Roller vs regular micro switches (endstops)

Does anyone know the difference between regular micro switches and those with a lever? Is one better than the other for use as endstops? Can't find any info on the net, and don't want to have to reorder if one kind doesn't work out. I'd imagine the roller offers some kind of advantage if they go to the trouble of putting it there, but I don't know what actually works better for detecting end of motion (especially for the sensitive z axis).

The ones with no lever are the most accurate but need more force. The lever adds leverage to reduce the force but also amplifies any variation in the trip point. Due to fact they move in an arc the end would scrape laterally against the striking surface, so a roller is needed to prevent it wearing down in devices that do many operations. Also rollers can be used as cam followers in applications that sense rotation.

You don't say which Reprap machine you are making. Typically ones with levers are used as they are easier to strike. Mendel90 uses ones without levers for better accuracy. It is only Z that matters, unless you want to home mid print, in which case X and Y need to be repeatable as well.

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[www.hydraraptor.blogspot.com]

I currently have a Prusa i3 (yet to start printing due to non-working mega 2560), but I'm also trying to design another printer myself, which is what these are for. So there's no formal name for it.

I used the horribly designed Sainsmart endstops for the Prusa, which are more expensive than a regular switch and have to be secured with zipties due to the hole obstruction. I'd like to go for a regular, quality micro switch for my own design. I don't anticipate having to home mid-print, but I'll probably be getting the same kind of switch so if it works for z it should work well for x and y.

You say the no-lever ones are more repeatable, but I don't see them used much in 3d printers. I assumed the lever was to lower the risk of excessive force dislodging the switch before it can be pressed, so I didn't consider them. Do you think these might actually be better? If not, would a switch with a roller sacrifice repeatability over one with a plain lever?

I designed the Mendel90 to use one with no lever or roller because I believe that type to be the most repeatable. The do need to be firmly attached of course. You can't hope for repeatability with a flimsy mounting.

I am biased of course but I think most repraps are less well designed, which is why they use the lever type.

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[www.hydraraptor.blogspot.com]

Interesting. So I'm guessing you're getting good results without the lever, with proper attachment?

I might just get several different types then and test them out, since I'll be designing proper mounts myself for this build. One disadvantage I see to the no-lever option is that the entire mass of the axis carriage will be crushing into the button when it finally stops, while the lever should mitigate that slightly due to its flexibility. Of course, that might hurt repeatability, especially if the lever bends over time.

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anvoice
Interesting. So I'm guessing you're getting good results without the lever, with proper attachment?

Yes none of the machines I have built have had levers, all the way back to HydraRaptor.

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anvoice
I might just get several different types then and test them out, since I'll be designing proper mounts myself for this build. One disadvantage I see to the no-lever option is that the entire mass of the axis carriage will be crushing into the button when it finally stops, while the lever should mitigate that slightly due to its flexibility. Of course, that might hurt repeatability, especially if the lever bends over time.

The motor should stop before it reaches the limit of the button. If not you are homing too fast.

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[www.hydraraptor.blogspot.com]

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anvoice
One disadvantage I see to the no-lever option is that the entire mass of the axis carriage will be crushing into the button when it finally stops

At least one firmware (Teacup) decelerates when hitting the endstop and when you have to set the deceleration distance (between switch trigger and mechanical crash) to something like 0.1 mm, you get rarther slow homing movements.

To me it's a bit questionable wether accurate homing switches give a substantial advantage. Homing is run only once at printer startup and doesn't more than defining the position of the print on the bed. You'd barely notice if it's 0.5 mm off.

Z axis is a bit different, needs to be more accurate. The trend here is currently to use bed probing, which is kind of a replacement for the Z endstop.

I've also seen people fine-adjusting Z height when the print starts. That's why Marlin has the "babysteps" feature. People start a print and then raise the bed with babysteps until the extrudate sticks to the bed.

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