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Author Topic: Beginner Looking for tips/advice on homing and limits  (Read 1762 times)

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Beginner Looking for tips/advice on homing and limits
« on: August 24, 2020, 10:00:40 AM »
Hi there~!

I'm new to the forum, and just built my first CNC machine. MDF and aluminum...  It's about 2'x4' in the X and Y,  with a Z of 5".  I have 'Wantai' chinese driver board with DIP switches to set micro step settings in intervals of 1, 1/2, 1/8, and 1/16 micro step. 270 oz. NEMA 23 steppers which came as a package with a power supply, lead screw for all three axis, 13 tpi coupled directly to the steppers. I'm currently running Mach3, with some success. 

I've done the math, and I'm pretty sure that in order for these motors to turn 1" of the lead screw at 1/2 micro step setting, I'm looking at somewhere in the ballpark of 5200 steps per unit. -Please check my math! I haven't accounted for backlash or anything like that because I haven't even gotten that far into the calibration process. Im currently just interested in one axis right now giving me consistent distances from the point of origin to wherever. 

As it stands now, every time I home, I trigger the limit switch, and I have to override the limits in order to jog off the switch. sometimes, I have to unplugged the switch just to move it off the switch. 

If I can get it to home and jog off the switch when I reference, I try to calibrate the axis.. TRY. If I'm able to home consistently, I use the axis calibration box in the diag screen to tune the motors, after I THINK I'm in the ballpark.  And the results are inconsistent, every time I take a measurement.

Questions:

NOOB question: Measure from where? ::) off the limit switch to the side of the Y gantry accounting for 3/4" for the material? The middle of the router collet to the limit switch? From the end of my shop to the other side of the street? I know this is a stupid question, hence the humor...

Why is homing fighting me so hard? Im sure Im not providing enough detail, Ill be happy to provide more.

Thanks for entertaining my stupidity.




Offline Graham Waterworth

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Re: Beginner Looking for tips/advice on homing and limits
« Reply #1 on: August 24, 2020, 06:45:43 PM »
If you are using a licence file that came with the board delete it and buy a real one, pirate ones DO NOT WORK SAFELY!

The home switch is no real problem yet.

5200 sounds right for the steps/per based on your hardware.

The measurement can be from anywhere to anywhere if you have a clock/dti then you can use that and do small moves using the MDI screen

If you are working in inches enter some thing like this :- G91 G01 X-.040 F2. and press enter

machine should move 40 thou if you have the range on the clock enter the same command again for a reading without backlash as it should have been taken up the first time.

The home switch should touch and the back off to clear the switch if its not then it could be a setting or a wiring issue.  Make sure when you press the switch by hand that the led lights in the diagnostic screen.

« Last Edit: August 24, 2020, 06:48:21 PM by Graham Waterworth »
Without engineers the world stops
Re: Beginner Looking for tips/advice on homing and limits
« Reply #2 on: December 02, 2020, 03:05:38 PM »
Yup I agree with this ... definitely delete it and buy a new one, you dont want to use a fugazzi one it wont work. Well put graham .