MR-1 using Rapid Changer ATC

Any one looked into Rapid Changer ATC that uses ER- 20 collets? The price on these units seem very reasonable. I learn that the MR-1 servo does not support reverse rotation? Is that true? Is there a solution or work around in the post processing? Thanks in advance.

This guy is as sharp as they get and will know the answer for you.Ballscrew protection Guards - #3 by AlexW

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Thanks! I have definitely used some of his ideas in my build. I’ll hit him up. Thanks!

The RapidChange won’t work with the MR-1 for a few reasons:

  • It requires a spindle that can turn in both directions, but the MR-1 stock spindle only turns clockwise.
  • It works by stalling the spindle as the nut tightens, and the MR-1 spindle will error out if stalled since it is a servo. Recovery requires power cycling the servo drive (220V circuit on the control box).
  • It requires a control system that allows for custom macros and commands, features that CutControl doesn’t offer.

The RapidChange was really designed and tested around high speed/low torque direct drive spindles, not servo drive like on the MR-1.

You could swap the spindle and controls on the MR-1 to make it work, but by that time you would probably want to consider just going to an ATC spindle.

Thank you for the feedback Alex. I was afraid of the answer. I hope Langmuir gets a changer soon. This would be a machine hard to beat! Thank you again.

It would be pretty interesting to see them sell a “base” MR-1 with no spindle or electronics for around $500 less so that people could build it out as they wanted. The someone who was interested could put on a spindle that is compatible with the RapidChange or ATC.

My guess is that we won’t see a factory ATC version of the MR1. Ideally it would have a higher clearance gantry (which will reduce it’s rigidity) or it would use very expensive HSK25 tool holders. HSK25 spindles cost about what the whole MR-1 costs. Proper “lights off” ATC is a lot of work to get right (requiring chip protection for the tool holders, interlocks to make sure that the tool change was successful, etc), but quick changing tool holders would really transform the stock machine.

For instance one of the first CNC machines that I worked with was a Bridgeport Boss that I upgraded the controller on, and it used this style of quick change tooling:

This isn’t designed for full ATC, but it’s a lot faster than dealing with ER20 collets.

I agree. I am sure selling custom configuration MR-1s may not be a great business model but it would be great for those of us that want to build it out in our own way. I think this is kind of the niche that MR fills. its almost a Haas but its the way we want it. Its a cool project to make other cool projects.

I would like to have a ATC for two reasons. To learn to design/code for it and make it a little easier for those that want to run it semi-supervised. This is a very simplistic example but one thing I love about a horizontal bandsaw is start it and walk away to do something else while keeping a ear out for issues or success. It may not be a heavy production situation but it is very satisfying thinking you are really getting stuff done. I have thought many times I wish I would have spent a little more money on my horizontal band saw since I use it all the time and I can do other things while it is running.

I am still very impressed with the MR-1. I look forward to shooting chips.

Everyone’s preferences and situation are different, but the quick change works pretty well for me in that “background job” scenario. I do end up staring at the machine while it runs for ops which are short (under a minute or two), but can walk away and let it just run for longer ops.

An off the shelf tool rack with chip cover would make ATC for this machine a lot more feasible, that is one thing that RapidChange seems to have done well. Hopefully someone with more time than me will figure it out and share 3d printable plans. I was working on it, but have been very busy with my day job recently and my machine is mostly idle at the moment.

I wonder how much torque is actually required to safely tighten and loosen the collet?
If we are stuck with a motor that turns only one direction, how about a collet rack that does the rotation?

It would take a little engineering but, some gears, a motor, bearings and a macro (programming) could make this a reality.
I’m thinking something that moves linear like a printer with a small motor that engages and disengages like a starter to spin the collets in the ATC rack.
The ATC could be triggered by an Arduino.

I think in time someone will come up with a way to make this happen.

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Interesting concept. The motor could spin all the collets sockets in reverse in the holder when I command is sent. Maybe a worm drive affair where a single worm shaft that turns all the sockets. This same motor or servo could also hold the sockets when the spindle did the tightening. The worm drive is a powerful gear reduction to aid in the tightening and the loosening. That just might work. Thoughts?


How do you hold the spindle while rotating the nut? Hmmm… I’ve seen a unit that has something like a keyhole around each collet assembly and engages when the spindle inserts the nut to hold the shaft.

This is starting to sound a little weird. Haha!

Could you use this guy’s concept? I’m sure tweaks would need to be made but conceptionally, it would work.

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Great find! Gator grips are an interesting solution. Pretty basic which is always good. According to rapid change atc 15-18 lbs of torque is more than enough to secure a collet. That should easily achievable with a servo and gear reduction. I like the guys shaft securing but I wouldn’t want it part of my spindle assembly. Cool solution none the less.

That’s exactly what I was thinking.

That’s where the macro comes in. Since the spindle is a servo motor.
A normal servo will stay in position when:

  1. It’s powered up (with enough current)
  2. You are feeding the control signal into it.

Servo - attach()
In Arduino the command is servo.attach() Servo’s should usually hold their position when attached. This is how servo’s work. They’ve got an internal feedback loop, which constantly adjusts the servo towards a setpoint.
I know LS uses a single direction servo so, I would need to see if that makes a difference?

I’m sure there’s a way to call out this command in the MR-1 controller software as a trigger.

That makes total sense. I know LS does not support reverse but like I was saying, maybe the servo in the changer could spin the nut on and off especially if the servo on the z axis will hold it solid.

I’ll look into this deeper once I have my machine up and running.
The worm drive looks to be the best choice because it can be ran in both directions with some accuracy.

The rack can be 3d printed fairly easy. There’s some really strong filaments out there.

Does anyone have any information on the board the MR-1 uses?
I see there are expansion ports labeled on the case but, I don’t know much about the board itself.
It would be nice to get 2 additional functions from the LS board.

  1. Trigger an actuator to move the ATC under the spindle.
  2. Send the signal to lock the spindle.

I’ve used machines that have multiple home positions.
I wonder how hard it would be to program more home positions for each tool location?
It would be nice to have around 8 to 12 for the ATC.

The documentation for the servo controller in the MR-1 is here:

You’d have to reprogram it to get it to hold position, but it is possible.

@warforged: I’ve documented a lot about the MR-1 here internals here:

The control board is custom and runs grbl. I don’t know anyone who has explored replacing the firmware on the microcontroller, it is unlikely to be that hard. You’d need to reverse engineer the circuit to figure out how the GPIO pins are mapped. Personally I just replaced the control board with a MESA 7i96S (under $150) and documented how I mapped everything in LinuxCNC.

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Excellent info @AlexW!
This can be done. It’s just going to take time.
I like the MESA boards myself but, I’m trying to come up with a way to use what we have so others can do it relatively easy. As cheap as the board is… It’s definitely a viable alternative at little cost to have an ATC.

gnea/grbl is pretty straight forward. If LS is using it and it’s open source… There shouldn’t be too much heat or barking if we modified the code? :wink:

@AlexW You have done some extensive work!

Thank you.

Langmuir hasn’t posted their grbl source since the MR1 came out (they’ve posted it on github, but it is 4 years old now). I’ve tried to complain to them about using GPL’d code and not sharing their changes, but it’s gone on deaf ears.

The stock control board is very limiting in terms of number of inputs and outputs, and grbl is also extremely limiting in functionality. So switching to something more powerful like LinuxCNC is a first step in my view. For the project that you are describing I think you’ll want a couple of binary I/O pins at a minimum to control the servo that you describe.

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