ULS focus tool question

[Jeremy Brown]

I don't remember where but I found a document somewhere that showed the actual measurement of the focus tool and how to verify that it is in focus. For the life of me I can not find it

Can any of you measure the 2" lens focus tool from the base to the focus line/kickout?

[Lee DeRaud]

1.94". Note that the 'kickout' isn't straight, it's about a 1/16" chamfer, so draw your own conclusions.

[Kev Williams]

The best way to verify 'actual' focus, and I just figured this out about a month ago after a ramp test failed miserably ;) --

Just take some black/white Rowmark and do some 'the quick brown fox...' test runs using 6 point Arial Narrow NOT bold.
Start at what you think is a good focus, and start at around 15% power 50% speed, and at least 600 dpi res.
Increase the power until you're just getting white to show.
Now make more test runs, increasing the focus distance in .01" increments, until you get whiter or darker. If you got whiter then darker, go back to the whitest and call it good...
If you only got darker, then go back to where you started and start decreasing the distance...
If need be, start with higher power.

Black anodized aluminum works well too. The trick is to adjust until the aluminum JUST BARELY starts to turn white, not going for the whitest-white, 'barely' is much easier to judge...

Once you've figured out your focus distance, get a piece of 1/4" plex, a 3/8" dowel rod, etc, anything you can cut to serve as your focus tool, and trim it till it's just right-
I have focus tools that I focus from the table to the bottom of the X gantry, works just as well as long as your lens holder never moves, and you only have to slew the Y axis down to the part...

[Jeremy Brown]

see, mine is 1.668 from the bottom of the base to where the chamfer starts. This makes me believe it's not set correctly. If this is off, then it explains some of the issues I've been having.

[Lee DeRaud]

see, mine is 1.668 from the bottom of the base to where the chamfer starts. This makes me believe it's not set correctly. If this is off, then it explains some of the issues I've been having.What model ULS? Mine is a VL200.
I can well believe the lens mounts are different on different platforms...then again, there's no part/model number on my focus widget.

(I think the tech used mine during initial setup in 2005, probably to see if the driver focus screen readout was correct and that the machine recognized when the honeycomb cutting table was plugged in. Since then, it's been out of the drawer exactly twice, both times so I could measure it for threads like this one.)

[Jeremy Brown]

VLS2.3, I worked at a place that had the same machine and I remember the white pole piece was not flush with the black base. Mine is flush but I didn't think anything of it as it was different machine at different ages. But some of the results I am getting is telling me I am out of focus but on the short side. I have an Email in to ULS so I am waiting on their response.

[Lee DeRaud]

VLS2.3, I worked at a place that had the same machine and I remember the white pole piece was not flush with the black base. Mine is flush but I didn't think anything of it as it was different machine at different ages. But some of the results I am getting is telling me I am out of focus but on the short side. I have an Email in to ULS so I am waiting on their response.I didn't measure how deep the indent was, but mine is NOT flush, probably a good 1/4" inset. (Let's see...1.938 - 1.668 = 0.27. Guess my eyeballs are still in calibration.)
I also noted (for the first time) that there is a set-screw in the side of the base, presumably so you can adjust it.

Followup question: what does the driver focus screen show for the Z-axis value when you use the focus tool to manually focus on the table? (Hint: should be close to 0.)

Second followup question: I'm almost afraid to ask, but why are you using that stupid widget on a VL series machine anyway? Just set the material thickness in the print settings dialog, enable 'auto Z', and hit 'start'.

[Nicolas Silva]

my tool on my M300 measures 1.96" from bottom to the inset.

[Jeremy Brown]

Received an email from Adam Norton @ ULS and he said it should be approximately 2". He also sent me a document on calibrating the focus which is very similar to what Kev Williams suggested.

I will post up the focus calibration document Adam Norton sent me.

Edit: the file is too big to post, here is the link to google drive.
https://drive.google.com/file/d/0BxZEGPaqOsakZHRnOVFtUlAyazNkX0ZaVWtjQjJETUJPMVJn/view?usp=sharing

[Joseph Shawa]

Seems like a bunch of messing around.

Here's my tool. A piece of wood or anything that will show a mark.

Set it vertically against the vertical path of the beam and drop cone down to touch the material. Fire the beam manually several times on low until your material has the whole hourglass shape that you would expect from a converging and then diverging beam.

Measure from the top the the wood down to the narrowest area and then cut a few pieces of stock to that size. I make a bunch of fat "T"s with long bases and keep a cup of them magnetized to the inside of my machine as I always seem to lose them....maybe I should make them bigger yet.

Make sure your table is level by checking in all 4 corners with your new focus tool.