Testing the effects of microstepping and segmentation on print quality

Testing the effects of microstepping and segmentation on print quality Following a discussion in another forum, I decided to do some tests to see what effect varying microstepping and segmentation has on the print quality produced by a delta printer. I printed the same gcode file with four different settings so that the results can be compared. Brief details: - The machine is the 1m high delta with 300mm build diameter described at at https://miscsolutions.wordpress.com/dc42s-large-kossel-build/ - The print is a spiral vase 50mm cube with 3 solid layers at the bottom, and the gcode file is here https://dl.dropboxusercontent.com/u/19369680/cube5050501.gcode. - Layer height is 0.1mm after the first layer - The printer uses 0.9deg motors and 16 tooth pulleys, so the steps/mm @ x16 microstepping is 200 - Controller electronics is Duet Wifi, with TMC2660 drivers supporting up to 256x microstepping - Firmware revision was 1.18RC1 - The extruder drive is a Titan with a 1.8deg motor and about 420 steps/mm. The extruder driver was set to x16 microstepping with interpolation to x256 for all prints. Click on the images for a full-size version. First a reference print using x16 microstepping with interpolation to x256 enabled, which is the default firmware configuration: [img]https://dl.dropboxusercontent.com/u/19369680/50-0.1-x16-on.jpg[/img] Next, still using x16 microstepping but with interpolation disabled (this is much noisier when printing): [img]https://dl.dropboxusercontent.com/u/19369680/50-0.1-x16-off.jpg[/img] Most firmwares divide any delta printer move other than a short one into short segments, calculate the endpoints of each segment, and generate motor steps at equal intervals within each segment, on the grounds that when a segment is small enough the difference between this approximated motion and true straight-line motion is small. Apart from the error within each segment, this forces each segment boundary to be quantised to the nearest microstep for each motor. RepRapFirmware is unique in that it calculates the precise step times for all the tower motors when driving a delta printer. The only time RRF normally uses segmentation is when using mesh bed levelling and a move is longer than the grid spacing. For this next test, I modified the firmware to force each move to be split into 0.5mm segments, still using x16 microstepping with interpolation off. Within each 0.5mm segment, each move is still executed precisely instead of using the approximation, so this doesn't fully simulate the way other firmwares behave: [img]https://dl.dropboxusercontent.com/u/19369680/50-0.1-x16-off-seg-0.5.jpg[/img] Finally, because it was suggested in another forum that high microstepping might result in a reduction in precision, I ran a test with x256 microstepping, not interpolated. To remain within the maximum step pulse rate of around 180000 steps/second per motor supported by RRF on the Duet WiFi I had to reduce the travel speed; but the print speed was still 50mm/sec. [img]https://dl.dropboxusercontent.com/u/19369680/50-0.1-x256.jpg[/img] I am aware that all the prints display ringing at the left hand edge, and I should reduce acceleration and/or jerk to reduce it. Other than that, I will leave readers of this post to comment on the print quality and how it differs between the prints. https://reprap.org/forum/read.php?178,759228,759228#msg-759228 Tue, 08 Sep 2026 04:55:06 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?178,759228,763893#msg-763893 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,763893#msg-763893
[forums.reprap.org]

Hopefully it helps someone.]]> nebbian Delta Machines Sun, 23 Apr 2017 09:12:38 -0400 https://reprap.org/forum/read.php?178,759228,762143#msg-762143 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,762143#msg-762143

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hercek
A4982 driver do not have fast decay mode. Only slow or mixed decay. The default mixed decay does not kick in when the current is raising. But it can be set so that mixed decay is active all the time (I guess that is what you meant by "always configured in fast decay mode").

You are right of course, I was getting confused with the DRV8825. From the A4982 datasheet:

Quote

Low Current Microstepping. Intended for applications where the minimum on-time prevents the output current from regulating to the programmed current level at low current steps. To prevent this, the device can be set to operate in Mixed decay mode on both rising and falling portions of the current waveform. This feature is implemented by shorting the ROSC pin to ground. In this state, the off-time is internally set to 30 μs.

The older Duets have a 0 ohm resistor between ROSC and ground to use this feature by default.]]> dc42 Delta Machines Thu, 13 Apr 2017 14:51:12 -0400 https://reprap.org/forum/read.php?178,759228,762142#msg-762142 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,762142#msg-762142 Their (patent filled) spreadCycle mode looks interesting but I do not understand how it is better than e.g. THB6128 mixed decay mode.
SpreadCycle mode creates a nice small wave in the PWM signal by inserting the fast decay segment into the middle. That means that the first harmonic of the PWM will be significant. THB6128 inserts its 1 µs fast decay segment at the end of the PWM cycle after which there is immediately the ON phase. This results in smaller first harmonic ... which sounds better to me.
Of course THB6128 has a significant disadvantage compared to TMC2660. It cannot offset the whole PWM cycle trigger level properly. Therefore its average value will have slight error (somewhere in the range of 0.6% for my steppers - mostly negligible). It looks to me that if THB6128 would have some way to offset the threshold current where compactor (connected to the sense resistor) triggers then it could be as good as TMC2660. And if the offset would be settable using some analog voltage input pin, then it could be even be used without some serial configuration interface (i.e. on our small stepper driver PCBs and compatible with old controllers).

Of course, it is typically better when one can configure stepper driver from software.

A4982 driver do not have fast decay mode. Only slow or mixed decay. The default mixed decay does not kick in when the current is raising. But it can be set so that mixed decay is active all the time (I guess that is what you meant by "always configured in fast decay mode").]]> hercek Delta Machines Thu, 13 Apr 2017 14:41:04 -0400 https://reprap.org/forum/read.php?178,759228,762051#msg-762051 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,762051#msg-762051

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hercek
The TMC2660 drivers on the Duet board seem to be pretty good. Unfortunately they cannot be put on a separate driver board for e.g. RAMPS since they need to be configured via SPI.

The configuration via SPI means that you can change the decay mode in software. See the TMC2660 data sheet for details. The spreadCycle mode with the parameters that we set by default in RRF works well for almost everyone. According to the datasheet, it automatically determines the optimum length for the fast decay phase.

On the older Duets that used A4982 drivers, the drivers have always been configured in fast decay mode (right from the first Duets shipped in 2013) because of the known problems with mixed decay in some situations.]]> dc42 Delta Machines Thu, 13 Apr 2017 07:35:20 -0400 https://reprap.org/forum/read.php?178,759228,762026#msg-762026 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,762026#msg-762026 this document.
The chip has 1 µs blanking time and it always inserts 1 µs fast decay segment at the end of the PWM cycle when current is rising. And it inserts one full PWM cycle of fast decay when current is decreased. That looks like the best option for simple driver which does not require special configuration through some serial interface (SPI, I2C, ...).

The mixed decay mode looks like the best option for SD6128. Can people who have SD6128 confirm this?]]> hercek Delta Machines Thu, 13 Apr 2017 06:32:00 -0400 https://reprap.org/forum/read.php?178,759228,761972#msg-761972 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761972#msg-761972

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GroupB

you have to mod them ? dont you just have to turn the decay pot to go fast or mix ... Got a decay pot on my thb6128

Mine had solder jumper pads. A pot might be easier, but the pads are pretty easy to understand and use. Same same I think. If you've turned the pot to fast, then I think we're both in the same mode :)]]> nebbian Delta Machines Wed, 12 Apr 2017 23:37:18 -0400 https://reprap.org/forum/read.php?178,759228,761969#msg-761969 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761969#msg-761969

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nebbian

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o_lampe

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I'm starting to really wonder why no drivers ever seem to be in the best mode by default. Why should we always have to mod them???

The best mode is a quiet stepper for some of us ( running and/or holding), others prefer the best torque.
Mixed decay is a compromise.

My SD6128's were quieter, and more accurate after modding.

you have to mod them ? dont you just have to turn the decay pot to go fast or mix ... Got a decay pot on my thb6128]]> GroupB Delta Machines Wed, 12 Apr 2017 21:02:36 -0400 https://reprap.org/forum/read.php?178,759228,761963#msg-761963 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761963#msg-761963
The TMC2660 drivers on the Duet board seem to be pretty good. Unfortunately they cannot be put on a separate driver board for e.g. RAMPS since they need to be configured via SPI.

Community designed A4982 do not need any modification. Well, I'm not sure whether all boards using this driver use also the right parts. But for example this driver is set up properly for a 3D printer by default: [www.reprap.cc]
I have one piece and I checked it out. It was done right.

My guess is that the drivers we use were designed for stepper motors with significantly higher inductance and resistance. Or they were not really intended to properly hold the position for slow movement.

Despite all the simplicity A4988 (or A4982) are quite good. The mixed decay mode will use the fast decay part only when the current decreases the first PWM cycle. If the spec is not lying. I did not check this with oscilloscope. This is better than mixed decay mode of DRV8825 which will use the fast decay part in all PWM cycles when the current is decreasing. Again only info based on the docs. Anyway all low inductance/resistance motors will have problems because of blanking time. The driver chip designers could mitigate this quite easily by simply always inserting a fast decay segment of the same length than the blanking time just after the on time. This would prevent the error accumulation over PWM cycles when current is rising. It is simple to do and to use and the PWM ripple would be small.

As for as the increased PWM noise in fast decay mode. It does not bother me. The difference is well noticeable when the printer is not running but as soon as it is running then the other noises dwarf the PWM noise. Young people who hear high frequency better may differ in their opinion.
The fast decay PWM error bother me a bit more when calibrating. But error of about 1/16 of a step is not such a big deal.]]> hercek Delta Machines Wed, 12 Apr 2017 19:29:22 -0400 https://reprap.org/forum/read.php?178,759228,761961#msg-761961 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761961#msg-761961

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o_lampe

Quote

I'm starting to really wonder why no drivers ever seem to be in the best mode by default. Why should we always have to mod them???

The best mode is a quiet stepper for some of us ( running and/or holding), others prefer the best torque.
Mixed decay is a compromise.

My SD6128's were quieter, and more accurate after modding.]]> nebbian Delta Machines Wed, 12 Apr 2017 19:06:57 -0400 https://reprap.org/forum/read.php?178,759228,761901#msg-761901 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761901#msg-761901

Quote

I'm starting to really wonder why no drivers ever seem to be in the best mode by default. Why should we always have to mod them???

The best mode is a quiet stepper for some of us ( running and/or holding), others prefer the best torque.
Mixed decay is a compromise.]]> o_lampe Delta Machines Wed, 12 Apr 2017 11:42:15 -0400 https://reprap.org/forum/read.php?178,759228,761888#msg-761888 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761888#msg-761888
Here's some more data from a user on facebook with an MKS SBase (32 bit board, 8825 drivers)

Left print is printed at 0.202 layer height, right print is at 0.161.

[attachment 92907 161vs202_layer_height_8825_Andrew.jpg]

From this I can see:
1) That he's using 20 tooth pulleys, so his steps/mm value is 80 or 160
2) That his drivers are not in the best decay mode

For him to get better prints, he should print at one of the following layer heights:
0.081, 0.161, or 0.243 mm.

After doing some research, his drivers are in mixed decay mode by default.

I'm starting to really wonder why no drivers ever seem to be in the best mode by default. Why should we always have to mod them???]]> nebbian Delta Machines Wed, 12 Apr 2017 10:50:18 -0400 https://reprap.org/forum/read.php?178,759228,761263#msg-761263 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761263#msg-761263 (*) As you can see on the picture, the new resistor has number 513 on its package.
[attachment 92808 a4988.jpg]

The results are as expected. The wall is significantly smoother. It is not visible well on the picture. Incredibly small details can be seen with good lighting. But the difference is very well felt when moving finger over the surfaces. And, as expected, the steppers are noisier now since the PWM frequency changed from about 35 kHz to about 22 kHz.
[attachment 92809 cmp.jpg]]]> hercek Delta Machines Sat, 08 Apr 2017 18:14:48 -0400 https://reprap.org/forum/read.php?178,759228,761032#msg-761032 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761032#msg-761032 hercek Delta Machines Fri, 07 Apr 2017 12:41:12 -0400 https://reprap.org/forum/read.php?178,759228,761030#msg-761030 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761030#msg-761030
The charts actually indicate that 8825 should be worse even for the motors I used if the driving current is less than about 1 A. Anyways the difference should not be big. If you are getting a big difference then your motor parameters are significantly different, or my model is wrong/tooSimplified, or something else is fishy.

At first look the charts actually make good sense. Notice that PWM frequency is fixed for 8825. Therefore the error slightly falls down when higher currents are used. The PWM frequency is variable for A4988 - it is falling with bigger currents(*), therefore the PWM error is raising with bigger currents.

(*) Because A4988 has fixed OFF time and variable ON time. The ON time is raising with higher currents. It takes longer time to rise current to higher values.

How the PWM error looks like for different motors depends especially on Tau = L/R of your motors, ... and the power source voltage.

The smaller the Tau (and the bigger the voltage) the higher the PWM error.

But with bigger Tau and smaller voltage (i.e. the combination which lowers PWM error) also drops the maximum motor speed you can precisely achieve. If you cross the maximum precise RPM then you will get much bigger errors than the errors from the PWM current control. This is because the errors are propagating from one PWM cycle to the next one and accumulating per one quadrant (electrical phase angle of 90°).]]> hercek Delta Machines Fri, 07 Apr 2017 12:35:36 -0400 https://reprap.org/forum/read.php?178,759228,761019#msg-761019 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761019#msg-761019

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hercek

Edit: Based on this schematic: [a.pololu-files.com]
The resistor you removed should have been 10 kΩ which corresponds to OFF time 12 µs, fast decay time 3.8 µs, blanking time always constant at 1 µs.

I just found that resistor on my bench (not easy, let me tell you!!) and measured it. Voila, 9.96k.

Those graphs are interesting. I haven't tested this directly, but I had the feeling that 8825's were worse (a lot worse) than A4988's, if you were comparing either unmodded to unmodded, or modded to modded. The graphs suggest otherwise.

Looks like I'll have to pull my mini apart again. I'm getting pretty good at it by now. My desk is being swamped with cubes.]]> nebbian Delta Machines Fri, 07 Apr 2017 11:16:20 -0400 https://reprap.org/forum/read.php?178,759228,761018#msg-761018 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761018#msg-761018 hydraraptor.blogspot.co.uk]. It's why the older Duet boards that use A4982 drivers have always had the Rosc pin shorted to ground.]]> dc42 Delta Machines Fri, 07 Apr 2017 11:14:26 -0400 https://reprap.org/forum/read.php?178,759228,761003#msg-761003 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,761003#msg-761003 [attachment 92753 A4988.png]
[attachment 92754 DRV8825.png]
The interesting part are the red lines. When you multiply them by 100 then you get the percentage which you can look up in the stepper driver microstepping tables and look how many microsteps you can be wrong because of current control using PWM (with mixed/fast decay) in the stepper driver. The tables will tell you that it is somewhere just below one microstep at 16 microstepping. Notice, these errors are valid after you switch the driver to the best decay mode. The drivers are not in the best mode by default. They do much much worse in the default mode ... as nebbian kindly figured out and let us all know :)

If you thing you see segmentation errors on your walls (as I did), well there is good chance you actually see the result of bad decay mode of your drivers.]]> hercek Delta Machines Fri, 07 Apr 2017 09:51:57 -0400 https://reprap.org/forum/read.php?178,759228,760797#msg-760797 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760797#msg-760797
When your pin was connected to the ground through resistor then the A4988 chip used slow decay in the raising current quadrant and mixed decay in the falling current quadrant. Provided that the removed resistor had resistance of 1 Ω, then the OFF time should have been 1/825 µs ... which does not make sense since it is less than the blanking time of 1 µs. 1Ω definitely looks like a wrong value for that resistor. I would expect either 0 Ω (i.e. shorted to ground) or at least 1650 Ω.

Thanks for posting the results. I think I have the same driver and if so then I will try this too.

Edit: Based on this schematic: [a.pololu-files.com]
The resistor you removed should have been 10 kΩ which corresponds to OFF time 12 µs, fast decay time 3.8 µs, blanking time always constant at 1 µs.]]> hercek Delta Machines Thu, 06 Apr 2017 11:16:50 -0400 https://reprap.org/forum/read.php?178,759228,760778#msg-760778 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760778#msg-760778

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o_lampe
edit: The ROSC pin is already connected to the pad and grounded through the 010 resistor ( maybe not in full fast decay mode though )
[attachment 92712 A4988_ROSC.jpg]

O_lampe, you are a gentleman and a scholar. Many thanks for this info. Mine turned out to be the first variant. I've no idea how the firmware can measure the difference between 1 ohm and 0 ohms, but it sure seems to have made a difference. I used a wire so that I could connect it to +v if required, but just grounding it seems to have worked.

[attachment 92736 IMG_6689.jpeg]

The cube on the bottom right is with a normal A4988 driver, the one on the top left has been hacked to ground the ROSC pin. It's quite a substantial difference.

[attachment 92737 IMG_6690.jpeg]

The hacked A4988 driver is about as good as an unhacked SD6128 (both at 1/16). If the moire pattern wasn't there then you'd never notice the stripes.

[attachment 92738 IMG_6693.jpeg]

So for the drivers A4988, DRV8825, SD6128, it's worth modding them to go into fast decay* if you can. The TMC2100 is good right out of the box, but has issues with torque.

* I don't know what you call grounding the ROSC pin on the A4988, but it gives better results, whatever it is.]]> nebbian Delta Machines Thu, 06 Apr 2017 10:03:41 -0400 https://reprap.org/forum/read.php?178,759228,760752#msg-760752 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760752#msg-760752

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dc42

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hercek
dc42, was your last picture printed at 50 mm/s? What acceleration? What kind of belts do you use?
The reason I'm asking: I do not care much about the patterns on the walls; I would like to get more info about the "ringing" on the left corner.

I did not experience this myself but I read that regular patterns on prints can be also caused by belts either not fitting the pulleys precisely or running the teeth side of a belt over a smooth idler (which happens when belt is not twisted before running it around idler). But I guess almost nobody has this problem.

I tried reducing printing acceleration to 1000mm/sec^2 and the ringing is much less:

cube505001-x16-on-m204p1000.jpg

The corners bulge slightly at both edges - looks like I may need to increase the pressure advance.

Belts are 6mm glass core GT2.
]]> dc42 Delta Machines Thu, 06 Apr 2017 07:44:36 -0400 https://reprap.org/forum/read.php?178,759228,760738#msg-760738 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760738#msg-760738 data sheet, you cannot set fast decay mode. You can set only mixed decay and in such a case you cannot control how much of the PWM period is fast decay and how much is slow decay. 31.25% of the period is always fast decay. Moreover the raising current quadrant is always in slow decay mode. That sucks. The blanking time (i.e. also the minimum on time) is 1 µs. If this time results in a too high current (which cannot be dissipated in the rest of PWM cycle) then you get "missed" micro steps. You need to slower the current rise (in the critical 1 µs peirod) or speed up the current decay.
The options you have are:

Decreasing the voltage (used to power steppers) will make current rise slower.
Steppers with higher inductance will make current rise slower. But it will also fall slower which can make problems at the falling current quadrant at higher speeds.
Steppers with higher resistance will make the current decay faster.
You can increase Toff time (therefore decrease the time percentage the driver spends in the forced-on 1 µs period). This will increase the audible high pitch noise because the PWM frequency will decrease. You would need to check the resistor connected to ROSC pin and increase its value ... at first maybe by about 2 times and try again. More precise value (to increase it to) can be find out using oscilloscope or even approximately computed if you know all the parameters (voltage, resistance, inductance).

Edit: Shorting ROSC to GND can be a good idea too. It should force Mixed mode for both rising and falling current quadrants with 30 µs period. Maybe it will be enough. It would be good if one can force mixed mode everywhere and also control the PWM period with ROSC. But this does not seem possible.]]> hercek Delta Machines Thu, 06 Apr 2017 06:08:53 -0400 https://reprap.org/forum/read.php?178,759228,760709#msg-760709 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760709#msg-760709

Quote

If you know how to easily change these drivers to fast decay, then I'd love to be able to do this test.
[www.ebay.com.au]

IIRC there is a resistor close to the reset and sleep pins that can be bridged to get fast decay.
But don't quote me until you get confirmation.... :/

I checked my old stock of a4988 and there are two versions.

1: Not exactly sure, if there is a track to be cut, before connecting the throughhole with the pad.
edit: The ROSC pin is already connected to the pad and grounded through the 010 resistor ( maybe not in full fast decay mode though )
[attachment 92712 A4988_ROSC.jpg]

2: Unsolder the 101 resistor and bridge the pads.
[attachment 92713 a4988_decay_mod_R4.jpg]

Use at your own risk...]]> o_lampe Delta Machines Thu, 06 Apr 2017 02:38:05 -0400 https://reprap.org/forum/read.php?178,759228,760688#msg-760688 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760688#msg-760688
The reason mine was making patterns at 0.202 was that full steps happen on my machine every 0.1mm in Z height (my steps/mm at 1/16 is 160). So 0.2mm layer height means a perfect alignment of steps, 0.202 means a slight drift.

On your machine with steps/mm of 200, full steps happen every 0.08mm. So printing at layer heights of 0.1 will spread any artefacts out over 5 layers. Printing at 0.08 or 0.16 will line up the full steps. Printing at 0.161 should make the steps drift in and out of phase with the layer height, possibly resulting in a moire pattern.

I'd be very interested to see your results.]]> nebbian Delta Machines Wed, 05 Apr 2017 20:57:36 -0400 https://reprap.org/forum/read.php?178,759228,760686#msg-760686 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760686#msg-760686
If you know how to easily change these drivers to fast decay, then I'd love to be able to do this test.
[www.ebay.com.au]]]> nebbian Delta Machines Wed, 05 Apr 2017 20:32:21 -0400 https://reprap.org/forum/read.php?178,759228,760684#msg-760684 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760684#msg-760684 If it is a decay related problem then:

It should disappear when you switch it to fast decay. Did you try it?
It should be speed dependent. The error should be smaller when you print quickly. Well, even segmentation error will be smaller at faster prints. But slow decay related problems should be more influenced by speed. Well, depends on the resistance and inductance of your motors.

It can be computed whether slow decay is a problem. I should check this on my printer. Maybe my lines are not related to segmentation but to the decay mode too. It makes sense. Decay mode problem on my printer should be in the range of about 0.1 mm. Segmentation error should be in the range of 0.0125 mm.

DRV8825 are known to have slow decay problem: [www.engineerination.com]
Fast decay is an easy solution for people who do not mind noise.

Decay related problems will degrade numerical based calibration too.]]> hercek Delta Machines Wed, 05 Apr 2017 20:05:35 -0400 https://reprap.org/forum/read.php?178,759228,760678#msg-760678 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760678#msg-760678
Layer heights were 0.2, 0.202, and 0.1618 (multiple of golden ratio to spread the peaks).

All prints were with A4988 drivers to accentuate the step issue.

Btw, this has absolutely nothing to do with segments, and everything to do with stepper drivers that are in mixed decay mode.]]> nebbian Delta Machines Wed, 05 Apr 2017 18:57:40 -0400 https://reprap.org/forum/read.php?178,759228,760667#msg-760667 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760667#msg-760667
There is tiny bit of "ringing" visible on my test print I posted before(*). I did it too at 50 mm/s (so that is comparable to your prints). But other parameters were different. Acceleration was 8000 mm/s², jerk 20 mm/s.

I use steel core T2 belt. I guess the same kind of belt some people reported problems with. Allegedly the steel core is failing on small diameter pulleys. Although I did not see this problem yet. My pulleys have diameter of about 12.7 mm (stepper) and 14 mm (idler).

"Ringing" is well visible on my setup when I print at 120 mm/s (everything else the same).

As far as I'm concerned, you do not need to do more tests relating to "ringing". I was just curious what were the parameters related to the picture you posted.

(*) Here is the best visible "ringing" from all 4 corners. On two corners it is not recognizable from the segmentation lines. On other two corners it is visible when lit properly.
[attachment 92704 ring.jpg]

nebbian: Well, based on you previous posts it should be layer height xor steps per mm changing on a firmware with delta segmentation. The bottom has layer height as a nice multiply of the micro step length. The middle has very small difference (something like layerHeight = (k+ε) * microStepLength. Where k is positive integer and ε is a very small rational number; let's say somewhere in the range of 1/1000. The top picture has ε much bigger, probably somewhere around 1/k.]]> hercek Delta Machines Wed, 05 Apr 2017 17:33:10 -0400 https://reprap.org/forum/read.php?178,759228,760624#msg-760624 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760624#msg-760624

Quote
hercek
dc42, was your last picture printed at 50 mm/s? What acceleration? What kind of belts do you use?
The reason I'm asking: I do not care much about the patterns on the walls; I would like to get more info about the "ringing" on the left corner.

I did not experience this myself but I read that regular patterns on prints can be also caused by belts either not fitting the pulleys precisely or running the teeth side of a belt over a smooth idler (which happens when belt is not twisted before running it around idler). But I guess almost nobody has this problem.

Print speed 50mm/sec
XY acceleration 3000mm/sec^2
Jerk 600mm/min
GT2 belts on 16t drive pulleys and 16t toothed idler pulleys
1.68A motors running at 1.0A

I'll try repeating the print with different acceleration/jerk/motor current.]]> dc42 Delta Machines Wed, 05 Apr 2017 14:42:01 -0400 https://reprap.org/forum/read.php?178,759228,760574#msg-760574 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760574#msg-760574
Which one setting was changed between these three cubes?

[attachment 92692 IMG_6688.jpeg]

Bonus points for guessing the actual setting values.]]> nebbian Delta Machines Wed, 05 Apr 2017 10:37:31 -0400 https://reprap.org/forum/read.php?178,759228,760542#msg-760542 Re: Testing the effects of microstepping and segmentation on print quality https://reprap.org/forum/read.php?178,759228,760542#msg-760542 nebbian Delta Machines Wed, 05 Apr 2017 06:40:24 -0400