably too much...

Quote
newbob
@cozmicray - I use a precision dial right now but I feel it could be almost fully automated...well if my bed had three lead screws with servo motors than it could be fully automated but that's probably too much...

Or 3 leadscrews driven by 3 stepper motors connected to separate drivers - although of course this requires 2 extra stepper drivers. There is a thread about doing this on the Duet WiFi at [www.duet3d.com].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

BTW There's a version of marlin which does guided manual bed levelling as do many turnkey printers.

The reality is when you start out 3d printing getting the bed level is a skill you haven't quite got the hang of yet, there's a sh1tload of other more interesting stuff to grapple with so you look to automate it with ABL which makes your flimsy printer much easier to live with.

Then provided you get at least 1% more satisfaction than frustration from it and keep printing you build a more substantial machine, with ABL and find that it's barely doing anything because you made a machine that's rigid, with a flat and level bed. So you switch it off.

Unless you own a delta in which case manually calibrating it is a time consuming pain in the arse, so you use a probe.

Edited 1 time(s). Last edit at 04/21/2017 05:45PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions