Dual endstops on MiniRambo

#1

I understand that the mini is one driver short, however, can I still use dual endstops for X and Y?

Does anyone have any info about adding the 5th driver externally?

Or should I just give up on the mini and buy a full rambo or archim? Kinda bummed I bought the mini to be honest… but Ryan lead me to believe it’s the right thing for the LR2.

I also had this idea to put micro switches to all max positions and hook it up to the board reset - so in case there would be an accidental command past the mechanical limit it would instead reset the board. What do you think? I can’t really understand how there’s not more seriousness about disabling movement if the mechanics don’t allow it. When I had an older 3d printer that only had min endstop switches, I had it happen way too many times where the machine started forcing the steppers because it wanted to go where it shouldn’t. If possible I want to avoid that to ever happen.

#2

If the board resets, the spindle will drop right into your table, which may start a fire depending on how far your collet sticks out. Skipping steps is safer than that. It’s not going to hurt anything skipping steps, the gear isn’t what’s making all the noise, it’s the electromagnets popping to the next full step. Most 3d printers ignore the stops unless they’re homing anyway, so max endstops won’t do anything for you. It’s also only going to do that long enough for you to hit the e-stop button, since you’re going to be in the same room the whole time it’s cutting. I only have stops on one side of both my machines, not doing dual for either. Also not many folks are running dual endstops on the lowrider, when it was designed, dual endstops were an experimental addon, it’s still kind of an experimental addon…

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#3

It’s hard, coming from 3D printers to trust this, but you don’t need any endstops. In CNC, the 0,0 is based on the workpiece, not the table. Dual endstops is really just to align the two motors at the start. After that, they move in lockstep. You can achieve the same thing with hardstops, by just moving the gantry to the edge of the table, and powering the motors up while they are aligned at the end of the table.

On top of that, if you have a 5’ long gantry, it’s really not hard to get it square. A few mms over 4 feet is really pretty square already. The dual endstops are really useful on a small mpcnc with some cuts, but I don’t have endstops on my LR and I didn’t have them on my MPCNC.

If you want single endstops, you can do it with the mini rambo and it will stop both motors. You can even pyt them at min and max. The software can be configured to do sane things. You need to be careful enough to not drive the machine too far though, because hitting the end while milling is going to be a pain for you no matter what. IMO, just skip them. Before you do a job, move the gantry to the max xyz and make sure it fits. CNC.js tells you the min and max when you load a gcode file. But if you’re just jogging around, hitting the ends won’t break anything. The motors don’t have enough torque to tear itself apart. You’ll probably be out of square afterward and you will lose your zero position, but you’d lose that with endstops too.

If you do want to wire up an external driver, you can. You just add an E2 to the PINS_minirambo.h and choose pins from the aux ports. It would help to not have an LCD. You might have to pick ones that have PWM, I’m not sure.

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#4

I agree with both of these reply’s 100%. I if thought it was even a good idea I would recommend it and it’s more expensive parts. I do not use dual on my LR, either one that I have had. Heck I have dual on my MPCNC and rarely use it, only when there is a tool change involved even then I got along fine without it for years.

To answer your other question, yes, you can add dual endstop to one axis with a mini rambo. So you can do Y or Z just not both…but I stand firm, it is not needed at all.

Sorry that somehow you feel I mislead you but I can’t imagine why you think you should have them.

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#5

Ok, thank you! I needed this reassurance as I still don’t know how it will be once it all comes together. I’m basing my assumptions on my previous experience, hence the question marks. Thank you for bearing with me!

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