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    BIGTREETECH SKR-PRO-V1.2 & TMC5160hv

    Dear Community

    I have recently purchased the Creality Ender 5 Plus 3D printer as the starting point towards developing this printer to new capabilities.

    To explain where I come from that is what drives my project. I am a naval modeler that started the project of a sailboat model nearly a decade ago. About 7 years ago I decided to use a stepper motor as a winch to control the sail of that sailboat. My goal was to be able to control the sail the way the original sailboats from the beginning of the 20th century. This required to change the length of the sheet used to control the sail by 8.3 meters on a sailboat just 1650 mm in length.

    I did study stepper motor technology by using the stepRocker board from Trinamic first, later with a board that was never released by Trinamic, the motionCookie for stepper motors. The IDE already in those early days of Trinamic gave me the opportunity to do experiments with the stepper motor controlled by a Trinamic IC on a Trinamic board. Here I got aware, not only what aspects influence the performance and noise generated by the stepper motor, but also how different functionalities of the Trinamic ICs used properties of the stepper motor to implement. Many of those today do appear throughout text published about the functionality of SilentStepSticks using the TMC2208 the TMC2130 and the TMC2209.

    I did operate the stepper motor I usethat has a nominal voltage of 3.6VDC with 24VDC. The Trinamic IC, when setup properly the current limit to that defined as nominal current for the stepper motor. The Trinamic functionality that uses PWM to limit the actual current through the coils of the stepper motor can even increase the current for the stepper motor by 20% for a short period of time if peak demand of torque appears and so prevent step losses and to make it possible to use weaker motors.

    So to start upgrading my Creality Ender 5 Plus 3D printer after getting some experience using the 3D printer as provided by Creality y did purchase the BIGTREETECH-SKR-PRO-V1.2. One reason was to provide my printer with the highest computing performance available in the market which uses an ARM Cortex M4 controller running at 168MHz. I did learn about the limits coming from the performance of one 8 bit controller card and 3 32 bit controller cards by watching the corresponding video from Mr. Kersey of the Kersey Fqabrications YouTube channel. So with the choice of the 3D printing controller board, I will have the maximum computing performance available build into my 3D printer.

    This same board allows to use of the SilentStepperStick with the TMC5160 and the V1.1 of the BIGTREETECH board allows up to 35VDC to be fed to the stepper motor via the SilentStepStick5160. Researching the Trinamic website I learned that Trinamic partners with Watterott to design and produce the SilentStepSticks. So I contacted Watterott to learn that they have a SilentStepStick with the TMC5160hv. That SilentStepStick tolerates up to 50 VDC, the datasheet from Trinamic about their TMC5160hv specifies the maximum voltage for their part to be up to 60VDC.

    As a result of these investigations, I did purchase a 600W Meanwell 48VDC power supply to feed the "Motor Power" port of the BIGTREETECH-SKR-PRO-V1.2. For the V1.1 the board specs of up to 35VDC on this port of their board. I did therefore consider it realistic that their board using the SilentStepStick with the TMC5160hv would tolerate a voltage of 48VDC. Today I must say, I was naive to expect the 3D printing community really understand stepper motors.

    Again and again, I get responses that go from the arrogance that follows ignorance responding not with facts, but with nonsense and personal attacks. But what surprised me, even more, was to find that support from BIGTREETECH apparently also had a little burden of understanding the intrinsics of stepper motors. But I also have to state that the support from BIGTREETECH had no arrogance, but was trained to respond to what seems to be the knowledge base in the 3D printing for consumers. In the last response I received today they stated the TMC5160 and correctly stating that this part tolerates only voltages up to 35VDC. I have responded once more indicating that I was talking about a SilentStepStick with the TM5160hv and that the "hv" in that part number referred to a version of the 5160 that is specified for voltages up to 60VDC and that the SilentStepStick from Watterott with the TMC5160hv allowed for voltages from up to 50VDC- So my intention to use that version of the SilentStepStick from Watterott, the selected partner of Trinamich for SilentStepSticks.

    As the platform on which I am opening this thread here is one part related to what I am doing as part of the DIY starting with the Ender 5Plus. On the other side, I would like to share with you readers some basics about stepper motors that have a huge impact on the torque a stepper motor can deliver. The fact that the stepper motors used on the Creality Ender 5 Plus apparently do not deliver information about their nominal values for voltage and current seems to reinforce that those important things to the torque a stepper motor can deliver is based on the nominal values for a given stepper motor. I have been researching in the Internet for NEMA 17 stepper motors. Apparently, those stepper motors are matches with what the knowledge base of the 3D printing community for consumer 3D printers. When you look for NEMA 23 you already find stepper motors that have 4x the torque.

    Let's start with some basics on stepper motors that probably many of you already know. I try to get all readers to the same level. The kind of stepper motors we are talking about for 3D printers are so-called hybrid 2-phase stepper motors with a full step being 1.8 what gets to 200 full steps for a 360 full turn.

    A stepper motor has the highest value torque when it does not do steps, which means holding its position. The reason for this is the induced voltage. What is the induced voltage? The induced voltage is a voltage with the inverse polarity of the voltage applied to a coil. Its effect? It reduces the voltage to which the coil is submitted. The voltage applied + (-induced voltage) = available voltage to create the torque. So when the stepper motor is holding its position, the value of the induced voltage = "0" and so the full applied voltage goes into the generation of the torque. This is why stepper motors are not a good choice when looking for a fast turning motor. The absolute value of the induced voltage is determined by the speed with which the voltage applied to the coil of the stepper motor changes. Absolute this value is called because it is a negative value and I am only referring to the value of the induced voltage ignoring the polarity. The faster a stepper motor does its steps the faster the applied voltage changes its value and the higher is the absolute value of the induced voltage. As a consequence, the sum of these voltages gets closer and closer to 0V and as a consequence, the torque available to the stepper motor goes down. So there is one speed at which the stepper motor cannot apply the required voltage to its coils and the stepper motor loses steps and finally just vibrates without doing any further step.

    Here is one point in my text where I can relate this to my suggestion to use higher voltage in feeding the stepper motor. It will take a higher absolute induced voltage to reduce the effective voltage to the point you loos steps and/or the stepper motor just stops and vibrates. Also, a stepper motor fed with y higher voltage than the nominal voltage can turn faster before having the same effective voltage and torque or said the other way around. The stepper motor will deliver a higher torque.

    And here comes a key function of a stepper motor controller, here the Trinamic chips on the SllentStepSticks, the PWM, the Pulse Width Modulation.

    pwm.png

    As you can see from the graphic, the length of the dust cycle of the PWM determines the amount of current that will flow through the SilentStepStick and from there to the stepper motor. The Trinamic IC properly configured will limit the current to the nominal value specified during setup and so prevent that a higher voltage applied will lead to more current. Now let's take the power equation to simplify the impact of applying a higher voltage:

    P[W] = I[A] * U[V]

    Let's assume a stepper motor is operated at its nominal values for current and voltage and related to which the torque is determined.

    P = 1A * 12V = 12W

    Now let us assume we operate another motor with the same nominal power:

    P = 4A * 3V = 12W

    Now we see that the second motor must have coils of higher performance to tolerate 4A of current. If now I do apply 12V to the second motor and have the Trinamic IC limit the current by using PWM to the same 4A of current:

    P = 4A * 12V = 48W

    The Trinamic ICs also have the capability to reduce the amount of current using PWM so that the resulting torque is sufficient for the current torque demand on the stepper motor. This was very important when I used the stepper motor as a winch on my model sailboat that was powered from 12 LiFePO4 batteries connected in series. This would reduce the rate at which the batteries would de discharge during operation. Another benefit of this is that the stepper motor remains cooler.

    So, this was a lot of information, but it explains what I want to achieve with the configuration I plan to build for my 3D printer. I also hope it explained to you why realistically we should know the nominal values of the stepper motors build i.e. in my Ender 5 Plus. If those are stepper motors with a nominal voltage value of 12V the choice for the stepper motors chosen was a bad decision.

    As the Ender 5 Plus allows to the operation of the SilentStepSticks with either 12V or 24V the Malin software should serve the Trinamic ICs to limit the current to the nominal value. Maybe that something I should do. Find where the current value is limited and to what value.


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