DIY Laser levelling using webcam and laser level

I have had an idea, or maybe remembered something previously discussed here. To get around the error in the laser line which is proportional to arc length how about first flattening the master rail in isolation with the laser projecting along the rail, this uses less that 1 degree of laser arc. The master rail is now flat. Now move the laser so it is orthogonal to the master rail and projecting across the frame as to encompass the slave rail we want to bring into plane with the master.

The height deviation from flat caused by the error in the laser line now we are using say 30 degrees of arc can be measured and the true deviation calculated for stations along the known flat master rail and then projected using simple geometry to stations on the slave rail so that it can be also be flattened bringing it into plane.

Sketch:
Attachment 27042

This should work shouldn't it, if we consider that a ray of light travels straight and that a very small arc of laser line is 'ray like', and if we consider the laser as a point source (which it isn't). Thoughts?

Hi Joe

The mirrored face prism has 6 sides

It is driven by small three phase board mounted disk motor and a Toshiba TC9242P Motor driver chip.

For a quick test I tried using a small laser pointer and spinning it by hand got a nice bright red line. Very sharp if the target was a short distance away however as suspected on first observation the beam focusing lenses as used by the HP printer were set for a short distance. The dot increased in size quickly as you moved the target away.

However the rotating mirror prism without the lenses worked well, I just spun it by hand for a quick test of the concept.

I will have to do a proper test once I sort out the interface. The laser diode I used was a cheap giveaway pointer!
I removed the invisible light diode as fitted by HP for safety, just two screws and it leaves a nice mounting face for the replacement visible red diode. For this test I just held it by hand....

Just read your post 161

The line is generated by the changing face angle, with 6 faces I am guessing the line generated will be about 60 degrees assuming 360/60 is the correct formula? The HP laser unit itself has a coverage of about 60 degrees.

Mechanical errors?

As I see it the rotating prism mirror presents every side to the laser in turn. The line generated should be straight if the laser is located perpendicular to the axis of rotation. if not on axis a slightly curved line would be generated.

The bearings of the rotating spindle may not be perfect, this may cause the edge of the optical plane generated to wobble up and down for each rotation turn? However your software makes multiple measurements and averages them, This should help cancel out this error.

Regards
John

Hi Joe
Edited above post

Quote:

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Originally Posted by John McNamara

Hi Joe

The line generated should be straight if the laser is located perpendicular to the axis of rotation. if not on axis a slightly curved line would be generated.

The bearings of the rotating spindle may not be perfect, this may cause the edge of the optical plane generated to wobble up and down for each rotation turn? However your software makes multiple measurements and averages them, This should help cancel out this error.

Regards
John

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Hi John,

A penta-prism doesn't suffer this problem, it has two faces at 90 degrees, then two other faces at 90+22.5 to the first two, the fifth face is not relevant, some might not even have it or maybe have multiple. Good picture on wikipedia.

In the pursuit of madness I have just done another test on the milling table with the better quality laser, I did 6 runs each with different parts of the laser line some with the laser inverted, with the angle of incidence to the table random, etc. Again 10 stations over 500mm. Results are very consistent which makes me think there was something wrong with my last test.

Attachment 27043

I don't think the laser mount is anywhere near stiff enough, it takes a few minutes for it to stop moving around on the screen to start a run and by the end of the run it has drifted by at least half the error of the run. Note that I haven't been testing with the laser on that desk rather out in the garage on a heavy bench over the bench leg.

Attachment 27044
Attachment 27045

I think this laser needs to be clamped to a vblock attached to a lump of iron. It also has a focusing ring attached which works well other than it wobbles the laser all over the place. This might need to be locked in place as well.I have now gone from 'borrowing' the laser to owning it so it might well get some locktite on the focus slider.

If anyone else wants one to play with they are sold here, £40.
https://odicforce.com/epages/05c54fb...Products/OFL72

Hi guys,


I recieved my cheap webcam today.

It is a ASHU H800 1080p cam, about 18 euro incl shipping.

https://a.aliexpress.com/Zos0Tdull


If internals are really 1920x1080 (windows says it is) this might be an ok device.

The chip size is ~6.5mm x ~3.2mm


So this sensor could be 0.003mm ish per pixel.

I wanted a bigger size sensor than the 640 pixel 2.5 mm one. Because of the width of the laser line on my bosch laser


Does the software account for not having the sensor 100% level?
I hope it does.

Or does not having it level actually help achieve sub pixel accuracy .

The lens can be screwed out and put back on so it is only exposed to dust while in use.

I wil drill 2 mounting holes in the housing and bolt it to a piece of 4080 profile.


I will try to install the software and try icw the bosch laser i have.

Will report back on progress.





Verstuurd vanaf mijn SM-A320FL met Tapatalk
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Quote:

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Originally Posted by driftspin

Hi guys,


I recieved my cheap webcam today.

It is a ASHU H800 1080p cam, about 18 euro incl shipping.

https://a.aliexpress.com/Zos0Tdull


If internals are really 1920x1080 (windows says it is) this might be an ok device.

The chip size is ~6.5mm x ~3.2mm


So this sensor could be 0.003mm ish per pixel.

I wanted a bigger size sensor than the 640 pixel 2.5 mm one. Because of the width of the laser line on my bosch laser


Does the software account for not having the sensor 100% level?
I hope it does.

Or does not having it level actually help achieve sub pixel accuracy .

The lens can be screwed out and put back on so it is only exposed to dust while in use.

I wil drill 2 mounting holes in the housing and bolt it to a piece of 4080 profile.


I will try to install the software and try icw the bosch laser i have.

Will report back on progress.





Verstuurd vanaf mijn SM-A320FL met Tapatalk
https://uploads.tapatalk-cdn.com/202...962c39dc6a.jpghttps://uploads.tapatalk-cdn.com/202...63d0601d31.jpg

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Ok so i set 3um per pixel and got this result for a stationary setup.

it looks like there is an upward trend... not sure what causes that yet.

maybe the laser is heating up in the bosch auto levelling system moving it over time.


This will be the best setup i can do so far to measure the flatness of the machine so far.

Happy so far.


Grtz. Berthttps://uploads.tapatalk-cdn.com/202...8d62679860.jpg

Verstuurd vanaf mijn SM-A320FL met Tapatalk

Quote:

---

Originally Posted by driftspin

Hi guys,


I recieved my cheap webcam today.

It is a ASHU H800 1080p cam, about 18 euro incl shipping.

https://a.aliexpress.com/Zos0Tdull


If internals are really 1920x1080 (windows says it is) this might be an ok device.

The chip size is ~6.5mm x ~3.2mm


So this sensor could be 0.003mm ish per pixel.

I wanted a bigger size sensor than the 640 pixel 2.5 mm one. Because of the width of the laser line on my bosch laser


Does the software account for not having the sensor 100% level?
I hope it does.

Or does not having it level actually help achieve sub pixel accuracy .

The lens can be screwed out and put back on so it is only exposed to dust while in use.

I wil drill 2 mounting holes in the housing and bolt it to a piece of 4080 profile.


I will try to install the software and try icw the bosch laser i have.

Will report back on progress.





Verstuurd vanaf mijn SM-A320FL met Tapatalk
https://uploads.tapatalk-cdn.com/202...962c39dc6a.jpghttps://uploads.tapatalk-cdn.com/202...63d0601d31.jpg

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The app expects the sensor is in portrait orientation wrt the laser line, it then sums the intensity over each pixel row (sensor column) to produce an intensity curve which it post processes to determine the centre. This means if the laser line is at an angle to the sensor it doesn't matter, it should always find the height of maximum intensity at the centre of the sensor width. You don't want a crazy angle as it will reduce accuracy, a few degrees is fine though.

I'm also going to move to a larger sensor, it takes too long to align the laser to the 2mm sensor over any reasonable distance.

So I just tried it with a very nice cheap 1920x1080 camera from Amazon, sensor is perfect for our use, easy to rip apart and about 6mm of vertical resolution. However there is a problem, the library I'm using to connect to the camera only supports YUV format, which is a raw uncompressed image format. This means that over the USB connection higher def cameras cannot deliver the full frame rate of the camera because there is too much data to ship, I can only get 5 fps.

I will have a look about for a different library, this would use MJPEG to compress the frames on the camera so they fit down the USB connection, that may in turn lead to other problems due to compression artifacts reducing the image accuracy, will have to see.

Are you aware of this: https://openmv.io ?

It is a single board computer with camera. You can develop machine vision algorithms in python or in C. They have different sensors but I am not sure they have one with a large enough area for what you desire.

I can see how you would setup a single rail in a straight line with a laser/camera combination but don't understand how you would use a generated laser reference plane to setup a second rail.

Dave.

Hi Dave,

The laser line is a plane so you can either zero both rails to this plane or create a virtual plane from any 3 height measurements and zero to that.

Quote:

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Originally Posted by davebaldwin

I can see how you would setup a single rail in a straight line with a laser/camera combination but don't understand how you would use a generated laser reference plane to setup a second rail.
Dave.

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Dave,
Welcome to the forum (I see this is your first post). Make a nice hot cup of tea and read this thread from the start.

Kit

Let me elaborate.

To make a rail straight you are changing one degree of freedom so by mounting your camera on a rail truck with the laser pointing parallel to the desired path (and obviously intersecting the camera). A simple measure of how far off the centre of the laser beam gives you the amount of displacement of the rail you need to make before the rail is in line with the laser.

Traditionally, to make a surface planar (or two surfaces separated by a gap) you would use a known good plane - i.e. surface plate and a marking out fluid. Blue up the surfaces and use the surface place to rub the marking fluid off the high spots. This then identifies where you need to scrape to bring both surfaces into the same plane. The marking process is essentially in 3D as it extends along the width, length and heigh of the target surface.

Now for the laser plane method. Mount the laser plane generator on the master rail. Set the plane generator up so it is casting a reference plane parallel to the master rail and not at some pitch or roll error. On the slave rail mount the camera on a truck facing the master rail. Now the offset given by the camera from the laser's centre is how much in heigh the slave rail need to be moved. This is one dimension that has been taken care off. Sliding the slave truck (and maybe the laser plane generator as well) along the rail allows you to sample the height difference along the rail. Second dimension taken care off.

The thing I am missing is how the 3rd dimension is taken care off? What we have done is to set the hight of a line on the slave rail to be the same height as the reference plane where it intersects the focal plane of the camera but not that the whole slave rail is in the same plane as the master rail. Looking at it another way we haven't set the roll (looking down the rail) of the master and slave rails to be the same. Is this a second order effect and it unlikely to be outside the planar tolerance of the trucks across the rails?

Maybe this is covered elsewhere in the thread - I have read the whole thread over the months it has been running, but not in one sitting - and I apologise for the repetition in that case.

On a separate note instead of having a fixed laser and rotating (expensive and hard to get) prism why not just rotate the laser? For this application I would have though the advantages of rotating a small piece of glass over a bulkier laser are necessary.

Dave.

Quote:

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Originally Posted by davebaldwin

Let me elaborate.

To make a rail straight you are changing one degree of freedom so by mounting your camera on a rail truck with the laser pointing parallel to the desired path (and obviously intersecting the camera). A simple measure of how far off the centre of the laser beam gives you the amount of displacement of the rail you need to make before the rail is in line with the laser.

Traditionally, to make a surface planar (or two surfaces separated by a gap) you would use a known good plane - i.e. surface plate and a marking out fluid. Blue up the surfaces and use the surface place to rub the marking fluid off the high spots. This then identifies where you need to scrape to bring both surfaces into the same plane. The marking process is essentially in 3D as it extends along the width, length and heigh of the target surface.

Now for the laser plane method. Mount the laser plane generator on the master rail. Set the plane generator up so it is casting a reference plane parallel to the master rail and not at some pitch or roll error. On the slave rail mount the camera on a truck facing the master rail. Now the offset given by the camera from the laser's centre is how much in heigh the slave rail need to be moved. This is one dimension that has been taken care off. Sliding the slave truck (and maybe the laser plane generator as well) along the rail allows you to sample the height difference along the rail. Second dimension taken care off.

The thing I am missing is how the 3rd dimension is taken care off? What we have done is to set the hight of a line on the slave rail to be the same height as the reference plane where it intersects the focal plane of the camera but not that the whole slave rail is in the same plane as the master rail. Looking at it another way we haven't set the roll (looking down the rail) of the master and slave rails to be the same. Is this a second order effect and it unlikely to be outside the planar tolerance of the trucks across the rails?

Maybe this is covered elsewhere in the thread - I have read the whole thread over the months it has been running, but not in one sitting - and I apologise for the repetition in that case.

On a separate note instead of having a fixed laser and rotating (expensive and hard to get) prism why not just rotate the laser? For this application I would have though the advantages of rotating a small piece of glass over a bulkier laser are necessary.

Dave.

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Hi Dave,

I think you are conflating the rail itself with creating a planar surface to mount the rail. Imagine we are trying to create a surface plate from a an uneven slab of concrete say. You would mark out a grid of X-Y points on the slab, setup your laser plane and measure height error to the laser at each point. Take any 3 non-co-linear points (there is a method to pick the optimal 3 but it doesn't matter here), compute the equation of the virtual plane that intersects these 3 points, then correct all the other point error heights to this plane. Now shim or scrape as appropriate every point other than the 3 chosen, rinse and repeat until you are happy with the planar error.

If this process was done using just two lines of points one under each rail centre then yes each rail would have a roll error (like setting up a perfectly planar razor blade under each rail and to them) but if you instead level a surface that the rail will sit on using this method (say level the entire 80mm steel beam in my case) then the roll error will be eliminated (sufficiently eliminated).

Rotating a laser without a penta prism wont work as you cannot build a sufficiently well aligned laser mount, it will always cause the rotated laser to project a cone rather than a plane, this is the entire point of a penta prism, it is agnostic to variance in angle of incidence. Remember 1 arcsecond (1/3600 of a degree) will equate to ~5um of error at 1m. If your mount is say 100mm across this needs to be both machined and the laser somehow aligned to it all to within a tolerance of 0.5um, I reckon this is impossible.

Cheers, Joe

Some notes on HD cameras for people wanting to move beyond VGA.

Why bother? In order to get more vertical range, VGA gets you ~2mm which is not very much when starting with a very unlevel surface, and it is quite hard to align the laser to within 2mm of the thing you are trying to level, but not impossible by any means.

Webcams usually produce two types of video stream, a compressed stream (usually MJPEG unless you have a 2-4k camera in which case it will be h264) and an uncompressed YUV stream. This app can only use the uncompressed stream, both because of how it interfaces to the camera, but also because compression introduces a load of artifacts into the image which will lead to alignment errors.

The problem, most webcams use the USB2.0 standard to connect to your PC. USB2.0 can ship VGA(640x480) uncompressed at 30 fps, moving to FHD(1920x1080) this drops to 5 fps. This means it takes 6 times longer to take a reading, I don't know if this matters much other than slowing the whole process down.

To get 1920x1080 at 30 fps you need a USB3.0 camera (and a PC with USB3.0 ports), these cameras are harder to come by and are more expensive. If you are looking for one then try and check what formats and rates it actually produces before you buy it.

Hope this helps.

Thank Joe. I understand now. I think my confusion came from your first reply to me where you said "... so you can either zero both rails to this plane..."


Have you seen this project. Looks like it shares some similarities but for a very different result.

https://hackaday.io/project/21933-op...solution-laser

Dave.

Quote:

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Originally Posted by davebaldwin

Thank Joe. I understand now. I think my confusion came from your first reply to me where you said "... so you can either zero both rails to this plane..."


Have you seen this project. Looks like it shares some similarities but for a very different result.

https://hackaday.io/project/21933-op...solution-laser

Dave.

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I hadn't seen that particular project, but yes they are using a prism to project a line, However note the accuracy of the prism, it is ~1 arcminute (290um over 1m), this is fairly standard and although readily available unfortunately useless for our purposes, we need <1 arcsecond which are a rather more expensive and difficult to get.

I've been thinking about actually using this system to level the X beams (80mm steel box section) on my new machine, I will outline my current thoughts on the process and welcome your criticism.

I'm thinking the basic process would be:
1. Deposit a 30-40mm wide strip of machinable rail bed material on top of the beams where the rails will go.
2. Use the laser system to level a piece of milled aluminium plate with a window cut in it over where the rail will go. The plate could be clamped and brought into plane with the laser using 3 jack screws bearing on the steel beam.
3. Take a trim router and using the plate as a router guide mill the rail bed down to height. Move the plate along the beam, rinse and repeat, then repeat for the second X beam.

The trim router would be height locked throughout the whole procedure, potentially tape could be used on top of the router guide for a roughing cut, then removed for a finish cut. The laser would also have to remain in location.

For the rail bed I'm thinking of polyurethane metal filler laid to a depth of 1-2mm, hardens quickly and is fairly easy to machine.

I don't have a trim router, although I don't mind picking one up. Does anyone know what sort of Z-play units like the small Bosch or Makita have?

Thoughts on success of this process?

Joe,
That's beginning to sound as fiddly as using the traditional West Systems 105/209 epoxy leveling method with more potential for errors. Gravity never makes mistakes. What do you see as the advantages to your proposed method?

Quote:

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Originally Posted by Kitwn

Joe,
That's beginning to sound as fiddly as using the traditional West Systems 105/209 epoxy leveling method with more potential for errors. Gravity never makes mistakes. What do you see as the advantages to your proposed method?

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Hi Kit,

I do have a pack of 105/209 here for this machine, trouble is the temperature in the UK in my unheated uninsulated garage is about 6 degrees, so would have to wait until summer.

I was also hoping we could improve upon the accuracy of epoxy, from the measurements taken in this thread:
http://www.mycncuk.com/threads/8197-...5194#post65194
and Jonathon's build here:
http://www.mycncuk.com/threads/6484-...8616#post48616
It appears with epoxy 60um (0.06mm) peak-peak error is possible, I think we can do better than this with the laser and also not have to wait 2 weeks for the epoxy to cure. It might be possible to perform the process I described above in a couple of hours. 0.06mm is 20 pixels on the image sensor to give an idea of comparable resolution.

Cheers, Joe

Quote:

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Originally Posted by devmonkey

Hi Kit,

I do have a pack of 105/209 here for this machine, trouble is the temperature in the UK in my unheated uninsulated garage is about 6 degrees, so would have to wait until summer.

I was also hoping we could improve upon the accuracy of epoxy, from the measurements taken in this thread:
http://www.mycncuk.com/threads/8197-...5194#post65194

It appears with epoxy 100um (0.1mm) peak-peak error is possible, I think we can do better than this with the laser and also not have to wait 2 weeks for the epoxy to cure. It might be possible to perform the process I described above in a couple of hours.

Cheers, Joe

---

We're having the opposite problem here. Last night's overnight low was 29C and the days have been up to 46C recently. I'm keeping our epoxy resin (wife and I are making some fancy stuff to sell in the local gift shop) in what used to be a wine fridge.
Maybe you could pour the resin and then come over to us for a fortnight's tropical snorkeling with whale sharks and manta rays while it cures? Then take your enviable winter tan home and use the laser to guide you hand-scraping the last 100 microns of errors out? Hand scraping resin shouldn't be to hard.

Hmm, so I now have another problem.

I set laser on the milling machine head, just needs to be attached to something solid, then levelled the laser to the machine frame which is sat on a sturdy bench. The problem is that walking near the laser causes microscopic deflections in the concrete floor, sufficiently large to show up as 10-20um of error 3m away on the machine frame. These are probably amplified by the height of the laser from the floor, about 1.5m as the same doesn't occur walking near the bench.

I think I will need to move everything directly onto the concrete to stand any hope of getting things stable enough to do any frame levelling. Problem will then be not kicking it during the process.

Hi All

Gee who would have thought this thread would have generated so much interest.

I am tempted to bring up the possibility of automating bed machining using software!

The following is just first draft of a possible solution. My plan is to level the surface by milling small sections of the bearing surface in an overlapping grid pattern. When finished the surface would look a little like hand scraping. As each "Peck" was made after aligning the cutting head to the laser or stretched wire. Once the cutting cycle is complete the surface flatness would be equal to any errors in the measurement system that we already know is pretty good from the experiments done so far my a number of testers. A final stoning of the machined surface would remove any high spots. Note the cutting head is aligned to the measurement system not the rail it slides on.

A quite small milling head with a small cutter (5 - 8mm) traversed along the bed using the rails to be later used on the machine itself temporarily fixed to the sides of the in your case 80x80 rail support frame.

I don't plan on using a high speed spindle just a simple Import
https://www.ebay.com/sch/i.html?_fro...motor&_sacat=0

It would need 4 axis.
One controlled by the leveling software

One that rotates the cutter head to vertical (Leveling IC's are cheap) a small stepper. The leveling could be done with 3 steppers for complete control or just one if only levelling transversely across the rail in the x direction. Therefore only one small stepper required.

One to drive the cutter head down and make a peck. Another small stepper and a simple screw drive ball screw not needed just low backlash.

One to move the small cutter across the work. the X axis has very limited travel maybe 50mm maximum.

There would also need to be a longitudinal drive.
Ideally using the timing belts to keep the cost down.
This drive could use the drive motor later to be used in the machine.

So the sequence would be:
Starting with the cutter head in the up position.

Move along the rail to the next cutting "peck"
Level the head

Find the center point with the alignment software to align the attached cutting head.
Move the cutter head down #N steps to engage the work.

Retract the cutter head.

Repeat cycle.

The temporarily fitted rails would only need to be roughly aligned. Within say 2mm Ideally 1mm. Not that hard, it can be done with simple measuring tools.

The accuracy of the system is derived from the measuring system not the supports for the temporary fitted rails.

I imagine that the mounting face of the Box tubes would be coated with a strip of say 5mm thick and wide enough to fit the rails, to be be machined flat with A mixture of epoxy and metal powder.
Easier to machine than steel. Thin box sections are often bowed. You don't want to weaken them.

I posted this a while back. I still run the lathe on the material. Inexpensive to prepare. For non sliding Iron or Aluminium powder alone and epoxy would be fine.
https://www.cnczone.com/forums/epoxy...al-method.html

If a few people are interested I would have a crack at drawing up a design that mainly uses laser cut sheet steel parts ground rod and Asian bearings for the Simple jig needed. Anyone could download the files and send them off for cutting to their local cutting shop. It will be quite small so low cost.

I am not planning a servo driven XY axis just point to point positioning via steppers,
An Arduino or similar processor could easily drive all the above.

Regards
John

Interesting idea John.

3 axes may be enough:
Rotation (few degrees may be enough). Likely the rotation should be clamped after achieving the correct level plane. Rotation adjustment could even be manual.
Cutter up/down (few mm, accurate depth very important).
Transverse (~50mm)

Longitudinal along the rail could be done manually with clamping at each position. This avoids the need for a temporary low backlash longitudinal drive.

Actually, all the movements could be done manually based on software feedback. Light cuts are expected only.

An important point is a fixed mounting place for the laser that allows both rails to be machined / aligned. This may be a bracket fixed to the middle of the machine bed, equidistant to the rails.

(By the way I am keen to see some updates to your epoxy granite mill!)

Hi Pippin

X and y positioning does not need to be done to CNC milling machine accuracy standards. the pecks cut a small circle and can overlap each other enough to allow for any positioning errors.

Using a rail that will later be used on the machine (it needs to be a profile rail if only one is used round rails will work but two will be needed) the cutting head will be mounted on one of the rail runner bearings that will later be used on the machine. The cutter head will be small, not a gantry across the machine. At a guess maybe a 250mm cube should be enough to contain the components. made from laser cut and 3d printed parts.

If the rail used is not ordered a little extra long the cut length will be equal to the length of the rail minus the width of the runner block, not a huge problem the small section at each end could be hand finished. Or the rail could be ordered a little extra long to allow for this.

How to mount them?

My plan is to clamp a piece of say 90 x 45mm (4x2" imperial) dressed timber on the side of the frame member to be leveled this would need to be manually straightened to within a mm or so, not hard with simple tools Or better still buy a good straight piece from the local building materials supplier

I plan to mount the rail on this timber with stout wood screws!

This is where the laser or wire alignment system comes into play. The rail and cutter head assembly
only needs to provide solid support for the cutter head. Positioning the cut is done by the measurement system not the frame.

The X axis is possibly the weakest link in this design, as is as long as a simply flat area is all that is needed it should work fine. If however you wanted to pilot drill the mounting holes it would not be sufficiently accurate without setting up the laser reference or wire reference at 90 degrees.
Doable at the expense of complexity, probably unnecessary.

Regards
John

PS: Yes Pippin the epoxy mill begs me to finish it. 2019 was a big year for me work wise with a heavy smattering of other issues. I hope to get back on it soon.

So I have made a small amount of progress this evening. With the laser mounted solidly to the mill head I was able to map the my machine frame. I clamped the laser solidly then left it well alone. This meant the machine frame had to be adjusted to the laser plane, which is much easier than vice versa. I lifted the frame at 3 points and shimmed each to get the best coincidence of the two planes, this was just done with a steel rule with the end on the frame and reading off where the laser hit it.

This is the frame and I'm trying to create a planar surface across the top two beams:

Attachment 27084

I then mapped the surface, I have about 1mm total peak-peak error, basically each top beam slopes down 1mm from end-end but in opposite directions. This isn't too bad.

I also took delivery of a little Makita trim router, I think it is the same sort as used on some peoples cnc routers. Anyway for £100 it is a very nice piece of kit, no measurable up-down play in the spindle, I also got a 6mm collet for it.

The levelling process I'm going to attempt I outlined earlier in the thread, but basically it involves using a trim router and a laser aligned router jig to mill down material fixed to the top the frame to bring it into plane.

So what material to use? I mixed up some metal polyester filler of the type used to fix leaks on engine castings. This stuff has some nice properties but it is too brittle and I think too soft (definitely softer then unfilled epoxy).

So what about epoxying an aluminium strip to the top of the steel frame and machining that? Would probably work but more effort, I checked the little Makita is happy milling aluminium and it is fine.

Whilst I had the router in hand with a 6mm carbide endmill in it, I thought I may as well see what it can do against mild steel, not expecting anything other than chatter and heat. Anyway it cuts it like butter, very cleanly. I only tried 0.5mm and 1mm DOC and it was fine and this is within the range I need for levelling this frame.

So I will pick up some 30mmx4mm flat bar stock tomorrow and weld it to the top of the frame where the rails will be mounted, then build the laser/router jig and hopefully have a planar frame very soon.

Quote:

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Originally Posted by devmonkey

It appears with epoxy 60um (0.06mm) peak-peak error is possible, I think we can do better than this with the laser and also not have to wait 2 weeks for the epoxy to cure.

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Question.!... Why do you need better than 0.06 for a router..? . . . . Answer.! . . . You don't.

With all the watts of brainpower you've invested in this, you could have heated the garage and built the bloody thing.! . . . Just get on with it and stop overthinking is my suggestion.

Quote:

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Originally Posted by JAZZCNC

Question.!... Why do you need better than 0.06 for a router..? . . . . Answer.! . . . You don't.

With all the watts of brainpower you've invested in this, you could have heated the garage and built the bloody thing.! . . . Just get on with it and stop overthinking is my suggestion.

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Yes I could have done, using maths I even worked out it would cost £84 in electricity ;-)

I may still use the epoxy if this doesn't work out but this thread is about developing a open source optical metrology system using very cheap components for the benefit of anyone who wants to measure anything accurately to few microns. I thought you'd be well up for that given your pet hate of people quoting accuracy figures they cannot measure.

Some projects do require better than 60um accuracy, or at least calibration of that level of error. For example I want to use the machine currently under construction or one of its offspring to position high power magnets into a halbach array for a coreless axial flux PMDC EV motor I'm developing, this needs 10um accuracy under quite significant magnetic load.

HI All

Well Put Joe. "Devmonkey"

This thread "is about developing a open source optical metrology system using very cheap components for the benefit of anyone who wants to measure anything accurately to few microns" The software you have written that forms the cornerstone of the project continues to evolve and mature.

When I first came across this thread in August 2019 It captured my imagination straight away, It continues to do this now 4 months later. It represents the work of many individuals now, all striving to improve it, by freely sharing their ideas on a world stage. The results will enable many builders and experimenters to achieve measurement accuracy previously only available at great expense.

Thanks Joe, the best is yet to come!

Regards
John

Joe,
Though the chances of me ever requiring the level of accuracy you are striving for here are minimal I agree with John completely. This remains a valuable and fascinating thread. Have you ever thought of sending your CV to NASA?

Dean,
For novice readers who are trying to work out what they should be doing to make a CNC router with performance that is both adequate and practically achieveable your comments are equally valuable.

Kit

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Originally Posted by devmonkey

I may still use the epoxy if this doesn't work out but this thread is about developing a open source optical metrology system using very cheap components for the benefit of anyone who wants to measure anything accurately to few microns.

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Don't get me wrong I'm not putting down or knocking this thread or what you are doing, so what ever floats your boat, I'm sure it will help someone with time to waste or true need for it.!
However, my comments are aimed to help those reading threads like this and think this sort of setup is what's needed to build a good router, you included. My point being it's NOT.!

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Originally Posted by devmonkey

I thought you'd be well up for that given your pet hate of people quoting accuracy figures they cannot measure.

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Yes, it is and I may just read this thread completely to see how you have validated that your setup is actually accurate because from the little I've read I'm seeing references to measuring against steel rules, etc and I've yet to see or own steel rule that is straight to micron levels.!

Unless you validate using calibrated measuring devices then you cannot possibly claim your accurate to micron levels. Because no matter how good the idea or wish it to be or fool self into thinking it is accurate, only a calibrated validation speaks the truth.

I know this only too well because as I've got deeper into building machines I've invested in better measuring devices and calibrated granite surfaces plates etc and for several years I believed my really expensive engineer's squares were square, right up till the day I bought my calibrated granite triangle.!!

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Originally Posted by devmonkey

Some projects do require better than 60um accuracy, or at least calibration of that level of error. For example I want to use the machine currently under construction or one of its offspring to position high power magnets into a halbach array for a coreless axial flux PMDC EV motor I'm developing, this needs 10um accuracy under quite significant magnetic load.

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Ye good luck with that using a router made from thin-walled steel tube which is less than well braced, that will between heat variations and resonance make low micron level machining a pipe dream.

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Originally Posted by Kitwn

Dean,
For novice readers who are trying to work out what they should be doing to make a CNC router with performance that is both adequate and practically achieveable your comments are equally valuable.

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Exactley why I make these kind of post's Kit.
I know lots of people think I'm just being a Dick head or awkward for the sake of it and don't like me saying what I do or how I say it. The truth isn't often welcome or popular.!
But they're not the ones who get hundreds of messages and emails from first time builders or people lurking in the background watching, reading these threads asking for help or clarity.

You wouldn't believe the amount of messages I get from people who have never posted or built a machine but have been on the forum for several years watching, trying to make sense of it all, only to get completely Kaffuddled by all the crap that gets spouted, often by those with little to no experience of building a machine but head a full of brains overthinking what's required. (This is not a go at anyone here either like I say whatever floats your boat),

However, I will never NOT say something when I see overly complicated ideas being applied to building a router type machine. Because it's not needed so needs to be said for the sake of others.
If you or anyone feels the need to go to these levels then fine crack on, I wish you well, but don't get upset when it's pointed out it's not needed for a router.

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Originally Posted by JAZZCNC

Yes, it is and I may just read this thread completely to see how you have validated that your setup is actually accurate because from the little I've read I'm seeing references to measuring against steel rules, etc and I've yet to see or own steel rule that is straight to micron levels.!

Unless you validate using calibrated measuring devices then you cannot possibly claim your accurate to micron levels. Because no matter how good the idea or wish it to be or fool self into thinking it is accurate, only a calibrated validation speaks the truth.

I know this only too well because as I've got deeper into building machines I've invested in better measuring devices and calibrated granite surfaces plates etc and for several years I believed my really expensive engineer's squares were square, right up till the day I bought my calibrated granite triangle.!!

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Hi Dean,

Maybe read the whole thread mate, it shows various calibrations of the line optics used against beams of light which travel in straight lines and also some other tests by other forum members, it does rely on the 3um pixel pitch of the cmos image sensor not being too variant across the sensor, not able to calibrate that I'm afraid.

Anyway suffice to say I agree you don't have do use or understand optical metrology, diy or otherwise, to build a working router, I haven't used it with any of the other machines I have built and all worked fine, although my mate does use a commercial optical kit to align his machining centres, but he builds stuff for F1.

Conversely if you want to measure your machines that you have built then download the software and have a play.

What is the DIN 876 grade standard of the surface plate you use?

Cheers, Joe

For me one of the great attractions of this forum is the mixture of common sense, common sense being not at all common in general usage, and cutting edge science that is available on an almost daily basis. I want to read Dean's and Boyan's blunt comments on what is sensible for someone wishing to build a first machine for cutting out wooden parts for their hobby projects, and I want to see what Joe and John can offer in the way of extreme accuracy for a home hobbyist on a DIY budget for those that are interested in achieving it. Our main problem is ensuring the novice reader is not confused regarding what is practical and achievable within their target spend of both money and time.

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Originally Posted by Kitwn

For me one of the great attractions of this forum is the mixture of common sense, common sense being not at all common in general usage, and cutting edge science that is available on an almost daily basis. I want to read Dean's and Boyan's blunt comments on what is sensible for someone wishing to build a first machine for cutting out wooden parts for their hobby projects, and I want to see what Joe and John can offer in the way of extreme accuracy for a home hobbyist on a DIY budget for those that are interested in achieving it. Our main problem is ensuring the novice reader is not confused regarding what is practical and achievable within their target spend of both money and time.

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I agree which is why I have confined the discussion of the optical stuff to this thread, and my current machine build to the build log thread. I will however have to use some parts of building that machine to demonstrate how one might use the optical system, no one need copy it, but there does seem to be interest which is why I keep posting.

The two tasks which I'm attempting with this system are
1. Making the X beams planar to carry the rails,
2. Straightening the master X rail (this is trivial, just attach sensor to a carriage and align to laser).

(1) as an alternative to epoxy, or scraping against a 876 grade 1 surface plate which I don't have and would be very expensive even for a moderate machine, or using a precision level.
(2) as an alternative to using a precision straight edge.

If a cheap penta prism can be scrounged from somewhere then this can be used for tramming the Z and squaring the gantry, but I'm not so bothered about that as there are other methods.

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Originally Posted by devmonkey

Maybe read the whole thread mate,

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I don't really have a need for it, so my time is better spent doing other stuff, like trying to understand the brain-numbing C++ macro's for an ATC.!!

However, again I'll repeat I wasn't knocking what you are doing or saying anything negative about what you are doing, merely questioning how it's validated, because without validation equipment it's all guesswork, highly educated guesswork probably but still guesswork none the less.
That said I'm sure some will have use for it, hell I may even have use for it someday, so please carry on. My post honestly wasn't to discourage or rubbish what your doing and It's good for everyone who needs it so I applaud you for it.

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Originally Posted by devmonkey

What is the DIN 876 grade standard of the surface plate you use?

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I've got 2 surface plates one BS817 6` x 4` x 10" Grade 0 forgot the name of maker but it's a old one on a metal stand, weighs about as much as a small car. The other is Din 876 made by Insize 9600 series 1000 x 630 x 140 grade 00. The granite triangle is a Mitutoyo Din876 500 x 300 x 60 Grade 00.

Ok Dean, cool. Let me know if you want a hand with the c++.

That Insize surface plate is a really good deal, I just looked up the price.

Continuing the mission of bringing my frame into plane I have welded on some flat stock to mill down to plane. Rather surprisingly I picked this up at the local Wickes, about twice what it costs when you buy it by the full length but available within 10mins, they had quite a selection of small flats and angles. Welds were ground down so as not to foul the jig.

Attachment 27085 Attachment 27086 Attachment 27087

I have also made the jig. It is very crude but I think will work well and is very solid once clamped to the frame. It consists to a piece of milled aluminium plate with a window cut in it for the router, and two pieces of angle iron that are clamped to the 80mm box section of the frame. Three M5 levelling bolts thread up through the angle iron and the plate sits on these, these form 3 adjustment points to bring the top of the plate into plane with the laser. Then 3 M6 locking bolts pass down through the plate into threaded holes in the angle iron clamp down the plate hard onto the tops of levelling bolts. The levelling works perfectly and is very quick.

The plate has a recess milled into it to clear the flat stock, the idea is to set the router height to the thickness of the plate, level the jig, mill off the flat stock, unclamp the jig and move along, repeat.

Attachment 27088 Attachment 27090 Attachment 27089

So that was all very cool and it looks like it will work, however now for the irritating part which will require some thinking. The frame is sat on my supposedly sturdy bench. Unfortunately a wooden bench will not cut it for this operation. With the sensor on top of the frame and the frame clamped hard directly over the 4x4" leg I can compress the leg about 0.1mm by pushing own as hard as I can on top. This is too much and means I need something much firmer to put the frame on before continuing.

You see you can find out all sorts of pointless things with this laser system, I now know that about 50kg on the end of 2 bits of 2x4 about 1m long will compress them 0.1mm, how useful ;-)

It maybe that now is the time to build the solid table that machine will sit on then use that to do the levelling on, or bolt the frame directly to the concrete floor even.

Quick question have you checked the end float of this trim router.? I've had quite a few of these trim routers and they are not the best-built things so I wouldn't be surprised if it didn't float more than the Um values your chasing.? . .Esp trying to mill steel with it.!

The frame doesn't look that large do you know anyone with a large surface plate could fit it on. If so then I'd suggest you use Metal Repair paste, like Belzona 1111. This is the method I use for machines that will fit on my surface plate. Better than Epoxy and about the same in costs. It can be Drilled and tapped easily and as strong if not stronger than the metal it's bonded onto. Isn't too fussy about temperatures and they even have types that can be used underwater or subzero temperatures. Dry's in hours not weeks.!

https://www.belzona.com/en/products/1000/1111.aspx

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Originally Posted by JAZZCNC

Quick question have you checked the end float of this trim router.? I've had quite a few of these trim routers and they are not the best-built things so I wouldn't be surprised if it didn't float more than the Um values your chasing.? . .Esp trying to mill steel with it.!

The frame doesn't look that large do you know anyone with a large surface plate could fit it on. If so then I'd suggest you use Metal Repair paste, like Belzona 1111. This is the method I use for machines that will fit on my surface plate. Better than Epoxy and about the same in costs. It can be Drilled and tapped easily and as strong if not stronger than the metal it's bonded onto. Isn't too fussy about temperatures and they even have types that can be used underwater or subzero temperatures. Dry's in hours not weeks.!

https://www.belzona.com/en/products/1000/1111.aspx

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Yeh I checked it with a DTI, if there is end play it is less than 10um so hopefully it will be ok. The little router seems quite happy with steel, I only need to take off about 1/4mm. The best approach is to use masking tape to shim the router off the plate by the the thickness of the tape, cut the surface, then remove the tape and re cut, cutting loads on the 'finish' pass are almost nothing as only taking off a tiny amount of material. I've tested this on a bit of scrap flat bar and it leaves a flycut quality finish, shiny.

I did ask my mate who has a precision machining shop if he would be happy to surface mill the whole thing, he said he would but there is a long queue and since it is run like a clean room for doing some specialised parts I don't think he was overly keen me on me dragging in a great lump of dirty steel ! Good idea with taking an impression of a surface plate, I don't know anyone locally with one though other than him.

If I screw up this optical levelling I might go back to him, there will be enough material left for surfacing.

I've fixed the problem of my compressible work bench by removing one frame of reference, laser is now fixed to a lump of box tacked to the frame:
Attachment 27091

EDIT
That metal repair paste looks fantastic, it is epoxy based as well unlike the polyester rubbish I have here.

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Originally Posted by devmonkey

That metal repair paste looks fantastic, it is epoxy based as well unlike the polyester rubbish I have here.

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Anyone who used to work down a mine will probably remember Belzona, it was a common and came in a sausage shape plastic packet about 12" long with hardener down the side. You cut it down the middle and mixed it straight away, you had about 10mins before it set like concrete. When I was a young mechanic just about every miner's car in yorkshire had some in the sills or chassis used as filler..Lol

It's come along way since then and the current Belzona is amazing stuff, esp the ceramics. I accidentally used some by mistake and while it was only 3mm thick it hate quality jobber drills for breakfast.

Got a question about this Laser setup.? How wide a beam can it throw and still be accurate.? Could it, for instance, cover a 6mtr x 4mtr area.?