Help with CNC 3018 from Banggood

[JeanB]

Good afternoon,

I need help in trying to run my 3018 CNC purchase on Banggood.

I installed 5 micro switches (2 X, 2 Y and 1 Z) to act as end stops and used for homing.

The homing cycle works fine. I home and zero my machine in the lower left corner of the table, however, when I want to carve, using Easel, it gives me a hard limit alarm as soon as I try to turn on the spindle.

After hours of reading, I changed all my limit switch wiring to shielded wires……..Nothing still same issues.

After homing,
• my machine positions are X = -284, Y = -2, Z = -2
• my work position is X = 0, Y = 0, Z= 0

If, after homing, I remove the limit switches using $21=0 and try to start a carve, my spindle will start but then, my table moves (Y axis) moves a few mm into the back frame (I have a 2 mm homing pull-off). It should move towards the front?????

Please help, thank you.

Jean

[JAZZCNC]

Sounds like you have a noise issue if only happens when spindle starts. Does the control software have an option to apply De-bounce filtering to the inputs.?

[JeanB]

Thank you for your reply.

Yes, there is a de-bounce setting and I have it at $26=250 which is the maximum..... it seems I can go. I tried various settings, as suggested by the pocket GRBL guide, but still nothing.

Do I need to change all the wiring to shielded cable? I already changed all the micro switch cable to shielded cable?

[JAZZCNC]

Thank you for your reply.

Yes, there is a de-bounce setting and I have it at $26=250 which is the maximum..... it seems I can go. I tried various settings, as suggested by the pocket GRBL guide, but still nothing.

Do I need to change all the wiring to shielded cable? I already changed all the micro switch cable to shielded cable?

Ok well if De-bounce allowed it to work then you are obviously suffering from noise issues so now you need to lower the de-bounce back to Zero, the reason for this is because it slows the switch response time so can be unsafe, and go with a solution like Doddy mentions where you pull the input high or low to stop it floating.

If after this you still get noise issues then there are other methods, like Opto's and Capacitors, etc but won't get into that now because I'm 99% sure fixing the floating input will work.

[JeanB]

Good morning JazzCNC,

I just tried the debouched at 0, as soon as I try to carve and start the spindle, I get an alarm. As I said to Doddy, I already tried the capacitors and that did not work.

[Doddy]

Complete guesswork here (without seeing your controller board - but you're suggesting some local controller, likely a microcontroller GRBL - complete guess, like I say), IF (guesswork again) the limit switches are couple to the ucontroller discrete inputs then you might be suffering with the intrinsic high-z inputs from the uC device with internal pull-up or pull-downs.

Are the microswitches wired to 0V/Ground? If so, is the switched input (the non-ground wire) floating at around 5V?, if so then you could try reducing the internal pull-up resistance by wiring a 1k resistor from the microswitch input to a local 5V pin. The point here to provide a low impedance path for noise introduced from the spindle to clamp onto the supply lines - by default the high-impedance input to the microcontroller is highly sensitive to signal voltage (and therefore induced noise)... If that makes sense?

If there's any joy with this a more practical solution would be to introduce opto-couplers on the input to the controller - they'd provide good noise immunity.

EDIT:

Can you provide any details of the controller card?, even a picture?

[JeanB]

Good Morning Doddy,

Thank you for your reply. Just to inform you I am not very proficient in electronics, so it may be difficult for me to answer your questions.

My CNC works with GRBL and I use the free version of Easel at this time in order to practice……..not much practice has been done at this time.  

My switches are wired as NO and when I check the voltage across the + and - pins, I get ~2 volts and if press the micro switch, I get 0 volts. From all the information I gathered, the bottom row of pins are all to ground???? Before changing my switch wiring to shielded wires, I tried, as suggested on the internet, to add a .47µF capacitor across the micro switch………nothing.

Please find attached a picture of my board. It says: Developower V2.0

Thanks

[Doddy]

JeanB - okay, that's fine. I'm just about to head out for a last night of drunken debauchery before our government clamps down on that - I'll get some detail to you tomorrow morning.

[Kitwn]

My switches are wired as NO and when I check the voltage across the + and - pins, I get ~2 volts and if press the micro switch, I get 0 volts.
Thanks

2v strongly suggests a lack of pull-up resistors which leaves the inputs floating as Doddy has suggested. The inputs are hovering in an indeterminate state and susceptible to every light switch and cosmic particle in the vicinity. No input to any electronics should be left like this and many devices include the pull-up resistors internally, typically 10 Kohms. Some microcontrollers allow inputs to be selected as floating or pulled-up from software.

[Doddy]

<deleted>