Machsupport Forum
General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: Tweakie.CNC on March 12, 2009, 12:53:53 PM
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A simple project for a rainy day.
I recently bought one of these laser cross hair pointers on ebay. Unfortunately they are not that well made (what can you expect from China and cheap as chips) the focus ring incorporating a prism assembly is a very sloppy fit in its mounting thread and any movement here alters the cross hair position. After some deliberation I made a clamp which bolts to the Z Axis and grips both the body and the focus ring of the pointer - this makes the whole thing rigid and it cannot be accidentally moved once set. Setting it up is a bit more tricky as the focus has to be adjusted for optimum at mid Z Axis travel, then rotated until the cross is exactly X - Y alligned (although this is not so critical if you are only interested in the center position of the cross) and finally the cross must not move position when the Z Axis is traversed up and down. Two or three goes at milling dust off the mounting and it was perfect. Because the reflectivity of different materials and surfaces varies I have incorporated a polarised disc beneath the pointer and this can be rotated 90 degrees. (The light from these laser pointers is plane polarized and by using a rotatable polarized filter the apparent brightness of the beam can be varied between full on and off - allowing for the optimum brightness to be set)
Thanks to posts by Hood and Greg I added a button to the Mach screen and pasted the modified button script (after carefully measuring the offset between the cross hair and tool position, using the Mach DRO's). Brilliant, it works so well I really don't know why I did not do this sooner. At the moment I am using a battery to power the pointer but a 3 Volt supply and on/off switch will be added tomorrow.
Tweakie.
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I have used this for quite a while now and yes, it's a VERY handy tool to have for quick locations on sheet material and or picking up edges.
The smallest I could get mine was .010" of an inch which is not too shabby but I'd like to know more about your polarizing filter and what you used. I have a glass one from an old camera but haven't cut it yet, may I ask what you used?
The sort of Delrin clamp I used has a through hole for the body and a counterbore for the knurled part and is pushed up into the counterbore and then locked down with the screw so it can't vibrate loose. I actually moved it since these pics were taken, over to the right side of the headstock to get it "out of the way".
I have it powered with a wall wart AC adapter and has been working for a little over a year now.
Thanks for sharing-
Dave
(http://www.machsupport.com/forum/index.php?action=dlattach;topic=7116.0;attach=6012;image)
(http://www.machsupport.com/forum/index.php?action=dlattach;topic=7116.0;attach=6013;image)
(http://www.machsupport.com/forum/index.php?action=dlattach;topic=7116.0;attach=6014;image)
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Hi Dave,
I saw your excellent post when I was researching my project - it just took a while to locate the laser pointer.
I bought the polarizing film as a small sheet. It is laminated plastic and easily cut into the shape required with scissors.
Here is an ebay uk link which will work for a couple of days at least.
http://shop.ebay.co.uk/items/_W0QQ_sopZ10?_nkw=polarising+sheet&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=cnc&_osacat=12576
Tweakie.
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Interesting, I will have to look locally for that material.
I appreciate the heads up, my friend- :)
Dave
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Tweakie
Just to give you something to think about, ;D
I have my cross hair laser directly powered from an out-put. No battery or wall plug.
BoB specs say 20 miliamp is available on each out-put pin. Laser only uses about ten miliamps.
A resistor in series with it just to drop the 5v down to about 3v.
The advantage is that an on-screen button turns the laser on and off.
Also the macro that positions the spindle over the spot also tuns the laser off.
Greg
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Thanks Greg,
I will try that today and see how it goes.
Tweakie.
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I am being incredibly lazy here but I wonder if anyone would be good enough to help with the VB Script to turn the laser on and off as Greg has suggested.
Thanks,
Tweakie.
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Pick an OUTPUT, lets say OUTPUT5, enable it under ports and pins and map it to your PP output Port and pin.
Then in a button put the Following:
If IsOutputActive(OUTPUT5) Then
DeActivateSignal(OUTPUT5)
else
ActivateSignal(OUTPUT5)
end if
scott
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Thanks Scott, you are a gentleman.
(I have now found the customization wiki which explains everything but will take some time to digest).
Thanks again and sorry that I am such a slouch.
Tweakie.
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You have helped me as well Scott (once again!) as I'm working on a console and I have a button already lined up for this purpose.
And Tweakie, you saved a fellow slouch from asking yet another slouch-ish question ;D
Thanks,
Dave
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:)
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I am being incredibly lazy here but I wonder if anyone would be good enough to help with the VB Script to turn the laser on and off as Greg has suggested.
I only use the cross hair laser on a router. It does not seem as appropriate to me, on a mill. Accuracy etc.
Therefore being a router, I don't need mist coolant. So I use mist coolant output to control laser on and off.
M8 turns it on and M9 turns it off. Better still OEMbutton 114 toggles it.
Cheating I know, but makes buttons and macros a no brainer.
Greg
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Greg, don't underestimate the power of that laser, it comes in very handy for those not-so-precise jobs where you just want to find the center or edge of material....even on a mill.
Besides, the cool factor adds to the fun - ;)
Thanks for all that you (and everyone else for that matter) contribute to this cnc community - 8)
Dave
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That looks great Tweakie, et al. 8)
I'll have to put it on the to do list, I'll never get my machine done. I guess that's the idea, keep improving. :)
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You are certainly right there Jerry - It is never ever finished.
Tweakie.
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Just a note for anyone else wishing to add one of these laser pointers to their machine.
The positive supply of these devices is often connected to the metal casing so it is best to use a Delrin (or similar) clamping arrangement, as Budman has done on his mill. This isolates the device from the machine frame and will enable powering of the device direct from the BOB and switching it on and off under Mach control, as Greg has suggested, a lot easier to accomplish.
As I have used a metal clamp the body of the device is connected to ground or 0Volts therefor I need negative volts (-3Volts) to power it. This has been accomplished using the guts of a 3Volt wall wart (fitted inside my control box) which is in turn switched on and off under Mach control using a solid state relay which is directly driven by the BOB. This has resulted in more expense than would otherwise have been necessary but what the hell it's my hobby and you can't put a price on that can you ?.
Tweakie.
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An update.
The initial mounting method for the polarising filter suffered with a major drawback in so far as it allowed machining dust to enter and settle on top of the filter disc. I have replaced the two alloy spacers with a turned part that should resolve this problem.
Tweakie.
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Looks "cleaner" too - ;)
Dave
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Thanks Dave.
This is the big advantage of making things for yourself - the boss doesn't moan at you when you don't get it right first time.
Tweakie.
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Another update. Just thought you may be interested in this.
I have added two buttons to the Mach screen one titled 'Laser ON/OFF' and used Scott's VB script to perform this function. The other button is titled 'Home to Laser' and uses the following script.
Xs=GetOemDRO(59) 'Xscale DRO
Ys=GetOemDRO(60) 'Yscale DRO
Xmove = -72.8719 * 1/Xs 'move distance adjusted for X scale factor
Ymove = 10.7156 * 1/Ys 'move distance adjusted for Y scale factor
DeActivateSignal(OUTPUT5) 'turn off laser
Code "G91 G0 X" &Xmove & "Y" &Ymove ' makes an incremental move the distances that you set
While IsMoving () ' waits while that happens
Wend
Code "G90" 'goes back to absolute moves
DoOEMButton (1008) 'zero X DRO
DoOEMButton (1009) 'zero Y DRO
As I use the DRO Scale settings to scale my engraving work to fit the size of the blank I have included a calculation to position the cutter relative to the laser irrespective of the scale settings.
Tweakie.
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I dont get it- how do you align the cross hair to the machine spindle? How do you use this?
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Ron
The laser cross is mounted so that it projects exactly parallel with the Z axis travel.
The offset from the spindle centreline is known and consistent.
So in practice the cross is manually aligned with a point of feature on the job or table by jogging.
Then usually by use of a button script the spindle centreline is moved to take up that position.
My experience is, precision is only about 0.02" so obviously it won't fill every setup need.
These lasers cost only a few bucks. Perhaps more money could buy greater precision.
Greg
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I *think* that with the use of a filter, the laser will put out a much finer line, therefore allowing for greater accuracy. I know I have seen them, but how much of a bonus is achieved I don't know.
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Hey Guys,
I ordered two of those lasers. Delivery is by boat, so should be here in about
3 or four weeks. ;D
Should be fun to play with.
RICH
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Hi Guys,
I only use the laser pointer on a router where precision is not an issue however, a polarizing filter is still essential. The actual beam width, as far as I can measure, is 0.3mm but our perception of coherent laser light is something different. The surface finish of the work is a determining factor here and highly reflective surfaces produce a sharp and fine image whereas sawn wood produces just the opposite. On Traffolite, engraving laminate, I am confident I could achieve a repositioning accuracy (on an engraved line or edge) of better than 0.2mm.
In reality I align my router work to a pencil line (how accurate is that ?) but this laser device saves so much time and makes positioning so easy that it is now an essential part of the machine.
Tweakie.
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One thing that should perhaps be mentioned in this thread is the danger associated with using lasers.
These little cross hair pointers are rated at 5 mW max output but prolonged staring into the reflected beam may well cause irreversible eye damage. For tool setting the beam is only viewed for a few seconds and the worst that could happen here is perhaps a bit of after vision - a lot less damaging than looking into the sun for example.
For the measurements that I made in the above posting I wore protective goggles but these are rated for the 1064 nm YAG laser that I am currently working on and they are only rated at Factor 4 for the 650 nm wavelength of the red pointers. If you are going to spend a lot of time staring at cross hair pointers please invest in a pair of glasses/goggles first - they also remove a lot of the fuzziness and make the beam appear much sharper.
Tweakie.
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Is that why you say...‘Do not look into the laser with your remaining eye’ ?
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Bad joke perhaps but I am glad that somebody looks at my website. :)
Tweakie.
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Tweakie,
Recieved the laser yesterday. As noted before before, fine for rough work, but won't be good for anythiing requring accuracy. Tried filtering, helped some some but not a lot. Camera when using Copycat still beats it by
a long shot.
RICH
BTW for $5 I'll find somethinig to do wiith it.
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Sorry to hear that you wasted $5 and that it is no good Rich.
As said in the posting above I have a beam width of less than 0.3mm and this is brilliant for a router but not for a mill perhaps.
Tweakie.
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Rich,
Is your laser similar to the ones that Dave and I have (with chrome color case) or is it the one with brass color case ?.
Just curious.
Tweakie.
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Chrome color case and has laser adjustment lens. best i could do is get the width donwn to about .030".
RICH
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Hi Rich,
0.030 inches resolution is no good at all - obviously not all these laser pointers are the same. I shall now consider myself lucky and perhaps buy a lottery ticket this afternoon.
Tweakie.
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Rich, dumb question but are you trying to focus the beam at all?
You do realize that the collar screws and unscrews and there is focal adjustment?
Also, distance comes into play here as well so maybe you're too close to the object?
Thanks,
Dave
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Dave,
Yep, that's when adjusted. I actauly bought two of them so will have to see if the other is any better, but expect not
RICH
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Ok, sorry to hear that >:(
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just my 0.02c.. why not rig two line lasers? on along X and one along Y, front and side of spindle.. same cross but 100% accurate as long as you align it to your spindle correctly? can power both together and stil control by one switch but you lose the offset tilt problem...
or did i miss the plot here completely?
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That sounds like the professional way to do it and would of course be far better.
Because Mach handles offsets so well and because these cross hair pointers are so cheap it was a simple approach to achieving the desired result. Having used this for some time now I certainly would not be without it but I agree, it could be improved upon.
Tweakie.
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Gotcha!