Hey guys,
I know you can use a Z-probe but, can I use a probe like this:
My board is a MKS SBASE.
And if yes, do I connect it to an endstops or so?
Yes you can use it but it seems a lot of money for an aluminium plate, a crocodile clip and some cable. You still need to fix the right end clips on for your board.
I made mine out of cable, a piece of thin steel that I found in my toolbox and I nicked a crocodile clip off an old multimeter. Only took 30 mins, you should be able to do this, have it tested, installed and working before you hit pay on eBay 
You need to measure the thickness of both your home made one and this, so you might need a decent vernier gauge or digital calipers.
Mine is attached the Z-min (I think) port on my SKR V1.3 board. You test it by simply touching the clip to the plate and it should stop the Z axis coming down. I would suggest you put the Z axis up higher than you need in case you need to hit the emergency stop
Rob
Thanks Rob for your reply.
What I think you mean is a Z-probe, and that is simple to make I guess.
But this one is a X, Y and Z-probe or edge-finder, so you put it on the corner of your work piece and let the machine find the edge.
I can make 1 of these, but then I need to machine alumium (which I haven’t done before).
I’m watching the video that’s in the eBay link to try and work out how to use it. So far I’m 4min 52 sec in and all I have understood so far is that the guy likes Shapeoko branded stuff and that he’s used speaker wire. The actual interesting bit is after 5 (!) mins into the 9 min video.
I now see that you turn it upside down so the right angle is underneath, you put that on the corner and the centre of the circle must be the (0,0) origin. You then set the Z axis which works the same way as I do, you then put the CNC bit into the circle so its below the top of the probe and it works out the (0,0) bu finding the edges of the circle. However the bloke has done it wrong as that method assumes a circular bit and he has a two fluted bit which is not circular. <sigh>, so one axis has the wrong calculation
It seems an awful lot of work to me AND I think your software would have to be able to run the gcode example. I’m not sure if Marlin can or can’t do this as I’ve never tried. He uses software I know nothing about.
As he paid $35 for his and this one is approx $9, it appears to offer excellent value, I’d check carefully how to integrate the centre finding software into your workflow.
All the best and let us know how it goes.
Rob
Rob
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I don’t believe that Marlin supports edge/corner finding at this time, so the edge/corner finding aspect is out. Grbl is more likely to have native support for this kind of device. I’m sure there is a grbl fork that has it, but I’ve never heard of a Marlin version having this functionality.
That’s a pity… then I won’t buy it.
Thanks for the replies.
I made a touchplate for Estlcam as my third or fourth project. Just do it! 
I can make a Z-probe and probably also an edge finder like the seller from EBay… but if I can’t connect it… it’s useless.
Using GRBL on the CNC Shield v3.00, the probe connection is separate from any of the axis end stops, so can be used to “find” on any axis in either direction. Don’t know whether Marlin supports that (yet) or not.
If I understand what you are saying, then the connections are not the issue. It is firmware support that is the issue. Watching videos of this device working, the bit is placed inside the circle. Then the firmware moves left and right to find two circle edges, then it is moves forward and backward to find two edges of the circle. From those touches the firmware can calculate the center point of the circle which will be the corner of the stock. In a couple of the videos, they were running GRBL, but I’m not sure if it was the main fork or if it was a custom fork. Plus in one of the videos I saw, the corner finder plate shipped with code that had to be added, but I’m not sure what firmware the code was for.
I think the G38 features can probe X and Y. But I really question the point.
It is easy enough to set the X and Y zero position to within 1mm. If you need more accuracy than that, then my next question is, “How do you make the workpiece square?”. That’s where it gets much trickier. The best way to do that would be to probe two places in X and then adjust the skew of all commands to account for that measurement. That is assuming the workpiece you are trying to mill is actually square to start with.
An easier method is to bolt down an L shaped bracket, and mill the faces in X and Y so they always hold the work perfectly square. If you do that, and you clamp your work into the corner, you can already know the zero for X and Y (you just milled it there). The next iteration on that thought is, do you need the whole length? Nope. You can do the same thing with 4 dowels.
IMO, if you are carving a very accurate piece, and you need to make sure you know the starting corner, and you need it to be square:
- home with your dual endstops.
- drill a hole sized for a dowel into the spoil board at: (20,10), 10,20), (100,10), (10,100). You might need to adjust this to fit your work.
- If your dowels are 6mm diameter, then your corner is at 13,13. Jog there and reset X,Y with G1 X13 Y13 and G92 X0 Y0.
- probe Z
- You can reuse those dowels, as long as you have a reliable way to home the machine each start up (dual endstops or hard stops).
If you don’t want to worry about square, then you don’t need to probe X and Y. Manually setting X and Y will be closer than your angle error.
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I think you can make a macro. But[quote=“robertbu, post:10, topic:21776”]
Plus in one of the videos I saw, the corner finder plate shipped with code that had to be added, but I’m not sure what firmware the code was for.
[/quote]
I think it’s a script you can save as a macro in for example CNCjs.
Well I need to engrave like 400 coasters and was looking for a repeatable way…the method you describe I also had in mind
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I believe a jig for mounting repeatable for X and Y and probing the top is going to get you through your 400 units faster than probing all 3 axis. You may not even need to probe Z depending on how dimensionally consistent your work pieces are.
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For coasters, I definitely would just cut an L bracket. 400 is so many. I might even set up two, so I could swap stock on one while it was milling the other one.
Jeff beat me to it. When I first started cutting scrabble tiles, I did them one at a time (smaller mpcnc) and popping them into a corner big was soooooo fast. Almost as fast as cutting out 9 at a time on the bigger machine, lol.
I want to make this system:
So basically a MFT spoilboard with dog holes and tubes as dowels… and an L shape.
Then home the machine (X and Y) and I have the coordinates of the intersection of the L shape, then G92 X0 Y0. Then all I need is a x-probe.
Yes I think so too. I was thinking of doing like 4x3 coasters at 1 go, but the depth is only 1mm or so. I don’t know how flat my MDF board is + how perpendicular my Z, so maybe it gets more inconsistent that way. Doing it 1 by 1 would be safer I think and still really quick.
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How big is your bed? Can you mount multiple coasters at one time? Work coordinate offsets would let you run the same single-coaster gcode 4x, 6x, 8x in a single job. Mount coasters in jigs, run job, repeat.
My work area is 460x300mm… one coaster is 100x100… but I think I will do 1 at the time in a L-shape jig.
I could see the benefits of doing a few at a time. But I assume it takes like 1 min per coaster, and you need to be there anyway. Being able to keep the machine working could double the speed, but doing 12-16 at a time would just give you a little longer to work on something else while it was running. That might be valuable enough to worry about it. But you might also get more accurate Z keeping it to 1-2 at a time.