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October 1, 2019 at 10:17 am #1155danParticipant
This is my 2 cents based on experiments with TMC stepper drivers installed in The Beast V1 and 2 as well as tests with our new Prototype V3 unit. Specifically the two types TMC drivers I have used is the TMC2208 and TMC2130.
You may have read about a different type of stepper driver made by Trinamics. This post is merely, my thoughts on the use of these drivers and an attempt to explain why we don’t use them.
The stepper drivers we specced into The Beast V1 and 2 are called the DRV8825. These stepper drivers are capable of producing around 1.5Amp of current per phase and can be Micro stepped down to 32x. Combined with gearing of a 20 tooth pulley, these drivers make our printers incredibly accurate, so much so that fine layer graduations in the X and Y axes are almost (if not) visually impossible to detect.
Alternatively, the last few years has seen a the TMC stepper drivers grow in popularity. They can potentially provide up to 512x micro stepping (albeit with some relatively difficult modifications to your electronics) or with little modification provide interpolated 16x native micro stepping to 256x Interpolation. Further, TMC drivers are as nickname “silent step sticks” suggest, cause your motors to run very quietly, much quieter than a motor connected to a DRV8825 stepper driver.
Given the relatively low price of the Trinamics drivers, it would seem an easy decision to upgrade your electronics to benefit from the better positional accuracy they have to offer. In theory, better positioning should mean a better print, however the reality in my experience is quite the opposite.
Firstly, TMC drivers in their “drop in” replacement configuration run very hot. This means that unless cooled properly, they will skip steps. How do you cool them properly? with some high RPM fans which as you could expect, can produce more sound than the drivers themselves prevent the motors from making.
The skipping of steps is a big one. Not only do these drivers run hot, but in order to be reliable across a large print, the drivers need to run cool, often for hours at a time, a slight change in ambient temperature can mean a driver which has been flawless for 12 hours can suddenly start to skip, ruining your print.
My second issue is power delivery. TMC drivers have no where near the guts of the DRV8825 drivers. DRV8825 can be driven hard, all day, every day without skipping steps, with relatively little cooling. With DRV8825 drivers, one can set the stepper driver output right up to the motors 2Amp limit, sure the motor runs noisy and hot, but it doesn’t skip steps. With TMC drivers, its not possible to achieve the same holding torque. Even if you get close, expect your drivers to overheat and skip steps despite being cooled with the fastest and noisiest high RPM fans available. This may not be an issue with small stepper motors (I haven’t tried) but with the stepper motors required by The Beast to move relatively large gantries around, reliable power output is a must.
The TMC drivers do have their place. Used in printers with relatively low gearing, using 30+ tooth GT2 Pulleys, they really do shine. In this configuration, the 16x native to 256x smoothing results in visibly smoother graduations of gently sloping surfaces than a DRV8825 set at 32x. Again even in this configuration any benefit obtained from quiet running motors is negated by the comparatively noisy fans required to cool the drivers.
Last point. If you’ve seen plug and play “Stepper smoothers” such as these floating around, at least with 20 tooth GT2 pulleys provided with our printer, don’t waste your money. I can detect absolutely no visual benefit :
What are your thoughts?
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