Hi Dirk
This is a long shot, but you're not the same Dirk the Danish engineer that used to work for QC Optics in Connecticut are you ??
Anyway ...
dirktheeng wrote:I can attest to this... when I used my leveling feet to adjust the frame without the skins on, I could go from end to end with a level foot and still have all 4 on the table.
Ouch, then you do need to stiffen up your frame
I take on board your concerns for the stiffness of my 'wee' laser cutter
I have owned an accurate machinist's level for a number of years and use it at each stage of the build process. If I screw one foot too high, then another one comes off the floor too - my frame is pretty stiff. The main frame, the 'optics table' is built from two sections of 20x40 - spaced at 80mm. The frame is held by eight core screws at each corner. The frame corner 'legs' are 20x40 as are the lower cross members. Everything else is 20x20. I'm satisfied that it's rigid enough (I think
) - sans skins. I'm wondering if there is an issue with using diecast brackets ? For sure, they certainly make life easier during the build, but I'm a tad concerned when they are used singularly. The one flexible part is the lid - but to be honest, that doesn't matter ( I haven't put the 6.35mm perspex sheet in yet so it might get better
)
dirktheeng wrote:I think you need to look into using much better mirrors than we have with very fine pitched adjusters. Even with the small travel we have now, just barely touching the adjuster on the mirror moves the beam significantly at the end. I can't immagine trying to adjust the beam with the mirrors we have if my travel were double what I have now.
I'm using 25mm Coletech mirrors and mounts along with their air assist final lens assy - not the slightly cheaper variety on the .2x (I'm not castigating the .2x BTW - far from it !!!) - the screw pitch looks to be around 0.25 to 0.5mm on the mounts FYI .
dirktheeng wrote:I think that is why most of the mounts you see have 3 screws around the perimeter. Moving the laser laterally isn't as critical becaue you can move the laser head forward/backward, but getting it up and down is not really easy... better to move the laser up/down.
- a bit of my history - I'm sixty years old and have worked in the semiconductor industry for the last 20 years and the previous 20 in the commercial military electronics business as a systems engineer and test equipment design engineer. My first experience of lasers was designing and building the laser PSU (using selenium stick rectifiers
) back in the late sixties then designing and building the mechanical mirror mounts to hold the primary and secondary mirrors (they weren't integrated way back then
). You had to align them manually with your last good eye and a bit of toilet paper
I have extensive experience of aligning laser systems in lithography systems - mainly LMS and exposure lasers - I have spent many painful hours aligning other people's systems. One of my pet hates is trying to align a laser using the three screw 'system'. I think it must have been a woman that invented it (did I just say that - the PC nazis will be after me
) - honestly, why would you want to offset the laser at 45 deg during an alignment when what you want is an orthogonal adjustment ??? My brain could certainly never connect with this. The best system (IMHO) is a dual XY stage - but like all things, compromise (cost usually) is a necessity - so we use something else (have a look at Newport's XY optical stages for laser/whatever alignment - then look at their horrendous prices). While my system may look a bit agricultural to the 'uninitiated', there is some madness in the design - it's based on friction. The tube is
VERY well supported in the two circular mounts, unlike the .2x system where the laser is ONLY supported on two 'points' (I am bashing the laser mounts, sorry Bart - I think you got them upside down ?). When the tube is loosely 'snicked up' in my mount, you can insert a flat bladed driver or allen key into the space between the frame and the mount and tweak the laser mount position - adjustment is available in X & Y -
INDIVIDUALLY and
NOT at 45 deg - laser alignment then becomes very much easier.
Rigidity in the rest of the system is also important - especially in the 'optics table' and anything attached to it. I'm using 6mm acetal plate (because I had two sheets really
) - it also machines well and is very rigid.
/rantModeOff
I cut and finished some acetal parts on my CNC this evening (
before the first glass of wine
) - the belt mounts and clips mainly along with the secondary mirror mount - all looking clean so far.
The rest of the stuff should hopefully get cut tomorrow.
It's getting to an exciting stage in the project now when all the electronics/mechanics/liquids/air come together - then you see all the faux pas that you made
Cheers
Neil