Blackhole 60W Laser

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Re: Blackhole 60W Laser

Postby TLHarrell » Mon Dec 12, 2011 1:06 am

I'm working through the concept for a 4'x2' laser table as well. For my Z-axis lift, I'm considering using a set of Sarrus linkages in the four corners. These would keep the table moving in only the Z-axis and would eliminate twist and tilt movements. It's a great way to constrain the axis. For the lift mechanism, I'm considering a two-ended stepper with a set of cams that will lift the table near the center on the top and bottom edges. Kind of like a scissor lift.

On my little 40w Chinese I don't like how the table floats around when I adjust up and down as the threaded rods are not perfect.
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
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Re: Blackhole 60W Laser

Postby mikegrundvig » Mon Dec 12, 2011 1:28 am

Sarrus linkages are a neat mechanism but it seems the better approach is to minimize the need to lift the table in the first place.
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Re: Blackhole 60W Laser

Postby TLHarrell » Mon Dec 12, 2011 3:31 am

True, but I like my little flying head on my little laser. It seems fairly straightforward to me to allow the table to raise and lower to set focus.

I've also seen a pretty cool laser head on a 400 watt machine that had a small plexiglass eye shield and a vacuum exhaust. I might be thinking of replicating that too...
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
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Re: Blackhole 60W Laser

Postby iGull » Tue Dec 13, 2011 1:44 pm

I was working on the machine last night after finishing some work on the power tray - I managed to knock the X axis and popped two of the vee wheel rims off again :oops: Fortunately, I had pre-ordered some 16mm bearings and new extra length M5 screws so I could modify the vee wheels if needed at a later date - so I just modified them all.

The modification requires a 16mm OD x 5mm ID x 5mm thick bearing (same as already in the wheel - I got mine from eBay UK - 10 GBP for 10 - you need 9), an M5 x 30mm screw (that's 6mm more than my original - yours may be different), a plain 1mm thick M5 washer.
Replace the old M5 screw with the new longer M5 screw + bearing + plain washer in that order - you are sandwiching the 1mm rim of the acetal vee between two bearings. The plain washer makes up the space between the two bearings. There's now no need to glue the bearings of course.

You may need to uncouple the steppers to ensure that the stage is free running and perhaps re-tension the offset.

It took me about 1/2hr to swap out the nine wheels - all works fine now.

You could of course just buy the new dual bearing wheels and new standoffs from Bart of course and fit those - but being a cheapskate ... :D :D

Here's a pic of the modification ...

P1000986.JPG
Original Vee Wheel Modification


No doubt I'll have to re-align the laser now :D

Cheers

Neil
EMOs are a sign of weakness ...
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Re: Blackhole 60W Laser

Postby educa » Tue Jan 03, 2012 9:11 pm

iGull, I see you use joined T5 belt from beltingonline.com for your Z-axis.

Can you please tell what belt type you use for your X axis? Also what steppers and what kind of pulley wheel (how many tooth) ?

Thanks,

Bart
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Re: Blackhole 60W Laser

Postby iGull » Wed Jan 04, 2012 9:53 am

Hi Bart

I used 3M HTD belt for x& y - http://www.motionco.co.uk/timing-belts- ... 38_39.html
They're 9mm wide 3mm pitch.
The pulleys were - http://www.motionco.co.uk/timing-pulley ... 35_50.html
You need to drill through and drill and tap to suit your shaft - in my case 5mm for the x nema17 and 6mm for the y nema 23. I used 6mm shoulder screws for the free pulleys - the screws are designed for this job with accurately ground 6mm 'shoulders' (hence the name :D ) - mine were cheap from ebay - they fit the 6mm bearing pair on the free pulleys.
I used the PLM025AL pulleys with a PCD of 23.87mm.
Step size is therefore pi*PCD/steps_per_rev (using 16 step =16*200=3200)=(3.1415*23.87)/3200=0.023434317700371mm
Steps per mm = 1/0.023434317700371=42.672
That's 0.0009" per step and 1,083.8805 steps/" in imperial FWIW :D
(PCD = Pitch Circle Diameter, multiplied by pi to give the distance the 'gear' [pulley] travels in one revolution)

I used a nema 17 hi current on the x and a nema 23 dual shaft on y - I'd change the nema 17 for the same as y as the 23 has a lot more 'oomph' for little mass gain.

Hope that helps

Cheers

Neil
EMOs are a sign of weakness ...
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Re: Blackhole 60W Laser

Postby iGull » Mon Jan 16, 2012 2:43 pm

Happy New Year to everyone :D

Work continues apace on the build - although it's essentially in place and complete now - even plumbed to the outside world.

I made a conscious decision to forget about the Z axis stepper and controller and all the paraphenalia that goes with it - I made a simple acrylic knob that fits on one of the M8 domed nuts that sit on the Z 'leadscrews'. It doesn't get any simpler really. Because I have the coletech laser head, I usually just drop the nozzle on to an 11mm gauge block on top of the material, but if I need more adjustment, then I can use the knob. I haven't gone the whole hog and replaced all the leadscrews yet - but I think I will at some point this year.

I still haven't bought any table material yet - while I realise that honeycomb/grid is a good way to go, I'm not fully convinced yet. I've been doing a lot of acrylic cutting recently and notice that I get a lot of flare-ups which only happen when I have the grid under (I have a small piece of metal grid and a plastic one too). It doesn't happen when the area underneath is fully open using the aluminium angle (I'm using air assist - no gas). I also don't get any flash marks due to laser reflection. My old Step-Four cnc system uses the same idea - just a bunch of C section aluminium across the bed - it's simple, accurate, easily and quickly reconfigurable - it's also relatively cheap. The downside is when using thin material like japanese tissue, you really need support, so I guess it's horses for courses. I may see if there are other alternatives to the honeycomb/lighting grid - something easily obtainable here.
While I'm on about tables, we had a discussion about material for under the table (can't find the post) - well, certainly in my case, even though it's de-focussed, the laser makes one mess of the underlying bed - it's about 250mm away from the head and makes a great camp fire :lol: :lol: I have white formica covered ply as a base - it certainly burns badly if you are running a slow job with high power - as in 10mm acrylic - if you are only moving at 300mm/min. I'll maybe drop in a few aluminium crumb trays if I can find some that fit.

While using the laser in anger, I missed the mark a few times when laying down my material to cut and thought I'd like a wee red dot marker. I lashed up a surface silvered mirror and red laser to run parallel to the beam from the fixed to the first flying mirror - while it actually worked really well, it was really another one of those pita alignment jobs I could do without. The arrangement was really simple, but could have done with some fine adjustments in all axes rather than using shims. Rather than go down this route, I chose the easy solution :D
I already had power up to the head as I have a capacitive sensor fitted (for Z height adjustment) - so I just removed that (the heavy cable was also causing some issues with the energy chain anyway) and made up a small acrylic adjustable mount that fits on the nozzle. I guess you could modify it easily for the 2.x if you wanted. I've attached a pic. Nothing complex, just a bit of laser cut 6mm acrylic with two holes and a couple of grub screws - knuckle joint in the middle to adjust the angle - the holes are aligned, so there shouldn't be any off centre problems.

Red Dot Laser.JPG
Red Dot Laser


On the controller front, I'm still using the Lasersaur setup. It's really showing signs of promise now (speed issue removed) and I'm keen to use it as I like the toolchain (it's also ultra cheap and it runs on the Mac :lol: ). I have nearly finished my LaOS board. The Lasersaur still has a few issues yet which I'm sure will be fixed. However, rasterising hasn't reared it's head yet and I feel that may well be an issue - however, perhaps not - I'd really love to be proved wrong.

While working with the software, there was really no 'test card' reference that we could use - so we can all 'sing from the same hymn sheet' so to speak. To that end, I lashed up a quick test card which I've attached. The data is in order, it writes the left hand diamond as part of a closure check, this is followed by the inner square working to the outer then across to the circles.The squares and circles are 100mm - inner ones are halved each time. It then jumps to the backlash patterns - a set for X and a set for Y - it writes a rectangular 'C' with overlapping centre bars - any gap in the bars indicates backlash for that axis. It then writes the outer frame of 287x200mm (that's 5mm inside an A4 sheet of paper - US B4 [or is it B5?] is about the same size) and finishes with the right hand diamond closure pattern - if the diamonds don't match up, then probably lost steps. You can check orthogonality too, the diagonal values are written in the file.
The file is in SVG format from Adobe Illustrator CS5 on Mac - it should convert easily to any other format. I believe Inkscape (and maybe in reverse - Illustrator ;) ) has a scaling issue - the sizes are written on the file. Any technical improvements that could be made to the card will be gratefully accepted (apart from making it imperial that is :lol: :lol: :lol: )
BTW, only write the red data, green data is just info.

Laser Test Card v1.02.svg.zip
Laser Test Card v1.02
(5.54 KiB) Downloaded 1494 times


Cheers

Neil
EMOs are a sign of weakness ...
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Re: Blackhole 60W Laser

Postby educa » Mon Jan 16, 2012 8:09 pm

iGull there is something I don't understand.

You say you need 11mm below the nozzle for the focal point.

But now I'm confused. What focal distance does your lens have? And is the lens mounted INSIDE the nozzle maybe and not inside the holder where the nozzle then slides in ?



I know the nozzle can be moved up and down and possibly fixed with a set screw, but why would we do that? Or is it for people without a moveable Z table so you can setup the right focal distance that way ?


Sorry if question sounds silly or dumb.


Bart
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Re: Blackhole 60W Laser

Postby iGull » Mon Jan 16, 2012 8:53 pm

educa wrote:iGull there is something I don't understand.

You say you need 11mm below the nozzle for the focal point.

But now I'm confused. What focal distance does your lens have? And is the lens mounted INSIDE the nozzle maybe and not inside the holder where the nozzle then slides in ?

I know the nozzle can be moved up and down and possibly fixed with a set screw, but why would we do that? Or is it for people without a moveable Z table so you can setup the right focal distance that way ?
Sorry if question sounds silly or dumb.

Bart


No, not silly at all, my lens has a focal length of 63.5mm - it's mounted in the bottom of the parallel section of the tube just where the yellow acrylic ring is sitting in the picture above. 63.5mm below that happens to be 11mm from the end of the nozzle. The 63.5mm lens gives a better depth of field (over a 50mm lens) at the expense of a slightly fatter beam (just under 0.2mm in my case). As with everything in life, it's all a compromise :D

As you say, my nozzle TUBE height is adjustable with a thumbscrew (the parallel part of the tube telescopes in and out of the main body) - the focal point still remains at 11mm below the nozzle of course - that way, I can accommodate different heights of material (within a range of about 30mm) without having to change the bed Z position. You don't actually need to change the bed position unless you have large variations in material thickness or a fixed position lens.



Cheers

Neil
EMOs are a sign of weakness ...
iGull
 
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Re: Blackhole 60W Laser

Postby educa » Mon Jan 16, 2012 9:05 pm

Just to be clear,


Are you saying now that I actually don't need a moveable Z table which goes up and down?


I also ordered a coletech laser head, but with 50mm focal lens (the larger diameter stuff)


So if I put my z table FIXED, I would normally just set the focus with the nozzle which I then set to do UP and down ?

You say your focal distance is 11mm below the nozzle. What I don't understand then is where it will be for me ? I have the same nozzle, but lens is 50mm instead of 63.5, so I expect my focal point to be 63.5 - 50 = 13.5mm above yours, but thats 2.5mm INSIDE the nozzle ????


Or am I completely wrong in my thinking here ?



If I don't need to make a up and down going Z table, then I would not do it :) I only want to handle plate material normally
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