# Specific 3D Printers, Scanners, & Hardware > RepRap Format Printer Forum > MakerFarm Forum >  so what causes this?

## sniffle

so i am printing a kossel mini set for a friend.  I am having some artifact on the base pieces around the lettering and i am not sure what is causing it.

here's a pic


the left hand side of the model is the base.

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## TopJimmyCooks

Usually called ringing.  it happens right after sharp turns like the 90 degree turn from the letter recess out to the face of the part.  Due to the Prusa's design not having a huge amount of rigidity in the Y direction.  Lower your acceleration rates to help with this.  printbus did a great write up of the several places you can set and change acceleration values.  2x in firmware and again in the slicing program IIRC.  Also, you can make a small improvement by  orienting the parts so the face with the worst ringing issues/best appearance needed is parallel to the X axis.

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## printbus

TJC beat me to it.  Sniffle, clarify how the X & Y axes are oriented when you print.  When I see ringing, it's usually on the side parallel to Y. Rereading TJC's post, I think he's saying the same thing. It's ringing because it fades away.  Also notice how the interval between the ringing pattern increases - this is because the printer is accelerating away from where the ringing started.  As it speeds up, the ripples will be farther apart. 

Fine and dandy. I personally think there are issues in Marlin move planning. 

A counter argument to ringing in this case is that we're not at a 90 turn.  At least not one where the axis was running full speed before decelerating to the corner.  My 90 degree corners come out pretty clean. Where I tend to always see ringing, and sometimes substantially, is on shallow artifacts like your lettering or on holes in relatively thin sidewalls.  In the case of your lettering, the print is moving along, stops at the recess created by a letter, shifts slightly perpendicular to the direction it was going, and then reverses direction.  At least that's what I've watched my printer do.  So, the ringing is supposed to be caused by that little bit it shifts for the depth of the letter recess? That's hard to buy.  

Same thing for holes on a thin sidewall.  Just yesterday I printed a small project box with a large hole on a 1.75mm thick sidewall, and got substantial ringing on one side of the hole.   The x carriage built up a lot of momentum crossing that 1.75mm sidewall?  The 90 degree corners came out far cleaner than the hole.  The inconsistency is what causes me to question what Marlin is doing. EDIT: It's almost like the X motor is being twitched during that turn-around in the Y axis - like Marlin is not starting the X movement out slow. The jerk setting should influence this, but again, 90 degree corners come out fine.   I really wish my oscilloscope had storage capability so that I could monitor what the driver signals look like for the X and Y motor where I see this ringing occurring. If nothing else, I may rotate that object and reprint it just to see what kind of ringing I get on the hole when it is parallel to X. With the aluminum v-rails on the i3v, I have a hard time understanding how the Y-axis is any less laterally rigid than the X-axis.     

If you want to experiment, the settings involved would be DEFAULT_XYJERK, DEFAULT_MAX_ACCELERATION for the axis perpendicular to the one where you see the ringing, and DEFAULT_ACCELERATION.  Details on how these interact are discussed in thread Marlin Motion Related Configuration.h Settings for MakerFarm i3v. It could also be argued that your belts are too loose. Others might argue too tight. Carriage wheels could be adjusted too loose.   

Hoping to hear other opinions on this.

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## TopJimmyCooks

Rigidity:  motion in the x axis is resisted by the primary square frame of composite wood in plane, which is super stiff in that direction.  In effect the stops and starts have something firm to push against.  In the Y direction the stops and starts are resisted by a very small piece of wood in the bendy direction especially at the front piece where the y idler attaches, hence more oscillation/ringing.  

If I'm right ringing might be reduced a good bit by stiffening that y idler mounting piece.  I need to test that.  I bet it's less of an issue with the original linear bearing I3 version because that piece was doubled up in that design.  Anyone who had both care to comment?  or are there too many other variables to compare?  From what I've read acceleration/jerk/move planning is a bigger factor, though. 

I also read somewhere that the more the machine is allowed to move overall during printing the less this happens.  An argument for rubber feet.

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## printbus

> Rigidity:  motion in the x axis is resisted by the primary square frame of composite wood in plane, which is super stiff in that direction.  In effect the stops and starts have something firm to push against.  In the Y direction the stops and starts are resisted by a very small piece of wood in the bendy direction especially at the front piece where the y idler attaches, hence more oscillation/ringing.  
> 
> If I'm right ringing might be reduced a good bit by stiffening that y idler mounting piece.  I need to test that.  I bet it's less of an issue with the original linear bearing I3 version because that piece was doubled up in that design.  Anyone who had both care to comment?  or are there too many other variables to compare?  From what I've read acceleration/jerk/move planning is a bigger factor, though. 
> 
> I also read somewhere that the more the machine is allowed to move overall during printing the less this happens.  An argument for rubber feet.


I think we're miscommunicating. In my case the ringing is observed on the print sides parallel to the Y-axis. In other words, the print sides that go from Y+ to Y-.  Since the ringing is observed on that axis, the ringing has to be lateral movement on the X-axis.  Right?  Or maybe not...  I guess I can kind of see that if the nozzle is moving in the Y direction and the frame is also ringing inline with the Y-axis, the net effect would be the nozzle accelerating and decelerating with respect to the print, and that could cause an artifact to show up.  TJC, is that your theory? Interesting possibility I'll have to ponder. 

I long ago added 1/2-inch wood reinforcement plates to both Y end plates. The 10 and 12 inch printers likely need something like that even more.  As of my last maintenance cycle, I've got the belts tighter than ever or I'd focus on that.  I've got the Sorbothane feet installed.  

I picked a bad day to do some power rewiring.  Might have to kluge things back together to get some test prints underway...

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## sniffle

Makes me start thinking about some type of triangular frame replacement to print to replace the stock wood.

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## AbuMaia

> I think we're miscommunicating. In my case the ringing is observed on the print sides parallel to the Y-axis. In other words, the print sides that go from Y+ to Y-.  Since the ringing is observed on that axis, the ringing has to be lateral movement on the X-axis.  Right?


That is my understanding. I would check the tension of your X belt, and anywhere on the X axis that may be a little springy. As I understand ringing, it primarily happens where the nozzle is undergoing a sharp change of direction, and something springy is letting it "bounce" a little bit.




> With the aluminum v-rails on the i3v, I have a hard time understanding  how the Y-axis is any less laterally rigid than the X-axis.


The X belt is mounted parallel to the wood plates of the X axis. The Y belt is mounted perpendicularly, in between the rails, to single-thickness wood. Didn't you have a modification in your build thread about putting another piece of wood in front because it was too bendy?

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## sniffle

So to eliminate bounce it wounfs like we need to repl a ce the belts with micro chain...

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## printbus

> So to eliminate bounce it wounfs like we need to repl a ce the belts with micro chain...


Not necessarily. The belts are supposedly pretty good at maintaining dimension. They're designed for that. But getting the right tension seems to be tricky, sort of like bed leveling. (lol)

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## AbuMaia

I found it easy to tension the Y belt, I just used a spring clamp to pull the Y motor to the rear, then tightened the motor mount bolts. The X belt was harder to tension, as there's not much room to get a good pull on the X motor. I've been thinking up a redesign of the X belt idler so one can turn a bolt to adjust the X belt tension.

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## printbus

> I found it easy to tension the Y belt, I just used a spring clamp to pull the Y motor to the rear, then tightened the motor mount bolts. The X belt was harder to tension, as there's not much room to get a good pull on the X motor. I've been thinking up a redesign of the X belt idler so one can turn a bolt to adjust the X belt tension.


But isn't there a risk that you can get too tight on the belts? That was part of the basis about it being hard to get the right tension - that you want enough but not too much.  And again, my belts are now tighter than ever, but I can't say that's made a difference.    

Remember that the ringing effect is showing up when the printer has only moved a millimeter or less in the lateral axis.  Acceleration and deceleration should have kept the speed for that small of a distance pretty low, at least in the meager bit I understand Marlin move planning.  Again - I can understand ringing on major 90 degree corners, but not so easily on cases like shallow recesses for lettering or holes on thin walls.  

------

My four-sided ringing test print is complete.  First, I realized that the case I printed yesterday had small radius rounded corners, so not having ringing there is no surprise.  The test object had an identical notch and round hole on all four sides of a cube.  Pretty equal ringing on all four sides.  I'm not sure pictures will reveal details well, but I may try to take some in the morning.

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## beerdart

For Our Y tension I slotted the bearing end and add two eye bolts through the frame to the bearing attach screw.

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## printbus

> For Our Y tension I slotted the bearing end and add two eye bolts through the frame to the bearing attach screw.


Please answer the more important part. How do you know when you've tightened the belt enough? That's really what people want/need to know.

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## MiniMadRyan

Printbus, you raise a good question. I have always wondered if mine are too tight or not enough, with finding very few actual answers online. 

I know that on my y axis, making the belt any tighter starts to warp the rear y bracket, to me that's too tight then. Both my belts are tight, and produce a very low "sprung" noise when plucked, but I always wonder if they could be better!

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## printbus

OK - just ran another of my test prints.  XY jerk set to 2 (effectively allowing no jerk).  Overall acceleration set to 400.  Top speed in Simplify 3D 70 mm/sec.  On the cube, everything is a perimeter, so printing is going at best half that. Still getting a lot of the artifacts around the holes and notches. Something definitely other than mechanical ringing is involved IMO. Mechanical ringing might be part of it, but it's not the whole story.

EDIT: It's almost as if what is really happening is temperature of the extruded filament varying a bit as the extruder slows down and speeds back up.

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## AbuMaia

As far as I know nobody's come up with a universal metric for determining "proper" belt tension. I did find one tool for measuring tension on Thingiverse, but I've not tried it yet.

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## beerdart

I dont know the sweet spot but ours is tension-ed so its difficult to force it to the table pushing down in the center of the long loop. 


> Please answer the more important part. How do you know when you've tightened the belt enough? That's really what people want/need to know.

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## beerdart

I could see where a longer heat soak on the filament would cause more ooze as the hotend is traveling slower.  


> OK - just ran another of my test prints.  XY jerk set to 2 (effectively allowing no jerk).  Overall acceleration set to 400.  Top speed in Simplify 3D 70 mm/sec.  On the cube, everything is a perimeter, so printing is going at best half that. Still getting a lot of the artifacts around the holes and notches. Something definitely other than mechanical ringing is involved IMO. Mechanical ringing might be part of it, but it's not the whole story.
> 
> EDIT: It's almost as if what is really happening is temperature of the extruded filament varying a bit as the extruder slows down and speeds back up.

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## printbus

Vacillation of the pressure in the hot end comes to mind as well.

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## AbuMaia

Do you see ringing on the inside of the box as well? That's what I would expect if it had something to do with the extruder.

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## printbus

> Do you see ringing on the inside of the box as well? That's what I would expect if it had something to do with the extruder.


On the holes and notches in thin sidewalls, yes it is on both the inside and the outside.  Whether it is on a corner, a hole, a notch, outside or inside, it's always on the right hand side looking at an upright surface. At least on my small test print, I know that's the exit direction of movement.  

In other words, it's not that the same ripple is showing up on both sides of an extrusion.  I should point out that with at least the test print I'm currently using for this, "thin wall" is still fairly thick - it's 1.75mm.  I'm seeing Simplify3D use three passes for this 1.75mm wall.

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## gmay3

From my experience, I'd say you know the belts are tight enough when you tighten each belt by pulling on the motor as hard as you can with one hand and use the other for tightening the screws to keep it in place. I wouldn't use tools or clamps since they can apply exponentially much more force than you'd expect and you can't get a good feel for how tight things are compared to your hand.

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## DanCope

Just to add some more data to this. I am experiencing a similar issue to OP. I found this nice test object by ocrinus (http://www.thingiverse.com/thing:277394) which will show up both X and Y axis ripple. The X and Y letters are aligned to their respective axis. 

I am printing with a Prusa i3v, 0.1 layer height. First print is with default settings.



Second print is with Jerk lowered to 15 (from 20) for the bottom half and then Jerk 10, plus AMaxX/Y down to 500 on the top half.



It is more noticeable in person, although the lower speeds do make it less visible. My guess would be that it is caused by rocking in the motors when they stop? It always ripples in the direction of movement, as printbus says above. It also looks fairly consistent between both axes so I wouldn't have thought it had much to do with give in the framing or vibration to the print head (but hey, what do I know  :Stick Out Tongue: ).

I am in the process of tightening the belts some more to see if that helps at all.

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## TopJimmyCooks

I would love to know what effect those astrosyn motor dampers would have on this.

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## printbus

DanCope - welcome to the board.  

As time permits, I've also been running a pile of prints, changing one parameter at a time. I'm not complete, but I've seen some results similar to yours. I dropped xyjerk all the way down to 2. While there was some improvement in the ripple, it certainly didn't make it go away as I expected it to. 

One observation on your settngs - you mention lowering Amax X and Amax Y to 500 mm/sec per second.  I assume you are referring to what were the MakerFarm default values of 1000 either on the LCD or in DEFAULT_MAX_ACCELERATION?  Note that there is another acceleration term Accel on the LCD and DEFAULT_ACCELERATION in configuration.h, which has a MakerFarm default of 500.  As I understand it, the acceleration one gets is actually the lowest of either the axis specific acceleration or the global acceleration setting.  With Accel set to 500, changing Amax X and Amax Y from 1000 to 500 actually had no effect since Marlin was already using that as the upper limit.  

I'm far from being complete in my test prints, but the most effective scheme I've seen so far to eliminate the ripple is to reduce the acceleration (either the axis specific or the global term) down to 200 or below.  I don't believe this eliminates the ripple - it may just compress it down to a shorter distance so that it isn't as apparent.

EDIT: Note that I am not suggesting people go lower their acceleration settings to 200 - I'm just sharing what I've observed. Slowing acceleration and lowering jerk can hurt print quality since the nozzle is moving a lot slower through direction changes like corners, leading to softening/blobbing in those areas.

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## DanCope

> One observation on your settngs - you mention lowering Amax X and Amax Y to 500 mm/sec per second.  I assume you are referring to what were the MakerFarm default values of 1000 either on the LCD or in DEFAULT_MAX_ACCELERATION?  Note that there is another acceleration term Accel on the LCD and DEFAULT_ACCELERATION in configuration.h, which has a MakerFarm default of 500.  As I understand it, the acceleration one gets is actually the lowest of either the axis specific acceleration or the global acceleration setting.  With Accel set to 500, changing Amax X and Amax Y from 1000 to 500 actually had no effect since Marlin was already using that as the upper limit.


Yes sorry I should have clarified, all settings where done through the LCD and defaults were as you described. I thought it odd that Accel was lower than the specific Amax X and Amax Y, but thought I would drop them both anyway. Ignore that setting change then. 

Is there a setting to control how the printer decelerates towards an edge? Lowering the Jerk and the Accel are only going to go so far to hide the vibration when I imagine the real cause is when a motor suddenly halts on an axis - surely you would have to lower the overall speed to make it less of a sudden stop?




> I would love to know what effect those astrosyn motor dampers would have on this.


I would love to have some of these, but I would be surprised if general motor vibrations were causing this. Unless it's like a resonance thing? Not sure.

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## truly_bent

I've been following this thread with some interest and have been doing a  little digging on the web. The general opinion seems to be that it's a  mechanical problem and, as has been mentioned here, one that can be somewhat improved by slowing down travel speeds and tweaking the accel/jerk parameters.

It also seems to me that this  problem is specific to Cartesian coordinate systems. I haven't yet found  any complaints about "ringing" on delta type machines. Can anyone confirm that delta machines are immune to this ringing problem?

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## printbus

> Is there a setting to control how the printer decelerates towards an edge?


The acceleration settings apply to both the acceleration and deceleration phases of a movement.

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## printbus

> I've been following this thread with some interest and have been doing a  little digging on the web. The general opinion seems to be that it's a  mechanical problem and, as has been mentioned here, one that can be somewhat improved by slowing down travel speeds and tweaking the accel/jerk parameters.
> 
> It also seems to me that this  problem is specific to Cartesian coordinate systems. I haven't yet found  any complaints about "ringing" on delta type machines. Can anyone confirm that delta machines are immune to this ringing problem?


I continue to have questions on whether this issue is strictly mechanical.  

Assuming it is primarily a mechanical problem, the extent of the rippling will be driven by the amount of weight being manipulated during printing.  True, deltas are typically moving less weight, but someone could possibly have a poor design for a delta with a printhead that is excessively heavy. If so, that might still exhibit some of the same issues.  EDIT: Thinking about it, that printer might have other print quality issues than the rippling... I really don't know.

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## DanCope

> I've been following this thread with some interest and have been doing a little digging on the web. The general opinion seems to be that it's a mechanical problem and, as has been mentioned here, one that can be somewhat improved by slowing down travel speeds and tweaking the accel/jerk parameters.
> 
> It also seems to me that this problem is specific to Cartesian coordinate systems. I haven't yet found any complaints about "ringing" on delta type machines. Can anyone confirm that delta machines are immune to this ringing problem?


I think you are right, I have also found more information about stepper motors in general now that I had a better idea of what to look for. The 'Vibration Problem' section on this page seems to describe the problem we have. It kind of seems it's just a limitation of these motors.

I imagine delta printers don't show this issue because of the way it drives the motors. It is probably less likely to bring a motor to a sudden stop and any vibration would be absorbed differently into a print than straight across an axis.




> The acceleration settings apply to both the acceleration and deceleration phases of a movement.


That makes sense. I would guess there is a lower limit to how slow it could go before it stops the motor completely so even decelerating slower might not help in terms of a sudden stop.

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## truly_bent

From *Dancope*'s reference:




> When a step motor makes a move from one step to the next, the rotor *doesn’t immediately stop*.  the rotor actually passes the final position, is drawn back, passes the  final in the opposite direction and continues to move back and forth  until it finally comes to a rest (see interactive diagram below). We  call this *“ringing”* and it occurs every single step the  motor takes. Similar to a bungee cord, the momentum carries the rotor  past its stop point, it then “*bounces”* back and forth  until finally coming to rest. In most cases, however, the motor is  commanded to move to the next step before it comes to a rest.


This is the "ringing" of the motor shaft as it comes to rest. Then there's the "ringing" pattern that shows up on some sharp edges of a printed part. It could be that the ringing of the motor shaft is exacerbated (amplified) by the inertia of the extruder's mass overshooting the stop position. 

Here again, the delta type printer has an advantage because most of them seem to be using the Bowden style extruder, which mounts most of the mass on the frame above, instead of being on the shuttle itself. Of course, that begs the question of which type of extruder is better, but that's for another thread.

When a delta makes a sharp change of direction, it involves at least two of the three motors driving in tandem. Most likely, none of the motors come to a complete stop (if ever), as is more likely the case in the Cartesian coordinate system. If none of the motors ever come to a complete stop, there's less opportunity for motor shaft "ringing" to occur.

Just a theory mind. Someone with a stronger math background would have to verify this.

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## printbus

> ...The 'Vibration Problem' section on this page seems to describe the problem we have. It kind of seems it's just a limitation of these motors.


But remember that for at least the i3v printers, we microstep the motors with 80 steps per 1mm of linear movement in the XY axes.  The ringing described in the article would occur every step.  At 80 steps per mm movement, this implies ringing would occur every 0.012 mm of linear movement. The article doesn't convey any magnitude to the position ring, but it'll be far less than the size of the step, right?  So, every 0.012 mm movement we'd have some ring effect far less than that.  I'm not sure we'd be able to see the effect of that.

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## DanCope

The ripple we see in the print is very tiny in terms of depth, so it could be possible that it is a fraction of 0.012mm. Maybe the ringing amplifies as the motor continues to move and overshoots by more when it finally comes to rest?

I am hesitant to say that the weight of the print head has much to do with it because then it would be much less noticeable in the Y axis due to the printer moving the bed for this axis.

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## AbuMaia

> But remember that for at least the i3v printers,  we microstep the motors with 80 steps per 1mm of linear movement in the  XY axes.  The ringing described in the article would occur every step.


*If* the motor came to a complete stop after every step.



> I'm not sure we'd be able to see the effect of that.


Yes, the ringing isn't very deep, but remember it's being stretched out by the other axis moving while the first is coming to a stop. If it was a stop and return movement with very little movement of the other axis, I doubt it'd be noticeable. It's a ripple, happening the same way in the same location over many layers. It doesn't have to be very large to become visible.

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## printbus

> *If* the motor came to a complete stop after every step.


Yeah, it's hard to gauge how the momentum of the rotating mass could mess with things, but I'm not ruling out the possibility that the motor does come to a stop between steps.  These motors aren't moving all that fast.  We know the XY motors can be rotated at the equivalent of a 250 mm/sec axis speed.  When I run a test print at 50 mm/sec, the steps are occurring five times farther apart than at the 250 mm/sec.   




> Yes, the ringing isn't very deep, but remember it's being stretched out by the other axis moving while the first is coming to a stop. If it was a stop and return movement with very little movement of the other axis, I doubt it'd be noticeable...


I'm trying to go where observations from test prints lead.  It's easy to grasp the possibility of mechanical axis ringing affecting major direction changes like a corner.  Where the mechanical axis ringing theory seems lacking in my test prints is in small perturbations like shallow lettering.  Does it make sense that the "ripple" from a shallow recess with only miniscule movement in the axis perpendicular to the primary printing plane is just as pronounced as with a 90-degree corner?   If Marlin move planning is doing its job, we should be getting only minor momentum built up in that perpendicular axis movement.  

Pointing a finger at the jerk setting causing problems with those miniscule perpendicular movements is natural.  But one of my diagnostic prints set XY jerk to 2 mm/sec instead of the MakerFarm default of 20 mm/sec.  The test object has identical holes, notches, and dimples on all four sides.  I did see some reduction in ripple on the surfaces parallel to the X axis, but there's no discernible difference to surfaces parallel to the Y axis.  In other words, in this test case the degree that the X and Y axis should have being slowing to a stop before even a minor offset and then creeping away from that offset didn't change the ripple observed on the Y plane.  At all.

EDIT: Yes, the weight of the X-carriage is higher than the Y-bed, but I was still surprised to see no reduction in the Y-plane ripple with the low jerk setting.

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## TopJimmyCooks

I hate to say it but until the science and physics is figured out on why this happens, I'm just being careful to design or modify parts so they don't have 90 degree outside vertices.  Even a 1mm radius roundover on any near 90 degree turn seems to take care of it.  

I would also be interested in results of ringing test objects that are oriented in a 45 degree angle to the bed.

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## printbus

> I would also be interested in results of ringing test objects that are oriented in a 45 degree angle to the bed.


Good idea.  I'll add that to the list of diagnostic prints for my test model.

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## printbus

> ...I would also be interested in results of ringing test objects that are oriented in a 45 degree angle to the bed.


Of course, I think sniffle essentially already touches on this by his picture provided in the first post.  The ripple caused by the shallow text continues throughout a rounded corner on the object.

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## DanCope

Hey printbus, any luck with your tests?

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## printbus

Fair question. I had even made promises elsewhere to publish test results by the end of last week.  So far I've evaluated 16 test prints.  Through these, I've been able to rule out at least a few possible sources of the ripple.  I've identified a few ways to reduce the ripple or at least the extent that it is noticeable, but most also have other negative effects on print quality.  Following a lead I read about elsewhere, the results from print 16 were very promising and I spent the time figuring out some complex translation and rotation math in openSCAD for a more elaborate test model that I hoped would be more useful in exploring it.  The model didn't work out.  I haven't quit digging into this - I've been easily distracted by just about anything else that comes up.  I may try another print or two on the original test model later today.  Perhaps that'll get me to the point where I can compile info on what I've tried and what I've observed.

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## DanCope

No rush, we all appreciate any results you come back with  :Smile:

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## printbus

My attempt at conveying the results from the ripple test prints has been added to the Marlin motion parameters thread at - http://3dprintboard.com/showthread.p...-MakerFarm-i3v

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