Blackhole 60W Laser

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Re: Blackhole 60W Laser

Postby iGull » Thu Sep 22, 2011 9:13 pm

More work over the past few days - and not a few c0ck -ups too :oops:

Seems that no matter how much 3D drawing you do, there's always something that bites you in the @ss :lol:
I'm kind of lazy when it comes to the fine detail in a model - I tend just to ensure that everything will fit accurately and leave the screws and nuts to themselves - I had to re-cut the belt mounts for both axes because of this - the pulleys then had to be mounted on the opposite side. On top of that, the travelling mirror mount was interfering with the top screws on the LH carriage - I just flipped it over and re-drilled the holes at 45 deg - sorted :lol:
And when I flipped the X axis stepper - I had to cut the lower vee rail - that's what God made Dremel discs for :D

P1000525.JPG
Aligning X axis to reference bar with a pair of 321 blocks


There's a matching 321 block at the opposite end. This was used to align the belts and pulleys for the Y axis. I'll recheck them tomorrow as one of them looks a little slack - although the alignment still seems orthogonal.

P1000526.JPG
Y axis belt mount


P1000528.JPG
Coletech laser head with air assist


Used 10mm aluminium tube to reduce mass and (hopefully) reduce any tendency to whip - turned alloy ferrules on ends held in with cyano.

P1000527.JPG
Y axis stepper


Coletech optical parts - reasonable quality - silicon mirrors with gold plating - adjustment screws about 0.25 to 0.5mm pitch.

P1000529.JPG
Three main optical parts from Coletech


I'm sure someone has used this in place of thermal receipt paper - Dymo labels - they're thermal, so you can print targets on them.
I'm selling the patent - you saw it here first :lol: :lol:

P1000532.JPG
Laser targets


All the mechanics seem to line up fine - no jam-ups apart from some cyano on a rail which I scraped off - really pleased with the rail alignment.
Had an issue with the black acetal rings popping off from the bearings - nothing will REALLY stick to acetal - I scraped the acetal and roughened the bearings with a dremel. The main problem was me playing with the X rail and it not being parallel to the reference rail - bit of side pressure. It's been perfect since putting on the belts and Y axis stepper shaft. I will be looking to buy the new version with dual bearings at some point, but I'll keep the current rails as they are perfectly OK

More work on the Z axis table and the dreaded chain drive tomorrow hopefully.

Cheers

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

Postby BenJackson » Thu Sep 22, 2011 9:30 pm

I think all of my V-wheels have come unglued at this point. When I caught the gantry with the lid stop that popped a bunch of them on Y. I accidentally ran the X carriage into an object I was engraving and popped a couple of those.

I think the "trapped" V-wheel design from Makerslide is a good idea.
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Re: Blackhole 60W Laser

Postby iGull » Fri Sep 23, 2011 3:29 pm

Hi Ben

I have put a post in the mechatronics section with an idea about adding an extra bearing to the original vee wheels - have a look and see if it would work on the .2x ...
viewtopic.php?f=13&t=791
I'm looking at retrofitting it to my cutter if it causes me any continuing issues (so far, it hasn't since adding the belts).

On my Z stage front today - garbage :x I thought things were all going too well :D
As expected, the horizontal chain is causing a problem - mainly because Mr Chain prefers to be in the vertical plane.
It was a pita to fit too. Unsure which way to move - can't get a closed toothed belt about 4.5 metres which is why I chose the chain in the first place.
Really want to have the centre of the stage open, so no single vertical leadscrew in the centre with a rail for each corner - those things always end up being lopsided. I don't fancy a sarrus linkage - I have a little experience of something very similar and it needs to ensure that the bearing tolerances are tight - too much construction for me too - I prefer to kiss :lol: One option is to put acetal supports on the chain to ensure that the feed to the sprockets is kept aligned. One other option is four steppers of course :|

Anyone with an elegant solution to this issue is welcome to comment !

Cheers

Neil
EMOs are a sign of weakness ...
iGull
 
Posts: 171
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Location: Edinburgh, Scotland

Re: Blackhole 60W Laser

Postby BenJackson » Fri Sep 23, 2011 4:21 pm

The Prusa Mendel (3D printer) uses 2 Z motors because they realized that a stepper motor was cheaper than any combination of belts and so on that would let you drive two Z from a single motor. You just connect them to the stepper driver in parallel (could work for your 4 as well).

I don't quite follow your chain problem.
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Re: Blackhole 60W Laser

Postby iGull » Fri Sep 23, 2011 4:56 pm

BenJackson wrote:The Prusa Mendel (3D printer) uses 2 Z motors because they realized that a stepper motor was cheaper than any combination of belts and so on that would let you drive two Z from a single motor. You just connect them to the stepper driver in parallel (could work for your 4 as well).

I don't quite follow your chain problem.


Chain problem - one of my problems is size ( :D ) - my table is 1240x630mm (about 4'x2') - the chain just droops across that expanse - it then grabs on the sprocket and jams. Increasing chain tension just serves to stall the stepper (even a hefty size 23 or my battery drill). The acetal guides may help align the chain to the sprocket.

OK on the mendel - that's certainly an option - replace the leadnuts with sleeves and the screws with rod then add a screw at each end with a stepper each. (or fours steppers which would mean no real mechanical changes - just a stepper mount) - the cost is becoming painfull :D

Cheers

Neil
EMOs are a sign of weakness ...
iGull
 
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Location: Edinburgh, Scotland

Re: Blackhole 60W Laser

Postby iGull » Fri Sep 23, 2011 8:03 pm

Just in from the workshop trying yet another approach to this Z table issue.

I was correct in thinking that the chain 'droop' was causing all the problems. I clamped four scrap pieces of 18mm MDF board just underneath each of the sprockets so it guided the chain in and out of the sprocket (the gap under a sprocket to the nearest extrusion). The jam-ups ceased - still pretty noisy as expected. I think a sprung idler to adjust the tension rather than just using the stepper position to adjust it may also alleviate other issues - too much tension on the stepper for one - occasional 'dinks' for two (where it will occasionally catch on a sprocket tooth - being sprung means it takes the slack up unlike a tensioned stepper mount where it will just jam).
Short of going for the four steppers and associated headaches, I'll lash up some decent acetal guides and take it from there for now (cheapskate ;) ).

I'm also thinking that a full board with cutouts for the screw shafts and maybe covered with thin polypropylene or acetal sheet would work too - could even form the base of the upper 'plenum'. I wonder if anyone that has been using their .2x has noticed any 'burn' on the shiny blue bottom skin of their cutter ? In which case, I could get away with using MDF or ply laminate sheet - maybe with tinfoil covering as a barrier to any laser burn problems.

Goodness, if only they made 4.5m belts :D

I don't suppose anyone knows how to join toothed belt - is there a magic spelle involved ?
EMOs are a sign of weakness ...
iGull
 
Posts: 171
Joined: Mon Dec 06, 2010 2:59 pm
Location: Edinburgh, Scotland

Re: Blackhole 60W Laser

Postby BenJackson » Fri Sep 23, 2011 8:30 pm

You can always "join" them by connecting loops by a shaft with two pulleys. You could connect the two sides front-to-back and the two back rails to each other and the motor, for example.

There's no burn problem on the bottom because once you go through the focus lens the beam converges at the focal distance and then diverges after. Before the final lens you can burn things with the laser from quite a ways away. I measure about 3 focal lengths below the focal point on the 2.x laser, so the beam has 3x the diameter of the original beam or 1/9th the power density of the original beam.

I do think you want a cleanable surface on the bottom: I cut some plywood with terrible smelling glue and the smell lingered until I wiped down the bottom skin.
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Re: Blackhole 60W Laser

Postby iGull » Sun Sep 25, 2011 7:18 pm

BenJackson wrote:You can always "join" them by connecting loops by a shaft with two pulleys. You could connect the two sides front-to-back and the two back rails to each other and the motor, for example.


Yes, when I started on this project, that was one of the options - in fact, I have about three A3 sheets with various flavours of this idea :D
It's probably one of the better ideas as it cuts down on long belt lengths, but trying to get four belts tight without putting idlers on them becomes painful - not to mention all the mounts/brackets/pulleys :lol: I also have some ideas with counterbalances to hold the table up (using shafts) and then just pull the table down.

I spent the best part of this morning again looking at the chain problem. I tested a piece of chain on its own in 'vertical mode' - it was just garbage - either the sprockets are badly sized or the 6mm 04B chain is - the chain would jump as the sprocket teeth entered the space between. I've decided to give up on the chain - I'll punt it to some fighting robot guy :( It's not as if the chain and sprockets were cheap either !

Moving on from this, I double checked the 'friction' on each of the four Z leadscrews - they are all very easy to rotate, so a good belt would definitely work.
I made a concerted attempt to look at different belt styles and options but couldn't get anything at 2980mm. However, I actually found a UK company that can supply joined PU belting ...
http://www.beltingonline.com/polyuretha ... elting-38/
Surprisingly, the belt is CHEAPER than the flipping chain !!!! Why didn't I see this before :o It does say that the strength of the belt is approx half of a contiguous belt 'though. Swapping out a set of sprockets for a set of pulleys and swapping the chain for a belt is an easy out for now - it might even work :D
I don't suppose anyone has any experience of 'joined' belts ?

BenJackson wrote:There's no burn problem on the bottom because once you go through the focus lens the beam converges at the focal distance and then diverges after. Before the final lens you can burn things with the laser from quite a ways away. I measure about 3 focal lengths below the focal point on the 2.x laser, so the beam has 3x the diameter of the original beam or 1/9th the power density of the original beam.

I do think you want a cleanable surface on the bottom: I cut some plywood with terrible smelling glue and the smell lingered until I wiped down the bottom skin.


Had it been my turn for the family brain cell that day, it might have occurred to me that the beam power density would be appreciably smaller at the distance of my bottom sheet :D - thanks for that - seems that brain cell volume is inversely proportional to age :D
I have some 7.5mm laminated plywood - called 'waterboard' I think (has a real formica skin on each side) - they use it for shower cubicles etc - I think that will be ideal - easy wipe etc.

Cheers

Neil
EMOs are a sign of weakness ...
iGull
 
Posts: 171
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Location: Edinburgh, Scotland

Re: Blackhole 60W Laser

Postby iGull » Wed Sep 28, 2011 5:17 pm

I just ordered the 10mm T5 joined belting and pulleys from beltingonline.com. I'll give that a try and see if it is any better. I'll need to add a wee idler to give the drive pulley a few more teeth to play with.

I built a dummy laser to get a feel for the whole alignment ...

photo.JPG
Dummy laser


Apologies for the iPhone pic. The dummy is a length of 40mm alloy tube and a couple of turned end caps from some acetal. The laser (a rather expensive red alignment laser that was a spare for some scrap equipment) is an 11mm small black tube with focus lens - laser is a bar - I just roughly focused it through a 1mm hole in the front mount - the laser is mounted at the back. A 60W laser tube is quite long - 1200mm and 56mm dia.
Trying to align the stupid laser through the front 1mm hole was a royal pita - even though everything was coaxial and accurately turned, the laser in it's own mount was not - to be expected I suppose. I don't for one minute think that the CO2 laser will be coaxial within it's tube either :lol:

Aligning the rest of the system took about five mins - I was pleasantly surprised, but the coletech adjustments were very accurate. One problem was in the way the mirror mounts are made - when mounted on a flat surface, the lower screw adjuster interferes with the surface - I added a 0.5mm brass shim underneath the mount - there are three mounting holes - 1xM6 axis and 2xM5 locks - this is enough to let everything move without raising the mirror too much from it's main axis.
All stayed aligned and focused from min xy to max xy and no-one more surprised than me !!

Onwards and upwards ...
EMOs are a sign of weakness ...
iGull
 
Posts: 171
Joined: Mon Dec 06, 2010 2:59 pm
Location: Edinburgh, Scotland

Re: Blackhole 60W Laser

Postby iGull » Fri Sep 30, 2011 9:23 pm

New joined T5 belt and pulleys arrived this afternoon from beltingonline.com - pretty sharp service.
Can't really see much of a join in the belt - it's an off-white colour belt and you can only see a slight degradation in texture on the outside face - I gave it a good pull test by hand (very technical :D ) but couldn't separate it (probably impossible by hand anyway looking at the original steel belt specs).
Centre drilled all the pulleys to size on the lathe and drilled and tapped for grubscrews. Removed all the original chain sprockets (what a pain) and refitted and re-adjusted the new pulleys. I added an idler wheel to give the drive pulley a bit more 'bite'.

New T5 Belt.JPG
New T5 belt and idler


What a difference ! All nice and smooth (relatively speaking :D ) - can even turn it all by hand - I'm really wondering if a z stepper is all that necessary - a small handwheel to catch one of the top M8 domed nuts would work equally well without all the attendant driver/PSU/software etc. Need to add another strut between the two 20x20 leadscrew supports as there is a little movement there.

I had given some thought to the z driver - rather than drive this axis from the main software/firmware (yet to be decided), I had intended creating an isolated z axis system with autofocus detector and integrated stepper driver - probably driven from a picaxe. Using 'yet another' arduino seems a bit of a waste of technology when a picaxe is only a couple of pounds compared to twenty-odd for an arduino (and it uses basic rather than c :D ) A single encoder 'pot' would work fine as the manual control and either a microswitch or capacitive sensor for the autofocus - all the ones I've seen on cutters use something like a small removable metal block for the sensor to operate on - I haven't seen a 'real' autofocus system as such.

Cut and fitted some mounting brackets for the x axis microswitches - I much prefer an old-fashioned microswitch as an end sensor to the optical variety.
EMOs are a sign of weakness ...
iGull
 
Posts: 171
Joined: Mon Dec 06, 2010 2:59 pm
Location: Edinburgh, Scotland

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