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Mars Pro "Set Z Home" seemingly not working
#11
I believe the "home" position is determined by monitoring the photo-sensor at the trolley's physical downward travel limit--NOT in firmware by tracking lead screw rotations against any parameter saved by the Z=0 function (even if it does do anything). One would have to disassemble the firmware to verify this (may do that yet, I have an old copy of IDA Pro kicking around somewhere).

The configuration G-Code file (see below) has a number of references to a Z-axis limit switch (unfortunately the comments for same are not in any form of conventional English making it difficult to determine just what is going on).

In any event the utilisation of both the firmware configuration setting and a physical "switch" (be it mechanical or a photo-sensor) would be redundant--and since the latter (a physical switch) exists, and has a real "per unit cost" associated with it, I believe it to be the active element, with the (perhaps) abandoned "Z=0" function only serving to complicate things.

I will have to see if my old version of IDA supports whatever micro-controller this thing uses.

Configuration G-Code, Z-axis limit switch settings:
Code:
            ;Z-axis limit switch position type
M8029 I0         ; 0: One-sided limit, only use Z-limit, do not use Z+
                 ; 2: Bilateral limit, if Z+ and Z- limit are used at the same time, Z+ can limit the maximum stroke of Z
                ;
                ;
                ;
                ;Z limit switch wiring type If this configuration is wrong, the motor will not move and the buzzer will be in a
                ; certain direction when the motor is operated by the manual interface will make a drop of sound.
                 ; Simple judgment method, if the configuration is normal, when the limit is changed to the limit,
                 ; the buzzer will make a drip sound.
                 ; When the limit is changed to the unrestricted position, the buzzer will not sound.
                 ; If the opposite is found, modify this configuration.
M8029 T0         ; 0: Limit switch normally open (when unrestricted - and s voltage is high level, low level when limit)
                 ; 1: Limit switch normally closed (when unrestricted - and s voltage is low level, high level when limit)
                ;
                ;Z-axis limit switch position
M8029 S0         ; 0: The position of the forming bracket is the closest to the platform, and the limit is connected to Z-
                 ; 1: The position of the extrusion bracket is the farthest from the platform, and the limit is connected to Z+
                ;
                ;Whether the Z axis returns to (0,0,0) after homing
M8029 C0         ; 0 : Back to Z (0,0,0) position, that is, the position of the molded carrier back to the coordinate zero position
                ; 1 : Stay in the limit position
;
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#12
I have had a round of email exchanges with "Leon" at Elegoo, a very helpful gentleman. Here is what I found about the z=0 function.

He graciously responded to my initial "What the heck does 'Z=0' do?" query:
Elegoo support Wrote:The Mars zero reset function is mainly to compensate for the large Z-axis error of the machine during long-term use of the machine, and the size of the Z-axis method of the model is not accurate. Does not have a physical impact on the LCD

https://www.youtube.com/watch?v=cqRBZUAE...rt&index=7

Best regards,

Leon

To which I responded:
cliffyk Wrote:Thank you for you swift and informative reply
If I understand correctly it would appear that what I will call the "Z=0" procedure (as shown in the video you provided) is adjunct to the initial alignment provided in the 07/22/2019 User's Manual, in the initial setup process.

in the User Manual procedure:
  • the platen locking screws are loosened;
  • the platen is moved to the Home position with the sheet of paper in place--Z-axis travel is limited by the photo optic sensor;
  • the platen aligned in the  X-Y axis manually and in the Z-axis by action of the spring internal the the holder;
  • the locking screws are tightened (front first);
  • the paper should move freely with just a bit of resistance;
  • the platen is raised, printing can commence;
In the "Z=0" procedure shown in the video:
  • the platen is assumed to be in proper X-Y axis alignment (the locking screws are not loosened)
  • the platen is lowered to the Home position with the paper in place (again I assume with travel limited by the optic sensor?);
  • the Z-Axis is adjusted logically via the platen positioning controls as needed to allow the paper to move about snugly;
  • the "Z=0" control is pressed to store the current Z-axis position as a logical end-of-stroke;
  • the platen is raised, printing can commence; 

MY further questions are:

From this point (after conducting the Z=0" configuration) is the Z-axis travel limit determined by a parameter saved by the Z=0 function, rather than the optical sensor?

It appears then that the Z=0 exercise is an "in-service" and as "as-required" adjunct procedure to be conducted at times as seen appropriate to validate and "fine tune" the z-axis Home position?

Would/could periodic use of the mechanical alignment procedure from the User's Manual could substitute for, and eliminate the need for the "Z=0" process? Which of course remains a valid quick-check and fine-tuning exercise  

I again apologise for this barrage or questions/concerns, however as a Mechanical Engineer (MSME '1971 MIT, PhD ME 2019 
MIT) with 45+ years experience in data processing it is my nature to know all I can of the machines I use.

Thank you,

-cliff-

Leon replied:

Elegoo support Wrote:
Yes Z=0 is just an additional command program, not related to limit switches,

Prolonged use may result in a 0 point offset, and it is rarely necessary to adjust after completing a 0 point setting.

Best regards,
Leon

So, there it is--the "Z=0" function is an on-the-fly procedure to validate and if necessary tweak the logical "0" position of he platen in-between performing the complete mechanical alignment--I.e. it sets the "0" position to be achieved by issuing the  "G0 Z0" or "G1 Z0" or "G28 Z0" G-Code commands.

The "Home" button will continue to position the platen to the hardware limit switch "0" position.
-cliff knight-
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#13
I am not understanding something here.  Sorry for my failure in that.

If the set z=0 function is only to put it back into spec after long term printing, then it is correct NOT to do that unless all leveling practices fail to print.  Correct?

If that is true, then what does change the '0' position during the leveling?  If you go into the manual movement, perform the process (and in my non-surveyor definition of 'leveling' to make (a surface) level, even, or flat:, not the plane of the earth Surveyingto find the relative elevation of different points in (land), as with a level. for my definition please see 19, 20 and 27 here) then is it the most important part to go up 10mm 10 times?  Is that what the software/firmware calculates as the home position or z=0?  Where you stop then -100mm???

Thank you for helping me out here.

PS.  My first print failed miserably.  I saw metal shavings on the top of the build plate after tightening the screws.  Cleaned it off and didn't think much of it.  Machining aluminum isn't always perfect.  Well, when I went to unscrew the entire bolt it was cross threaded from the factory.  I have contacted Elegoo about this as they really should send me a new plate and screw, but if they don't then I just may return it to Amazon and go with a different brand.  I was able to get one of the spare screws (I see why they include them now Wink ) and it tightened down just fine.  I will need a new one if I start getting some prints.  As long as it works, I am fine with buying new parts for it as this was partially my fault for following the directions...
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#14
(07-19-2020, 09:11 AM)maximumbeef Wrote: I am not understanding something here.  Sorry for my failure in that.

If the set z=0 function is only to put it back into spec after long term printing, then it is correct NOT to do that unless all leveling practices fail to print.  Correct?

If that is true, then what does change the '0' position during the leveling?  If you go into the manual movement, perform the process (and in my non-surveyor definition of 'leveling' to make (a surface) level, even, or flat:, not the plane of the earth Surveyingto find the relative elevation of different points in (land), as with a level. for my definition please see 19, 20 and 27 here) then is it the most important part to go up 10mm 10 times?  Is that what the software/firmware calculates as the home position or z=0?  Where you stop then -100mm???

In the mechanical alignment process, initiated by loosening the lock screws and pressing the "home" button, the machine's "0" (furthest downward travel) position as determined by the limit switch does not change. What does change is that the physical position of the platen is changed to coincide with the limit switch "0" position.

Using the "Z=0" function establishes a logical "0" position , independent of the limit switch controlled "0" position. That logical "0" position is then used when G-Code Z-axis positioning commands are executed.

The go to "Home" positioning command will still send the Z-axis trolley to the limit switch controlled downward position. 

(07-19-2020, 09:11 AM)maximumbeef Wrote: Thank you for helping me out here.

PS.  My first print failed miserably.  I saw metal shavings on the top of the build plate after tightening the screws.  Cleaned it off and didn't think much of it.  Machining aluminum isn't always perfect.  Well, when I went to unscrew the entire bolt it was cross threaded from the factory.  I have contacted Elegoo about this as they really should send me a new plate and screw, but if they don't then I just may return it to Amazon and go with a different brand.  I was able to get one of the spare screws (I see why they include them now Wink ) and it tightened down just fine.  I will need a new one if I start getting some prints.  As long as it works, I am fine with buying new parts for it as this was partially my fault for following the directions...
-cliff knight-
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#15
I think that is what they intended it to do, but if I hit that button it buzzes like mad and is so tight I couldn't fit an atom in there.  If I skip that step, it works pretty good.  I don't think it is setting the position properly.

I was able to get the test print to work, but it was supposed to print 2 rooks and I only got one.  The second one got about 5mm and stopped sticking to the build plate.  Still, the finished one came out almost perfect, so I am pretty impressed at the resolution of this thing.

At any rate I am printing a One Piece Zoro for my son and a dragon for my daughter right now.  I leveled it again, this time pressing down very hard and flat.  I am hearing quite the suction sound all the way to 300+ at this time.  I hope they both print well.

I did contact Elegoo and told them that I had a screw that was stripped and they are going to send me something.  I was able to loosen the front screw and tighten it down again, so maybe it will be ok.  No shavings on the top of the plate this time.

At any rate I recommend not hitting that set z=0 button.
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#16
Did you see my thread here about "What the 'Z=0' function really does..."...
-cliff knight-
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