Laser engraving output doesn't match preview in Studio


#1

Using:
FLUX Studio verson 0.3.13 (running on Mac OS X 10.11.5)
Flux Delta firmware 1.1.7
Flux toolhead firmare 1.2.1

I have found that the laser engraving output is slightly but noticeably inaccurate compared to what the output should be based on what I’m seeing in FLUX Studio. This is true for both the alignment of the engraving as well as its size, compared to the source file.

I produced the test case below to demonstrate what I’m talking about.

Here is what I see in Studio:

Note the following:

  • the height of 94.6mm is based on the height of the wooden square onto which I am engraving, measured with a vernier caliper
  • the top edge of the bounding rectangle is aligned (to the best of my ability) with the top edge of the second row of squares above the highest horizontal dark line in the grid
  • the right edge of the bounding rectangle is aligned (to the best of my ability) with the rightmost vertical dark line in the grid
  • in photoshop, the source image also has a height of 94.6mm, matching the wooden square. The distance from the right edge of the bounding box in photoshop to the nearest edge of the right-hand “V” shape is 3.5 mm. The distance from the top & bottom of the bounding box & the horizontal lines is 4.0 mm in each case.

Based on all of the above, the output on the wooden square should be the same as what is shown in FLUX Studio, provided I am aligning the wooden square properly on the metal grid.

Here is what I get instead:

The bars along the top & right are magnets, which I use to ensure that I am placing the wooden square precisely. It may not be apparent due to the photo quality, but rest assured that the edges of the magnets are placed along the corresponding lines on the grid as accurately as possible.

As you can see just by visual inspection, the distance separating the top horizontal line from the top edge is not the same as the distance between the bottom horizontal line and the bottom edge. Specifically, the discrepancies are as follows:

  • the distance from top edge to the top line is 3.0 mm, i.e. the vertical displacement is 1.0 mm less than what it should be (4.0 mm)
  • the distance between the bottom edge and the bottom line is 4.2 mm, i.e. the vertical displacement is 0.2 mm greater than what it should be (4.0 mm)
  • the distance between the right edge and the nearest edge of the “V” shape on the right is 3.2 mm, i.e. the horizontal displacement is 0.3 mm less than what it should be (3.5 mm)

The most confusing aspect of these discrepancies is that the displacement on the top is not equal to the displacement on the bottom. In other words, if the entire image were simply being displaced upward on the Y axis by a fixed distance, e.g. 1.0 mm, you would expect that to yield an output distance of 1.00 mm less than 4.00 mm between the top edge & the top line, or 3.00 mm, as is the case here, and you would expect the same amount of displacement on the bottom, i.e. from 4.0 mm to 5.0 mm. But this is not the case; instead of a displacement of 1.0 mm we find a displacement of only 0.2 mm. Therefore, not only is the image displaced, but the aspect ratio is slightly off as well.

Furthermore, these discrepancies aren’t consistent from engraving to engraving. On a different engraving, with a height of 120 mm, I found vertical discrepancies of 1.8 mm on the top and 0.8 on the bottom, and a horizontal displacement of 1.5 mm.

So a displacement of the entire image in either the horizontal or vertical planes is not a sufficient explanation, which is unfortunate, because that would be easy to correct for. There must be some error in the way the toolhead or the machine is rendering the input it is receiving from FLUX Studio, which is resulting in displacement as well as aspect ratio inaccuracies for the engraving output.

Please note that I don’t know whether the same errors would occur in the latest FLUX Studio software version (0.3.18) because I am getting a connection error with the FLUX Delta that doesn’t happen with 0.3.13, which prevents me from engraving anything at all.


#2

I’m getting weird results, too; I haven’t been able to get consistent greyscale output from the laser head even with halftoning, so I decided to test it with lines of various widths. I created an image with a series of increasingly-wide lines:

<img src="http://i.imgur.com/uGsHGoz.png>

I imported it into Flux Studio, taking all the defaults, and what it produced was:

<img src="http://i.imgur.com/4yMlCNk.png>


#3

Holy crap, that output is terrible! Are you importing the image as a vector or bitmap file? I’ve had terrible luck thus far with .svg (as have many others in the forum, apparently), but have found .png & .jpg files give much better results.

Also, what material are you engraving on?


#4

The top image is the file I’m importing, a PNG image I created in Paint Shop Pro – 100-pixel-wide lines 10 pixels apart vertically, grading from 1 pixel wide at the left to 10 pixels wide (and, hence, a solid vertical bar) on the right. I made the image after the laser test image tizio posted in this thread gave me profoundly crappy results, and tests with images that had been converted from greyscale using the halftoning tool in PSP gave me cause to think that there was something buried in the rasterization being done before passing drawing data to the Flux was altering the image resolution (which doesn’t really make sense, given the fine detail I was getting with an SVG file (albeit with extra lines in the image).

I’m engraving on cardboard, specifically comic book backing boards – 0.9mm thick, white on both sides, coated on one side. Whether I’m using the coated or uncoated side doesn’t seem to matter.


#5

Yes, I tried the one posted by tzayren and even with shading on, at 100% power, got essentially no visible output below about 50%, with full output thereafter, so basically it just looked like I used shading off with threshold of 50%.

However, I just realized something… the toolhead firmware needs to be individually updated for each toolhead, and I’m pretty sure I only ever updated the printer toolhead to v1.2.1 (not going to trust v1.2.2 as stable until it’s been out & tested a while longer), so maybe updating the engraver toolhead to v1.2.1 would solve or at least improve this problem?

I will try that & post my results here.


#6

[quote=“cpaleos, post:5, topic:1871”]
the toolhead firmware needs to be individually updated for each toolhead, and I’m pretty sure I only ever updated the printer toolhead to v1.2.1[/quote]

That’s something I hadn’t thought about; I got my laser toolhead as an afterpurchase, not as part of my Kickstarter pledge, so I just assumed that it didn’t need updating. I’ll have to do that when I get home and see if it makes a difference with the files I’ve tried.