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Then I'd redo the bed calibration and print a big circle, say 100 mm diameter, you only care about the first layer, you're looking to see if the first layer has consistent thickness.

Ok, I have checked the Z height and all the axis several times. Short of measuring the amount of force required to pull the piece of paper not sure what to do. It seems right to me.

I took you suggestion regarding the large circle and this is how it turned out. You can the the z axis for reference. Hopefully this makes sense to somebody.

You need to recalibrate the 3 points on the bed, Note how the extrusion is thinner mostly towards the bottom tight, that tower is lower than the others, infact the top tower is also slightly lower than the bottom left tower.
Try visualizing a disk which is the plane the head is moving in, it's tilted relative to the bed, adjusting the screws corrects that.
You're probably off by 0.3mm at a guess, they need to be within 0.1mm of each other, ideally better than that, the paper needs to "feel" the same under each of the 3 locations I find a feeler gauge a bit easier to deal with.

0.3mm??? I don’t think so, I have done the bed leveling several times. Maybe a belt is slipping or something but at the time I am done with the leveling everything is fine. I test the 3 locations as well as several others and I get the same "tension" on the paper tug test. I then immediately go to print and I get this.

I did not have the time last night to reprint the concentric circles to test the repeatability of the results. I hope to do that this evening.

When you did the leveling procedure did you have your heated bed at temperature? What is your build surface under the tape? Each can have an impact on consistency of prints along with belt tension and backlash.

I had my heat bed and hot end heated up. Using glass

If you are absolutely certain that the 3 points are in a plane equidistant from the bed, then a missed step, or a belt slipping will cause that plane to offset.
The most common cause for this is the head dragging on the bed, if this is the case I'd expect you to see it happen, it would be the result of the Zoffset being set too high, if this is happening repeatedly it can damage the belts.

@aerouta Have you taken a straight edge and measured your glass print surface to ensure no warping is happening? Doubt it, but always good to check!

I use a piece of paper as my 'feeler' and ensure the "grip" is the same when testing right in front of each rail (IE, for the z rail I would send the command G1 Z0 Y110 F2000)

Warping is a major PITA for every reprap 3d printer, not just this one. But there are several helpful tools built into slicing software. I prefer to add 'brims' to all my prints (3 or 4mm is sufficient usually). But with the Slic3r 0.9.9, you can now add rafts - Rafts help build up a few layers before the actual print starts.

But I agree with everyone else here, it looks like you need to re-calibrate the adjustment screws for the endstops. I'm experiencing a similar issue currently, but my issue is caused by a warped aluminum print bed, need to get a piece of glass to put on top.

Alright, I will tighten up the belts, ensure no dragging occurs, and re check the z height. Just to be clear, the max height setting on the individual axis do not need to be changed in the config file, just the z_home, right? Also how can you determine if you have missed steps?

aerouta wrote:Alright, I will tighten up the belts, ensure no dragging occurs, and re check the z height. Just to be clear, the max height setting on the individual axis do not need to be changed in the config file, just the z_home, right? Also how can you determine if you have missed steps?

I personally did not adjust the max height setting whatsoever. I left it as it came in the configuration files. I also didn't edit the Z_home position. I use my adjustment screws on each skate to adjust my height precisely on each rail (Turn right to raise, Left to lower the skate).

I knew I had my microsteps set wrong when I sent the command G1 Z5 F2000 and my carriage stopped halfway down (I could never get anywhere near the print surface when I would home and send Z0). Once I fixed my steps per mm in the eeprom, I could reach the bed with no issue (Don't try G1 Z0 F2000 if you haven't before! You risk slamming your nozzle into the bed! Start with G1 Z5 F2000 and lower down 1mm at a time). For my extruder, I simply used a sharpie and made 2 marks, 1 where my filament entered the extruder, and another mark 50mm down. I then extruded 50mm. Of course I could tell right away I had the steps per mm wrong!

As far as "Missed" steps - don't know, never had that issue, my belts were tight enough and the pulleys were tight the first time I built it, haven't had any real issues yet

Just spent the last 4 hours working on bed leveling. I still get the same pattern. Not sure how to fix it. Can someone explain "missing steps"

Do you still have the same pattern of thin by the Y tower?

aerouta wrote:Just spent the last 4 hours working on bed leveling. I still get the same pattern. Not sure how to fix it. Can someone explain "missing steps"

If there is too much mechanical resistance for an axis, or insufficient current from the stepper driver, then a motor can fail to move forwards on every step, missing steps.
You can usually hear it happen, but if you don't know what you are listening for it's not obvious.
The drivers can also overheat and cause the same issue.

But the primary reason you might see this is if the head hits the bed during a move, increasing the amount of force required to move the head as commanded, it looks like at least one of the areas in your print is low enough this could be happening.

Have you tried just adjusting the screws based on the printed ring instead of trying to measure?
There are several factors that make measuring accurately difficult, the most obvious being that the values reported value in repetier host is not accurate, you must use M114 to get the extruder position. And if you hit the bed while measuring even that can be wrong.
What I'm suggesting is on the tower where the ring is thinnest turn the adjustment screw clockwise say 1/4 turn, home and reprint.

mhackney wrote:Do you still have the same pattern of thin by the Y tower?

yes I do.


Why bother with checking the z height at (0,0,0). It does not seem like this value is independent of the x,y,z rails? Or am I missing something.

Polygonhell wrote:

aerouta wrote:Just spent the last 4 hours working on bed leveling. I still get the same pattern. Not sure how to fix it. Can someone explain "missing steps"

Have you tried just adjusting the screws based on the printed ring instead of trying to measure?
There are several factors that make measuring accurately difficult, the most obvious being that the values reported value in repetier host is not accurate, you must use M114 to get the extruder position. And if you hit the bed while measuring even that can be wrong.
What I'm suggesting is on the tower where the ring is thinnest turn the adjustment screw clockwise say 1/4 turn, home and reprint.

Yes no luck.

I am beginning to wonder if its not a belt or loose pulley.

slipping pulley is possible. I ground a flat into my stepper shafts http://forum.seemecnc.com/viewtopic.php ... 8&start=10
once you tighten the screw against the flat of the shaft. It doesn't give any room for the pulley to slip.

In the illustration below you can see how the flat on the shaft keeps pulley from slipping. The screw locks the pulley onto the shaft preventing it from slipping under load. crude drawing i know.

This was my thought to. Perhaps a slipping pulley on the stepper shaft.

I also filed a flat onto the shaft for the pulley. Then threadlocked it for good measure.

aerouta wrote:

mhackney wrote:Do you still have the same pattern of thin by the Y tower?

yes I do.


Why bother with checking the z height at (0,0,0). It does not seem like this value is independent of the x,y,z rails? Or am I missing something.

Because there are 2 parts to calibration, the first ensures that any circle around the center of the bed is colinear with the bed, the second involves changing the DELTA_RADIUS value in the firmware to remove any doming of the motion. The doming can be quite significant.

Quick question when you calibrate do you always visit the 3 corner positions in the same order, if you visit them in the opposite order do you get the same values?

aerouta wrote:

Polygonhell wrote:

aerouta wrote:Just spent the last 4 hours working on bed leveling. I still get the same pattern. Not sure how to fix it. Can someone explain "missing steps"

Have you tried just adjusting the screws based on the printed ring instead of trying to measure?
There are several factors that make measuring accurately difficult, the most obvious being that the values reported value in repetier host is not accurate, you must use M114 to get the extruder position. And if you hit the bed while measuring even that can be wrong.
What I'm suggesting is on the tower where the ring is thinnest turn the adjustment screw clockwise say 1/4 turn, home and reprint.

Yes no luck.

I am beginning to wonder if its not a belt or loose pulley.

OK I'd adjusting the screw is not affecting the error, you likely have a significant mechanical issue somewhere, when you adjust the screws and home you're changing the offset of that tower, if it doesn't change there is something odd going on.

Polygonhell wrote: OK I'd adjusting the screw is not affecting the error, you likely have a significant mechanical issue somewhere, when you adjust the screws and home you're changing the offset of that tower, if it doesn't change there is something odd going on.

Turning the screw as an effect on the height. It's just that after leveling my test prints still shows errors.

Polygonhell wrote:

aerouta wrote:

mhackney wrote:Do you still have the same pattern of thin by the Y tower?

yes I do.


Why bother with checking the z height at (0,0,0). It does not seem like this value is independent of the x,y,z rails? Or am I missing something.

Because there are 2 parts to calibration, the first ensures that any circle around the center of the bed is colinear with the bed, the second involves changing the DELTA_RADIUS value in the firmware to remove any doming of the motion. The doming can be quite significant.

Quick question when you calibrate do you always visit the 3 corner positions in the same order, if you visit them in the opposite order do you get the same values?

Well, I have not kept track of the order. But I'm sure I have done both.

Someone mentioned the glass plate. I rotated the glass plate and got the same results, i.e. glass seems fine.

Polygonhell, if you could explain what you are saying further it would be helpful. Also, you mentioned collinear but is the issue here not coplanarity? But here is what I understand, and I could be wrong. 3 points make a plane, 4 points is overdetermined or over constrained. The calibration steps say to adjust the z_home and screws for (0,0). And then it says to go to the 3 towers and adjust it's respective screw to match the results at (0,0). But in reality, making adjustments to any screw changes the height at (0,0). It may be small but it changes. The change becomes more significant if you need to adjust more than one tower in the same direction. If this is the case, would it not make more sense to first adjust the 3 towers and then verify at (0,0).

You mentioned doming and DELTA_RADIUS. This is the first time I am hearing of both of these terms. Can you unpack these concepts some more?

Sorry I meant coplanar not colinear, obviously I was very 2D last night.
Basically on a Rostock like design motion is not linear, since move requests are linear the firmware corrects for this, but it depends on having an accurate model of the geometry. The only dimensions that actually matter are the length of the arms and planar distance between the pivot points when the platform is in the middle, the later is referred to in the firmware as DELTA_RADIUS, if it's off even by fractions of a millimeter it introduces doming into the motion (either up or down). Given the manufacturing and assembly tolerances, any effective calibration has to modify it.

I would recommend following this setup guide, rather than the one in the manual http://minow.blogspot.com.au/ there is some discussion on the board and a more or less equivalent calibration guide here http://forum.seemecnc.com/viewtopic.php ... DIUS#p5692 .

Initially setting Z at 0,0,0 at irrelevant, since you have to set it a the very end anyway, all it does is get you in the ballpark.

Polygonhell wrote:Sorry I meant coplanar not colinear, obviously I was very 2D last night.
Basically on a Rostock like design motion is not linear, since move requests are linear the firmware corrects for this, but it depends on having an accurate model of the geometry. The only dimensions that actually matter are the length of the arms and planar distance between the pivot points when the platform is in the middle, the later is referred to in the firmware as DELTA_RADIUS, if it's off even by fractions of a millimeter it introduces doming into the motion (either up or down). Given the manufacturing and assembly tolerances, any effective calibration has to modify it.

I would recommend following this setup guide, rather than the one in the manual http://minow.blogspot.com.au/ there is some discussion on the board and a more or less equivalent calibration guide here http://forum.seemecnc.com/viewtopic.php ... DIUS#p5692 .

Initially setting Z at 0,0,0 at irrelevant, since you have to set it a the very end anyway, all it does is get you in the ballpark.

Thanks for the info!!! Following the procedures in the link now.

So I have noticed that ever so often when I home in my axis I get this pulsation in all the axis. It seems to follow any high speed commands. But it is not very repeatable. I have included a video that captures this.

http://youtu.be/9tU5tS7eo2k

Any clue what this is?

Assuming you don't hear the steppers missing when it happens and assuming you are probably running Marlin firmware though mine never did it that badly (usually only one or 2 pauses when homing) it's a side effect of Johan's hack to get the rostock geometry working in Marlin.

What I think it is and it's hard to know for sure..
When you give a linear move to the firmware, that translates to a quadratic move by the carriages, the firmware doesn't handle this natively and there is a hack on the frontend where it breaks the motion down into a large number of linear segments this floods the planning buffer and I think under some fairly repeatable conditions the motion interrupts interplay with the large number of small segments being pushed into the planner causes the motion to run faster than the planner or the motion buffer to starve resulting in the pauses you see.
The 16MHz ATMega on the RAMBO board isn't exactly the fastest uController in the world.
Repetier will also do it, but much less frequently and I've neer seen it while homing