Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)  

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

I still have the parts for the chimney mod, used it before and it does work.

I widened the hole a little. Already ran into that issue.  Chamfered the top to help the filament enter easier too.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

The skelestruder is similarly configured at the inlet side with a tight plastic profile above the gears. The only times I've had jams there are when strands build up and get impacted, causing grief.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

I had troubles getting the filament to load, it was just a little off, so chamfering the hold let it slide in easily.

Since the page tube in the extruder is 1.85mm ID, the tips should be smaller than 2mm.  It I think that was the plan.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

That fixed the loading issue.  I was under the impression that the new extruder parts made it so the chimney sensor was not needed, but I was wrong.  It is only needed if you have the MMU2S, not needed without it.

Lesson learned for the future.  Just downloaded the firmware again (your Kuo firmware is amazing!!) and flashed, set the steps, etc, and it auto loaded like a champ.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Careful with PWM_GRAD values. Also, remember they are for stealth mode, not spread cycle.

Going lower than 5 gets you into really big current spikes. I would watch the current spikes with a current probe and scope. Don't let the spikes get more than about 50% overshoot. I've already tuned to reasonable values in my firmware for  OMC and Moons. 

From ages ago...

Low values for PWM_GRAD 1 to 4 give good carriage control, but you hear an annoying squeak during fast decels. Also, you see large current overshoots on the scope.

High values for PWM_GRAD 10 to 15 give very good current clamping and no more squeaks, but the y-axis is too heavy to use high values. If one over-regulates the overshoots, the y-axis will layer shift due to insufficient torque during big velocity changes.

Mid values PWM_GRAD 5-6 seems to be a good compromise. It's going to require additional print jobs to verify all is good.

 

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

clave-a, honestly, you're going back over territory explored months ago. For the two recommended 0.9 motors, my firmware already has my recommended valeus.

You are welcome to work on an LDO motor tuning, but it's really up to you to understand and measure your setting results when doing motor tuning. You should be using a current probe and scope to watch the waveforms as you alter the parameters. 

Here are some motion movement gcodes I used to slew the axes around during current measurements. 

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Posted by: guy.k2

For the two recommended 0.9 motors, my firmware already has my recommended valeus.

This is why I use your firmware.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Hi, i am playing around with some new motors and want to increase the Motor current of X and Y a littel bit.
TMCs has heatsinks and a fan is installed.

I think i read About it but i can't find it again 🙁

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Be cautious about increasing current. EINSY is not designed for much motor current drive capacity. It is barely adequate for stock 1.8 motors. Going to 0.9, even the low current ones I recommend, pushes loads a bit above stock thermal tolerance. Adding heat sinks gains enough extra dissipation to run the recommended 0.9's indefinitely. They aren't necessarily going to let you go much higher. What seems okay for the first 9 hours of printing can fail in a TMC2130 overtemp error. Whatever you end up setting, do some 24 hour prints with lots of motion and accelerations before declaring victory. 

Stealthchop and spread cycle need are adjusted independently. 

Stealth currents are set in my configuration.Prusa.h  

The pertinent lines are "hard to find" because they are marked with a //Kuo comment.

///Kuo TMC2130_PWM_GRAD & TMC2130_PWM_AMP tuned for 09 motor.
//Better axis motion control with lower TMC2130_PWM_GRAD 2,3,4 but can squeak during fast declerations.
//TMC2130_PWM_GRAD too high causes y-layer shifts
//TMC2130_PWM_GRAD_Y 4 is reasonable choice on Y. 
//Raised TMC2130_PWM_AMPL_Y to 250 to prevent y-layer shifts on weaker motors

#ifndef X_AXIS_MOTOR_09
#define TMC2130_PWM_GRAD_X 2 // PWM_GRAD 
#define TMC2130_PWM_AMPL_X 230 // PWMCONF
#else
#define TMC2130_PWM_GRAD_X 4 // PWM_GRAD Kuo 0.9 degree motor tuning
#define TMC2130_PWM_AMPL_X 235 // PWMCONF Kuo 0.9 degree motor tuning
#endif
#define TMC2130_PWM_AUTO_X 1 // PWMCONF
#define TMC2130_PWM_FREQ_X 2 // PWMCONF

#ifndef Y_AXIS_MOTOR_09
#define TMC2130_PWM_GRAD_Y 2 // PWM_GRAD 
#define TMC2130_PWM_AMPL_Y 235 // PWMCONF
#else
#define TMC2130_PWM_GRAD_Y 4 // PWM_GRAD Kuo 0.9 degree motor tuning 
#define TMC2130_PWM_AMPL_Y 250 // PWMCONF Kuo 0.9 degree motor tuning
#endif
#define TMC2130_PWM_AUTO_Y 1 // PWMCONF
#define TMC2130_PWM_FREQ_Y 2 // PWMCONF

#ifndef Z_AXIS_MOTOR_09
#define TMC2130_PWM_GRAD_Z 4 // PWMCONF
#define TMC2130_PWM_AMPL_Z 200 // PWMCONF
#else
#define TMC2130_PWM_GRAD_Z 4 // PWM_GRAD Kuo 0.9 degree motor tuning
#define TMC2130_PWM_AMPL_Z 200 // PWMCONF Kuo 0.9 degree motor tuning
#endif
#define TMC2130_PWM_AUTO_Z 1 // PWMCONF
#define TMC2130_PWM_FREQ_Z 2 // PWMCONF

#ifndef E_AXIS_MOTOR_09
#define TMC2130_PWM_GRAD_E 4 // PWM_GRAD 
#define TMC2130_PWM_AMPL_E 240 // PWMCONF
#else
#define TMC2130_PWM_GRAD_E 4 // PWM_GRAD Kuo 0.9 degree motor tuning 
#define TMC2130_PWM_AMPL_E 245 // PWMCONF Kuo 0.9 degree motor tuning
#endif
#define TMC2130_PWM_AUTO_E 1 // PWMCONF
#define TMC2130_PWM_FREQ_E 2 // PWMCONF

You should use a current probe and observe the overshoots as you slew the axes at various rates ranging from slow to very fast. Try to limit current overshoots to max 50% overshoot. More and you pretty much ensure an eventual over temp error. Read through Trinamics's TMC2130 documentation for more insight.

Spread cycle (normal mode) currents you can see a bit further down in the code. I don't adjust the spread cycle currents but instead selected motors that are spec less than 1 amp. The spread cycle current settings are at...

//new settings is possible for vsense = 1, running current value > 31 set vsense to zero and shift both currents by 1 bit right (Z axis only)

#define TMC2130_CURRENTS_H {16, 20, 35, 30}  // default holding currents for all axes

#define TMC2130_CURRENTS_R {16, 20, 35, 30}  // default running currents for all axes

#define TMC2130_UNLOAD_CURRENT_R 12 // lower current for M600 to protect filament sensor 

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Thanks

Can you explain also the value of current?
In SpreadCycle 16 means how much Ampere? Or in StealthChop 230?

I prefer SpreadCycle because there is no big differnce in noise Overall.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Posted by: michael-1

Thanks

Can you explain also the value of current?
In SpreadCycle 16 means how much Ampere? Or in StealthChop 230?

I prefer SpreadCycle because there is no big differnce in noise Overall.

For SpreadCycle current calculations, take a look here.

Another word of caution: more current isn't always better, since it also increases back EMF. I've found the EMF Calculator at http://RepRapFirmware.org to be quite useful.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

I've had to ditch the Taurus Y axis motor mount and go back to something more stock. I was getting to many self test failures no matter how tight I have the belt and it was not the belt jumping teeth.

The problem was that the Taurus motor is mounted in the middle of the printer whereas a stock mount is at the rear.

When the printer is carrying out a self test, it runs the bed to the back and drives it against the end stop. With the motor being in the middle, there was still at least half a length of belt between the belt mount and the motor, this is slightly elastic and allows the motor to turn a little as the belt stretches, rather than get a dead stop or near enough a dead stop, and I'm using a genuine Gates belt as well!.

With the motor at the rear, there is approx 1.5 cm's of belt to stretch when the bed drives against the end stop, this is hardly able to stretch enough to affect homing.

So in reality, if we want improved homing detection and esp. self test, we really should be using a wider belt which will stretch less.

For now, I'm back to the motor being mounted at the rear and self test passes every time.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Thanks for the follow up, Chocki. 

BTW, I changed one of my machines to 26 volts like yours. Thus far OK in enclosure at 42C x 30 hours print time.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Did you re-run PID tuning?, it makes a difference to the PID values now your 40W heater is a 43.3W heater 😊  (It all helps).

I'm ordering Gates GT2 9mm belt and a gates toothed idler for the Y axis as I don't like how the 6mm belt can stretch this much, hopefully this will also reduce Y axis ghosting as well, drive pulley is already 10mm so just need to remake the belt clamp for the heated bed and tensioner for the front of the printer.

There is not much scope for reducing bed weight like there was with the extruder (Skelestruder), so reducing springing of the belt is the only real improvement without increasing motor size.

Once I get all the parts together I'll do a print with the 6mm belt then swap to the 9mm belt and see if there is any noticeable improvement in Y axis ghosting.

My Y axis running on oiled bearings is really free to move, so there is virtually no resistance in the bearings.

This is with the belt removed and shaking the printer, the bed stays still!. (The blue tape is just temporary until I print a cable guide).

Free Y Axis

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Yes, repeat PID after going to 26 volts. Actually on a 50 watt Slice heater. Nice steady temps at 290C on Octoprint graph after redoing PID.

26 volts by DVM at the power supply. EINSY support voltage menu says 25.7 volts, much like you reported.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

BTW I think it's actually 40 watts ---> 46.9 watts since it goes up with the square of the amperage increase.

W= I^2 R

Which means my 50 watt heater is now running at 58.7 watts

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Damn, I thought 43 seemed a little low. Your right P=I^2 R

Rushing about too much trying to post to forums whilst being late for work!, it's no good, work gets in the way 😉 

I don't suppose you know what the power rating is of the heated bed, I can't seem to find this information readily.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

They do hide that spec. I don't see it anywhere. The expected resistance of the bed is between 3.5 and 4 ohms.

24 volts / 3.75 ohms is about 6.4 amps

6.4 * 6.4 * 3.75 is about 150 watts. That seems reasonable an estimate for the bed.

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

At 26v using the resitance value of 3.75 ohms, the power comes in at 180W. thats an increase of 18% over 153Watts.

Not a bad little increase.

No wonder I notice the heated bed coming up to temperature quicker

RE: Stepper Motor Upgrades to Eliminate VFA's (Vertical Fine Artifacts)

Just don't let Jo catch you void your warranty 😉

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