Ripple Eliminator

Hello to everyone.

Today i find such an interesting thing as Ripple Eliminator. I think it is especially important for delta-printers.
Interested in your expert opinion will it really work?

Hum. Hum.
Till we have some technical details how it does work, that shall be considered as a lotion to have hair growing back on bald head.

If stepper are adjusted to 1/16 microstep and a driver known to work without ripple (say NOT a 8825), you may have ripple, but not as large as shown.

If you have ripple linked to the board stepping, it is time to change firmware for a better one, or even upgrade the hardware.

On a delta, ripple linked to machine resonance may be reduced by adding friction in articulations, with some sort of spring.

---

Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

As near as I can make out those boards add a couple of diodes to each motor circuit.

What these would do is isolate any regenerative current from the motors that may cause some rippling, but if your using bipolar stepper motors will also mean they will cease to work.

How do you know if your getting regenerative current from the motors?, well just turn off your control system and move the axes up and down manually, if you see any of the fans running or LED lighting up, then you have regenerative currents.

Deltas can suffer from regenerative current issues because the axes are essentially fighting against each other, this normally doesn't cause a significant problem because the effector is designed to give, but if there is excessive resistance at the effector then it will increase the force induced at one of the motors.

---

RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

There is something important to note, this equipment is supposed to be installed on the Tinyboy printer, which does have very small steppers, nothing comparable to any other printer. This is a quite special configuration and there may be specific problems.

What could be the net effect of diodes ? adding forward voltage ? but as you underline, if they are on the main coil, they prevent it working ?

This printer (the tinyboy) have very light mobile mass, so regenerative current may be smaller than on other printers.

For deltas, I don't get the point of arms 'fighting' each other, while I agree you may have more regenerative current than for other printers from a descending carriage due to own mass and inertia.
Regenerative current is normal for stepper drivers, and on a working printer, this current may be much lower than the heater electrical consumption.

Moving manually the carriages on my printers, I run some fans, but others barely turn, so that is not very large current/voltage.

There is something on Pololu drivers, you don't find large capacitors as you have on Duet or Smoothie.

---

Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

It's got nothing to do with isolating regenerative current.

It's to do with reducing the dead zone. Lots more information available here:
[cabristor.blogspot.com.au]

ah right... don't understand the electronics, but no, diodes on that configuration will do squat for regenerative currents and wont have an adverse effect on bipolar motors only

---

RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Yes, but the DRV8825 chip is known to have a minimum on time three time larger than the A4988/A4982, driving to current overflow with low inductance steppers (low inductance stepper are desirable). That was the reason of my comment not to use/refer to 8825.

Tinyboy is using Allegro A4988 chips. With shorter minimum on-time, in principle A4988 don't have any problem with common Nema17 steppers, [edit] especially on a 12V printer.
Again, the Tinyboy steppers are not standard and that may drive to same problems with A4988 than other steppers get with DRV8825.
If someone have the references and inductance of these steppers, that may help understanding.

Quote
nebbian
It's got nothing to do with isolating regenerative current.

It's to do with reducing the dead zone. Lots more information available here:
[cabristor.blogspot.com.au]

Edited 2 time(s). Last edit at 05/09/2016 07:16AM by PRZ.

---

Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

Quote
PRZ
low inductance stepper are desirable

interesting remark.

I want to build 12v delta with 42BYGHM809 (0.9 °) which has a higher inductance instead of 42BYGHW609 (1.8 °)... must i worry about that?

The inductance of 42BYGHM809 is 4 mH, while it is 3mH for the 609.
4mH is not huge, and with a nominal current of 1.68A, you may use 1.5A with well cooled drivers (best is integral board or at least 4 layers independant drivers with good cooling - Pololu black edition).

But the big problem here is a 0.9° stepper need twice the steps for the same speed. That is roughly as if you want to run a 1.8° stepper twice as fast. For a 0.9° stepper, it is recommended to use 24V supply, which is approximately equivalent as having 12V on a 1.8° stepper of same inductance.

I use this exact stepper (42BYGHM809) on my D-Box [rouzeau.net], but in 24V.

To explain the stepper choice motive, have a look on the wiki page 'Choosing stepper for a delta' [reprap.org].

And you will also find in this page some info about the DRV8825 problem.

---

Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

Thanks for your answer.
But i afraid to use LED 24v PSU with my poor electrical skills. Now i am using the Xbox PSU (~203w), in my opinion its safer to use and look nice instad of PC PSU or LED PSU.

But reading other forums threads i understood that using 0.9° stepper will give more accuracy... if it's realy true, i am ready to sacrifice print speed and try them in my setup.
As for the driver now i will wating the new DuetNG board with embedded drivers.

Quote
uvarovkv
Thanks for your answer.
But i afraid to use LED 24v PSU with my poor electrical skills. Now i am using the Xbox PSU (~203w), in my opinion its safer to use and look nice instad of PC PSU or LED PSU.

But reading other forums threads i understood that using 0.9° stepper will give more accuracy... if it's realy true, i am ready to sacrifice print speed and try them in my setup.
As for the driver now i will wating the new DuetNG board with embedded drivers.

The 0.9deg motors on my delta have a very similar specification to the ones you propose to use. With 12V supply, I found I was limited to about 150mm/sec travel speed. 24V is recommended for these motors. OTOH if you intend to wait for the Duet NG then you may find that a motor with a current rating of around 2A instead of 1.68A and correspondingly lower inductance would give you higher speed at 12V.

I presume your planned machine has either a small bed or an unheated bed. If the bed is large or heated, then you need to use 24V or mains power to heat the bed anyway.

---

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'm using these .9deg steppers from StepperOnline and they don't have any trouble reaching 300mm/sec with a 12V power supply. The controller is AZSMZ and is using DRV8825s hardwired (unfortunately) to 32 microsteps.

Quote
dc42

Quote
uvarovkv
Thanks for your answer.
But i afraid to use LED 24v PSU with my poor electrical skills. Now i am using the Xbox PSU (~203w), in my opinion its safer to use and look nice instad of PC PSU or LED PSU.

But reading other forums threads i understood that using 0.9° stepper will give more accuracy... if it's realy true, i am ready to sacrifice print speed and try them in my setup.
As for the driver now i will wating the new DuetNG board with embedded drivers.

The 0.9deg motors on my delta have a very similar specification to the ones you propose to use. With 12V supply, I found I was limited to about 150mm/sec travel speed. 24V is recommended for these motors. OTOH if you intend to wait for the Duet NG then you may find that a motor with a current rating of around 2A instead of 1.68A and correspondingly lower inductance would give you higher speed at 12V.

I presume your planned machine has either a small bed or an unheated bed. If the bed is large or heated, then you need to use 24V or mains power to heat the bed anyway.

It's a good news!
But i want to ask, if i'll use 42BYGHM810 with 1.8 mH inductance which rated at 2.4A... the new Duet and its drivers will be able to survive this current?

Thanks for your advice! And yes, i am planing to use tiny heated bed with Ø170mm.

Quote
uvarovkv

It's a good news!
But i want to ask, if i'll use 42BYGHM810 with 1.8 mH inductance which rated at 2.4A... the new Duet and its drivers will be able to survive this current?

One of our design goals has been to achieve a modest increase in available stepper motor current for the same board cooling. We won't know to what extent we have achieved that until we do thermal tests with the pre-production boards. As you don't usually run stepper motors at more than about 85% of their rated current, it may be that 2.4A motors would be a reasonable match. But I think it might be safer to go with 2A motors rather than 2.4A.

---

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].

We are making this Ripple Eliminator according discussion from HK 3D Printer Forum base on Kossel Mini Delta 3D Printer

[www.hkepc.com]

For Delta type 3D Printer, it reduce the noise from motor and get great appearance impovement,
For cardesian type 3D Printer, it will reduce the noise from the motor

Quote
fredchan
We are making this Ripple Eliminator according discussion from HK 3D Printer Forum base on Kossel Mini Delta 3D Printer

[www.hkepc.com]

For Delta type 3D Printer, it reduce the noise from motor and get great appearance impovement,
For cardesian type 3D Printer, it will reduce the noise from the motor

is it available to buy?
thx

yes, please find from www.hkmakers.hk