How precise can your Smartrap print? - Alignment issues Hi all, I am in the process of assembling my smartrap. The mechanical part is more or less done, so that even if I cannot print yet, I am starting already to see some of the well known the problems it will give (perpendicularity, Z wobble, etc.). As soon as I am able to print I would like to try to improve the current design in many respects, but before I start I would like to know if you found this kind of issues too, if you already started addressing them and how. Here are a couple of remarks to start the discussion: [list] [*] [b]the design is not entirely symmetric[/b]: the threaded rod is on one side, the belts (I have one of the last kits with GT2 belts) are often attached to the corners, which causes a deformation of the X and Y carriages to make them look as trapezoids instead of rectangles (and probably they slide less smoothly); [*] globally, [b]the structure seems a bit weak[/b] and prone to oscillations and vibrations (I noticed that some of you already modified the original design to improve this issue in particular); [*] there is [b]no obvious way to tune the alignment[/b] of the printer: most of the possible tuning must be done during the initial assembly, if something goes wrong one has probably to restart from scratch and if some plastic pieces came slightly deformed one is doomed. [/list] What is your experience? You are also invited to share here all your tips about alignment issues, so that they are all collected in one forum thread for quick reference later on. Cristian https://reprap.org/forum/read.php?344,383028,383028#msg-383028 Mon, 20 Jul 2026 00:32:07 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?344,383028,513830#msg-513830 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,513830#msg-513830 rcjoseb Smart_Rap Tue, 26 May 2015 11:39:33 -0400 https://reprap.org/forum/read.php?344,383028,513631#msg-513631 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,513631#msg-513631
Link to Thingiverse



It can be improved but it works for now... i have now the same distance between nozle and plate all over the plate ;) (and it's adjustable).
]]> neolinux Smart_Rap Tue, 26 May 2015 04:22:33 -0400 https://reprap.org/forum/read.php?344,383028,512751#msg-512751 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,512751#msg-512751 madmike8 Smart_Rap Sat, 23 May 2015 23:42:19 -0400 https://reprap.org/forum/read.php?344,383028,512710#msg-512710 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,512710#msg-512710
Find the following code in Marlin_main.cpp, which should be around line 800:

    plan_bed_level_matrix = matrix_3x3::create_look_at(planeNormal);

Actually, there should be two such lines, one in the function set_bed_level_equation_lsq() that you use for bed autotramming with the grid of points, the other one in the function set_bed_level_equation_3pts() that you use for the procedure with just 3 points. Depending on which procedure you use (or both if you use them both), add this code *immediately*after* the line that you just found:

    plan_bed_level_matrix.matrix[6] += XZ_SHEAR;
    plan_bed_level_matrix.matrix[7] += YZ_SHEAR;

Then print the attached calibration model [attachment 55193 calibration_xyz.stl] or [attachment 55194 calibration_xyz.scad] for the parametric version, and measure the skewness for XZ and/or YZ with a (metric) square ruler and a ruler as shown in the attached picture.

[attachment 55196 shear.jpg]

You can see in the picture that the piece is not square: the angle is too wide so that at the end of the piece you have an error of about 2 millimeters. Do this measurement for both XZ and YZ, then open Configuration.h and find the following code, that should be around line 350: 

     #ifdef ENABLE_AUTO_BED_LEVELING

After that line, add the following lines of code:

      #define XZ_SHEAR      THE_MILLIMETERS_THAT_YOU_MEASURED_FOR_XZ_DIVIDED_BY_100
      #define YZ_SHEAR      THE_MILLIMETERS_THAT_YOU_MEASURED_FOR_YZ_DIVIDED_BY_100

Of course, you should replace the last part of the above instructions with what you measured before. So, supposing that in the picture I was measuring the error for XZ, to fix it I should add this line of code:

      #define XZ_SHEAR   0.02

You would have a negative sign there if the angle is acute instead of obtuse.

As I said, this is not a complete fix because the chord should be replaced with the angle, and the scale on the Z axis should also be adjusted. However the error is so small (some micrometers over a whole print) that nobody will notice (read: I was too lazy to add that too :) ).]]> cristian Smart_Rap Sat, 23 May 2015 19:57:44 -0400 https://reprap.org/forum/read.php?344,383028,512686#msg-512686 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,512686#msg-512686 madmike8 Smart_Rap Sat, 23 May 2015 18:04:14 -0400 https://reprap.org/forum/read.php?344,383028,512678#msg-512678 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,512678#msg-512678 cristian Smart_Rap Sat, 23 May 2015 17:43:14 -0400 https://reprap.org/forum/read.php?344,383028,387773#msg-387773 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,387773#msg-387773 Alignment ain’t a sin

I just happened to come across this video.

So alignment is a real feature and not just a thing to compensate 'inaccurate design'.

It's all about getting the best out of a machine.
Less is more. I agree, but in this case less hassle is more printing. :-)]]> BackEMF Smart_Rap Fri, 25 Jul 2014 21:32:37 -0400 https://reprap.org/forum/read.php?344,383028,386242#msg-386242 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,386242#msg-386242
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CellJeffe
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regpye
If the magnets are mounted on the bed plate, that plate would also have to be positioned in exactly the same place each time as well, or there will be bed crashes for sure.
I guess all of these things can be worked out.

Yes. The existing servoless Z enstop switch would probably need to be kept to sense head crashes. Of course an alternative would be a piezo-resistive sensor on one of the bed mounts (ala some of the Delta designs) to detect the head pushing on the plate. Luckily, the newer Z-axis floating mounts to the lead screw protect a little against tragic head crashes - so there is a little leeway. In other words, some existing method would be better to autolevel the plate before finding the skew.

Thinking about this a little further - It might also be easier and better for noise sensitivity to reverse the orientation. Put a magnet on the hot-end head and a couple of hall-effect sensors under the plate at two relative X positions. Hall sensors are quite cheap. Slide the bed back and forth along Y with the bed at one X position to find the best Y. Then slide the bed back and forth along Y with the head above the other hall sensor to find the proper Y at the other X position. You might even be able to mount two hall sensors on one of the Y arms - either the left or right side. One might also be able to integrate a piezo-resistive sensor into one of the Y axis glass attachment points and get rid of the sensors on the hot-end altogether. The problem with this arrangement would be insuring that the hall effect sensors lie along a line that is *exactly* perpendicular to the Y axis rods to make the measurement work.

I definitely agree with you that having perfectly aligned axes is ideal!

But I wrote the deskewing code because there was no way to get perfect axes with my skewed printed replacement parts. Some day soon I hope to have a backup printer... But designs are still in the works.

Another problem to think about is the false triggering of the Z sensor. How can we stop it triggering when the printer is in use? Maybe some additional code within Marlin to turn off the sensing after the bed has been probed?]]> regpye Smart_Rap Tue, 22 Jul 2014 00:54:47 -0400 https://reprap.org/forum/read.php?344,383028,386239#msg-386239 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,386239#msg-386239
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regpye
If the magnets are mounted on the bed plate, that plate would also have to be positioned in exactly the same place each time as well, or there will be bed crashes for sure.
I guess all of these things can be worked out.

Yes. The existing servoless Z enstop switch would probably need to be kept to sense head crashes. Of course an alternative would be a piezo-resistive sensor on one of the bed mounts (ala some of the Delta designs) to detect the head pushing on the plate. Luckily, the newer Z-axis floating mounts to the lead screw protect a little against tragic head crashes - so there is a little leeway. In other words, some existing method would be better to autolevel the plate before finding the skew.

Thinking about this a little further - It might also be easier and better for noise sensitivity to reverse the orientation. Put a magnet on the hot-end head and a couple of hall-effect sensors under the plate at two relative X positions. Hall sensors are quite cheap. Slide the bed back and forth along Y with the bed at one X position to find the best Y. Then slide the bed back and forth along Y with the head above the other hall sensor to find the proper Y at the other X position. You might even be able to mount two hall sensors on one of the Y arms - either the left or right side. One might also be able to integrate a piezo-resistive sensor into one of the Y axis glass attachment points and get rid of the sensors on the hot-end altogether. The problem with this arrangement would be insuring that the hall effect sensors lie along a line that is *exactly* perpendicular to the Y axis rods to make the measurement work.

I definitely agree with you that having perfectly aligned axes is ideal!

But I wrote the deskewing code because there was no way to get perfect axes with my skewed printed replacement parts. Some day soon I hope to have a backup printer... But designs are still in the works.]]> CellJeffe Smart_Rap Tue, 22 Jul 2014 00:28:38 -0400 https://reprap.org/forum/read.php?344,383028,386232#msg-386232 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,386232#msg-386232
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CellJeffe
I haven't looked to much at inductive sensors on an aluminum plate, but an arduino can easily drive a hall effect sensor. I am thinking about a hall effect sensor on the bottom of the head and three magnets glued to the underside of the glass plate such that they form a right angle. The sensor might be useful for both bed leveling and skew. Wave the head in XY over where the magnets ought to be to search for the peak signal. Use Gaussian interpolation to estimate the position and amplitude of the peak. The XY position of the peak would be used to calculate skew. If the glass plate is of uniform thickness, the amplitude of the peak signal should also tell you how far the head is above the plate to estimate Z. Potential problems could be the noise from the fan magnets, the metal hot-end heater block, the temperature curve of the hall sensor, etc.

I have been using hall effect sensors for a while on my other machines and they are very accurate. ( and cheap too)
To use for ABL and use magnets are you have mentioned, the probing would have to be very accurate too, so that the probe would land exactly over the magnet.
If the magnets are mounted on the bed plate, that plate would also have to be positioned in exactly the same place each time as well, or there will be bed crashes for sure.
I guess all of these things can be worked out.]]> regpye Smart_Rap Mon, 21 Jul 2014 23:43:05 -0400 https://reprap.org/forum/read.php?344,383028,386231#msg-386231 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,386231#msg-386231 CellJeffe Smart_Rap Mon, 21 Jul 2014 23:38:14 -0400 https://reprap.org/forum/read.php?344,383028,386220#msg-386220 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,386220#msg-386220
I prefer to build a machine that is perfect by default. Though even perfect machines can get wonkey when dragging them around. (in the back of a car, backpack etc.)
And i think it would be a great if you can just slap the thing on a table, hit print and just get a good print. Building a perfect printer is expensive, though this way even a low cost machine thats strapped together can just print.

Wait, i'm reading your reply several times and i'm feeling like i'm not 100% on the same page. (could be the heat...)

What i'm trying to say is: If the inductive sensor is next to the hotend then you can use it to detect the height as in auto bed level, but you can also scan over the alu bed and detect where the alu bed ends then you know edges of the alu plate and thus also the mis-alignment.

Now there are a few obstacles... for instance screws, iron has a different inductance then aluminium, so that can cause errors in the sensing values.]]> BackEMF Smart_Rap Mon, 21 Jul 2014 21:33:24 -0400 https://reprap.org/forum/read.php?344,383028,385754#msg-385754 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,385754#msg-385754
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BackEMF
@ CellJeffe

Serge was working on the inductive sensor., Now i'm not sure if my next idea will work but maybe if the inductive sensor is moved to the edge of the buildplate that it is possible to sense if the edge is "more" or "less" under the sensor. Or better detect all 4 edges off the plate.

[attachment 36929 sensor.png]
grey square = Alu plate
grey dots = Z axis
red dots = inductive sensor (attached to X axis)

After auto bedlevel we know where to expect induction, so when then moving over the edge then there will be no induction so thats the end of the bed. Since the alu plate is square then we know how skewed it is.
The only essential thing is then that the alu plate has to be 100 linear to the guiding rods, but that shouldn't be an issue.

The issue described can be easily fixed by using my separate Y axis and mechanically set it up square. The problem that needs to be overcome that I haven't worked out yet is to take your example and turn it around 90 degrees so that it shows the Z axis in relation to the X axis, at is the Z axis is vertical and the X axis running square to the Z axis. Y can easily be set, but the X is a little harder. Maybe this is where the software needs to come in?]]> regpye Smart_Rap Sun, 20 Jul 2014 22:29:42 -0400 https://reprap.org/forum/read.php?344,383028,385752#msg-385752 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,385752#msg-385752
Serge was working on the inductive sensor., Now i'm not sure if my next idea will work but maybe if the inductive sensor is moved to the edge of the buildplate that it is possible to sense if the edge is "more" or "less" under the sensor. Or better detect all 4 edges off the plate.

[attachment 36929 sensor.png]
grey square = Alu plate
grey dots = Z axis
red dots = inductive sensor (attached to X axis)

After auto bedlevel we know where to expect induction, so when then moving over the edge then there will be no induction so thats the end of the bed. Since the alu plate is square then we know how skewed it is.
The only essential thing is then that the alu plate has to be 100 linear to the guiding rods, but that shouldn't be an issue.]]> BackEMF Smart_Rap Sun, 20 Jul 2014 22:16:17 -0400 https://reprap.org/forum/read.php?344,383028,385344#msg-385344 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,385344#msg-385344
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CellJeffe
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cristian
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BackEMF
I think it would be great to be able to slap together 3 axis and hit the print button, let the machine figure out the wonkeyness and spit out a perfect print.
That woudl be great, but even after thinking about it for some time I cannot find ways to detect automatically skew. It may probably be detected without printing a calibration object by using some fanciful measurement method, but all the ways I can think about require at some point a measurement done by a human.
And let's not forget that the "simple" autoleveling procedure is not so neat for the smartrap, yet.

Hmm... How about semi-automated method using a reference object. Put a short plate with a good 90 degree angle on top of your existing bed plate, slide it up against the Z axis rods and tape it down. Lower the extruder until the Z endstop engages. Then slide off in one direction and make a note of where the extruder falls off the edge and the endstop disengages. Do this at four points to get the relative edges of the glass test plate. That gives you two vectors that are at right angles to each other. The difference between that and where the extruder thinks it slid off can be used to calculate the existing skew.

I would think about doing it, but I'm going to be away from my printer for a couple of weeks. And, I find the marlin code to be a bit... cobbled together.

[attachment 36882 AutoDeskew.jpg]

If the Z axis and the Y axis are separated, like my last version, then it wouldn't be too hard to make the Z axis adjustable with reference to the Y axis.(or make the Y axis adjustable to the Z axis, same difference)
It would be possible to have a mounting bolt that the Z axis can swing on and then using a good square, line up the Y axis and put in the second or third (or more if needed) mounting bolts for the Z axis.
That way you will have the machine mechanically square in those two axis. I actually had to do that when I assembled my machine. I mounted the Z axis first and then eye-balled the Y axis to put in the first mounting screw, and then used a square to line up the Z rods to the Y rods and put in the other three screws. The separated Y axis makes this quite easy to do.
Maybe something could also be worked out for setting the Y and X axis in a similar way? I will have to think about that one.
The closer we can get the machines squared up, the easier it will be for auto bed leveling too, and better prints as well.]]> regpye Smart_Rap Sat, 19 Jul 2014 18:40:04 -0400 https://reprap.org/forum/read.php?344,383028,385341#msg-385341 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,385341#msg-385341
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cristian
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BackEMF
I think it would be great to be able to slap together 3 axis and hit the print button, let the machine figure out the wonkeyness and spit out a perfect print.
That woudl be great, but even after thinking about it for some time I cannot find ways to detect automatically skew. It may probably be detected without printing a calibration object by using some fanciful measurement method, but all the ways I can think about require at some point a measurement done by a human.
And let's not forget that the "simple" autoleveling procedure is not so neat for the smartrap, yet.

Hmm... How about semi-automated method using a reference object. Put a short plate with a good 90 degree angle on top of your existing bed plate, slide it up against the Z axis rods and tape it down. Lower the extruder until the Z endstop engages. Then slide off in one direction and make a note of where the extruder falls off the edge and the endstop disengages. Do this at four points to get the relative edges of the glass test plate. That gives you two vectors that are at right angles to each other. The difference between that and where the extruder thinks it slid off can be used to calculate the existing skew.

I would think about doing it, but I'm going to be away from my printer for a couple of weeks. And, I find the marlin code to be a bit... cobbled together.

[attachment 36882 AutoDeskew.jpg]]]> CellJeffe Smart_Rap Sat, 19 Jul 2014 18:10:13 -0400 https://reprap.org/forum/read.php?344,383028,385105#msg-385105 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,385105#msg-385105
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BackEMF
I do understand why some people would bounce it on 'bad hardware design'

The "bad hardware design" (I would rather say that Smartrap is young and on its way to evolve) is true, still I do not see how it justifies that "hardware problems shouldn't be recovered by software".

Actually I would like to have both a better hardware design where skewness (and other minor problems) can be at 95% (or up to "eye" and "hand" precision) removed by manual tuning, and the remaining part corrected by software if one needs super-high precision.

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BackEMF
I think it would be great to be able to slap together 3 axis and hit the print button, let the machine figure out the wonkeyness and spit out a perfect print.

That woudl be great, but even after thinking about it for some time I cannot find ways to detect automatically skew. It may probably be detected without printing a calibration object by using some fanciful measurement method, but all the ways I can think about require at some point a measurement done by a human.

And let's not forget that the "simple" autoleveling procedure is not so neat for the smartrap, yet.]]> cristian Smart_Rap Sat, 19 Jul 2014 03:23:06 -0400 https://reprap.org/forum/read.php?344,383028,385016#msg-385016 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,385016#msg-385016
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BackEMF
I do understand why some people would bounce it on 'bad hardware design' though i also see the advantages of having clever software solutions.

And since autolevel already exists and the addition of this skew correction looks like it is only a small extra addition i don't see why it shouldn't be included.
Actually it would be great if this somehow could be included IN the autolevel procedure.

Pitty that the guys at marlins github don't see the advantage in this yet. I think it would be great to be able to slap together 3 axis and hit the print button, let the machine figure out the wonkeyness and spit out a perfect print.

I agree, we can't have enough options available, more the better.]]> regpye Smart_Rap Fri, 18 Jul 2014 17:02:16 -0400 https://reprap.org/forum/read.php?344,383028,384848#msg-384848 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384848#msg-384848
And since autolevel already exists and the addition of this skew correction looks like it is only a small extra addition i don't see why it shouldn't be included.
Actually it would be great if this somehow could be included IN the autolevel procedure.

Pitty that the guys at marlins github don't see the advantage in this yet. I think it would be great to be able to slap together 3 axis and hit the print button, let the machine figure out the wonkeyness and spit out a perfect print.]]> BackEMF Smart_Rap Fri, 18 Jul 2014 09:19:04 -0400 https://reprap.org/forum/read.php?344,383028,384719#msg-384719 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384719#msg-384719 http://forums.reprap.org/read.php?344,383743. I dropped auto bed leveling since it wasn't perfect for me. I added manual bed leveling and Z homing with hot end tip probing and I had very reliable prints since then.]]> ldanut Smart_Rap Fri, 18 Jul 2014 04:32:50 -0400 https://reprap.org/forum/read.php?344,383028,384311#msg-384311 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384311#msg-384311
seriously, i'm very curious about it .. but i'm sure it will run very good. It's nice design , no doubt]]> smartfriendz Smart_Rap Thu, 17 Jul 2014 08:50:41 -0400 https://reprap.org/forum/read.php?344,383028,384306#msg-384306 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384306#msg-384306
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smartfriendz
I can't tell why it's not in marlin, I've asked there on github but people just laughed at me ?!?! . I've been said that " A hardware problem shouldn't be recovered by software .. you must do a better design ! period. Your smartrap is not that smart :P "
Then i asked why all the reprap developers where running after auto level, which IS a software recover from bad hardware design ? ..no answer :( .

Indeed such an answer is totally illogical and contradictory, as you pointed out. It is only justified by some laziness or narrow-mindedness. There is no reason why software should not recover something, as long as it is an optional procedure that one may or may not apply. Moreover, nowhere is written that all the printers must have orthogonal axes by design...

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regpye
Still working on this model, not had time to wire it up yet and test.

Looking forward to watching it moving!]]> cristian Smart_Rap Thu, 17 Jul 2014 08:46:54 -0400 https://reprap.org/forum/read.php?344,383028,384296#msg-384296 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384296#msg-384296
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smartfriendz
Hi Christian,

Thank you for those feedback. I can only agree with all that :)

About the Z , I think that making a triangle would be the best too, with maybe two threaded rods going on the back , behind the steppers and attached on the top. That would make a solid triangle reducing the flexibility of those two smooth rods. It is that or using M12 smooth rods like in the ptrintrbot simple. I would choose triangle structure personally. i started a design about that . i will maybe put it here to think about :)

About the wobble, with the last system , i had very good result ? The support need to be maybe adjusted under the Plate_x to be free ( with a little grease under ). My M5 threaded rod is shaking like crazy now , but all the wobble goes into this support, not on the plate.

About the GT2, it just works well and i choose to use them for assembly easiness for the commercial kits. Especially the aluminiums pinions . Maybe it could change in the future . I had indeed very good result with fishing line, but it needs to be very straight , and we need to fin the good one. Too small an it brakes..too big and it's not so accurate anymore :( .

I love the rack&pinions too, i have one machine in production with it and it works like a charm. I add some vaseline on it and it's very smooth. The problem here is to adjust very precise because if too large, you will have backslash , and too tight, it will make waves on the printed parts. I would easy go back to r&p with a better design, more adjustable. And maybe without the long threaded rods inside. I think it's possible to have just racks printed and attached to both ends.
For the Y, we are maybe going to switch to aluminium plate because of a new auto level system using proximity sensors inductive ( so , metal needed). In that case, we could rework the Y ends and racks so we can fix it directly on the aluminium plate.. maybe.. it's just ideas :)

I would love to have an all printed structure one day . Not because it's better than other solutions, but because it's just sooo reproductive without human intervention ( click : print ! ) and because it's the only way i know to have community interactive design ( everyone model and test on its own printer in almost real time ). Canot be practically done with other technologies actually.

But let's work on the Z reinforcement for now ? I'm working on it in spare time lately ( with the auto level too, as it's very important to have one without touching the bed..with the Smartrap's design).

Still working on this model, not had time to wire it up yet and test.



















]]> regpye Smart_Rap Thu, 17 Jul 2014 08:32:23 -0400 https://reprap.org/forum/read.php?344,383028,384278#msg-384278 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384278#msg-384278
I can't tell why it's not in marlin, I've asked there on github but people just laughed at me ?!?! . I've been said that " A hardware problem shouldn't be recovered by software .. you must do a better design ! period. Your smartrap is not that smart :P "
Then i asked why all the reprap developers where running after auto level, which IS a software recover from bad hardware design ? ..no answer :( .]]> smartfriendz Smart_Rap Thu, 17 Jul 2014 07:49:46 -0400 https://reprap.org/forum/read.php?344,383028,384251#msg-384251 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,384251#msg-384251
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cristian
It will detect correctly the Y-Z skew I think

Actually this is false. If the plate is perfectly parallel to the Y rods, the auto-leveling procedure will not detect any skew, even if there might be some.

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CellJeffe
If there is Z skew, it shouldn't be too hard to come up with a correction matrix to adjust it! There are just several possible skew matrices - depending on the skew plane. We could probably get away with an XZ skew or YZ skew matrix in addition to the XY skew matrix if it comes to that. I should probably update the vector3x3 code to formally do matrix multiplication, but then I would be very tempted to convert it to a 4x4 affine transformation matrix.

Yes I think we will need some general approach which can handle any skew on XY, ZY and ZX. The affine transform may be even too general, unless one wants to put there all the transformations including the auto-leveling and length adjustments, which in the end may even be a very good idea, much cleaner than it is now...

Are you going to add it to smartrap marlin firmware, CellJeffe? To tell the truth I do not undestand why the authors did not put already something like that in the original marlin.]]> cristian Smart_Rap Thu, 17 Jul 2014 06:40:23 -0400 https://reprap.org/forum/read.php?344,383028,383582#msg-383582 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,383582#msg-383582 Very nice addition, i wonder if there is a way to auto adjust this.]]> BackEMF Smart_Rap Tue, 15 Jul 2014 23:22:11 -0400 https://reprap.org/forum/read.php?344,383028,383574#msg-383574 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,383574#msg-383574
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Lukashuk
And what if in the bed center depth is 1 mm? The detail top too will be with a hole? Or gradual alignment? Or back? ! ! ! NO! ! ! the hole will be! ! ! It is better to level a bed hands of 1 times in 1 month.
forgive for my English

If I understand what you are meaning, that the centre (Australian spelling) of the bed has a hollow that is 1mm lower than the outside edges, then yes you will start with a low point in the middle that would make it very hard to do a print at all. The print may not attach to the bed properly in that case. If however the first layer does attach, the following layers would soon level out and after maybe three layers the print would now continue as normal. The bottom of the pint however would have a bulge that would be very slight, depending on the size of the print base.]]> regpye Smart_Rap Tue, 15 Jul 2014 22:20:44 -0400 https://reprap.org/forum/read.php?344,383028,383573#msg-383573 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,383573#msg-383573
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Lukashuk
And what if in the bed center depth is 1 mm? The detail top too will be with a hole? Or gradual alignment? Or back? ! ! ! NO! ! ! the hole will be! ! ! It is better to level a bed hands of 1 times in 1 month.
forgive for my English

If you can manually level the bed as best you can do it will remove a lot of the additional movement made from the auto bed leveling adjustment. This will reduce wear and tear on the machine and also reduce additional actions by the machine which is what we all should be aiming for.
Auto bed leveling was originally designed to remove the hand leveling operation which is a bit of a pain, but now maybe it is good to do it at least once when doing the initial build to make the machine as accurate as possible.]]> regpye Smart_Rap Tue, 15 Jul 2014 22:13:15 -0400 https://reprap.org/forum/read.php?344,383028,383572#msg-383572 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,383572#msg-383572
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madmike8
My z stepper/threaded rod connector had broke, so I tried the fish aquarium air hose mod that someone suggested. It worked great, but also had the benefit of cleaning up the z wobble.

The wobble of the threaded rod doesn't matter a hoot.
If the top end of the threaded rod is left to wobble it will reduce or even eliminate the Z wobble at the print because the rod is able to move instead of transferring the movement to the printhead.
I know it looks bad if the Z thread is wobbling, but actually it is a good thing.
If you can straighten the rod and remove the wobble that way it is better, but leave the top end of the threaded rod free to wobble if it must.

Biggest mistake of all is to add a bearing at the top of the Z thread, all that does is transfer all the load from any wobble to the printhead via the X axis]]> regpye Smart_Rap Tue, 15 Jul 2014 22:09:00 -0400 https://reprap.org/forum/read.php?344,383028,383511#msg-383511 Re: How precise can your Smartrap print? - Alignment issues https://reprap.org/forum/read.php?344,383028,383511#msg-383511
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cristian
It seems to me that the autolevel matrix cannot detect everything. It will detect correctly the Y-Z skew I think, however for the X-Z skew the autolevel will only correct the difference of skew between the bed and the X/Z rods. Of course the X/Z rods skew should be negligible unless the plate_x is faulty. Nevertheless I would like to measure it to be sure.

If there is Z skew, it shouldn't be too hard to come up with a correction matrix to adjust it! There are just several possible skew matrices - depending on the skew plane. We could probably get away with an XZ skew or YZ skew matrix in addition to the XY skew matrix if it comes to that. I should probably update the vector3x3 code to formally do matrix multiplication, but then I would be very tempted to convert it to a 4x4 affine transformation matrix. I have been avoiding merging my marlin codebase with the smartrap github. I'm slowly learning git since I have worked primarily with subverion in the past. Hmm.. Maybe I should ask smartfriendz nicely for push request permission on the marlin autolevel folder... :)

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cristian
It is very important indeed to have this software calibration to allow a correct evolution of the "Smartrap species": otherwise, after every generation of Smartraps the precision of the printed parts would quickly degrade and the new born Smartraps would not be able to procreate :)

Yes. That was why I went in with the skew correction. I printed upgraded plastic for my smartrap, then went to upgrade again only to find that my original upgraded parts introduced a skew into everything :X. There was no way to go backwards to a rigid system since I had cracked a couple of the original parts. I also had to go back from rack-and-pinion to string because of the warping. I had too much GT2 belt slippage over the tension bearing to go back to the belt drive. But, I discovered that GT2 pulleys work well enough with string. The string kept slipping off of my bare, short motor shafts.

My smartrap has been busy printing test pieces for some other ideas, but eventually I will switch back to de-skewed 0.4.9 parts and a reprinted rack-and-pinion.]]> CellJeffe Smart_Rap Tue, 15 Jul 2014 17:05:36 -0400