How to Set the Switches on Your Prusa i3 3D Printer

By Kalani Kirk Hausman, Richard Horne

The Prusa i3 3D printer has switches to let the electronics know when the X, Y, and Z carriages are at the home position. These can very often require an inverted signal for the electronics to understand they’re being activated. If your new RepRap machine refuses to move when you first set it up, it’s quite likely you need to change the following settings either to or to :

  • (or change to )

  • (or change to )

  • (or change to false)

  • You have to do likewise with the motor directions if the carriage moves away from your end-stop when you home the machine. You’ll have to change the motor direction, using the settings that follow. Then you’ll have to do the same with the extruder if it pushes the filament in the wrong direction when you drive it forward. Change it here:

  • (or change to )

  • (or change to )

  • (or change to )

  • (or change to )

  • (or change to )

  • (or change to )

With and the all other axes, you can set a maximum travel distance. This is handy if something goes wrong or if you accidentally try to print an object bigger than your platform; the firmware will stop the axis rather than crash it into the end of the machine. Movement settings are as follows:

  • The setting tells how fast the X,Y, and Z axes move when doing the command. If it’s set too fast, motors will skip and cause machine misalignments.

  • has a sequence of numbers — for example. This number sequence relates to the X, Y, and Z axes, and to all the extruders fitted to the printer.

    It’s crucial to enter this set of numbers correctly; doing so tells the firmware exactly how many steps each stepper-motor must move the axis or filament to move exactly 1mm. If this setting is not correct, your machine won’t produce accurate parts, and will under- or over-extrude material. To start with, you can use 200 for the number of extruder steps.

    Read on to see why this figure is a good starting point — but expect to change this number after we’ve completed extruder calibration. The axis movement is determined by what belts and pulleys you’ve fitted; the kit or machine type will give you that information.

  • is the maximum speed at which your 3D printer can safely move while printing without causing skips or motor stalls. Again, an example of the setting for X, Y, Z, and Extruder is.

  • defines the fastest rate of change in acceleration, printing, and travel moves. An example for X, Y, Z, and Extruder is .

  • is connected to the maximum setting mentioned earlier; this is the starting speed for acceleration. If it’s set too fast, it won’t allow the stepper motors enough time to ramp up to speed and they’ll stall or skip. An example is for all motors apart from the that of the extruder.

  • is the same as the previous setting, but it’s specific for all extruder retractions; they have to be fast to be effective in combating strings and blobs on your emerging 3D prints. An example of such a setting is.

The last movement settings you can alter are the values; these define the safe levels of instantaneous movement of the axis and extruder. It’s common for a Z axis — which usually consists of threaded rods moving in a nut — to move slowly. The fastest acceleration of a Z axis is still usually much slower than that of all the other motors.

Extruders also require a lot of torque and for that to develop correctly, they need a low starting point for their acceleration. Finally, the X and Y axes can’t start moving fast instantly; they need a setting value that tells the machine so. Typical values for a Prusa i3 machine could be , , and . Values are in mm/second.

With a Delta printer such as the RostockMAX, you don’t have a slow Z axis, so the value would be the same as that of the setting.