new Microsmt / openpnp2 build, limit switches?

[CK Man]

Hi all, 

Just assembled a microsmt kit for a friend of mine. Trying to do some basic setup and tests before I give it back to him.. I have no experience with either OpenPnP or this system, just doing the labour for my buddy.

I've copied the .xml config files from the Microsmt sd card into the .openpnp2 directory. 

I've got microswitches installed and wired for x stop min and y stop min, but when I hit Home in OpenPnP, the x carriage went full min, ran into the switch and the motor kept spinning, skipping the belt. I cut the power quickly to stop it happening more. 

Do I move the carriage to min-x and min-y by hand and then tell OpenPNP to learn the point or is there something else I have to do?

thanks..

[CK Man]

Well, that didnt help things.. on the 2nd or third time it crashed, the mount broke haha. Getting another printed now, but need to figure out my limit switches apparently.

[Jarosław Karwik]

It works a bit differently.

The procedure goes blindly until it reaches end position switch.

Usually if there is an issue with the signal - it will not stop as it needs hard reference ( specific signal from switch to stop)

So you might need to check your cabling.

There is a way to read the switch state from console in OpenPnp - before executing homing, but I am not sure how to do it for Smoothiware ( which is used by MicroSmt board) - I am Duet user.

[Mike Menci]

Did you follow the video https://www.youtube.com/watch?v=CnlIPwArhIc

and the manuals in GitHub ?  https://github.com/microsmt/Microsmt-PNP-hardware/blob/main/Microsmt_pnpboard_v1.7_manual-0618.pdf

SD card - you have placed it into the PCB slot ?  (there should be only the config.file   on SD Card (all the rest copy to one of new folders under your documents for future if you need them again)).  - screen shot please what you have on SD card? 

DO NOT DRIVE 100% speed for the first tries - limit it down to 30% so you can react if steppers do not have right directions.... 

[Brett Fraser]

Thanks for the reply. I have, prior to running and again after the failure, confirmed 5vdc at the board connector when limit is hit/active on both x min and y min and 0vdc when the carriage off the limits.

I've poked around in OpenPnP GUI and can't find reference to hard limit switches yet.. will go find some docs on smoothie and see what I can find.

thanks..

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[Mike Menci]

Here; Read https://smoothieware.github.io/smoothieware-website-v1/endstops.html#reading

[Mike Menci]

The most important might be Z home LS   - if this one is not working - nothing works!

[CK Man]

Hi, thanks for the reply..

I have followed Bings machine/frame/electrical assembly video, I hadnt watched the one you linked as I havent assembled the 0816 feeder that was purchased with the machine, and that one appears to be for his newer Bing feeder?

I have read the manual you linked forwards and backwards, its got me this far  :)

The SD card is installed in the pcb slot, it has never been out. Image of its contents is attached.. 

I did note one thing when looking through the supplied config file, while endstop.minx.enable is true, endstop.minx.limit_enable is set to false .. and the comments suggest that this limit will then not be used?

Im off to read the Wiki you linked in your other reply, thanks again for the help.

[CK Man]

I have confirmed that m119 returns x_min:1 and y_min:1 when the carriage has reached those stops and 0's when its off the stops.

[bing luo]

It's not that complicated. If you connect the wires of this limit switch incorrectly, it will be like this.

[bing luo]

[Jonathan Oxer]

A good practice when checking limit switches is to start the machine moving towards it at a very low speed from some distance away, then manually push the switch *before* the machine reaches it.

If the switch doesn't work, that gives time to take action and stop the machine before it physically collides.

Jon

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[bing luo]

https://github.com/microsmt/Microsmt-PNP-hardware/blob/main/Microsmt_pnpboard_v1.7_manual-0618.pdf

The configuration file and command line do not need to be understood, and there is no firmware that needs to be set. Just follow the instructions in this PDF manual to correctly link the cable of the limit switch.

[bing luo]

Yes, as long as you close the limit switch by hand, the motor will stop, but the PNPV3 kit is very sturdy, so there is no problem of collision. At most, it will damage the 3D printing bracket. Then you need to press the restart button to restart the control board once.

[bing luo]

We haven't sold the 0816 feeder kit for half a year .    Because    now  the sprocket feeder that comes with PNPV3 only costs $8, so we think the push-pull feeder should be phased out.

[Uncle Buzz]

I own your PNPV3 kit, if everything is done correctly, it will work flawlessly... But like all other machines I saw, this is an awful misconception to allow the body of the electric limit switch to serve as a mechanical limit and support the impact of any anomaly where the axle goes with speed to the limit (never in normal use, but wrong things can happen), a good conception would allow the electrical switch to do his job but with a mechanical stop who would not be the electric switch body...

The electrical switch should be covered by a mechanical limit to avoid the electrical stroke of the limit switch from being overpassed, or be mounted so the stroke of the limit switch could never be overpassed (mounted parallel to the movement and not perpendicular)

[bing l]

           What you said makes perfect sense. Just because this limit switch is very cheap, with a selling price of approximately $0.2 on AliExpress, we assume that the machine has a wiring error that causes uncontrolled movement and impacts the limit switch, resulting in its damage. The replacement cost is $0.2.

So we didn't design complex mechanical limits.   Of course, this is definitely not a perfect solution, but we are limited by costs.

           We can even consider using 2020 Aluminum profile and iron sheets (or ABS) to make this kits, just like other kits you have seen, and then use the saved money to design a mechanical limiter.  But it's definitely not worth it.  so  If there is a better solution, please let us know.

[Uncle Buzz]

If you remove the limit switch, the machine still has a mechanical limit it can't exceed, the idea would be to place the limit switch so that the switch sends the stop command just before the mechanical limit, but the mechanical limit will stop the machine before the end of the stroke of the switch, no need to replace the cheap switch, it's just about placement, so just about the 3D printed parts.

I only own one machine and it works, so I didn't look for a better place to put the switch, but it's the first thing I saw when I assembled it. As a manufacturer, you could look for a better way of placing the switch without spending more money on new parts or switches, it could just avoid situations like the one reported by CK Man. If you rotate the switch 90° so that when the moving part passes in front of it, the switch is commutated, but if the switch is out of the way of the moving part, the switch and the 3D printed part will never break again.

[Mike Menci]

Well, You need to set up your "soft end stops" and you do not need to worry about braking something....  

[bing l]

At the beginning of installation, some people may connect the wrong wires (such as reversing the limit switches for the X and Z axes). This type of movement beyond the limit switch may occur. So setting software limits is also useless. But as long as it's correct, such problems won't happen in the future. So I think since the cost of the position switch is only $0.2, there isn't a lot of cost spent on mechanical limit switches.