Mirror adjustment on K40

[Mark Malley]

Hi All

As Expected I've hit a snag on the setup of my new K40

The beam is hitting mirror 1 about 3mm high of centre so should I

a) 3d print some adjustable brackets and attempt to lower the tube.

b) Shim up the mirror mount and will the rest of the mirrors need shimming also.

c) just ignore it as the whole of the beam is actually hitting the mirror it's not being clipped as far as I can see.

Best Regards Mark

[Gene Uselman]

That will be OK on mirror #1- as long as 2 & 3 will align.

[Jeffrey Aley]

That will be OK on mirror #1- as long as 2 & 3 will align.

Note that if Mirror 1 and Mirror 2 are in the same plane, then you won't be able to hit Mirror 2 dead center at both the front and the back of the machine. You should be able to hit it consistently 3mm above dead center (again, only if 1 and 2 are in the same plane).

Given that it's often helpful to hit Mirror 3 a little above dead center, this may be a Good Thing.

[Dave Vigness]

I will add one caveat to Jeff. Hitting high is only if it's necessary to get your beam centered in the tube. Mine happens to be just a hair low to hit center of the tube. Once I had my #1 and #2 running parallel, I had to shim my head up by 3mm to get it back int he beam path !

[Jeffrey Aley]

I will add one caveat to Jeff. Hitting high is only if it's necessary to get your beam centered in the tube. Mine happens to be just a hair low to hit center of the tube. Once I had my #1 and #2 running parallel, I had to shim my head up by 3mm to get it back int he beam path !

Fair enough - that's why I said it's "often" helpful. Your situation may be different, and the OP's situation may be very different since he's using a K40, which probably has a very different mounting for mirror 3 and the lens tube.

[Dave Vigness]

The sad part is that for as different as they all are, they are almost universally out of alignment as shipped.

I cut, and then cursed my work for the first few weeks until I hit on Russ' videos.

I was centered on #1, but it was angled down slightly to catch #2 at it's furthermost forward travel..

Once that was aligned, it was hitting #3 near the top edge, and heating the lens tube. I got it aligned across the X but it was hitting the hole even higher than Russ'.

Playing with a two sets of metric allen wrenches had me stunned that I had to put a pair of 3mm wrenches in to get almost on center of the hole, and almost the center of the lens tube. A sheet of 3.3mm acrylic made the perfect spacer. Prior to Russ' lens tube extensions, it also became the new mount for my red dot.

Adding 50mm to the lens tubes thanks to Russ to let my China Red become the pass through it was advertised as, took that out of commission. I would have had to hang the red dot about an additional 50mm off to one side to clear the nozzle. I'm back to the old lens tube clamp near the nozzle pending my upgrade to the SPT TR90 tube. Having the red dot integrated into the laser tube has GOT to be one of the best ideas I have ever seen for a laser.

[Mark Malley]

Thanks to all for quick replies on this

Being a standard K40 head (at present) I do not have a lens tube or anything to worry about so as long as I can get the beam to hit mirror 3 in a consistent position at all 4 corners the exact position of the beam is less critical I guess.

Will I lose any output by not quite hitting the centre of the lens ? I could steer the beam to do so by means of mirror 3 but that would make my beam slightly skewed along the vertical axis.

I think having the beam very slightly off centre is preferable to having it skewed.

The distance involved is likely to be small anyway as by then it will be a focussed beam having passed through the lens.

Dave Vigness "they are almost universally out of alignment as shipped" very true but considering the battering they must get in shipping it's amazing that any of them arrive working at all.

Best Regards Mark

[Mark Malley]

Hi all

Mirror adjustment has been delayed a little due to the awful weather we've been having in the U.K. Wind and Rain aplenty, it feels like most of the country is underwater. I have had to repair a friend's shed apart from other things.

He is disabled and his mobility is limited so I had to re-roof his shed for him, this took a little time as I had to do it during breaks in the weather.

I have now got my beam almost spot on on mirror 2 but found a strange phenomenon which had me baffled for a while.

IMG_20200304_105205_7.jpg

As you can see from this picture the top piece of tape shows the first firing with the carriage at it's closest to mirror 1 (top left), and the bottom one with two firings one at carriage closest and one at carriage farthest (bottom left).

the beam is almost coincident and very slight tweak more should see it bang on. (for scale the tape is 1" wide)

This was fine but I appeared to have 2 BEAMS !

This caused some head scratching for a while, I was suspecting a cracked mirror or a very odd laser tube indeed !

Then I noticed a very slight pit mark on the laser head just below the mirror aperture and the reason suddenly became clear. The laser head is aluminium and cylindrical so what was happening was that the beam was passing through the two mirrors hitting the laser head being displaced very slightly and reflected back through the mirrors.

I have not adjusted mirror 2 yet which is why this situation occurred, but at least I know roughly where my beam is when it gets to the head. I Had to use a piece of A4 paper to find it initially coming out of mirror 1, it wasn't even hitting the mirror mount let alone the mirror.

So far this has not been as difficult as I first expected despite my "multiplying beams" but I suspect setting mirror 2 might be a little more tricky.

More Adventures in Mirrorland to come (weather permitting)

Best Regards Mark