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Here's an experimental magnetically detachable probe for the Rostock MAX. DXF files also on our SeeMeCNC GITHUB.

BOM:
1-3/8 dia x 3/16" thick neo magnet
1-6-32 x 3/4"L ferrous steel flat head machine screw
1-6-32 x 1"L flat head machine screw
2-6-32 stainless nylon lock nut
1-1/4-20 x 1/2"L button head
1-10-32 x 3/16"L ferrous steel set screw (grub screw)
1-t-nut for t-slot rail
1-limit switch (micro switch)
1 each of the three laser cut wood parts 1/4" thick


The 6-32 x 3/4 ferrous flat head screw is used to attach the "Probe Guide" to the platform of the R-MAX. It also attracts the magnet on the "EZProbe". Next, the 10-32 x 3/16"L ferrous steel set screw (grub screw) is inserted into the "Probe Mount" and attracts the neo magnet when you return the "EZ Probe". The hooked portion of the "EZProbe" catches the 6-32 x 1" flat head. The bevel on the 6-32 x 1 flat head also helps guide the probe when it is returned.

The "Probe Mount" is attached to the Z axis (rear vertical rail). Adjust the tightness of the 6-32 x 3/4"L ferrous steel flat head to adjust how well the "EZProbe" fits when magnetically held in place. I programmed the probe to pick up, touch the indicator, and return the probe many times. Using an indicator, I measured a repeatability of .002".

Steve, can you talk about how you see this working? How it gets integrated electronically?

The only thing I can assume is that it is a measuring / leveling device - and that's quite a bit easier than the laser switch I did - maybe.

How does it hook up to the rambo or does it?

Do you have a video you can post?

I'd really like to see how this all works!

http://www.youtube.com/watch?v=dyleBUd25wo

The probe has a limit switch type connection to the RAMBo. The wires are not attached yet to the probe shown in the video. I was planning on using a piece of PTFE tube stuck into a hole which would be drilled beside the probe. Picture two wires coming out of the end of the PFTE tubing (like a whip) and leading down to the probe.

The software to integrate this has not been written yet. The algorithm will probe 4 points. One at each tower and one in the center. While the three tower points define a plane, the center point will allow for spherical calculations, like center point and radius. The software stores the new values and begins your print.

This should eliminate the need manually set the z height as well as eliminate the need to manually set the delta radius offset. Basically, this saves you a bunch of time. And if the machine is moved from place to place, you can quickly auto-calibrate and start printing.

Got it! Excellent idea!!!

So it would get the variables and issue Gcode to store them in EEProm too? Pretty cool.

Thanks for sharing this! Good luck with it.

You will, I hope, offer this as a kit when the code is ready.
Every Rostock Max and other delta owners are going to want one.

Correct, a kit it will be...

But when, please not months from now...

OH ! wow, that is pure cnc porn... great idea

Please do the code, I am sure there would be loads of users that would pay just for the code alone......

SHUT UP AND TAKE MY MONEY!!!1111!!111!!

... not that you haven't already...

The only nitpick I have about the design is the requirement that you have to take the top off the machine in order to install the probe rest.

You could solve that by using a smaller diameter bolt that would allow the proper sized t-nut to fit in the extrusion slot and rotate a bit in order to catch the interior sides of the tower. You could also clip it to the tower in a similar fashion to how I'm mounting the wire guide.

I can't wait to get one cut.

g.

geneb wrote:The only nitpick I have about the design is the requirement that you have to take the top off the machine in order to install the probe rest.

You could solve that by using a smaller diameter bolt that would allow the proper sized t-nut to fit in the extrusion slot and rotate a bit in order to catch the interior sides of the tower. You could also clip it to the tower in a similar fashion to how I'm mounting the wire guide.

I can't wait to get one cut.

g.

I don't know if I'd want to use a clip - seems like you wouldn't want any chance of it moving position once its installed and setup in firmware, or whereever the coordinates for its location will be stored. Your idea about the smaller t-nut is solid, though. Taking the top off doesn't strike me as the most efficient way to install it.

Or, could you not use one or two of the preexisting holes in the bottom platform and skip attaching it to the tower altogether?

Well the clip would keep it just as firm as the screw would for the purposes of being a probe rest.

g.

geneb wrote:Well the clip would keep it just as firm as the screw would for the purposes of being a probe rest.

g.

Well, if that's the case, that would be my preferred method, I think.

They make a T Nut for that series of extrusion that goes in from the front, they have rubber "handles" on them so you can hold on to them while inserting into the slot.

The problem I see at the moment is that the mount that goes on the effector interferes with how I mount the LED light rings I use.

g.

geneb wrote:The problem I see at the moment is that the mount that goes on the effector interferes with how I mount the LED light rings I use.

g.

You're right and that is going to affect a lot of people. We'll have to come up with a work-around for that one.

Print an effector with built in holes and lead routing for LEDs, or make LED mounts for the arms themselves.

Not practical for the lights I use.

http://dx.com/p/t10-15-led-white-light- ... eter-25513

They're a PERFECT fit. They put out a ton of light too!

g.

Eaglezsoar wrote:They make a T Nut for that series of extrusion that goes in from the front, they have rubber "handles" on them so you can hold on to them while inserting into the slot.

I'll second that. They're usually called "push-in" or "drop-in." I work with t-slot a good deal in the field and these things are life savers.

You can get them from just about every t-slot provider, but here's a quick link from McMaster for those that aren't familiar: http://www.mcmaster.com/#extrusion-nuts (the ones at the bottom).

Also, a point regarding Steve's comment about 0.002" repeatability...that's ~0.05mm. With people ever decreasing their layer heights, (e.g., I can get good results at 0.2mm with the stock hot end, so 0.05mm is 25% of a layer) doesn't that seem like too much? I mean, that doesn't seem to build a very accurate map...

I don't this want to sound pessimistic as the results aren't fully in, I'm just trying to add to the discussion.

You have to put the error in context of the machine..
If the reading is off by say 0.05mm it really only impacts the first layer since every subsequent layer is relative to it. You can see this when you level by hand, the limit switches probably aren't repeatable to better than 0.05mm, so you work with that much error on every run.

geneb wrote:Not practical for the lights I use.

http://dx.com/p/t10-15-led-white-light- ... eter-25513

They're a PERFECT fit. They put out a ton of light too!

g.

Gene, how do you mount these rings to the effector?

Two ways - you can use small (4") tie wraps, or custom clips. I've done it both ways.

I'll post pix later.

g.

geneb wrote:Two ways - you can use small (4") tie wraps, or custom clips. I've done it both ways.

I'll post pix later.

g.

I have the exact same angel eyes and I'm looking forward to seeing your custom clips. The tie wraps almost have to cover the leds because they are so close together.
I'll wait for the pictures to decide.

Polygonhell wrote:You have to put the error in context of the machine..
If the reading is off by say 0.05mm it really only impacts the first layer since every subsequent layer is relative to it. You can see this when you level by hand, the limit switches probably aren't repeatable to better than 0.05mm, so you work with that much error on every run.

There is a guy on Youtube who is using Hall effect endstops on his custom-built Kossel. He has magnets clamped to the timing belts and they trigger the sensors, which he has mounted at the base rather than up top. I don't know if it's any more accurate.

I didn't manage to get pics of the light ring mount, but I changed it to two wire ties this evening. The issue is that the auto-probe blocks where I had one of my clips attached, so I punted and went back to tie wraps.

I was able to come up with a method of tweaking Steve's design a bit to allow it to co-exist with the light ring.

Here's a series of pictures:
http://www.geneb.org/rostock-max/probe

The first one shows Steve's original parts on the left, my mods on the right.

Instead of the probe guide being attached to the bottom of the effector platform, I extended it a bit and mounted it to the top surface. Works great.

g.