To give you some impression of the features of the Trinamic motion and motor drivers. It is far easier to understand the advantages with a real world example. Let’s do some configuration walkthrough of the development machine.
It is all in the code
The biggest advantage of the motor drivers we are using is that everything is defined in software. All aspects of the motors can be configured from the central printer configuration. As you seen in the screenshot above it is done in JSON to make it super simple to configure.
Step by step
We want smooth running motors with fine resolution – so we set the
micro-steps to 256, because we can. All other settings like the
max-speed is given in mm (mm/s to be really precise) so we have to give some
steps-per-mm to convert the micro steps to mm. And since we have constant jerk motion wo do not only configure the
max-acceleration (in mm/s^2) but also the
bow-acceleration (in mm/s^3, which is jerk and may become renamed during development).
At high speeds we do not want to run at micro stepping – we give up some torque since the motor coils are not always running at the maximum rating. So we set the
full-step-speed after which we fall into full steps (this settings of 25mm/s proved a bit on the high side).
The basic power applied to the motor is configured in
current – the nominal motor current. The Trinamic drivers ensure that the voltage is adapted so that always the correct amount of current goes into the motor. The setting is (like all current settings) done in Ampere – the software converts it to internal values for you. So forget fumbling with tiny SMT potentiometers and your multimeter to get a rough estimation of the motor current. It is in the config.
But we have much finer control over the motor. If the motor is not running we do not need the same amount of current as if the motor is running – hence we can reduce it with
hold-current – here a relaxed 0.5A. When accelerating we add some more current to ensure that we do not miss steps – so
acceleration-current increases it a bit to 1.2A. Also if the motor is running real fast we increase the motor current in
high-speed-current to 1.2A too.
And to ensure that we do not reduce the current to early we set the
downscale-delay to 100ms – so that the driver always waits 100ms before it changes to a lower current setting to ensure that the mechanic already settled …
Configuring the bed
This printer works with some real
end-stops – so we have them configured here. We are still in the process to switch to a complete end-stop free setup. We have a
right end-stop with negative polarity – which means it is active low. the
left ends-top is virtual and 220mm from the right end-stop. The Trinamic motion driver will treat it just like real endstop – so we can ensure that X never goes below 0 and we never drive beyond 220mm from the right end-stop.
homing-speed is configured separately since we want it a bit faster than normal speeds – since we just want to hit the endstop – the high
homing-acceleration ensures that we stop abruptly after we have hit the end-stop. The much lower
homing-precision-speed is used to gently find the exact location of the home switch – just like most other rerap firmwares as well …
Is that all?
Yes, for now …
Ok, but that may not be the end. In the Reprap Forum somebody asked what about the possibility of configuring the exact power distribution between the motor coils for each micro step. This is some very detailed motor current configuration which may be exposed in later development steps. The Trinamic motor drivers allow two very interesting configurations to smoothen and improve the motor run:
- There is some detailed chopper configuration which can be used to perfectly adapt the current chopping to the motor used.
- The detailed structure of the micro stepping table can be configured to distribute the micro steps exactly across the full step, or to improve the torque of each micro-step.
Those settings are really advanced and allow very detailed configuration. They also done in software and not very hard to implement. But for the first step we left it you. But surely they will be accessible in the near future.
So stay tuned and get your T-Bone on indiegogo!by