Is the Y-Axis endstop correct? Bed buzz during homing axes

[swbluto]

I followed the instructions and have my Y-axis endstop setup like so (Per the instructions):



However, when the printer homes in during the start of the print, I noticed the bed just rams into the plastic spacer and starts buzzing and never engages the Y-endstop, and then starts lifting upto the Z-stop after 5-10 seconds of buzzing. Is this normal behavior? I noticed that the X-axis and Y-axis endstops work like they should on the printrbot I have (Both endstops are engaged during the homing procedure and no ramming and buzzing involved), and I'm thinking the M2's instructions pictures are incorrect or I misunderstood the instructions or something.

I'm concerned the physical trauma involved might be messing up my bed's levelness which I took painstaking care in calibrating. (Burned a few polycarbonate beds that way)

[jsc]

No, that is not normal. Make sure the end stop is getting engaged by the bed at the end of travel, and make sure the motion stops when it is engaged.

Move the bed all the way forward, then command a -100 Y move with your finger on the end stop. Trigger it while it's in motion and see that the bed stops. If it does, then the bed is not engaging it properly. If it doesn't, then the other end is not plugged into the RAMBo correctly.

[insta]

I thought the wires go between the two outer pins on the switch, not the middle & outer. Make it match the X axis.

[jimc]

center pin on a switch is usually always the common. all the switches on your m2 should be center pin and one of the outer pins.

[ednisley]

center pin on a switch is usually always the common.

Except, of course, when it isn't...

The Y-axis switch on my early M2 looks like this:

Closeup of Y-axis limit switch on early M2

img_5638 - M2 Y axis limit switch.jpg (175.57 KiB) Viewed 13386 times

With a bit of luck, the legends will be visible even after you install the switch. Some ancient Microswitches in my stash have legends written in molecular-scale characters on the edge of the switch between the solder-post terminals.

Trust, but verify:

• Disconnect the electronics
• Use an ohmmeter to find the two terminals with zero resistance: they're Normally Closed
• Push the lever and do that again: those are Normally Open (closed on activation)
• One terminal will be in both sets: that's the Common terminal

As with transistors, any layout is possible, but one wire must go to the Common terminal, wherever it may be.

Folks who do CNC configuration for a living use NC connections for limit / home / panic switches, because a broken wire will open the connection, trigger the endstop, and produce an immediate halt. Of course, 3D printers do things differently...

[jimc]

Haha i did say usually lol. All mine here are center common so there has obviously been a change in the switch used on the m2. I guess just double check it.

[swbluto]

Yes, that's what my configuration looks like, wiring and everything. I'm trying to understand, is the bed SUPPOSED to ram into the plastic spacer, which then the plastic spacer is supposed to press the Y end stop and activate the switch?

In mine, it presses the plastic spacer which partially presses against the End stop's lever, but doesn't push the lever far enough to activate the switch.

EDIT: I removed one of the end stop's screws and rotated it so that the plastic spacer was already partially pressing the switch, then tightened down the one screw remaining in the endstop to secure it and the platform now engages the endstop thru pressing the spacer. Jeez, why did they give me two screw holes for the endstop that are too far away from the spacer to begin with?

[ednisley]

is the bed SUPPOSED to ram into the plastic spacer

Nope, there should be a doodad attached to the bottom of the Y axis stage that hits the switch roller. My old M2 has a round nylon spacer that (IMO) isn't quite right for the job, but it suffices:

cimg7797 - M2 Y-axis home switch peg.jpg

Old M2 Y-axis home switch and actuator peg

(194.96 KiB) Downloaded 143 times

It's entirely possible the peg doesn't trip the switch before the Y stage smashes into the hard stop. If the peg went missing along the way, that would also explain everything.

When I put the M2 together, I planned to print up a square peg, but that just never happened...

[swbluto]

Yep, don't have one of those guys installed on the carriage.

Wonder where that was hiding in the official M2 picture guide?

[ednisley]

Wonder where that was hiding in the official M2 picture guide?

You can certainly be forgiven for missing that roller among all the other parts left over after you've finished building the kit, but see page 5 of the PDF Assembly Instructions manual:
http://www.makergear.com/pages/m2-assembly-instructions
http://cdn.shopify.com/s/files/1/0030/7 ... 110913.pdf

Of course, I've never left a vital part of something lying on the bench... [grin]