This was addressed two weeks ago in release 96. Finishing the chain calibration moves to 0,0.
That doesn’t help much if the steps in the middle go off the top or bottom of
the work area.
Especially if you are doing a smaller machine, the current process can run out
of chain in the middle.
Thinking a cross laser will be a good aid to and measure the chain. if someone could put a laser beam and a camera that is directed between the engine and one of the lower corners would like to watch movies moving on a small square there to see the movements on the chain with and without cutting the material
I’m not visualizing what you are talking about.
In any case, the problem isn’t measuring the chain, we do a pretty good job of
that by counting the rotations of the sprocket. The problem is in measuring the
other things (see the accuracy page on the wiki mentioned above).
We do a pretty good job of measuring the distance between the motors by
feeding the chain out from one until it reaches the other and then pulling it
tight.
It’s all the other measurements of the machine after that that get hard. If we
had the accurate measurements, the standard kinematics work. The problem is in
getting those measurements. That’s why the tringular kinematics are so nice,
they eliminate a LOT of variables.
I use google translator so is a bit hard to explain! What I want is watching the chain sag with load. reason tells me that the chain will have trouble when moving towards the end of X. since we use gravity
That is true, and we currently think this translates to an error of areound
±1mm in the bottom corners.
Can you make a diagram to show what you are thinking of?
Right now, I’m thinking that the best we can do is measure the sag at a known
amount of chain and then calculate ‘extra’ chain to let out to compensate for
the sag.
However, At the moment, this error from the sag is down in the noise compared to
errors cause by improper machine measurements (i.e. bad calibration)
David Lang
But that doesn’t allow itself to be automated. Eventhough it’s a very straightforward procedure.
It would be cool if a Maslow could take human error out of the equation by letting it measure itself .
EDIT:
I just realised that this isn’t the Auto calibration topic.The idea just popped into my mind and I bounced it as an instant reply… Is it possible to move my previous reply to the Auto calibration topic? Or would that be a bit chaotic?
how much are you willing to pay for the automatic calibration?
As something that only needs to be done once, I don’t see it being worth paying
any noticable amount.
David Lang
On a stationary machine then you indeed need can do with a single calibration.
However, this design would eventually allow to be very portable and flexible.
As in transportable and reconfigurable to whatever size you need or space you have available.
Then an auto calibration would be a huge help.
This is why it keeps bouncing trough my mind like a ball in a pinball machine. I just keep sharing my thoughts in the hopes that it sparks an idea to make a simple and effective auto calibration.
For now I pay by sharing and by having all the patience in the world for this idea to grow arms and legs. 
Not something that has to be build right now, but it sure would be awesome if it comes to life one day. Once all the critical stuff is ready and someone gets that spark of imagination how to solve it
With triangular kinematics, you have three numbers (two of which really matter)
- Y offset (not a big deal, just alters where 0,0 is on the workpiece
- the distance between the motors (measureable by feeding out chain, done
today) - the extra chain distance to the bit.
#3 only changes if you change the sled.
So a portable, variable sized maslow can be made by mounting the motors on
telescoping metal poles like
https://www.industrialmetalsupply.com/Products/telescoping-tube and you just run
the motor measurement and type in the distance value for your sled.
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I know we’re really close to getting the desired accuracy by accounting for chain sag and other refinements, but I just found this adhesive measuring tape on ebay that might be handy for calibration: https://www.ebay.com/p/911440472
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What if we used a laser edge and center finder like this:
http://lasercenteredgefinder.com/product/bp-mini-lcef-14-shank-dot/
I know, a little pricey, but hear me out… instead of printing patterns on paper, use sheets of paper squared up on the corners of the workspace to find 4 points to calibrate to. Knowing that a sheet of standard paper has exact dimensions (8.5” x 11” for instance) allows you to find a precise point a specified distance away from each corner of the work space by aligning to the (on board) corner of the paper itself. 4 datum points at the extreme areas of the space should allow for pretty accurate calibration, correct?
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so, it just projects a dot where the router is located?
Yes, it has adjustment so you can calibrate precisely to the center of the collet. I would imagine you turn on the router to see if the laser wobbles, adjust until it doesn’t, and now you have a very precise way to calibrate to given points on the work area. I think a permanent mark at center and maybe a known point or two near the extents of the space will allow you to “zero”, then check for accuracy.
I saw in an earlier post that someone was able to use a bit just under 3” long with the ridgid router. These seem to start around 3” long, so hopefully they also fit…
Interesting idea. Seems like a $5 laser diode module in a DIY adjusting housing sized to fit the router might also work?
https://www.amazon.com/McIgIcM-laser-Adjustable-Module-Copper/dp/B06VVDZZTH
I mainly suggest something like that bc I think I have a few lying around left over from another project.
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Yea, that would work too. Definitely cheaper, just have to come up with a way to calibrate and hold up to the rpm’s. I guess you could just flick the router on and off again quickly to keep it from spinning up to full speed. Probably smart anyway. a few rotations is all you need to see if the laser is centered and aligned. Definitely better than trying to guess where the center of a bit is.
another option is to use line lasers. Two mounted on the router can be calibrated to the center point and used without the need to spin anything. Indeed, without needing to put anything in the router. Would probably take a bit to figure out where and how to mount them.
I use a similar set up on my drill press.
I am curious why that website is charging so much for their lasers. Even precision borescopes for rifles are only $20-$50. I guess if people will pay that price…
Yea, I think it’s because they house them to withstand high rpm for calibrating machines. The laser itself is probably cheap, the housing and calibration mechanisms are what cost. I thought about line lasers also. Crosshair lasers mounted off axis and focused on center. Maybe able to pull one off another machine (like your drill press) and adapt to the rigid? Either way, eliminating slop here will definitely add towards the tighter tolerances everyone is looking for.
Looking at the instructions for use, they say to move the spindle by hand a couple times, so I don’t think you are supposed to spool it up with power.
Totally agree.
the accuracy issues we are fighting are in sending the sled to a particular location under computer control, not in trying to manually position the router in a specific location.
When doing CNC work, you very seldom need to position the router in a particular absolute location to start cutting, most of the time exactly where you start doesn’t matter much, once you start cutting, all that matters is that the relative movement to the starting point is all that matters
unless I am misunderstanding your proposal. why would this be more accurate than just using a v-bit as a pointer.
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