4' x 4' x 8" Router Build

[JonnyFive]

Looks good to me. The only thing I would point out is that you have the proximity sensor end-on. There's very little room for deceleration between detecting the gantry and being smashed by it. A safer option is to have the sensor pointing uipwards so that it detects the gantry riding above it. You already have a non-smashable mechanical end-stop in case that fails.

Kit

I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?


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[Kitwn]

I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?


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You need about the same length as a piece of string! All depends on the weight of the gantry, your approach speed for homing (crashes at rapid speed will hopefully be avoided by soft limits once the machine is homed which is the first thing you will do after switching it on) and some stuff to do with drivers that other regulars will understand better than me.

Your Z and other axis (it's Y on my machine but X on many) sensors are right. In practice the overlap of the sensor and your target will not be very much when it triggers. I put slots in the mountings of my targets to make things adjustable but this does increase the risk of something moving and messing up the repeatability of homing.

Kit

[JAZZCNC]

I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?


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The distance is determined by the sensor spec, if using just for homes then 2-3mm won't be a problem but if using for limits then usually you will be traveling at fairly high velocity when tripped so the inertia will easily travel 1-2mm if at high feeds.
Also, the accuracy and sensitivity are affected by distance, so it's best to keep the distance on the smaller side of the sensor spec. This way it will react faster but obviously if end on you have less room to stop. 90deg is a much safer setup.