Custom CoreXY - -Linear Rail Vibration

I have build a custom made Corexy machine with Linear rails.. running Marlin UBL on a Rumba

[www.youtube.com]

a few issues im having.

I cant set travel speeds higher then 100mm/s it seems to bind or run into a cpu limit or something else.
i thought it might be a missed step issue but i have carefully adjusted voltage on the Nema 17 400rev steppers to around 0.8Amps, and it warm but not too warm.

getting some weird vibrations/resonating in the rails as well.
thinking of getting some teflon Silicone Dry Lube not sure it will help.
rails are MGN12 Chinese knockoffs.. they move pretty smooth.

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Quote
makerparts
I cant set travel speeds higher then 100mm/s it seems to bind or run into a cpu limit or something else.
i thought it might be a missed step issue but i have carefully adjusted voltage on the Nema 17 400rev steppers to around 0.8Amps, and it warm but not too warm.

That's hardly surprising. Even 100mm/sec X or Y moves will need a combined step pulse rate of around 50KHz for that configuration, assuming 16x microstepping, and a 8 bit processor will struggle above those speeds. You need 32-bit electronics. The Duet WiFi is proving popular with CoreXY builders right now.

Quote
makerparts
getting some weird vibrations/resonating in the rails as well.
thinking of getting some teflon Silicone Dry Lube not sure it will help.
rails are MGN12 Chinese knockoffs.. they move pretty smooth.

Is the vibration triggered by moving at particular (and probably slow) speeds? If so, higher microstepping should help to avoid exciting the resonance. It will also make the printer quieter. Again, the Duet WiFi provides this (up to 256x microstepping). Or you could try installing silent stepsticks in your rumba board.

There is a separate forum section for CoreXY printers.

Edited 2 time(s). Last edit at 10/10/2016 04:17PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks I will use the corexy forum next time.

im running 1/8 Microstepping, to help speed things up.
I have avoided the Duet as im waiting for Marlin to natively support a 32bit board.

I was considering step sticks.. but im confused.. if im overloading the CPU with 1/16 microstepping.. then wouldnt going to something really high like 1/128 or 1/256 be crazy?

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makerparts
im running 1/8 Microstepping, to help speed things up.
I have avoided the Duet as im waiting for Marlin to natively support a 32bit board.

Marlin and other older firmwares are severely compromised by being constrained to run on 8 bit hardware with limited performance and memory. When firmwares are designed to run on 32-bit hardware only, there is much more flexibility to implement things properly. For example, precise step pulse timing instead of using the Bresenham approximation, including in some firmwares precise step pulse timing during acceleration. 32-bit hardware has been around for 3+ years now, so why wait any longer to get the benefits of it?

Edited 1 time(s). Last edit at 10/10/2016 04:28PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

400 rev/step steppers should work fine, especially at 1/8 stepping. I'm using 400rev/step motors at 1/32 stepping on a RAMPS/Arduino board, and it works fine at higher speeds. What steps per mm have you ended up at in your firmware?

Have you tried:
1) Lowering your acceleration
2) Trying Repetier firmware

I must say, the constant spruiking of a certain member's "financial interests" is getting a bit tiresome.

Quote
nebbian
400 rev/step steppers should work fine, especially at 1/8 stepping. I'm using 400rev/step motors at 1/32 stepping on a RAMPS/Arduino board, and it works fine at higher speeds.

I am happy to be corrected if you have that working. I agree that at 1/8 stepping - which the OP didn't mention in his original post that I replied to - should allow higher speeds then he is getting. But your experience seems to me to be at variance with [reprap.org] which has a table of maximum step rates, including this:

Quote

Marlin/Repetier on ATmega 16 MHz in Quadstep-Mode (uneven step distribution): <40 kHz.

So that's 40KHz max. The typical belt steps/mm using 400 step motors and 32x microstepping would be 320, so the maximum single belt speed is 125mm/sec. OK so far; but to move along the X or Y axis, we need to move both belts at the target speed, which doubles the aggregate steps/mm. So if 40kHz is the maximum total step rate, I would expect your machine to top out at around 62mm/sec. Maybe Marlin has improved and the figures on the wiki are out of date? How fast can your machine do an X or Y move, and are you certain that it actually reaches the requested speed when that speed is high?

Quote
nebbian
I must say, the constant spruiking of a certain member's "financial interests" is getting a bit tiresome.

If you read all of my post, you will see that I suggested silent stepsticks in the existing electronics as another way of reducing vibration. So it isn't all about my financial interests, I am genuinely trying to be helpful. But where a 32-bit board is indicated, I will not hesitate to recommend the Duet WiFi, because it is the best 3D printer control board available at present.

Edited 2 time(s). Last edit at 10/11/2016 04:44AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I'll throw my two pence worth in here. I was reluctant to try 32 bit as I didn't see the need and to be fair with 1.8 deg steppers and ramps/mega on my corexy I can print at 150mm/s, fairly well.

But... Duet Wifi is good, I have one on the new delta which I have tried to spare no expense on (for the first time ever), and if they were cheaper I'd buy one for the corexy too. The 1/256 interpolation on the TMC2600's is the smoothest and quietest I've seen a stepper move in a 3d printer and the general layout and features are very good. Also the development is very active, the forum is very helpful and the users feel a part of moving something forward.

I'd still say if your budget is modest and the printer not expected to go to very high speeds, the fact that ramps/mega is £20 and duetwifi is £150, is an issue for a lot of people. Plus I felt comfortable, indeed competent, in Marlin and apprehensive about learning a complete new board, new firmware and a new interface. It wasn't difficult to be fair.

Maybe our OP should consider something like the MKS S-Base which will offer the step pulses required, but at a much reduced cost.

Marlin have IMO been far too slow to react to the fact that things are moving on from 8 bit arduino.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I just measured my delta's top speed. Doing a 100 mm downward jog as fast as it can go took 0.875 seconds, so each axis tops out at around 115 mm/s.

This is with 1/32 microstepping enabled, and all 3 motors going, on a very cheap RAMPS/Arduino electronics platform. It works out to a step rate of 23kHz on each step pin (3 drivers going at once). I don't know how that works out as a combined step rate, as I don't know if the repetier guys do something clever like driving multiple step pins with the one signal.

I would imagine that 1/8 stepping would quadruple that speed, which seems to me to be fast enough for most purposes.


While there is no doubt in my mind that 32 bit electronics would be superior in terms of performance, saying that "You need 32-bit electronics" to achieve speeds above 100 mm/s... just seems disingenuous to me.


Back to the OP's problem: Have you checked that the maximum travel speed isn't limited somewhere? What's your DEFAULT_MAX_FEEDRATE set to?

not sure how to measure the time it takes accurately to determine actual speed that its running at.

I did place an order for a Duet Wifi With panelDue to help resolve this issue.

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One method would be to video the printer on your phone then get some free video editing app which will give you a time for each frame. Then you can measure the time taken to perform a move accurately.

Print a tripod adaptor for your phone and you can do timelapse videos of prints too. And its stable enough to see sometimes where resonance is coming from.

I'm wondering now if there is a way to do high speed filming which would reveal a lot, I suppose the camera modules on phones probably can't go above 30 fps?

Edited 2 time(s). Last edit at 10/11/2016 11:27AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Um, wow, I think it was a real mistake to call it disingenuous - that is not the tone we should use here.

Quote
makerparts
I cant set travel speeds higher then 100mm/s it seems to bind or run into a cpu limit or something else.

I recognize the symptoms. I started out with a similar setup for my delta - using a Rumba. I had 8825 drivers in it. I did not use a graphics display. Over a certain speed I started to hear an overtone - clearly the steps were starting to get rougher. Faster and it would start to shudder. I tried both Marlin and Repetier. I tried quad stepping. I tried less micro-stepping. Only slightly better, and the motors were much louder! It still could not go very fast, and printing around curves was problematic - there would be very slight hesitations due to the extra delta calculations, resulting in blobs possibility missed steps. I don't think this was mid band resonance, I ran into that when I could go much faster with 32-bit. Switching to a Smoothie was the best thing I ever did. Time is money, and the frustration caused by 8-bit limitations was not worth it.

I think DC42 has asked the proper questions and given good alternatives.

What we still do not know yet (because the OP has not said) is:
- exactly what drivers is he using?
- what the pulley diameter is, or:
- what the steps per mm is? Critical to know.
- is he using a graphic display?

Other than that, ugh! I'd rather not try to fix 8-bit!

I guess we will see if the Duet fixes it!

Edited 1 time(s). Last edit at 10/11/2016 11:39AM by Paul Wanamaker.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Hmm well i just want it to run as quickly as possible while giving a good print quality.
doesnt need to run at 100, 150, 200.. exactly.

Hoping that 1/128 or 1/256 microstepping will reduce vibration, and that the reduced torque wont be that noticeable.

any other thoughts on other ways to reduce rail resonance /vibration?

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BTW I am using 8825 Drivers on my rumba
currently at 1/4 microstepping with a 400 rev Nema 17s running 14 tooth pulleys

Using a 4 lines LCD display XXL reprapdiscount.
current steps per mm is 57.14

I have also tried it with 1/8 Micro stepping with a XY step of 114.28 and it had similar performance.

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makerparts
any other thoughts on other ways to reduce rail resonance /vibration?

The vibration is from the motors. Unless your rails/bearings are also loose and resonating. I think the good DR (the_digital_dentist) had some cars with undersized bearings, he replaced the bearings.
Just try the Duet with higher microstepping.
If necessary you can get external DSP based drivers, but those are usually only needed for larger (NEMA 23) motors. Too soon to tell.

Edit:
You could try turning off the display in firmware.

Edited 1 time(s). Last edit at 10/11/2016 11:47AM by Paul Wanamaker.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

I do use one Nema 23 to run my Z as its turning 4 Acme Screws.
with a 2:1 gearing

A

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I'd try 1/16th and test again. If things are no worse then you can probably discount the lack of step pulses from the list of possible causes. It will be much quieter even if no faster. I've got MGN12H chinese rails, one is slightly sticky on my new delta, the effect on print quality - zero. With Duet Wifi I can move the carriage at 250mm/s no problems.

Edited 1 time(s). Last edit at 10/11/2016 12:17PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
makerparts
not sure how to measure the time it takes accurately to determine actual speed that its running at.

First, make sure that you don't have a low speed limit configured in firmware. See the end of nebbian's second post in this thread.

Next, make sure the acceleration configured in the firmware is high enough that you have enough length to actually reach the speed you are aiming for. Let's assume you are aiming for 300mm/sec. The distance taken to accelerate to this speed from standstill will be 300^2/(2 * A) where A is the acceleration. So if A is configured in your firmware as 3000mm/sec^2 then the acceleration distance will be (300 * 300)/(2 * 3000) = 15mm. The deceleration distance will be the same.

Then execute a move that is much longer than the accel/decel distance and time it. In this example, if you do a 200mm move, only 30mm of it will be taken up by acceleration and deceleration, which is OK.

As well as measuring the time taken to do the move, check that the distance moved is what you asked for. If it is less, but it OK at slower speeds, then your motors are not supplying enough torque during the acceleration phase.

Work out the expected time. In this example, we have 170 mm of steady movement, which should take (170/300) = 0.57sec. The acceleration and deceleration parts take (300/3000) = 0.1sec each, so that's 0.2sec. Total time 0.77sec.

To measure the time more accurately, you can set up a gcode file to execute e.g. 10 moved, for example (starting at X=0):

G1 X200 F18000
G1 X90 F18000
G1 X200 F18000
G1 X90 F18000
...and so on.

Achieving high speeds when using 400-step motors may require using more than 12V power, depending on the specifications of your motors. You can calculate the back emf due to inductance and the approximate back emf due to rotation using the formulae at [duet3d.com].

Quote

I did place an order for a Duet Wifi With panelDue to help resolve this issue.

You won't be disappointed! However you will find the firmware configuration very different from Marlin, if that's what you are using. See [duet3d.com] and [duet3d.com], and join the forum at [www.duet3d.com] for assistance.

HTH David

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Cant wait until Grid leveling is on Duet Wifi, I have been using the Marlin UBL Branch with Auto Grid levelling and it works very well Roxy3D has done some great work.
I am also increasing my printer to a 300x600 bed so grid levelling is going to get even more important.

Edited 1 time(s). Last edit at 10/11/2016 12:41PM by makerparts.

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Grid levelling is scheduled for implementation in November.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I had the very same problem and it is solved really easy:
The DRV8825/4 Stepper needs a higher latency more than (1.8ms when I'm right)

Just set the delay to 1 in the firmware
STEPPER_HIGH_DELAY 1

Edited 1 time(s). Last edit at 10/13/2016 10:25PM by mrc.

Quote
Paul Wanamaker
The vibration is from the motors. Unless your rails/bearings are also loose and resonating. I think the good DR (the_digital_dentist) had some cars with undersized bearings, he replaced the bearings.
Just try the Duet with higher microstepping.
If necessary you can get external DSP based drivers, but those are usually only needed for larger (NEMA 23) motors. Too soon to tell.

Actually, I had some missing balls from the ball screw in the Y axis in my printer. I measured the balls and discovered that though the screw is metric, and made by NSK, the balls were 1/8" diameter! I ordered a 100 pack and replaced all the balls and the awful noises the thing used to make occasionally have been greatly attenuated. However, it still makes more noise than my wife would find acceptable, so the printer will be at the makerspace for the foreseeable future.

Edited 1 time(s). Last edit at 10/13/2016 11:20PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Ah, that's right.
You also used a DSP driver to make it somewhat quieter before that too?

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Yes, but that only goes so far. Even with DSP running at 64:1 ustepping, it's still pretty noisy.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
However, it still makes more noise than my wife would find acceptable, so the printer will be at the makerspace for the foreseeable future.

You may want to consider a hybrid servo drive. They are much quieter. These are a combination of a special servo driver and a special stepper with encoder - driving the stepper as a multi-pole brushless servo. This has advantages for cost, and also reduces seeking. You also get the advantages of a servo, including higher speeds and no lost steps, + you get the high torque at low RPM of a stepper. There is still some torque curve drop-off with higher RPM.

There are both integrated and separate driver + hybrid servo packages. They are reported to have 1/10th the noise (don't quote me). They have the familiar step/direction interface, so it should be plug and play for you, since you use an external driver already. I found an integrated drive once on ebay that was around $68 + shipping, can't locate it now, but the Purchase a Sample links through Leadshine USA below may give you search terms.

I'm planning on updating the motors on my printer + the extruder to the integrated drives once I find them again (all motors on my printer are already Nema23).

Here is an example on ebay

Here is the Leadshine USA page.

There is another brand that has these kind of hybrid servos. I have seed a direct comparison video. Very hard to tell apart in service, but the Leadshine was reported to be slightly better.

The Leadshine driver has two model numbers: one for the USA and one for China. These are functionally identical, but the HBS507 is for the local Chinese market (cheaper), and you have to use the Chinese version of their tuning software - download links and discussion are available on CNCzone. The software has the same layout as the english version, so it's just a matter of following along in an English manual. I've not found anyone that has used this driver with their own steppers - i'm inclined to not recommend it.

BTW, the recent Kickstarter that was discussed somewhere here recently, with a board that attaches to the back of a stepper - and has an encoder - that is in fact doing the exact type of thing - it is in fact a "Hybrid Servo Driver". Might work well for Nema 17 etc.

The differences between the Mechaduino Kickstarter board and the Leadshine drivers: the Leadshine drivers are obviously much more mature - and already can handle high power motors, are perfectly matched with the more powerful motors they are made for, and are able to handle large mechanical mismatches without further tuning. (Time is money).

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

These leadshine servos still appear to need a servo driver.. vs the ustepper/mechaduino which still just use standard stepper drivers. found on ramps/rumba etc.
also finding a Nema 17 is ideal... Clearpath makes some nice Servos. but not in Nema 17 sizes i believe.

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Yes, with a hybrid servo you need a driver and matched motor, or buy one that is integrated. NEMA 23 sizes and above.

The reason I suggested the hybrid servos is because both the OP and the_digital_dentist are using Nema 23 - which can be noisy with ball screws. About half the price of regular servos.

Mechaduino is a replacement for the stepper driver, not in addition to one. It runs the motor with it's built in h-bridge as a multi-pole hybrid servo, using the encoder for positioning. Has a step/direction interface, so you just run those lines to it, + power. It does look ideal for NEMA 17, but lacks the power for Nema 23 (needs a larger H bridge). If they had one for larger motors, I'd try it.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Interesting discussion, but I'm using a 3 Nm motor in my printer's Y axis and that's pushing it right to the edge. I frequently have access to industrial scrap via the makerspace, so I'll keep my eyes open for a servo motor/driver setup that I can swap in. I have a NEMA-34 motor mount on the machine that I adapted to NEMA-23, so I'll be able to fit a wide range of motors. One of these days a machine will show up with the right parts...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

So who makes an integrated Nema 17 Servo ideally 24v that can just plug into a standard 4 pin motor connector

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makerparts
So who makes an integrated Nema 17 Servo ideally 24v that can just plug into a standard 4 pin motor connector

No one does. The "standard 4 pin motor connector" is not standard - that connector is a reprap feature for energizing the two coils of a particular kind of stepper motor. The output from that connector is an analog higher voltage signal that also has rough waveform the driver chip uses for current control - so that signal is not suitable for delivering step pulses to a different kind of motor. There is a good article here about the waveform.

The inputs to a servo driver would be either PWM or digital step/direction pulses (logic level voltage), the latter being what you would want. The servo driver then outputs voltages to the motor (servo, or stepper in the case of a hybrid servo) with a smoother waveform than most a stepper drivers would, allowing it to run quieter, and with less power. Many hybrid servo drives use three phase (three windings) instead of two. Hybrid servo drives have much less settling time than a conventional servo, and they are rock solid when stationary, no hunting, no overshooting.

Note: a "hybrid servo" is entirely different from a "hybrid stepper motor".

If you have a socketed stepper driver, then the step and direction lines are there and could be easily fed to a servo drive's input, + add power. Many other boards also have pin headers for each axis with the step/dir lines.

The real question is, who makes a Nema17 hybrid servo. I've not seen one yet, closest is the board by Mechaduino to convert a stepper into one. Note that it does require tuning to run properly.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

The mechaduino is very similar to the ustepper. but i assume both of these cannot take advantage of very high microstepping rates as they ignore the built in driver

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