Calibration square assistance, height is too short

Hey Steve,

The biggest issue I've run across with this print is stringing. Thus far I haven't been able to crack the code when it comes to changing print locations without leaving an artifact behind or introducing one to the new site. This problem isn't isolated to this complicated lamp shade build either.

The problem is likely a mixture of temperature and retraction - retraction is likely the larger problem. If I posted a picture and my entire base of settings would you be open to giving them an evaluation?

 

Is the stringing so thick that it can't be wiped off? Some of my filament gives fine stringing on a print like that but it can be removed and does not leave artifacts.

Here are my retraction settings (for Slic3r).
Length: 1.5
Lift Z: 1
Speed: 30
Extra length on restart: 0
Minimum travel after retraction: 2
Retract on layer change: Yes

The temperature settings are going to be specific to the filament.

 

Those settings are very close to my own. Once my current print completes I'll run a test and share the results.

 

Hey folks, the latest MatterControl update rolled by my "steps per mm (z)" fix for stock metric rods. Take a look if your Z heights are coming out bad post update.

Cheers

 

Hi everybody, noob user with brand new Robo3d R1 here (two weeks).
I think something is very wrong with my printer since the calibration ring came out like an egg, the Z-axis are off to, how can i fix this?
I´m using Mattercontrol 1.1.7.2932 with no tweaks or modifications, printing PLA.

Regards,

Mattias

 

Which dimension is incorrect? X or Y? How much is Z off? If you print is twice are the errors the same?

 

The X dimension came out 160 and should be 140, the y dimension seems correct.
I don´t know how much Z is off, i have to print something tonight and measure.
The error seems to get larger when printing big prints, seems like a pitch error.
And yes, the error is in the same direction everytime i print.

The EEPROM-settings are 80,80 and 2560

 

OK this is strange. Can't tell what is going on from the photo, we would need to get a clearer top view of the oval (not at an angle). Just is case I suggest that you check the set screw on the X stepper pulley. This does not make sense though because any slipping would make the X dimension smaller not larger.

Are you sure that you did not accidentally scale up the X axis in your host program or slicer? Or perhaps Robo3D changed the diameter of the X stepper pulley without changing the firmware. Just reaching here...

 

Ok, new test print...

Y and Z is very accurate, just 0.05 mm off.

Y is 99.95, Z is 15.05 between two levels which are 15.00 in the model.
X should measure 100, turned out 116.1...

The computer is new with a fresh install of Matter control, so i don´t think i have scaled anything wrong in the software, i´m guessing something must be wrong with the pitch in the X axis.
I have noticed a strange thing, after the auto leveling program starts and the machine touches the home switch for the X-axis it goes all the way and crashes into the right side.
I think that this is evidence that the scaling of the x-axis is wrong, or what do you think?

 

Again very strange. Can you count the teeth on your X pulley? Mine has 20. The pulley should have a 2mm pitch. So that's 2mm x 20 = 40mm/revolution. The stepper has 200 x 16 = 3200 microsteps/revolution. So (3200 microsteps/rev)/(40mm/rev) = 80 microsteps/mm. There is nothing else that could cause it to be 16% high unless that 80 not in the firmware or the stl file or gcode are wrong. Are you absolutely sure that you have 80 micro
steps/mm in the configuration.h file that was used to build your firmware? Sounds like you are using some host command like M501 to read back the EEPROM.

Perhaps you can try to temporally override whatever is in there with M92 X80.
http://reprap.org/wiki/G-code:

M92: Set axis_steps_per_unit
Example: M92 X<newsteps> Sprinter and Marlin
Allows programming of steps per unit of axis till the electronics are reset for the specified axis. Very useful for calibration.​

You can also just use your host program to move the carriage in the X dimension 100mm and measure to see if you get 100mm. That will eliminate the gcode as being the problem if it comes out to 116mm.

 

Ok, so i measured the 100mm move, it moved 116mm...

I changed the EEPROM settings from 80 to 68.96 steps/mm, a quick test print of the calibration circle showed that it helped!
Thanks for the help!

Is this the best way to correct the error or should i change something else?

/Mattias

 

I guess it works but it is really strange problem. If you have a 2mm pitch, 20 tooth pulley then it must be an issue in the firmware or a constant somewhere right? It would be nice to understand what is happening in case it has other side effects. I would rebuild and download the firmware.

 

Steve and Yamattias; I've been going through vast explorations of calibrating, ribbing, etc. of late and found that my Z steps were off by a fair amount. What is more odd about this is that my measured percentages worked out to ~771 steps (from 723.38) but my actual correction has come in ~756. mine is a beta ROBO, so the actual numbers may be much different than later ones but things are now dimensional on all the calibration cubes, pyramids, etc. Now I'm trying out different temp and speed settings to really get dialed in. Though things are improving, and it is actually doing well, I still get frustrated with all of the variables that don't always seem to remain constant. Belt tension is a real bugaboo for me on the x carriage. I add anything beyond a dull thud and things get messy - contrary to many people's experience here and with other machines as well. I'm thinking about adding two additional guide rails for the x carriage on the front side of the machine for greater support/stability. Or will that add a greater degree of error if it all works without that extra support? I have gotten great prints many, many times with the standard configuration but it doesn't seem to remain stable long enough to really trust.

 

Sorry I probably am missing something in understanding a lot of what you wrote.

First you mention Z steps are off, then you mention ~771 , 723.28 and 756 steps? What do those numbers mean? I know the firmware has E (for extruder) steps/mm around 760 or so. Are you talking about E steps/mm or something else? The E value really depends on the diameter of your particular hobbed bolt and and should be calibrated for.

If you never changed your firmware to the March or February version (http://forums.robo3dprinter.com/index.php?forums/official-documentation.14/) then I know that X, Y steps/mm constants in the configuration.h file were off. I forget about Z value though.

The values for the kickstarter version should be this (other than the 4th value the E steps/mm which depends on your machine):

#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,2267.72,753} // default steps per unit for RoBo 3D R1
(those numbers above in order are {X, Y, Z ,E} microsteps per millimeter)
​

Your Z steps/mm should be 2267.72 It is an exact calculation (with some rounding) with no calibration possible. I understand that the latest shipping printers use metric Z threaded rods so that third constant will change for them.

That 4th number, 753 is the E steps/mm and was calibrated for my particular hobbed bolt.

I've had no problem with the X belt tension. I have had the stepper pulley set screw loosen and the bolt holding the idler bearing on the other side loosen. Is your X stepper skipping? Perhaps you need to adjust the stepper driver current. A link to the procedure for setting it was posted somewhere here many times. (edit here http://bootsindustries.com/portfolio-item/pots-adjustments/ ) I don't understand "two extra guide rails for the X carriage on the front side". Are you thinking of two more horizontal rails? That really seems like it will add a lot of friction and will not work at all. (are you talking about Z axis rails? Do you have Z stabilizers?)

 

My apologies to everyone I thoroughly confused. I was rushing and half asleep and I did indeed, F-up. The numbers I quoted were e-steps as you noted, Steve. Now then, the z-steps may indeed be a calculated number with no calibration needed, but in order to get a full height on variously sized calibration cubes, I needed to change the z-steps from 2267.72 to 2582.8 (8mm screws). It is working consistently well so maybe it won't ever need changing again.
As to the x belt, I get random layers just slightly out of form or, sometimes, the ribbing problem but it isn't necessarily consistent with a matching z-screw thread pattern. If I increase the tension at all, I get a ribbing pattern, consistently. With no added tension it works fairly well, but is not anywhere near a "dull twang"; no, it's a "thud". So, my thinking is that increasing the tension doesn't result in tighter tolerances but instead highlights an inherent lack of stability in the basic ROBO frame configuration. If so, would adding vertical guide rods attached to the x carriage at the front of the frame (just like the rear ones), in line with current z rods help increase strength/stability (see pic). Also, something I am going to try today, stabilizing the rear guide rods by rigidly joining them horizontally across the top. If everything is square, there should be no added binding.
Yes, I have the stronger guide rod mounts. Yes, I have a 3mm bearing at the bottom of the 8mm screws. Yes, everything, including pulley set screws, is tight. But if you put a little front to rear pressure on the x carriage, it will move a bit - maybe enough that too much belt tension would also cause it to follow the "dance" of the z screws. My z screws do not move around very much at all, but it is evident they do have some off axis movement. Perhaps, as Mike Kelly has explored, a stronger, squared frame will help to offset that, or, perhaps, just highlight it. That's what I need to find out....
Again, sorry for my confusing post last night. I hope this helps...

 

Hi 1d1,
No apologies needed. For the X random distortion issue - does the X carriage move smoothly? If not perhaps your linear bearings are bad. I would also check the stepper driver current as I mentioned above. If you manually move the X with your host program do you hear any skipping?

From above I understand that you do not have Z guide rail stabilizers, right? These stabilizers mount to the upper inside of the Robo3D case and hold the guide rail tops still. If you don't have them I would add them way before doing anything else like the horizontal connector. I think the horizontal connector will not do anything useful relative to the stabilizers. I think a second front set of Z guide rails will be a waste of time.

I printed my own Z stabilizers from a set modified from thingiverse and these make my X carriage rock solid. If I push the X carriage from the front I get no movement at all, none. There are a number of designs for this out there. I choose to make one that attaches to the sides with 3M double sided sticky tape and required no adjustment screws. I carefully measured from the Robo case side to the rails and modified the guides in Sketchup. The Robo case is really very stable and even with the double sided tape holding the guides I get no movement at all. Did I tell you that my X carriage has no movement at all? I enclosed the STLs for my supports below. I suggest you try these or a set from thingiverse before you do anything else. The right one includes a hanger for the wire harness. The rail holes may need filing to get them to fit exactly. I put them on without the tape and marked the corners on the case inside then took off the case and mounted them. There is a chance that your case has a different side to rail dimension than mine. If you want to try them and have trouble with the STLs being non-manifold let me know and I can fix them. I made them quite a while ago with an old version of sketchup.

My only problem with the X carriage is that the front bearing seems to have a lot of play such that I can torque the carriage a bit. I got new 8mm rails and bearings and will try swapping them out.

 

Yes, I just replaced all the linear bearings on the verticals. I do think that the key is stabilizing the z however, I've always printed "topless" due to so many issues along the way. It was just easier than disassembling all of the time. Perhaps I should try reinstalling it with the stabilizers. Now that I have printed everything I need printed and have got extra pieces to do the rest of my plan. Thanks for the files - I use netfabb for repairs so should be no problem on the non-manifold part.
Uh, let's leave this thread for its original purpose. Damn. Another unintentional hijack.

 

OK we will end this hijack. I think you will be surprised at how stable the Robo3Ds top case is. It makes a very good structure to support the Z axis.

 

Wanted to let you know, I had the same problem!
Purchased my unit from Amazon on May 16, 2015 and it came with the 8mm smooth rods.

Used the value you provided for the Z steps, and everything is great now!

Thanks!