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- Grbl v1.1 Configuration
- Junction Deviation Explained and Visualized
- Motion control
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Subscribe to RSSGitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. Just updated to the new 2. One of the big features I wanted to try is junction deviation, but as soon as I was going to enable I noticed that I don't really know how to tune it. I've actually read through all discussions involving it here on the Marlin's git but practically I'm still not sure how to go about it. But how do I start? I guess I could use the defaults and go from there, but I'm not sure if I should lower Junction deviation value or acceleration if I find too much ringing, or even a starting point for my Max Accel. For example, I'm trying this on a tevo tornado, I use printing Accel and travel Accel, 7 jerk for x and y. What values would be sensible to start with? How do I tune travel and printing Accel if there is only one single max Accel? I saw the formula relating max Accel and junction deviation value to old jerk, so I could do that to get a starting point with the default 0. Edit: This is the most relevant comment for tuning this parameter I think: comment But after reading all I still can't help but feel like this guy: comment. I would always appreciate a how to tune junction deviation I kinda understand how to tune it. Basically there are two parameters: acceleration and deviation. The higher the acceleration the higher will be speed at corners, also, the higher the deviation also, the higher speed at corners. Deviation applies only for corners, acceleration for everything. So, set needed acceleration, print, check your corners, if okay then okay, if not, reduce either acceleration or deviation. However, what i do not understand now is how it behaves on just straight lines. Let the axis rest. How it was before. How does it work now? According to This guide its measured by. Well, the question still remains: How does it work now for streight lines when starting movement from rest. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue. Jump to bottom. Labels T: Feature Request. Copy link Quote reply. Edit: This is the most relevant comment for tuning this parameter I think: comment But after reading all I still can't help but feel like this guy: comment Thanks for the awesome work Marlin team, you're doing the world a great service! This comment has been minimized. Sign in to view. I second this request :. Junction Deviation
Grbl v1.1 Configuration
Most people know that 3D printers can move in X, Y, and Z. These movements are tuned using the parameters Velocity, Acceleration, and Jerk now being replaced with Junction Deviation. These parameters can truly make or break your print quality so understanding what they do is critical. It is intuitive that a printer with movements that are slow and controlled will likely have better print quality than one with high speeds and jerky movements. In order to understand how each of the parameters work we can think about a common scenario of applying the brakes in a car. Imagine you are driving down a road at 45 miles per hour velocity, Zone A and the stop light in front of you turns red. When you hit the brakes your car begins to slow down negative acceleration, Zone C. Eventually you will have decelerated all the way to 0 miles per hour and you will no longer be moving Zone E. The concepts of velocity and acceleration are easy to understand because we deal with them everyday. Jerk on the other hand is referring to how quickly you experience a change in acceleration. For many this is much more difficult to understand. If you look at our oversimplified scenario in the graph above, jerk is represented by points circled B and D. If you think about the moment you applied the brakes you likely feel a sudden change in acceleration and again at the exact moment your car comes to a complete stop. This is because the magnitude of your deceleration suddenly changes from zero to some value at points A-B and then from some value to zero at points D-E. This is jerk. The graph above assumes we are not controlling jerk at all which means we apply the brakes in the beginning abruptly at point B and then come to a complete stop abruptly at point D. Now lets image instead of constant deceleration we gradually press the brake at the beginning and then slow down gently to a complete stop. The new graph would look something similar to what you see below. Notice how the kinks in the red line have disappeared and instead are smooth contours. We have essentially reduced the areas with high jerk values. It is also important to notice that the slope of the line acceleration has not been changed. This means that acceleration and jerk are completely independent of each other. The speed in which your print head or extruder is moving at any given time. By setting M, you are limiting the maximum speed the printer is allowed to move during a print. The limit on how fast you can change velocity. In the example graphs, it is the slope of the line at any given point. The steeper the line, the greater the acceleration. The rate at which acceleration is changing. If you are looking at the slope of the line, that is acceleration.
Junction Deviation Explained and Visualized
Grbl should respond with:. These either immediately change Grbl's running behavior or immediately print a report of the important realtime data like current position aka DRO. Grbl should respond with a list of the current system settings, as shown in the example below. All of these settings are persistent and kept in EEPROM, so if you power down, these will be loaded back up the next time you power up your Arduino. In prior versions of Grbl, each setting had a description next to it in parentheses, but Grbl v1. This was done to free up precious flash memory to add the new features available in v1. However, most good GUIs will help out by attaching descriptions for you, so you know what you are looking at. To manually change e. If everything went well, Grbl will respond with an 'ok' and this setting is stored in EEPROM and will be retained forever or until you change them. Everything else is the same. Stepper drivers are rated for a certain minimum step pulse length. Check the data sheet or just try some numbers. You want the shortest pulses the stepper drivers can reliably recognize. If the pulses are too long, you might run into trouble when running the system at very high feed and pulse rates, because the step pulses can begin to overlap each other. We recommend something around 10 microseconds, which is the default value. Every time your steppers complete a motion and come to a stop, Grbl will delay disabling the steppers by this value. ORyou can always keep your axes enabled powered so as to hold position by setting this value to the maximum milliseconds. The stepper idle lock time is the time length Grbl will keep the steppers locked before disabling. Depending on the system, you can set this to zero and disable it. On others, you may need milliseconds to make sure your axes come to a complete stop before disabling. This is to help account for machine motors that do not like to be left on for long periods of time without doing something. Also, keep in mind that some stepper drivers don't remember which micro step they stopped on, so when you re-enable, you may witness some 'lost' steps due to this. This setting inverts the step pulse signal. By default, a step signal starts at normal-low and goes high upon a step pulse event. When inverted, the step pulse behavior switches from normal-high, to low during the pulse, and back to high. Most users will not need to use this setting, but this can be useful for certain CNC-stepper drivers that have peculiar requirements. For example, an artificial delay between the direction pin and step pulse can be created by inverting the step pin. This invert mask setting is a value which stores the axes to invert as bit flags. You really don't need to completely understand how it works. You simply need to enter the settings value for the axes you want to invert. This setting inverts the direction signal for each axis. By default, Grbl assumes that the axes move in a positive direction when the direction pin signal is low, and a negative direction when the pin is high. Often, axes don't move this way with some machines.