Sergey Pastor / grbl

doc/markdown/laser_mode.md@0:f1834a63f7c1, 2017-09-04 (annotated)

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Sergunb
Date:
Mon Sep 04 12:03:42 2017 +0000
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0:f1834a63f7c1
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Sergunb 0:f1834a63f7c1 1 ## Grbl v1.1 Laser Mode
Sergunb 0:f1834a63f7c1 2
Sergunb 0:f1834a63f7c1 3 **_DISCLAIMER: Lasers are extremely dangerous devices. They can instantly cause fires and permanently damage your vision. Please read and understand all related documentation for your laser prior to using it. The Grbl project is not resposible for any damage or issues the firmware may cause, as defined by its GPL license._**
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Sergunb 0:f1834a63f7c1 5 ----
Sergunb 0:f1834a63f7c1 6
Sergunb 0:f1834a63f7c1 7 Outlined in this document is how Grbl alters its running conditions for the new laser mode to provide both improved performance and attempting to enforce some basic user safety precautions.
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Sergunb 0:f1834a63f7c1 9 ## Laser Mode Overview
Sergunb 0:f1834a63f7c1 10
Sergunb 0:f1834a63f7c1 11 The main difference between default Grbl operation and the laser mode is how the spindle/laser output is controlled with motions involved. Every time a spindle state `M3 M4 M5` or spindle speed `Sxxx` is altered, Grbl would come to a stop, allow the spindle to change, and then continue. This is the normal operating procedure for a milling machine spindle. It needs time to change speeds.
Sergunb 0:f1834a63f7c1 12
Sergunb 0:f1834a63f7c1 13 However, if a laser starts and stops like this for every spindle change, this leads to scorching and uneven cutting/engraving! Grbl's new laser mode prevents unnecessary stops whenever possible and adds a new dynamic laser power mode that automagically scales power based on current speed related to programmed rate. So, you can get super clean and crisp results, even on a low-acceleration machine!
Sergunb 0:f1834a63f7c1 14
Sergunb 0:f1834a63f7c1 15 Enabling or disabling Grbl's laser mode is easy. Just alter the **$32** Grbl setting.
Sergunb 0:f1834a63f7c1 16 - **To Enable**: Send Grbl a `$32=1` command.
Sergunb 0:f1834a63f7c1 17 - **To Disable:** Send Grbl a `$32=0` command.
Sergunb 0:f1834a63f7c1 18
Sergunb 0:f1834a63f7c1 19 **WARNING:** If you switch back from laser mode to a spindle for milling, you **MUST** disable laser mode by sending Grbl a `$32=0` command. Milling operations require the spindle to get up to the right rpm to cut correctly and to be **safe**, helping to prevent a tool from breaking and flinging metal shards everywhere. With laser mode disabled, Grbl will briefly pause upon any spindle speed or state change to give the spindle a chance to get up to speed before continuing.
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Sergunb 0:f1834a63f7c1 21
Sergunb 0:f1834a63f7c1 22 ## Laser Mode Operation
Sergunb 0:f1834a63f7c1 23
Sergunb 0:f1834a63f7c1 24 When laser mode is enabled, Grbl controls laser power by varying the **0-5V** voltage from the spindle PWM D11 pin. **0V** should be treated as disabled, while **5V** is full power. Intermediate output voltages are also assumed to be linear with laser power, such that **2.5V** is approximate 50% laser power. (A compile time option exists to shift this linear model to start at a non-zero voltage.)
Sergunb 0:f1834a63f7c1 25
Sergunb 0:f1834a63f7c1 26 By default, the spindle PWM frequency is **1kHz**, which is the recommended PWM frequency for most current Grbl-compatible lasers system. If a different frequency is required, this may be altered by editing the `cpu_map.h` file.
Sergunb 0:f1834a63f7c1 27
Sergunb 0:f1834a63f7c1 28 The laser is enabled with the `M3` spindle CW and `M4` spindle CCW commands. These enable two different laser modes that are advantageous for different reasons each.
Sergunb 0:f1834a63f7c1 29
Sergunb 0:f1834a63f7c1 30 - **`M3` Constant Laser Power Mode:**
Sergunb 0:f1834a63f7c1 31
Sergunb 0:f1834a63f7c1 32 - Constant laser power mode simply keeps the laser power as programmed, regardless if the machine is moving, accelerating, or stopped. This provides better control of the laser state. With a good G-code program, this can lead to more consistent cuts in more difficult materials.
Sergunb 0:f1834a63f7c1 33
Sergunb 0:f1834a63f7c1 34 - For a clean cut and prevent scorching with `M3` constant power mode, it's a good idea to add lead-in and lead-out motions around the line you want to cut to give some space for the machine to accelerate and decelerate.
Sergunb 0:f1834a63f7c1 35
Sergunb 0:f1834a63f7c1 36 - NOTE: `M3` can be used to keep the laser on for focusing.
Sergunb 0:f1834a63f7c1 37
Sergunb 0:f1834a63f7c1 38 - **`M4` Dynamic Laser Power Mode:**
Sergunb 0:f1834a63f7c1 39 - Dynamic laser power mode will automatically adjust laser power based on the current speed relative to the programmed rate. It essentially ensures the amount of laser energy along a cut is consistent even though the machine may be stopped or actively accelerating. This is very useful for clean, precise engraving and cutting on simple materials across a large range of G-code generation methods by CAM programs. It will generally run faster and may be all you need to use.
Sergunb 0:f1834a63f7c1 40
Sergunb 0:f1834a63f7c1 41 - Grbl calculates laser power based on the assumption that laser power is linear with speed and the material. Often, this is not the case. Lasers can cut differently at varying power levels and some materials may not cut well at a particular speed and/power. In short, this means that dynamic power mode may not work for all situations. Always do a test piece prior to using this with a new material or machine.
Sergunb 0:f1834a63f7c1 42
Sergunb 0:f1834a63f7c1 43 - When not in motion, `M4` dynamic mode turns off the laser. It only turns on when the machine moves. This generally makes the laser safer to operate, because, unlike `M3`, it will never burn a hole through your table, if you stop and forget to turn `M3` off in time.
Sergunb 0:f1834a63f7c1 44
Sergunb 0:f1834a63f7c1 45 Describe below are the operational changes to Grbl when laser mode is enabled. Please read these carefully and understand them fully, because nothing is worse than a garage _**fire**_.
Sergunb 0:f1834a63f7c1 46
Sergunb 0:f1834a63f7c1 47 - Grbl will move continuously through **consecutive** motion commands when programmed with a new `S` spindle speed (laser power). The spindle PWM pin will be updated instantaneously through each motion without stopping.
Sergunb 0:f1834a63f7c1 48 - Example: The following set of g-code commands will not pause between each of them when laser mode is enabled, but will pause when disabled.
Sergunb 0:f1834a63f7c1 49
Sergunb 0:f1834a63f7c1 50 ```
Sergunb 0:f1834a63f7c1 51 G1 X10 S100 F50
Sergunb 0:f1834a63f7c1 52 G1 X0 S90
Sergunb 0:f1834a63f7c1 53 G2 X0 I5 S80
Sergunb 0:f1834a63f7c1 54 ```
Sergunb 0:f1834a63f7c1 55 - Grbl will enforce a laser mode motion stop in a few circumstances. Primarily to ensure alterations stay in sync with the g-code program.
Sergunb 0:f1834a63f7c1 56
Sergunb 0:f1834a63f7c1 57 - Any `M3`, `M4`, `M5` spindle state _change_.
Sergunb 0:f1834a63f7c1 58 - `M3` only and no motion programmed: A `S` spindle speed _change_.
Sergunb 0:f1834a63f7c1 59 - `M3` only and no motion programmed: A `G1 G2 G3` laser powered state _change_ to `G0 G80` laser disabled state.
Sergunb 0:f1834a63f7c1 60 - NOTE: `M4` does not stop for anything but a spindle state _change_.
Sergunb 0:f1834a63f7c1 61
Sergunb 0:f1834a63f7c1 62 - The laser will only turn on when Grbl is in a `G1`, `G2`, or `G3` motion mode.
Sergunb 0:f1834a63f7c1 63
Sergunb 0:f1834a63f7c1 64 - In other words, a `G0` rapid motion mode or `G38.x` probe cycle will never turn on and always disable the laser, but will still update the running modal state. When changed to a `G1 G2 G3` modal state, Grbl will immediately enable the laser based on the current running state.
Sergunb 0:f1834a63f7c1 65
Sergunb 0:f1834a63f7c1 66 - Please remember that `G0` is the default motion mode upon power up and reset. You will need to alter it to `G1`, `G2`, or `G3` if you want to manually turn on your laser. This is strictly a safety measure.
Sergunb 0:f1834a63f7c1 67
Sergunb 0:f1834a63f7c1 68 - Example: `G0 M3 S1000` will not turn on the laser, but will set the laser modal state to `M3` enabled and power of `S1000`. A following `G1` command will then immediately be set to `M3` and `S1000`.
Sergunb 0:f1834a63f7c1 69
Sergunb 0:f1834a63f7c1 70 - To have the laser powered during a jog motion, first enable a valid motion mode and spindle state. The following jog motions will inherit and maintain the previous laser state. Please use with caution though. This ability is primarily to allow turning on the laser on a _very low_ power to use the laser dot to jog and visibly locate the start position of a job.
Sergunb 0:f1834a63f7c1 71
Sergunb 0:f1834a63f7c1 72
Sergunb 0:f1834a63f7c1 73 - An `S0` spindle speed of zero will turn off the laser. When programmed with a valid laser motion, Grbl will disable the laser instantaneously without stopping for the duration of that motion and future motions until set greater than zero..
Sergunb 0:f1834a63f7c1 74
Sergunb 0:f1834a63f7c1 75 - `M3` constant laser mode, this is a great way to turn off the laser power while continuously moving between a `G1` laser motion and a `G0` rapid motion without having to stop. Program a short `G1 S0` motion right before the `G0` motion and a `G1 Sxxx` motion is commanded right after to go back to cutting.
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Sergunb 0:f1834a63f7c1 77
Sergunb 0:f1834a63f7c1 78 -----
Sergunb 0:f1834a63f7c1 79 ###CAM Developer Implementation Notes
Sergunb 0:f1834a63f7c1 80
Sergunb 0:f1834a63f7c1 81 TODO: Add some suggestions on how to write laser G-code for Grbl.
Sergunb 0:f1834a63f7c1 82
Sergunb 0:f1834a63f7c1 83 - When using `M3` constant laser power mode, try to avoid force-sync conditions during a job whenever possible. Basically every spindle speed change must be accompanied by a valid motion. Any motion is fine, since Grbl will automatically enable and disable the laser based on the modal state. Avoid a `G0` and `G1` command with no axis words in this mode and in the middle of a job.
Sergunb 0:f1834a63f7c1 84
Sergunb 0:f1834a63f7c1 85 - Ensure smooth motions throughout by turning the laser on and off without an `M3 M4 M5` spindle state command. There are two ways to do this:
Sergunb 0:f1834a63f7c1 86
Sergunb 0:f1834a63f7c1 87 - _Program a zero spindle speed `S0`_: `S0` is valid G-code and turns off the spindle/laser without changing the spindle state. In laser mode, Grbl will smoothly move through consecutive motions and turn off the spindle. Conversely, you can turn on the laser with a spindle speed `S` greater than zero. Remember that `M3` constant power mode requires any spindle speed `S` change to be programmed with a motion to allow continuous motion, while `M4` dynamic power mode does not.
Sergunb 0:f1834a63f7c1 88
Sergunb 0:f1834a63f7c1 89 - _Program an unpowered motion between powered motions_: If you are traversing between parts of a raster job that don't need to have the laser powered, program a `G0` rapid between them. `G0` enforces the laser to be disabled automatically. The last spindle speed programmed doesn't change, so if a valid powered motion, like a `G1` is executed after, it'll immediately re-power the laser with the last programmed spindle speed when executing that motion.