CNC Control Box Part 3 / Probe Button

In this video I’m going to make a housing for a probing button which I’ll then attach to my new CNC machine and it’s control box. This is a test piece that I 3D printed. It took a while to do, and I’ve already made some changes in that I’m going to use a pilot light which I’ll also wire to the switch which will illuminate when the button pressed. I think that’ll be a nice feature. This took a fair while to print maybe over an hour if I remember correctly, the the milling of this material will probably only take about 20 minutes so much quicker. So the first thing I need to do is secure this down, so I’ll drill a couple holes and screw it to the wasteboard.

I’m going to now area-clear this main chunk of this component as well as the opening for the button. I’ve got an 8mm up-cut bit in there already, which I’m going to move to the probe location on this CNC machine so I can work out the length of the bit and then I’ll change over to a spot bit to mark up where I’ll drill the smaller holes and then back to the 8mm bit to cut out the final shape.

I’ve got a separate video about the whole procedure on this probe, and how it works and what macros I’ve set up on bCNC so I’m not going to repeat myself here and what I will do is link to that in the information card.

Several things went wrong there including forgetting to press the macro to zero the z axis to the wasteboard, which resulted in the crash. And if you were to re-examine the crash footage carefully you may also notice some spot markings not landing where I was expecting them too. I should have also noticed when I performed the second probe cycle that it didn’t exactly land in the centre of the button. I’ll replay the two probing sequences at the same time so you can see for yourselves. The tip of the v bit doesn’t look centred on the button. This could have happened for a few reasons such as not completing a homing cycle properly or missing steps due to travelling too fast or a loose motor coupler. I think I may have ran the previous job with a tool selected that had a much higher feed rate then I had previously used, and that my max rate settings for $110 and $111 were set too high to limit this. I dropped those down from 1500mm/min to 900mm/min, amended the tool file, flipped the board around the cut this out.

So Valchromat is very similar to Chemiwood which is a modelling material and it can take these particular type of shapes and thin edges quite well. If you tried to make something like this out of MDF it would most likely have broken apart before it got off the wasteboard.

I’m now drilling and counter-sinking the spot markings on the piece which will accept the mounting machine screws and pilot light.

Ok this is the button. The button I’m using is a 30mm flat momentary button with a normally open and normally closed set of terminals. It’s sold as vandal resistant which is convenient because CNC machines have a tendency to break into themselves. I got the button from RS components for about £20 plus vat while the light was a lot cheaper and from ebay. That’s a 24v 6mm white pilot light, but it’s unbelievably bright. I wanted the red light but that out of stock and I bought a this one instead which I now regret. I may try pour some red enamel paint over the top to reduce the brightness.

And the locking nut is wider than this section here so you don’t assemble it in any particular order. It simply clips into place like that and then fits like there, and this ties in and the light will go through that hole. I managed to damage that so I’ll give it a little sand.

I’m going to wire up the touch probe now. The lights going to be wired to the normally open terminals so that when it’s pressed it closes and turns on. And the normally closed will go to the centre, and that will go back to the signal. And if you use this set-up you’ll just have to remember to use the g38.4 or .5 command and not the others. Now I’ve wired the red 24v power cable to terminal number one, and the black ground to terminal number two – which . This will turn the pilot light on. The other two terminals will be for the probe mechanism. As I mentioned earlier the pilot light connect to the normally open terminals on the probe button, and the signal for the probe goes to the normally closed.

So this is the end that’ll go to the aviation panel mount. So what I’m going to make sure I do is wrap this drain wire for emi interference, onto the out casing of the socket. I’m going to wrap the drain wire in a figure of eight around the cable clamps screws. This will connect the shielding to the wiring inside the enclosure, which I can later terminate at a star earthing block – this will help with EMI.

I’m now wired the probe button and pilot light to the cable. I decided to do this before fitting the part so I could test it out. But later I’ll have to make sure that I drill an opening slot large enough to pass the panel socket through as well as provide clearance for the wiring soldered to the terminals, as they extend further than the depth of the valchromat piece. I’ll also need to make sure I cable tie the wire somewhere onto the machine so it acts like a strain relief and prevents the soldered section or clip-in-place terminals becoming damaged because of movement.

I then wired the panel mount to the cabling that will go to the inside of the control box. As long as you keep good records of what colour wires go to which terminals you shouldn’t make any mistakes. And at the end you can double check the connections with a voltmeter before turning on the juice.

Sometimes I get so engrossed when using heat shrink that I forget I’m filming myself.

Ok I’ve just wired it in. God that is really bright. I’m just going to press the probe button and make sure this actually does what I’d like it to do.

This bit here is one of the widest bits I have on a 1/4 inch or 6mm shank. And I normally use this for surfacing the wasteboard. I’m going to place this in – it’s hand tight. And I’m going to work out where… I’m trying to work out where to place the probe button, and I have the choice of either at the front or the back of the machine. Initially I thought about placing the probe button at the front of the machine but realised I would have a couple problems. Because I need to drill or router a hole for the cables to go through, the piece of aluminium at the front of the machine will obstruct that and I’d have to set the button further back which would make the waste-board and overall cutting size smaller. However there would be the advantages that the button would be more visible, and if I were to put the machine in an enclosure, I could use the probe location as the same place to change tools and that I wouldn’t have to lean into the machine to do so. If it’s at the rear I’d get a deeper waste-board and moving from the home position to the probe position would be quicker, but I loose visibility.

I re-homed the machine and then moved the spindle with a v bit in the collet, roughly to a location I’d like the probe button to be. I then made a mark on the wasteboard and shuffled the gantry forward, so I could access and drill the open.

In theory I could use the spindle but I haven’t wired it up yet, and this will just be a bit easier. I’m going to put a bit of wood underneath so I don’t… I drilled two holes by hand, with a wooden block underneath to prevent the melamine surface breaking out, and then cut out the space between them with a jigsaw.

The plug I’d wired to the other end of the probe buttons cable was too wide so I drilled a new hole with a diameter just wider – I used a piece of wood with a hole the same size as the fornester bit to guide the drilling.

I then marked through the openings of the valcrhomat using a parallel punch, and drill the holes with which to secure the probe button down to the sub-wasteboard. I fixed it down with socket-screws but later I’ll replace those with countersunk ones – which are still commuting to me in the post.

As I said earlier I have a more in-depth video about probing and the macros involved, so I’ll linked to that in the information card if you are curious. The process is very simple. I home the machine, to find the machine coordinates and toggled the spindle so it was centre over the probe button. I can now begin updating my macros so after homing I move to the new probing location– which is a g53 command. And there I can perform a G38.4 probing cycle, and once the probe has been triggered, to then set the tool end to zero on the waste-board with a known x and y position, which I do with a G10 command. But I can’t do this now as I don’t have a wasteboard.

I’ll provide a copy of the probe button mount to my patreons, so don’t forget to support this channel there for those little perks, and for the rest of you hangeronners, you’ll see me in the next video where I’ll be installed some laser engraving and… where I’ll be installing some laser engraving electronics and under gantry warning lights.

One thought on “CNC Control Box Part 3 / Probe Button

  1. Hi, which button exactly have you chosen? How are your experiences regarding the accuracy. Would you recommend this type of probing?

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