DIY Laser levelling using webcam and laser level

[JAZZCNC]

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.

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.!

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

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.!!

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.

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.

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.

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.

[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

[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.

[devmonkey]

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.

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.

[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]

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.

[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.?