Fracktal 3d Printers come with 3 Limit switches.
Whenever these switches fail the printer faces certain issues like not being able to move in certain direction or going and crashing at the edges.
Below we have listed out the indicators of limit switch failure and how to fix them.
1. Checking Limit Switches.
1. Access the printer via octo print.
2. Bring the carriage and Bed to the center. If you cant control them using the onscreen buttons turn of the machine and manually push them.
3. Give M119 command in terminal.
4. You should get this output
Reporting endstop status
Here the open status indicated that the limit switches are not triggered. Since the carriage and bed are at center the limit switches are not pressed. So they are showing open. In case a limit switch is faulty it will show triggered even without getting pressed.
5. If all limit switches are showing correct output do the next step. Incase they are showing wrong values note the limit switch and later in this article you will be told how to fix it.
6. Home the XY carriage and Bed to Z home. With XY and Z at home position all limit switches should be triggered.
7. Give M119 command in terminal.
8. You should get this output if all switches are correct.
Reporting endstop status
NOTE: Limit switches work on OPEN or CLOSE status. There are chances of the switch giving both False open and False close status. So you need to check the switch in both the statuses.
Note: The limit switches on Fracktal Printers are normally open types. There will be small voltage flowing through the switch. Whenever the switch is press the flow of current is stopped and it shows the Status as TRIGGERED. In case there's a loose contact or wiring issue, it will show as TRIGGERED because there is no current flow.
Once you identify the limit switch which is giving faulty reading there can be 2 possibilities.
1. Faulty Limit switch.
Limit switch can be tested by 2 methods.
1. Using Multimeter.
To check the limit switch using multimeter
set the multimeter in connectivity mode> connect to ends of limit switch wire to the multimeter probes> If the switch is fine it should give a beep. If the switch is spoilt it will not give beep.
Check without pressing the button. you should get a beep is switch is fine
If you get the beep, Press the limit switch and the beep should stop. If the beep does not stop when you press the limit switch, it means the switch is damaged.
Check while pressing the button. If the limit switch is fine you should not get beep when button is pressed
2. Trial and error (In case you do not have multimeter)
If you do not have multimeter replace the faulty limit switch with other limit switch in your machine. If X limit switch is damaged, remove the Y limit switch and plug it into X limit switch port. And check Octaprint and m119. If the output is fine, then limit switch is the issue. If the same issue repeats even after changing limit switch then wiring is the issue. You need to check the connectivity and decide which part in damaged.
If the limit switch is fine still the octoprint is showing wrong values you need to check connectivity.
To check connectivity
How to Test for Continuity with a Digital Multimeter
Basics idea on using ammeter.
- Turn the dial to Continuity Test mode. It will likely share a spot on the dial with one or more functions, usually resistance (Ω). With the test probes separated, the multimeter’s display may show OL and Ω.
- If required, press the continuity button.
- First insert the black test lead into the COM jack.
- Then insert the red lead into the VΩ jack. When finished, remove the leads in reverse order: red first, then black.
- With the circuit de-energized, connect the test leads across the component being tested. The position of the test leads is arbitrary. Note that the component may need to be isolated from other components in the circuit.
- The digital multimeter (DMM) beeps if a complete path (continuity) is detected. If the circuit is open (the switch is in the OFF position), the DMM will not beep.
- When finished, turn the multimeter OFF to preserve battery life.
Continuity testing overview
- Continuity is the presence of a complete path for current flow. A circuit is complete when its switch is closed.
- A digital multimeter’s Continuity Test mode can be used to test switches, fuses, electrical connections, conductors and other components. A good fuse, for example, should have continuity.
- A DMM emits an audible response (a beep) when it detects a complete path.
- The beep, an audible indicator, permits technicians to focus on testing procedures without looking at the multimeter display.
Fracktal printers have custom made PCB's and use FFC instead of normal wires to reduce the mess by having too many wires. To check connectivity issues you need to use a multimeter.
Note: Certain components follow closed loop circuit. Closed loop systems will show connectivity even though there is breakage in circuit. So if you are testing for continuity of the closed loop circuit make sure you remove the end component and make it a open loop (Ex: Remove Limit switch, hot end, thermistor etc incase you need their connectivity )
To check the continuity of the circuit there are test points on the PCB's.
Check the component whose continuity you have to check. (Ex - Limit switch)
Find the test point for the component in the first board, consider Carriage board. (ex: X axis Limit switch has test point X-LIM)
Find the test point in other board. consider Chassys board. Keeping the two multimeter probes on the required test point should give you beeping sound if there is no problem with the continuity of the circuit. If there is breakage/Issue with the circuit the probe will not beep.
Ex: When you keep probe on X limit test point of carriage board and on X limit test point of chassys board it should beep if the connections are fine. If the connection has issue the multimeter will not beep.
4. Once issue is found with the connectivity you need to check the FFC for breakage or damage.
5. If you are checking connectivity between 2 boards where there is a PCB in between you need to check connectivity between the individual boards to determine where the connection is faulty.
Ex: If you check connectivity between a point in carriage board and between MKS daughter board and find the connectivity to be faulty, you need to check connectivity between Carriage PCB and Chassys PCB. And then between Chassys PCB and Daughter board of MKS.
Note: If the connectivity is fine but still there is no power output at the connecting pin there are chances that the board is damaged. To confirm if the board is damaged you need to check connectivity between the test point and output pin like JST pin or FFC connector.
Checking connectivity between FFC connector pin. Normally these pins get burnt due to various reasons) Checking JST pin terminal and test point. Sometimes due to loose connection or short circuit the connectors get burnt.