Adding Limit Switches

Hi all,
I want to add limit switches to my X50 and I noticed that it came with some bolts that I can’t see any function for. I am hoping someone can support my idea of using them to mount the limit switches.
They appear on all of the mounts in the right place, so . . . . . . (see pic)

The BOB has connections to wire them up and they are listed but I have not seen anyone else show them fitted. Is the software to use them in the 1F controller?
I’m a belt-and-braces type, I like the idea of limit switches okay?

Above is a picture of the bolts I am referring to. Note also my home made drag chain fittings. My machine is not quite ready to run but it is close. It has a HuangYang VFD and water cooled spindle.

I think that may be atramming bolt.

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Hey Greg,

I would not touch that bolt unless you want to adjust the tilting of the rails.

Retrofit proximity sensors (here: inductive sensors) as limits switches are shown here (including 3D-print files) and here.

Stall homing is explained here, the datasheet of inductive proximity sensor Omron E2B is here.


Thanks Aiph5u, I won’t be adjusting them just now. I will make my own mounts elsewhere.

This looks like a simple solution but the ID of the clamp would need to be made larger for the Onefinity.

The Buildbotics forums have several posts about limit switches too

Thanks for the posts folks. I have purchased some small reed switches encased in protective casings that I hope to use as limit switches (see pic). I will make my own brackets for them and use small magnets to trigger them. Let me know what you think of this idea.

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Hey GregZo,

reed switches are hermetically enclosed in glass cylinders so are dust-tight, not subject to corrosion and maintenance-free. However, unlike inductive proximity sensors (e.g. Omron E2B), it seems their life is not endless:


The mechanical motion of the reeds is below the fatigue limit of the materials, so the reeds do not break due to fatigue. Wear and life are almost entirely dependent on the electrical load’s effect on the contacts along with the properties of the specific reed switch used. Contact surface wear occurs only when the switch contacts open or close. Because of this, manufacturers rate life in number of operations rather than hours or years. In general, higher voltages and higher currents cause faster wear and shorter life. Depending on the electrical load, life can be in the range of thousands of operations or billions of operations.

– Source: Reed switch – Wikipedia

Reed switches still have mechanical contacts, photoelectric sensors like on the Onefinity Elite Series or inductive proximity sensors not, so only the latter two have really infinite life.

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Hey thanks Aiphu5u,
Next part- question: Here is a photo of the carriage and it has these two M5 bolt holes that are empty and don’t seem to do anything. I want to mount my limit switch magnets on them.
Will this work? It looks like it will be fine but I’m asking just in case.

Hey Gregzo,

in these holes you find the grub screws that hold the linear bearings in place. You can put short bolts on top of them, but I would measure the depth of the hole to the grub screw beforehand so it doesn’t reach it.

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Great, thankyou very much !

I did the same thing to mount the trigger half of my proximity sensors.


That’s correct, those are tramming bolts for the router.

I just thought of something. I have been assuming that all I do is wire them up and they will work.
Is this correct or do I need to set something in the software to make them work?

Hey Gregzo,

you just need to enable them in the correspoding “MOTOR” page. If you select “min-sxwitch” or “max-switch”, the options will change this way:

Switch-min and Switch-max Homing

When homing in the ‘switch-min’ homing mode, the axis will travel towards its minimum position until the limit switch at the minimum position is activated. This option requires that a switch is installed at the minimum position and configured in the min-switch field for the axis. In this mode, the Position and Absolute fields in the Axis table are set to the value in the ‘min-soft-limit’ field and the Offset field in the Axis table is set to zero.

When the homing-mode is ‘switch-min’ or ‘switch-max’, the following additional configuration fields are presented:

search velocity
latch velocity

The following sequence describes the actions taken when homing is initiated on an axis that uses ‘switch-min’ or ‘switch-max’ homing.

The axis travels toward the switch at the velocity that is set in the ‘search-velocity’ field.
When the switch is found, the axis backs away from the switch until the switch de-activates or the distance defined in the ‘latch-backoff’ field is reached. If the ‘latch-backoff’ distance is reached before the switch de-activates, the homing sequence fails and is aborted.
When the switch deactivates during the ‘latch-backoff’ step, the axis once again approaches the switch at the velocity specified in the ‘latch-valocity’ field.
When the switch activates a second time, the axis backs away from the switch by the distance defined in the ‘zero-backoff’ field.
The Position and Absolute fields in the Axis table are set to the ‘soft-limit’ and the Offset field is set to zero. The state of the axis is set to ‘HOMED’, ‘OVER’, ‘UNDER’, or ‘NO-FIT’ as described the Axis table section of the Control Page

– Source: Buildbotics Manual v1.0

How to connect them see here