Moderator: twehr
naPS wrote:So, I got the LO DSP in yesterday, and made up a cable to interface to the v2 interface board today to test it out. Overall first impressions are... meh. The documentation is absolutely horrific for these things, which makes me a sad panda. Regardless, the controller definitely seems workable.
naPS wrote:I've got it up and running and doing everything it's supposed to be doing. It's just not doing the majority of it very well. I'm 99% sure it's operator error, but you never know. I've got the homing, direction and table sizing all pretty much correct. I've got the units set to mm/seec. The first thing I'm finding confusing is that the units don't appear to be standard. The pulse per unit is an interesting way to do things, and I've got it dialed in so I can cut 50x50mm boxes in vector all day long with 100% precision. So I know that part is at least good to go. The thing that I'm somewhat confused about is the rest of the speeds. When it says acceleration, and speed, and whatnot in all the different locations (x and y axis setup, etc.) is that all in mm/sec? Or is it in pulses / unit? It's confusing, and the values in the setup documentation seem extremely high for what I've been able to reliably use with Mach3.
naPS wrote: I've also been using a .001" scan gap in the Mach3 plugin, which is approximately the size of the laser dot, and it's been working very well. That should mean that my scan gap for engraving in the DSP should be (.001 *25.4) = .0254mm. I see whmeade using .1 and .09mm, which should be fine for most of what I'm doing as well.
naPS wrote: I just can't get that to work. Any time I use a scan gap while engraving of below .2, It gets skewed in the Y direction pretty badly. Once I get up around .2 and higher, the problem goes away, but the resolution suffers slightly. I tried fiddling around with the speed and acceleration of both axis, but it didn't change what was actually happening during the engrave. The only thing that had a noticeable effect on the skewing was the scan gap setting.
naPS wrote:
The second issue I'm having with the engraving is that it's giving me strictly monochrome results, with no shades of grey at all. It's either basically black, or white. I'm able to get several shades of grey using the Mach3 plugin, so I know it's possible. Anyone have any insight on this?
naPS wrote:Also, what settings do folks use when you import photos? Do you leave all three of the tick-boxes checked when bringing in images? What settings are you using for the actual layer properties screen? Can I get a screenshot of someone's setup?
twehr wrote:I hope you are talking about the LO documentation and not the installation document I wrote and has been used by several people very successfully for installation. If you did not use it, you probably spent too much time trying to figure things out on your own.
twehr wrote:As for high speeds, I can run quite well up to 700 mm/s, do I don't think you are misreading or misunderstanding anything there. The max speed that your particular machine can run will be determined by the mechanical features (how loose, tight, smooth, etc.) and the drives you are using along with the micro-step setting. If you are not getting the results you think you should, try adjusting the micro-steps AND simultaneously adjusting the pulse units accordingly (either halving or doubling to compensate for changes in micro-steps).
twehr wrote:The scan gap is how you control the effective DPI of your output. For scanned images (photos) it should be set to match the DPI of the photo image - i.e. a 254 DPI photo should be set at .10 mm scan gap. For 300 DPI, you should set it at .09 mm. Mismatching your scan gap and the actual photo DPI will likely cause you to have skipped lines or double engraved lines in the output. They will be visually unacceptable in many cases.
When doing filled vector engraving, you are free to set the scan gap to anything you want. I generally leave mine at the default .10 mm. Bill Meade, on the other hand, likes using .09 for a slightly higher resolution (300 vs 254). You can go do to the .02 or .03 for really high resolution but doubt you will find it worth while.
Even though your laser may be mechanically capable of a 1000 DPI resolution, you will likely never need that high of output. The time necessary to do 1000 scan lines per image inch is 4 times as long as it takes to do 254 scan lines per image inch. For MOST things, the difference in true output will be unnoticeable.
twehr wrote:If you are having issues with the Y axis on scanned images or vectors not coming out at true height, you likely have a combination of micro-steps and pulse units that does not work well for your particular drives. Read my thread http://buildlog.net/forum/viewtopic.php?f=13&t=584&p=4141&hilit=missing#p4083 where it is discussed at length.
EDIT - I just re-read your post. If you are getting skewing (not compression) then it is likely that you are dropping some x axis steps. Could still be the say kind of issue, but be sure to look closely at your x axis. Specifically, decrease your acceleration a little and/or decrease your start speed (mine is at 10, I think).
twehr wrote:The results ANY laser will give you on engraving is 1st a function of the quality of the image you are asking it to engrave. That being said, it sounds to me that you MAY have skipped an important step in importing your photos to PHCad. AFTER you import the photo, you still have to tell it to dither the image (menu function). If you don't do that, it will do a strictly histogram based output - any pixel greater than 50% gray is BLACK and any pixel less than 50% gray is WHITE. Usually, this is not the effect you want. Make sure you dither the image after import and before downloading to the laser.
twehr wrote:The best solution is to do your own dithering in Photoshop (using the Gold Method plugin) or in CorelPaint (a manual process) or PhotoGrav (best but most expensive solution). Then just import the image into PHCad or send the image to PHCad from CorelDraw. You will get much better results than if you try to use the dithering from PHCad.
naPS wrote:And therein lies the problem I'm seeing. I'm beginning to think this is a software issue, as I'm having issues in the X direction, only at scan gaps of about .14 and lower. .15 and up, it's great. But the scan gap should have no effect on my X movement, only on my Y movement. But, it's having a pretty interesting effect on my X movement. I've created another profile, and I'll chuck the picture up at the end of the message here.
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Do I still have to do the dithering in PHCad when I import the image?
twehr wrote:This is very similar to the behavior I had in the Y direction. For me, there was a definite speed at which it stopped/started working. Adjusting the micro-steps and pulse width allowed me to change where that speed break was. I don't know that it is a software bug as much as it is an issue with the speed at which the data needs to be generated/sent. Changing the steps/pulse unit will increase or decrease the amount of data that needs to be generated/sent.
naPS wrote:But you would think there would be distortion in Y as well if that was the case. Also, the circles are identical in speed and power, the only thing that changed was scan gap.
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And thanks for the dithering info - that did the trick. The image actually came out pretty good - it's almost as good as the Mach3 plugin was giving me, and with some tweaking, I'm sure I can improve it. Improving my scan gap will help that immensely.
twehr wrote:Y is getting a lot fewer signals than is the X.
twehr wrote:If you get good at creating your original artwork and dithering it well, you will beat Mach3 by a long way.
naPS wrote:I'm at 2000 steps per inch, I might try dropping that down to 1000 steps per inch on the drivers and see what effect that has on it.
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