DPI Scan Gap Chart

[Axeman]

Thought you guys might make good use of this.

Thanks goes out to Rabbit Laser for compiling it.

http://www.rabbitlaserusa.com/manuals/s ... dpi_25.pdf

[Hermes]

Thanks a lot! I was actually working in something similar.

Hermes Sandoval.

[Axeman]

Oh and...300 DPI is nearly the max you can reach with engraving wood.

400-600 is recommended for Glass/Acrylic.

[Greolt]

That is a good chart but unfortunately it is of little use to AWC608 users.

For some crazy unknown reason, LaserCad will not accept more than two decimal places in the scan gap setting.

No matter what you enter, it rounds that number to two decimal places.

I have asked if this can be fixed a number of times over the last couple of years, but without any success.

Tim has a write up about this issue on his blog. He also has a chart there, which is more use to AWC608 users.

http://diylaser.blogspot.com.au/2011/09 ... n-gap.html

Greolt

[Tech_Marco]

To Greolt:

I didn't forget to ask it but forgot to follow up with you. I talked to Li, the programmer and he said that by adding once more decimal it would take so much processing time and power to do it. So, it is "mission impossible". It would cause a big impact to the performance of the DSP.

To educate me, do you really need 3 decimal for the scan resolution?? A laser dot seems having diameter much bigger than the scan value. Just curious.


Marco

[Greolt]

Marco

Tim has done a good write up on this. Read his description. It is much better than I could write.

LaserCad and all other laser control software that I have seen from China, are almost identical. You just have to look at them.

It seems that they have diverged from the what would appear to be the same parent software, as individual programmers have developed them.

Yet some of those other siblings, such as LaserCut, have the ability to have three decimal places.

Greolt

[Tech_Marco]

Greolt

Thank you for the info, I'll check it out

I talked to "Li" and he said that he allow me to do my own design of LaserCad front end by opening ports for the connection. But I don't know C# and I got to find someone able to do it. I want to add some feature on the LaserCad like a video capture screen allow a camera to be installed on the laser head (my next project). Plus, I want to do "Imperial system" that Li promised me long ago but was too busy to do it for me. In fact, I got a lot of idea of making good features on the LaserCad but just couldn't get him to move quick enough. It is very frustrating. I know some feedback from you folks were good. Unfortunately, I was not "Li" and I wish I could do it for you folks to make it happen. I've a few quarrel with him about the direction of how LaserCad or the DSP should go. But he seldome listen.
For example, two years ago I asked him to do "Touch screen" on the DSP card but he didn't untill recently. But he was late already. In a few months, I may be able to test a '7" color touchscreen' DSP controller. Let's double finger the project comes on time and runs smoothly

Marco

[Axeman]

Well with that chart, I would simply round up to the nearest decimal point. To that level of accuracy for a scan gap makes little difference, like Marco was saying, it's not a huge deal considering the width of the laser. Unless you are using a 1.5" focal lens, the scan gap to the 3rd decimal (Thousandth of an inch, a human hair is 2 thousandths) is negligible.

Marco, if C# is what it is written in...maybe I can do some digging around and talk to some coding folks that I know and see what they might be able to help out with.

[Greolt]

Well with that chart, I would simply round up to the nearest decimal point. To that level of accuracy for a scan gap makes little difference, like Marco was saying, it's not a huge deal considering the width of the laser. Unless you are using a 1.5" focal lens, the scan gap to the 3rd decimal (Thousandth of an inch, a human hair is 2 thousandths) is negligible.

You would do well to read Tim's write up.

http://diylaser.blogspot.com.au/2011/09 ... n-gap.html

I hope Tim will not mind if I quote a section of it here.

The reason is that, when scanning an image, the controller is not creating those scan lines directly, as it does with vectors.
It is getting the bits that define the scan line from the image. So, if we have a scan gap of .09, for every inch of image height, the controller is going to try to extract exactly 282 lines of data.
If the original image has a resolution of 300 DPI, then which 18 lines should it ignore? Conversely, if we set the gap at .08 it will request 318 lines of data. But there are only 300 available.
So it has to repeat 18 lines along the way to make up the difference. So in the first case, you are loosing data. And in the second, you are repeating data.
Either way, you are not going to get an output that will likely be close to the original, but with a higher degree of uncertainty (error).

Sometimes you will get away with saying "that level of accuracy for a scan gap makes little difference". Other times you will get banding and wonder why.

Greolt

[Axeman]

Aha! You are correct sir...I did not take into account the conversion from the archaic Imperial to Metric when dealing with that level of accuracy. That IS a problem...

I spoke before reading all the material properly. Thanks for the correction.

[Tech_Marco]

Well with that chart, I would simply round up to the nearest decimal point. To that level of accuracy for a scan gap makes little difference, like Marco was saying, it's not a huge deal considering the width of the laser. Unless you are using a 1.5" focal lens, the scan gap to the 3rd decimal (Thousandth of an inch, a human hair is 2 thousandths) is negligible.

Marco, if C# is what it is written in...maybe I can do some digging around and talk to some coding folks that I know and see what they might be able to help out with.

Thank you for your offer. I need to find someone I can discuss 'face to face' otherwise it will take too much effort to tell one what I want to do. Plus, not sure how much port that "Li" is going to open for programming. Beside the front end, he won't let anyone to touch the 'back end' programming. It is the 'heart' of the controller and if anyone got the source code, then everyone could fabricate the DSP card easily. That's something most programmer in China are not wanting to see happen

Marco

[SWMS]

I've heard mention of a wish list for the software. Is there a sticky on the forum for this?