DIY Laser levelling using webcam and laser level

[devmonkey]

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.!!

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

[JAZZCNC]

Maybe read the whole thread mate,

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.

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

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.

[devmonkey]

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.



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.



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.

[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

[devmonkey]

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

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:


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

[JAZZCNC]

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

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.?

[devmonkey]

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.?

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?

[driftspin]

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.?

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.



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[devmonkey]

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.