RDWorks Learning Lab 101 the Importance of Scan Interval
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- Опубликовано: 15 окт 2024
- If you own a Chinese laser cutter this little series of videos about me learning how to use the free software provided, may solve the problem of trying to learn from a virtually unreadable manual.
I am nothing to do with RD Works, I am not an instructor and I am no expert. This series will document the essential bits of many hours of trial and error
Just wanted to say thanks for all these videos, I'm at #75 and don't know how I would have managed without them. Of course I did not get a manual with my purchase so you have really saved a lot of hair pulling. I need to keep what little hair I have left. Thanks and take care!
Russ, sorry to butt in -Recently we updated the RDWorksLab forum software. Some folks need to refresh their caches or reset. In Chrome it is Press & Hold CONTROL Key & Press F5 (Ctrl. F5)
In Firefox, it is Press & Hold SHIFT and click the Circle Arrow
(REFRESH)on the site bar to the left of the Search Bar in the header.
(SHIFT REFRESH).
For other browsers sometimes just close it & restart might work.
No way to tell the folks if they can't read the forum.
Hi Keith
I'll post a little video over the weekend with your instructions . I'm rushing around today trying to get a job finished to deliver tomorrow. My 20% of non-retirement seems to be growing again so tomorrow is truly the last job I shall be doing for this client. I can then get back to playing lasers again.
Best wishes to you both
Russ
great video. I will say that's ppi and dpi aren't really the same thing. ppi is a physical constraint of a device and dpi is a print media setting. doesn't really matter in this case but it can matter and tends to confuse people. there are some great articles about the two terms
Thanks for the clarification.
Thanks! Your channel is fantastic! I've learned so much watching your videos
Have you considered testing how spot size is affected by using the scanning "Special Mode" inconjunction with Facula Size?
i believe you can reduce the spot size by up to 50% which has obvious advantages.
when setting the min and max powers would it be best to choose percentages from the power vs % plots that are in the linear range of the tube?
Hi Dwayne
A nice idea but if you limit the range the shades of "grey" get compressed and there is not as much tonal range in the picture. I have experimented but in the end I use 10 and 67% and adjust the scan speed to get the right contrast in the picture. Dithered pictures seem better than pure greyscale.
Best wishes
Russ
Great! a very technical explanation ....thank you, very, very much! thumb up!...i will try a few experiments with your technical guides...
One thing to bear in mind is that you can't have an arbitrary scan interval. The machine has to move in multiples of stepper motor microsteps. If the scan interval is not an exact multiple than you might get uneven steps.
Hi
You are absolutely correct but the machine claims a resolution of 0.01mm which theoretically means I can work with pictures at about 2500ppi. That is actually ludicrous because the IF I can make my 1.5" lens work to it's theoretical spot size (0.075mm) the best dot-adjacent-to-dot resolution I could achieve is 330 dpi. which is a line pitch of 0.077mm. Even if I miss a microstep or 3 it's will not show up as a missing scan line. However, if I do not match the step interval to the pixel resolution ( or a multiple) then there is a chance that every Xth scan line will jump a pixel line and cause a visual problem.
Thanks for a great comment
Best regards
Russ
Yet another quality video, thanks Russ
Thank you very much for doing these lessons, they are very helpful!
Hi great video thanks but for now, (I have only seen the first 4 mins.) there are a couple of errors. The digital values on a computer in a greyscale image is Black=0 White is 255 you had it the other way around. And there are 255 different tones of black/grey, not 254 as you said because we are also counting 0.
Thanks Klaus. I now have to add another item to my long list of age related problems. Old ,grey fat, ugly and now stupid!!!. I do in fact know that black is zero and white is 255 but I have noticed that sometimes my mind gets ahead of my mouth. In this case I did not spot the error. Let's see how many others do.
On the other issue my point was that black is 0 and white is 255, that's a total of 256 elements. Black and white are the extreme absolutes and the 254 increments in between are shades of the mix. The first shade of grey must be 1 because 0= pure black and the last shade of grey is 254 because pure white is 255. Which ever way I look at it it seems there are 254 shades of grey........................or is there something else I must add to my list???
Best regards and lots of smiles
Russ
Thanks a lot! So much value in your videos sir! 🤓👌
Great video
Hi, in RDWORKS, i don't understand what mean the flag "Optimized scan" in scan mode and for second i would ask you a best photo glass engraved you ever made. I'm not able to understand the max dpi resolution, thank you very much
Hi Alessandro
If you do not know how to calculate the best scan interval ticking the Optimized Scan is supposed to choose it for you.However, I have no reason to trust that because if you have a 300 pixels per inch resolution picture the ideal pitch will be 0.084mm. If you leave the interval box empty it seems to choose 0.001mm which creates a stupidly huge file and not very good picture. If you follow the two simple calculations shown in the video you will get to a good setting. It may be possible to find better settings under certain conditions but this will generally work well.
Glass engraving has all sorts of complexities. First you need to produce a negative image because anything that is dark will be etched and anything white will be unetched. . With glass (or claer acrylic) the black will be etched and produce a white mark and the white will leave clear glass. If you mount the glass on a black background then it will look like a negative. You must make your picture negative to start so that it comes out looking correct.. The same goes for etching on any dark marble, granite or slate. The second problem with glass is controlling the dot size. Basically you cannot control the mechanism by which the etching takes place. With wood or card or leather, the pin prick of focused heat makes a mark the size of the beam (maybe 0.1mm) but with glass it heats up that little pinprick area so rapidly that it causes a little glass shard to break away from the parent material.That shard may randomly be 2 or 3 times bigger that the 0.1mm beam. It is not a controlled process but much more like a stone chip on your car windscreen. I have played with engraving and various materials but have no stunning examples to show you. I just know of many problems that I have discovered and am still trying to make sense of all the parameters.
In the very near future I intend spending several sessions on trying to understand all these variables and how to best exploit them for various materials. I can see that it is a HUGE subject. Sadly I am an engineer and not an artist. One of the main requirements is to have a vision of how the picture will translate to various materials because you will need to adjust the original picture so that it looks hideous , just to make it look good on its final medium.
Best regards
Russ
Hi, for first thank for your answer. ok i understand the resolution scan interval is easy to calculate, my question is about the software because when i click on "Optimized scan" nothingt happen. the textbox of scan interval don't change the value. This i don't understand.
Another more techincal question is about the speed engraving. i saw that there is big difference quality of detail fromm 100mm/s to 400mm/s. Is possibile to think the laser switch on/off is not to fast??
Hi Alessandro
I have played with the optimized scan and to be honest apart from putting a stupid value in when the interval box is empty I have also found it does nothing detectable or obvious. I personally ignore it now.
This is the quoted explanation from the user manual
"Choose optimized scanning to automatically adjust the scan to the scanning interval for best effect. Otherwise, the user settings of the scanning interval scan pattern are applied. It is generally advisable to choose "optimal scanning".
I am currently experimenting with scanning as I am preparing a video on various scanning modes. This is a large and complex subject becasuse there are so many variables to play with and understand. From what I have seen so far, when you are trying to scan a dithered pictiure and there are billions of dots. the faster the scan speed the lighter the picture you produce for a fixed power. Although you may think this is to be expected, I am puzzled by it. If a dot is a burst of laser power defined by the %power that you set and lasting for a minute but fixed period of time then the "burn" would be the same for all speeds and the colour would remain the same for all speeds. I was anticipating that the power was controlling of burn colour. This is where my investigation is currently at, trying to establish what factor makes the burn longer as the speed reduces.. I am working with a 600 pixel per inch resolution picture at present and have many more trials to conduct before I start varying the pitch and then then interval. Currently I cannot answer your question but maybe in a few days time I will be able to understand just what is going on with control of the laser. The laser is capable of changing power and switching on and off incredibly quickly so I don't think it's a physical problem you are seeing, more an issue with HOW the beam is being switched on and off.
Keep watching
Best regards
Russ
Russ, how does the resolution of the stepper motor factor into your calculation?
I asked this on another channel and belt type and gear type all effect the steps per millimeter (in RD Works that would be the interval). A CO2 laser can focus down to 10 micron but what good is that if your minimum steps per mm can't go that low? edit: Let me add that in Russ's case his .2mm line his laser makes is really freaking huge as the dot size of a CO2 laser beam (the smallest it can go) is .01mm (10 micron) so .2mm is pretty crappy when a 3d printer can do .1 or even less.
The positional accuracy of the stepper system on most of these machines is claimed to be 0.01mm. This is 100 dots per mm capability or 2,540DPI. This is way more than ANY lens is capable of. hence the stepper resolution is unimportant
Best regards
Russ
I think you have confused two important facts. The wavelength of the CO2 laser beam is indeed 10.6microns (0.0106mm). This is NOT the size that the beam can be focused to. That depends on the lens focal length and the diameter of the beam. This is clearly explained at
www.parallax-tech.com/faq.htm
I set my beam out of focus to achieve a nice even number (0.2mm) for demonstration purposes. Theoretically my 1.5" lens may achieve a spot size of 0.075mm. I have never been able to get better than 0.012mm but this may be because my beam is almost 10mm diameter.
Best regards
Russ
Why is your beam 10mm diameter? The finer your spot the better the picture quality potential.
Wiki lists the CO2 beam as 10 microns not 10.6 microns (that is a big difference at that level) so what are they talking about? I am getting a suspicion that it starts out at 10 microns but because of the travel path it takes until it hits the lens makes it spread out too much.
Hi
I think you are confusing beam diameter with the wavelength of the coherent light emitted buy a CO2 laser. The closest anaology I can use to help explain the difference is with sound. High notes and low notes are the wavelength and the volume of the note is the beam diameter.The beam diameter depends on the size of the exit window from the laser tube and also the energy density pattern within the laser. My tube claims to have a 6mm beam diameter. It has a 12.7mm exit window and at full power the energy profile across the beam should ideally be Gaussian (bell shaped)where the majority of power is towards the centre of the beam. However there is still power right out to the window diameter at full power. In my case about 90/95% of the power is within a 10 mm diameter but it can still burn a 12.7mm hole in a piece of masking tape!!!!
A coherent beam of laser light does not diverge(spread out) as you are imagining or change its wavelength. NASA regularly fire a laser bean (albeit a different wavelength) at a 2ft target on the moon and knowing the speed of light and measuring how long the light takes to travel there and BACK they can track the distance of the moon from earth to within a few centimeters. That just would not work if the beam diverged like a torch beam.
I will shortly be publishing a video about measuring your laser beam diameter.
Best regards
Russ
ROFL. no wonder it took me so long to cut my inlay. I had an interval of .1. I will have to experiment with intervals to find the right number. Mind you the inlay did turn out fantastic.
why you no print the pretty lady....:(
Stay tuned he has it planned so remain patient. :) The pretty lady is when Brittany Spears was very young.
very educative !
Thank you!
Thank you so much
Hello dear friend. I'm from Portugal. Before something else, congratulations for your channel. I bought in February a Chinese laser machine, and I have a few problems. Can I send a email for you or private message?Thanks
Hi Ricardo
Private message me with your email and I will get back to you
Best wishes
Russ
SarbarMultimedia thanks. But I didn't see your email. How can I find?
Hi Ricardo
If you click the following link you find a message button top right. That will send me a private massage where you can let me have your email address. I will then write back to ypou.
Best regards
Russ
was looking forward to an amazing engraved Britney spears :p
Hi Jeordan
I shall be using this picture to demonstrate the preparation and effects of different resolutions and interval settings in a future session. So watch this space.
Best regards
Russ
Thank you Russ! Great very important presentation. Appreciate your help.
Regards,
Ray In Omaha
Russ, unbelievable...that is one of my ex wives! Richard
Thank you very much