DIY Laser levelling using webcam and laser level

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Originally Posted by JAZZCNC

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.?

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So the way to think about it is as a bunch of rays leaving the laser, each will travel in a straight line. If the optics are good then all these rays will also lie in a plane forming a line on whatever vertical surfaces they hit. I haven't tested the straightness at that distance only that it can be focused to a tight beam at around 10m.

One thing you could try with your large surface plate is setup the laser on the plate, take a bunch of readings in a 1m radius with the sensor sat on the plate, this will tell you whether the laser is planar and if not what the error is for each arc segment, i.e. you can calibrate the optics. Then you can project this error as far as you like to whatever you are actually measuring.

The biggest issue will be whatever you mount the laser on will have to be really solid as just 1 arc second of wobble on the mount will be 0.05mm at 10m. One solution to this is using differential measurement like they do with electronic precision levels, setup one or more fixed sensors and use these to offset any error caused by you breathing near the laser ;-)

This is the part of the system I'm really struggling with. With my laser mounted on that piece of box section with sticks out 400mm from the machine, reasonable finger pressure
is sufficient to bend the box section enough to cause a ~10um deflection in the height of the beam at the other end of the machine say 1.5m away.

When looking at this stuff where the sensor is measuring 3um pixels everything looks like it is made of jelly, at least everything in my garage including the 6 inch concrete slab.

What are you planning that is so large?

Quote:

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Originally Posted by JAZZCNC

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.?

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Hi Jazz

Well, i think we arrived at the point were the cheap cam +software used as a levelling sensor proved it is very good.

The new problem is the lens you use to spread the laser into a beam....

The projected line can be a non straight because of the deviations caused by the optics used to spread the beam.


Does that summarize it?

I plan to use it to level check Y and X 1 axis at a time in the axial direction where the line is straight. First for vertical then horizontal deviation. maybe the diagonal

After that i will see...

Not sure how to do Z yet.

My laser crosshair only aligns in 1 orientation. +/- 0.8 mm /mtr out of plum
according to factory spec.

So Z could stil be non straight


Grtz Bert.



Verstuurd vanaf mijn SM-A320FL met Tapatalk

There is an optical lab a few miles from my house and it has been built into a cave at the base of a rock cliff at the back of a disused quarry, presumably to reduce these problems with flexing buildings and temperature. It is literally behind a steel doorway set into the cliff.

Quote:

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Originally Posted by driftspin

Hi Jazz

Well, i think we arrived at the point were the cheap cam +software used as a levelling sensor proved it is very good.

The new problem is the lens you use to spread the laser into a beam....

The projected line can be a non straight because of the deviations caused by the optics used to spread the beam.


Does that summarize it?

I plan to use it to level check Y and X 1 axis at a time in the axial direction where the line is straight. First for vertical then horizontal deviation. maybe the diagonal

After that i will see...

Not sure how to do Z yet.

My laser crosshair only aligns in 1 orientation. +/- 0.8 mm /mtr out of plum
according to factory spec.

So Z could stil be non straight


Grtz Bert.



Verstuurd vanaf mijn SM-A320FL met Tapatalk

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Hi Bert,

The optics should be better than that even for a crap laser, usually the quoted accuracy is out of plum as you say, this is error relative to whatever reference the laser is bolted to, i.e. a pendulum usually, this is not usually a measure of how 'straight' the projected line is.

Cheers, Joe

Quote:

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Originally Posted by devmonkey

What are you planning that is so large?

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Large double gantry machine for cutting and polishing granite and marble slabs. The two Gantry's will be mounted on linear rails which are basically fixed on top of a high wall on adjustable stainless steel plates. Accuracy to the Micron level isn't required but still needs to be reasonably good for the polishing.

Quote:

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Originally Posted by JAZZCNC

Large double gantry machine for cutting and polishing granite and marble slabs. The two Gantry's will be mounted on linear rails which are basically fixed on top of a high wall on adjustable stainless steel plates. Accuracy to the Micron level isn't required but still needs to be reasonably good for the polishing.

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Sounds like a proper installation!

I can only suggest you pick up a laser and try it, or even just borrow a rotary laser from a local builder or window fitter.

Quote:

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Originally Posted by devmonkey

Sounds like a proper installation!

I can only suggest you pick up a laser and try it, or even just borrow a rotary laser from a local builder or window fitter.

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I know a few machine installers who use lasers for large machines and lathes so I'll probably speak with them when the time comes. It's a long way off yet and could change in design before then so will see.

Quote:

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Originally Posted by devmonkey

Sounds like a proper installation!

I can only suggest you pick up a laser and try it, or even just borrow a rotary laser from a local builder or window fitter.

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Jazz will need something far more accurate than the cheap rubbish your typical builder will likely have.

My parents neighbour is a highly regarded surveyor, and has many tales to tell about builders and cheap kit. One was a job to do an independent inspection of a private swimming pool, which after being filled with water, had a 4" height difference between ends.
After a bit questioning, it came to light the builder had used a 'precision' laser to do the setting out, as lasers are "accurate" and less hassle than using a basic water level (aka a bit clear hose). Turned out his 'precision' laser was a special from Screwfix that had never been calibrated, but the builder was really pleased with it as it only cost him a couple hundred pound.
As the neighbour highlighted to him, it had just cost him far more than a couple hundred pound, as the whole swimming pool was going to have to be stripped out and redone.

Quote:

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Originally Posted by m_c

Jazz will need something far more accurate than the cheap rubbish your typical builder will likely have.

My parents neighbour is a highly regarded surveyor, and has many tales to tell about builders and cheap kit. One was a job to do an independent inspection of a private swimming pool, which after being filled with water, had a 4" height difference between ends.
After a bit questioning, it came to light the builder had used a 'precision' laser to do the setting out, as lasers are "accurate" and less hassle than using a basic water level (aka a bit clear hose). Turned out his 'precision' laser was a special from Screwfix that had never been calibrated, but the builder was really pleased with it as it only cost him a couple hundred pound.
As the neighbour highlighted to him, it had just cost him far more than a couple hundred pound, as the whole swimming pool was going to have to be stripped out and redone.

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LOL, my swimming pool is within 2-3mm when full and I used a cheap dewalt laser when I pumped the concrete for that, your eyeball can tell 4" at the length of the pool. Anyway you are confusing the pendulum laser alignment error with the optical error, quite different things, surveyors only care about the former. Similarly a window fitter, specifically someone who fits bespoke bi-folds will have a laser scanner for scanning the openings as the units are manufactured to fit.

Attachment 27095 Attachment 27096

Still would have required some shimming to attach linear rails rather than sandstone ;-)

Quote:

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Originally Posted by m_c

Jazz will need something far more accurate than the cheap rubbish your typical builder will likely have.

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I agree Moray, my experience of builders laser level hasn't left me blown away either.
If this build happens then I'll look deeper into laser leveling and probably go hire the equipment I need or get one of the guys I now in when setting up the rails.
To be honest the precision doesn't need to be super high because one gantry will be used with Circular saw attached so no great accuracy required at all. The other will be mostly 2D profiling and edge molding using special profile edge tooling and polishing heads. Only making Kitchen countertops so flatness isn't to precision levels and most of the finishing is done by hand. At the moment all of the cutting, shaping, and polishing are done by hand so will be a massive improvement. They just need to save up some penny's or speak nicely to bank manager...Lol

I recon you're missing an opportunity here Dean. Get Joe in as optical consultant and then get John to pop over from Melbourne and build you an add-on Z-axis assembly that can grind kitchen bench offcuts into surface plates for cash at the weekend when nobody's looking.:welcoming:

Kit

PS Joe is that really a swimming pool in Pommieland?! I hope it's got solar heating. Even in Perth we only used ours for a few months around Christmas.

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Originally Posted by Kitwn

PS Joe is that really a swimming pool in Pommieland?! I hope it's got solar heating. Even in Perth we only used ours for a few months around Christmas.

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Yeh I was sceptical too but the kids and missus were rather insistent ! I used ICF for the walls helps a lot with heat loss, and it uses a 39KW air sourced heat pump which has a COB of about 10-15, you put in 3kw of electricity get out 30kw of heat, that together with global warming lets us keep it at 28 degrees from May-Sept, it has ice on it today though. Biggest electrical expense is the water pump, going to convert this to DC and run it directly off a couple of solar panels next season. Hardest part of making it was wiring together 3km (I kid you not) of rebar before pumping the concrete, I had bloody hands doing that for a fortnight.

Getting a bit off topic but anyone interested in getting a swimming pool, build it your self as I did. It cost less than a decent CNC router, £1k for rebar, £5k concrete, £1k ICF and then £3k for some locally licensed rip off merchant to fit the liner. Local pool company came round to have a look when it was finished and told me they would have charged me £80k for building it.

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Originally Posted by devmonkey

Local pool company came round to have a look when it was finished and told me they would have charged me £80k for building it.

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80K for a hole in the ground, they must be on drugs. To be honest, I wouldn't pay 11K either, living in Yorkshire we are surrounded by dozens of old Pit sites and brickworks which all had great big clear blue ponds(well not all clear blue.!), which as kids we lived in. most are still there and know nature reserves or fishing ponds so who needs a heated swimming pool... Lol

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Originally Posted by JAZZCNC

80K for a hole in the ground, they must be on drugs. To be honest, I wouldn't pay 11K either, living in Yorkshire we are surrounded by dozens of old Pit sites and brickworks which all had great big clear blue ponds(well not all clear blue.!), which as kids we lived in. most are still there and know nature reserves or fishing ponds so who needs a heated swimming pool... Lol

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Everything with swimming pool in its name has a 10x price multiplier. The guy to fitted the liner has a 'swimming pool liner vacuum pump' to suck the plastic liner onto the pool shell, this machine cost him £2k. It was a £60 machine mart dust extractor fan like we use in our workshops with a nice stainless steel pool company badge plate riveted over the 'Clarke' label, unbelievable.

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a 39KW air sourced heat pump which has a COB of about 10-15, you put in 3kw of electricity get out 30kw of heat

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I would be interested in the make and model of the air sourced heat pump as I thought that they were only about 3-4 times the input.

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Originally Posted by Clive S

I would be interested in the make and model of the air sourced heat pump as I thought that they were only about 3-4 times the input.

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Here you go,
https://www.heatpumps4pools.com/prod...ol-heat-pumps/

"Excellent COPs – from 5.8 to 15.8 due to Inverter technology"

Depends how hot the air is relative to the water temp, I don't think you can expect the same when you use them to heat your house in the winter as some people are starting to do. Mine is the 27kw single phase one, not 39kw as I originally posted, brain glitch. Once up to temp it just runs at tick over for most of the summer and stops all together on hot days.

Back to the job in hand.

I found a rather obvious flaw in my sensor setup for setting my routing jig into plane today. I have the sensor mounted in a nice true cube and this sits on the jig plate. I then alternate its position above the 3 levelling points bringing each up to the correct height with the jack screws. The problem is unless the sensor is positioned in exactly the same location at each point for subsequent rounds of this procedure you will get different readings. This is because the sensor is effectively rotated around the axis of the jack screw and since the plate is not yet planar to the laser the height of the sensor relative to the laser plane changes based on this rotation. This makes it bloody difficult to do, and it is not until the plate is planar with the laser that sensor reads the same height right across the plate.

To put it another way with the sensor sitting on a plate that is not planar with the laser if you rotate the sensor about any point that is not the vertical axis of the sensor chip itself then the reading will change since the height has changed, similarly if you slide the sensor up and down this plate the height reading will change. This means you can trick yourself into thinking the heights are zero'd by moving the sensor, which I noticed I was doing.

There are two options:

1. Machine up a new sensor mount with some mechanism (likely a dowel pin) inline with the vertical axis of the sensor to that can be used to relocate the sensor consistently at 3 points across the plate.
2. Use 3 sensors simultaneously (would need software change) each fixed to the plate for the levelling operation.

Quote:

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Originally Posted by devmonkey

Here you go,
https://www.heatpumps4pools.com/prod...ol-heat-pumps/

"Excellent COPs – from 5.8 to 15.8 due to Inverter technology"

Depends how hot the air is relative to the water temp, I don't think you can expect the same when you use them to heat your house in the winter as some people are starting to do. Mine is the 27kw single phase one, not 39kw as I originally posted, brain glitch. Once up to temp it just runs at tick over for most of the summer and stops all together on hot days.

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Over here it's called 'reverse cycle air conditioning' you can either heat or cool your house depending on the season. Heating is no good when it's so cold the outside unit freezes up but in more temperate climates like most of Australia it works well. If you need air-con for the summer anyway it's a cost effective heating system to install and to run.
OK, back on track:welcoming:

Thinking out loud, but is there a three-sensor option that works the the other way round? Set up three sensors around the router frame and firmly fix the laser in one position on top of the moving plate. only the plate needs to be moved and adjusted for constant numbers out of the sensors. No trailing wires from the plate to tread on either. This does require the design to allow the laser to stay in place during routing or to be accurately replaced between cuts.

Quote:

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Originally Posted by devmonkey

Here you go,
https://www.heatpumps4pools.com/prod...ol-heat-pumps/

"Excellent COPs – from 5.8 to 15.8 due to Inverter technology"

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Thanks for the feedback. But it also states this

"Bear in mind though that there is no international standard for stating COPs and therefore each manufacturer will state the maximum COP obtainable for their units under optimum temperature and humidity conditions. In reality you may not therefore always acheive the COP rating stated."

I have been involved in installing a few heat pumps air source and ground source and I believe that they were in the region of about 3-4 to 1. My next door neighbour has had his gas taken out and put in an air source pump. I am very interested to see the results over time.

Quote:

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Originally Posted by Clive S

Thanks for the feedback. But it also states this

"Bear in mind though that there is no international standard for stating COPs and therefore each manufacturer will state the maximum COP obtainable for their units under optimum temperature and humidity conditions. In reality you may not therefore always acheive the COP rating stated."

I have been involved in installing a few heat pumps air source and ground source and I believe that they were in the region of about 3-4 to 1. My next door neighbour has had his gas taken out and put in an air source pump. I am very interested to see the results over time.

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Hi Clive,

All I can tell you is throughout a season the total kwh used by the heat pump is is about the same or less than the 1hp water pump that is switched on for exactly the same time, I have clamp on current monitors on both going to the main energy logger in the house. The heat pump pulls about 2.9kw max and will bring 60m^3 of water from 18 to 28 degrees in a couple of days. Costs about £1k in electricity to run both per season. I have no experience of them in houses although a friend who has also just rebuilt his house is now relying solely on an air sourced heat pump for house heating with hot water boosted with immersion and tells me he is saving a fortune, but he wasn't on mains gas rather oil delivered by tanker which is expensive.

What maybe of interest is I had a 10kw pump heating a much smaller 10m^3 above ground pool, this was the older generation pump without the inverter and therefore constant compressor speed / current draw. The electricity cost of running this unit was the same per season as the new pool system, therefore it must have been much less efficient.

Clive
I looked into heat pumps several year ago, obviously ground source is the most efficient but due to my building plot this is not an option, max for air source is in the region of COP 5
https://www.viessmann.co.uk/products...s/vitocal-300a
Regards
Mike

OK.I think I have hijacked this thread and taken it off topic sorry. But thanks for the feed back.

As I said, the limiting factor on air-sourced reverse-cycle air con for heating is when the outside temperature is so low that the external heat exchanger freezes. In the UK I would expect you'd need some additional heating system for the coldest parts of the year (September to May in Cumbria if I remember correctly). In Perth (The Australian one rather than the original) we had a few occasions when the heat exchanger froze but but not many. A well insulated house obviously makes a big difference. It's been a while, but I think that unit used 4kW of electricity for the equivalent of 14kW of heating.

I have realised something about these sensors. They are colour sensors, and the colour detection is done by layering a grid of colour alternating RGB filters over the individual pixels which are all identical photodiodes (i.e. the pixel is monochrome) in what is called a Bayer pattern. These are laid out to match the human eye's response to colour, with 50% of the pixels green and 25% red and 25% blue. See https://en.wikipedia.org/wiki/Bayer_filter

Attachment 27114

This isn't ideal as I'm using a red laser. This means only 25% of the pixels are useful and the sensor will be interpolating the values between 'red' pixels.

Anyway someone pointed me towards some super crazy people in astrophotography who 'de-bayer' their very expensive DSLR sensors with a toothpick so the sensor becomes monochrome at its native resolution, effectively scratching off this colour filer layer to expose the raw sensor.
https://stargazerslounge.com/topic/1...-bayer-matrix/

I have just tried this procedure and ruined a webcam sensor (ripped it off the pcb) so I don't recommend it.

EDIT
The first casualty of this miss-adventure, don't think it is still worth £7 !
Attachment 27117

I suspect this is not the greatest limitation on the acuracy of your system. Making the concrete floor of your shed more rigid should be a higher priority.:whistle:

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Originally Posted by Kitwn

I suspect this is not the greatest limitation on the acuracy of your system. Making the concrete floor of your shed more rigid should be a higher priority.:whistle:

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You may think that Kit, however I believe the (presumably linear) interpolation on the sensor is messing with my non-linear intensity fitting algorithms. It makes no sense to resolve down to sub-pixel resolution when 75% of the sensor information is estimated (Nyquist would have a fit).

For example imagine the raw intensity at the peak of our gaussian laser line looks like this:
100, 100, 101, 101, 100, 100
Now if this falls under the bayer filter on a green+red filter line arranged as:
G, R, G, R, G, R, G

With only red laser light, nearest neighbour linear interpolation would look like this:
100, 100, 100, 101, 100, 100

If the bayer filter is offset 1 pixel the other way you would get
100, 100, 101, 100, 100, 100

Therefore you have 1 pixel (3um) uncertainty and this is for a green+red filter line. I think is worse for a green+blue filter line where all the information is interpolated, i.e the information rate is zero.

I have some ideas to detect and strip this out but it is guess work without a datasheet for the camera chip, or maybe just reduce the resolution of the system from 1 pixel to say 4 pixels (6um).

I have a few RPIs here with cameras which I can get the raw bayer data from and just use the red pixels (can't get the raw data from a webcam), might we worth an experiment but would need entirely new code.

An alternative would be to use an IR laser as the bayer filter is transparent to IR therefore the sensor will behave as monochrome at full resolution, but then you couldn't see the laser for rough alignment.

Monochrome usb cameras (that are made without the bayer filter) are expensive as there is no mass demand.

Wow ... I stopped visiting this thread on page_15 when it went quiet after my post.

I have a lot of reading to do !!

MichaelG.

Quote:

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Originally Posted by devmonkey

An alternative would be to use an IR laser as the bayer filter is transparent to IR therefore the sensor will behave as monochrome at full resolution, but then you couldn't see the laser for rough alignment...

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May I also mention that, for the same reason, they are very dangerous things to have around.

MichaelG.

Been a bit busy with other jobs, however I have been playing around with a raspberry pi version of this system. I took a PI zero W (with builtin wifi), a small TFT screen and an OV5647 (pi camera v1) and wrote some more software. This will form a simple standalone unit and addresses a number of the problems I was having with a simple webcam, specifically:

1. I access the raw camera sensor directly, read the bayer data and only use the red pixels. This removes a load of noise that was being introduced by the blue an green channels and interpolation. There is no interpolation done at all on the sensor using it this way which means I get the true intensity per (red) pixel. Pixel pitch is 1.4um and 1/4 are red so system resolution is 2.8um.
2. Vertical range is much improved around 4mm.
3. With lens removed there is no glass (or a very very thin glass maybe) over the pixel array unlike the VGA webcam which had about 0.5mm of glass which gave some diffraction patterns.
4. I put in an algo to dynamically adjust the exposure, this means I increase exposure until the detected gaussian starts to clip (sensor saturates) then back it down a bit. This makes things much more accurate and repeatable at varying distances from the laser source.
5. No more cables!

I printed a case for it today and mounted the camera to a piece of Aluminium, still need to fix it all together. It has a lipo cell on board that I salvaged from a dead rc pack, a usb charger / ups and lasts for about 3 hrs before needing recharging.


Attachment 27233 Attachment 27234 Attachment 27235 Attachment 27236

https://youtu.be/m-zK3vz7bbQ

Cheers, Joe

That’s a great development, Joe

Will we be able to select our colour ?
... methinks green would be worth a try.

MichaelG.

Quote:

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Originally Posted by John McNamara

Hi All

My Recovering from the holliday's brain has been thinking on line generation.

Having disassembled many laser printers over the years I found in many of them the single point laser was scanned across the page by a (single point) laser beam reflected by a rotating polygon prism […]

If this concept proves doable we can generate a nice scanned plane.

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An excellent idea, John

Incidentally: More years ago than I care to remember, I did some environmental tests on a scanner for reading bar-codes at the supermarket check-out [the type that generates a criss-cross of lines] : The interesting thing about this one was that they had dispensed with most of the real hardware and optics ... They were spinning a hologram !!

I don’t know if it ever went into full production.

MichaelG.
.

Edit: ... Just found supporting evidence: https://books.google.co.uk/books?id=...canner&f=false

This monochrome camera [with 2.2 micron pixels] may be of interest:

https://www.e-consystems.com/ar0521-...nir-camera.asp

MichaelG.

Work has been getting in the way of progressing my machine, but where I left off the laser system is working well enough to perform the operation (particularly with the raspberry pi version) however the process of position a jig and routing the steel frame into plane with a trim router was highly error prone.

1. It was difficult to level the jig since I didn't use concentric adjustment and clamping bolts,
2. The process requires that the laser doesn't move, the trim router height gauge doesn't move and the cutting tool doesn't break or chip throughout otherwise it has to be started over. Also the jig has to remain a planar plate and not wear, since I used tooling plate the surface got quite a lot of wear from the trim router.

This is what stopped me attempting it across the whole machine frame.

So I've had a bit of a rethink and come up with a different process that is hopefully a bit more forgiving and controlled. Rather than attempt to level the frame by grinding it the new processes will attempt to attach rail bearing sub plates to the frame such that these sub-plates are planar.

I'm thinking of using 10mm aluminium for the sub-plates. The plates would run the full length of the X axis on top of each steel beam and eventually the rails will be bolted to these plates. The plates will themselves be bolted to the steel frame in an adjustable manor such that they can be brought into plane using the laser, then they will be permanently fixed in place with a potting compound taking up the gap between plate and frame.

A few people have tried this using set screws to level the plates which seems quite fiddly unless you go the trouble of making concentric adjustment/locking bolts.

What I'm proposing is to take each plate and drill two sets of holes along the centre line. The first set will be counterbored and used to bolt the plate down to the steel frame, the second set will be used to inject the potting compound. To allow the plates to float above the frame but also be held accurately in height by the bolts I'm thinking a compressible gasket could be run down each side of the plate. As the bolts are tightened the gasket would compress pushing the plate up hard against the bolt, this is simpler than grub screws and locking bolts.

To prevent the two plates (one for each X rail) tilting they would be coupled together with lengths of angle during the process.

The laser would be setup and both plates adjusted into plane using the bolts, once everything is level potting compound would be injected through the remaining holes. The compressed gasket will now act to contain the potting compound.

I think this has a number of advantages,
1. The entire leveling process can be completed before making a permanent adjustment to the machine,
2. I would be directly leveling the final machine surface (the sub-plate) rather than some tool that is then used to machine the frame.

I have sketched this up, would welcome thoughts on it.

Attachment 27431

Quote:

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Originally Posted by devmonkey

Work has been getting in the way of progressing my machine, but where I left off the laser system is working well enough to perform the operation (particularly with the raspberry pi version) however the process of position a jig and routing the steel frame into plane with a trim router was highly error prone.

1. It was difficult to level the jig since I didn't use concentric adjustment and clamping bolts,
2. The process requires that the laser doesn't move, the trim router height gauge doesn't move and the cutting tool doesn't break or chip throughout otherwise it has to be started over. Also the jig has to remain a planar plate and not wear, since I used tooling plate the surface got quite a lot of wear from the trim router.

This is what stopped me attempting it across the whole machine frame.

So I've had a bit of a rethink and come up with a different process that is hopefully a bit more forgiving and controlled. Rather than attempt to level the frame by grinding it the new processes will attempt to attach rail bearing sub plates to the frame such that these sub-plates are planar.

I'm thinking of using 10mm aluminium for the sub-plates. The plates would run the full length of the X axis on top of each steel beam and eventually the rails will be bolted to these plates. The plates will themselves be bolted to the steel frame in an adjustable manor such that they can be brought into plane using the laser, then they will be permanently fixed in place with a potting compound taking up the gap between plate and frame.

A few people have tried this using set screws to level the plates which seems quite fiddly unless you go the trouble of making concentric adjustment/locking bolts.

What I'm proposing is to take each plate and drill two sets of holes along the centre line. The first set will be counterbored and used to bolt the plate down to the steel frame, the second set will be used to inject the potting compound. To allow the plates to float above the frame but also be held accurately in height by the bolts I'm thinking a compressible gasket could be run down each side of the plate. As the bolts are tightened the gasket would compress pushing the plate up hard against the bolt, this is simpler than grub screws and locking bolts.

To prevent the two plates (one for each X rail) tilting they would be coupled together with lengths of angle during the process.

The laser would be setup and both plates adjusted into plane using the bolts, once everything is level potting compound would be injected through the remaining holes. The compressed gasket will now act to contain the potting compound.

I think this has a number of advantages,
1. The entire leveling process can be completed before making a permanent adjustment to the machine,
2. I would be directly leveling the final machine surface (the sub-plate) rather than some tool that is then used to machine the frame.

I have sketched this up, would welcome thoughts on it.

Attachment 27431

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Hi devmonkey,

I think you might need 2 rows of bolts rather then the 1 row in the middle.

This will allow for correction of axial deviations.

Did you calculate the expected flex of the plate in relation to the gasket compression forces? This would dictate the number of bolts in relation to the maximum expected compression.

As said before all thing look like made out of gummy now we can measure things in microns.

I might be able to start measuring my machine tomorrow unless shmbo thinks of something more important.

Grtz Bert.



Verstuurd vanaf mijn SM-A320FL met Tapatalk

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Originally Posted by driftspin

Hi devmonkey,

I think you might need 2 rows of bolts rather then the 1 row in the middle.

This will allow for correction of axial deviations.

Did you calculate the expected flex of the plate in relation to the gasket compression forces? This would dictate the number of bolts in relation to the maximum expected compression.

As said before all thing look like made out of gummy now we can measure things in microns.

I might be able to start measuring my machine tomorrow unless shmbo thinks of something more important.

Grtz Bert.



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Hi Bert,

I was hoping that bolting the two sub-plates together with angle would go a large way to reducing the axial deviation (twist), but we'll have to see.

I will calculate the compression forces required after measuring various gasket materials by squashing them with a known mass. If I start with plate that is relatively flat then most of the adjustment will be bringing these two flats into plane, not so much will be bending the plates into plane which requires significantly more force from the gasket. It maybe that a combination of gasket and hard shims under plate bends is required.

Will go hunting for some 10mm aluminium tomorrow and some gasket materials.

Cheers, Joe

Hi Joe (Devmonkey)
Hi All

Firstly I am assuming profiled rails are being used not round rail for high accuracy, repeatability and negligible backlash.

Lateral adjustment of rails is difficult, particularly when you take into account the small amount of adjustment allowed by the clearance around the mounting screw in the bored hole in the linear rails. for type 25 rails typically a 6mm hole and a 5mm machine screw. This only allows +- 0.5 mm of lateral adjustment, and this is if all the mounting holes are perfectly placed. Note in the description the order of processing to minimise chips creeping into the joining surface and lifting the rail.

To solve this problem I devised method where the rails were positioned laterally first using cams. Once this was done I drilled and tapped the mounting holes using an inexpensively built jig. You can make the cams yourself or get them laser cut. You still have to countersink them as detailed in the link.

It is documented here:
https://www.model-engineer.co.uk/for....asp?th=139042

The method worked very well. Alas I have not completed the machine.
I can't wait to get back to it! Alas work has been getting in my way too.

Regards
John

Quote:

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Originally Posted by devmonkey

I have realised something about these sensors. They are colour sensors, and the colour detection is done by layering a grid of colour alternating RGB filters over the individual pixels which are all identical photodiodes (i.e. the pixel is monochrome) in what is called a Bayer pattern. These are laid out to match the human eye's response to colour, with 50% of the pixels green and 25% red and 25% blue. See https://en.wikipedia.org/wiki/Bayer_filter

Attachment 27114

This isn't ideal as I'm using a red laser. This means only 25% of the pixels are useful and the sensor will be interpolating the values between 'red' pixels.

Anyway someone pointed me towards some super crazy people in astrophotography who 'de-bayer' their very expensive DSLR sensors with a toothpick so the sensor becomes monochrome at its native resolution, effectively scratching off this colour filer layer to expose the raw sensor.
https://stargazerslounge.com/topic/1...-bayer-matrix/

I have just tried this procedure and ruined a webcam sensor (ripped it off the pcb) so I don't recommend it.

EDIT
The first casualty of this miss-adventure, don't think it is still worth £7 !
Attachment 27117

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I managed to buy a monochrome webcam years ago, it was expensive over £200 and I had to buy it from China has highly specialised.

It only saw Far Red (Near Infrared) specifically to see phytochrome reactions in plants.

I found a few different self adhesive glazing gaskets to experiment with. The one that works best is a 5x10mm rectangular profile neoprene strip, no idea where it came from. It isn't the very soft foam draft stop stuff, nor is it full rubber, it is designed to be compressed between the rebate and the glass on a fixed window. It is a closed cell structure not the sponge.

I also picked up the aluminium from SPA, huge stocks and fantastic price with cash at the door, perfectly happy with me picking up a couple of lengths.

So the experiment was to check the compression rate of the gasket and also whether I could inject some potting compound. I used around 400mm of 50x6 flat bar and clamped it into two lengths of the gasket stuck to a bit of 4x2. With the clamps at maximum pressure the gasket was compressed to about 2mm, the clamping force from the bolts I'm planning to use will be at least as much as from these hand clamps. Also the gasket is strong enough to just distort the aluminium which is perfect.

A 6mm hole was drilled in the middle for injection and countersunk. I used a normal decorators caulk gun to inject glazing sealant which has about the same consistency as West's 105/205 colloidal silica thickened epoxy which is what I will use on the actual job. The gun was pressed hard against the countersunk hole and sealant injected. I had to use quite a lot of force but it pushed the sealant through easily,.

So not very scientific but all very promising. Next step is to drill up the sub-plates and get them mounted on the machine frame.

Attachment 27436 Attachment 27437 Attachment 27438

Ok so i found a little time to do a leveling test at the new home of the machine.

I have setup the laser pointing along the long axis crosshair at about the middle of the gantry.

My flexing concrete floor is making things much harder then i expected while measuring adjusting and measuring again.
Walking around influences measurements.

My concrete floor is cast on sand, dont have any more information about it now.


In general all 4 x,y corners are in the same plane now .. within about 5 um.
Trying to get it any better seems silly compared to what walking around does to the measurements.

In the end my goal is checking the machine for general flatness and setting it up level

Both the long axis now look like they are within 10um deviation over 1800 mm of travel, this is far better than i expected.
Thank you epoxy.

Having the laser setup on a solid object other than the cnc table frame is a must.
When connected to the frame things get complicated quickly when 1 corner is adjusted everything changes.

Like mentioned here before, now we can visualize micrometers everything looks like made of jelly.


The gantry though looks like it has a deviation of about 50 um upward in the middle. This is a bit weird to me, the epoxy proces was done the same way and the axis is much shorter. There was no welding after epoxy.


I am going to re test this axis by moving the laser 90deg and in line with the gantry.
This should cancel out some optics quality issues. I guess the projected line could be non straight.

Thank you guys, for this cool solution.


Grtz Bert.



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