Not Just Another Laser Engraving with PVC

[dlgabry]

oops, forgot to mention lead screws are 10 pitch acme thread.....
Dave

[JJWMACHINECO]

Thanks Brian for the information on the shades in PVC.

I just finished these 2 of the same picture and settings. I downloded the picture from the link that Dave posted. .0155" depth of cut, .0002" retract and .01" stepover running at 60IPM. Both engravings are 9.5"X6.5" and took 1 hour and 45 minutes each to engrave. I started Z zero this time at zero volts, well pretty close to it without it jumping to 5V when it retracts. The first one that opens and showing on the screen has no image processing and when opened, it will show the other one and the difference of the 2. The second one I used Auto Adjust and slightly embossed it.

Jeff

[JJWMACHINECO]

Dave,

this may be an interest to you. I found this on a Hungarian web site where this guy posted the info of my results with the modulated laser and engraving shades with PVC. He talks about another way to vary the power using Mach instead of using an encoder. I believe this was what you were trying to do before you added the encoder to your router. He explains in some detail on how it may be done using the step and direction pins. This may be a way to increase your gray scale count instead of relying on the stepper motor and only getting 64 shades. With that setup you could set PVC to cut Z-.0256 depth and get 256 shades and still use your Z axis stepper to position and focus your laser based on material height. I may look into this also as it sounds like an interesting idea to increase the grey scale count on mine. There is always room for improvements. FYI

[dlgabry]

Thanks Jeff! Yes, sounds like what I was attempting to do with some binary counters and a digital to analog chip, but so far I've not been able to get the counters working reliably - counting in the up direction is fine, counting down skips steps so it's not usable. I've put that idea on the shelf after getting the encoder. It'll be interesting to see what they come up with.

I made up a test pattern with vcarve pro to help me set the potentiometer for max level output on different woods. The pattern darkens smoothly with no sign of steps in the shading that I can see. Did a 7x9" version of the cat face this morning, looks good to me tho it ran for just over 2 hours.

I may do some experimenting down the road with 1/4 or 1/8 micro-stepping on my controller board to get more steps and redo the motor tuning in mach3, but I'm happy as a clam with it right now.

Dave

[JJWMACHINECO]

Yea, I'm happy with the results I'm getting also. I did try one of these.

http://www.ebay.com/itm/180950243100?ss ... 3609wt_932

I wanted to see if I could get more burning power out of my laser to speed up the engravings. It definitely gave 30% more power and burned the wood hard, but it appeared the beam was not as precise as the 3 element glass lens. The engravings came out blurred and did not come out as detailed and defined. It may have been because I was trying to engrave at 80IPM and between Mach and my router they may have lost some responsive accuracy at that speed. I may be able to cut balsa wood with that lens though.

When I get my laser power meter, I will post the actual power I'm getting out of both lenses.

[dlgabry]

Hi Jeff,
Most of my trouble with bluring was due to the Mach CV settings, and it got worse as the feedrate increased. I got around it by setting a small value in the CV distance tolerance parameter. Try setting it to around .015 as a test to see if it improves things.
I used a single pixel wide line and rastering at 90 degrees to it for testing, and found that there was a difference in the placement of the line between Y+ and Y- directions.
Dave

[JJWMACHINECO]

Hi Dave,

I did play around with that yesterday after reading it in your other post. This was after I put my 3 element lens back in. It can't run at 80IPM because lack of burning power and I was running it at 60IPM instead and did not notice any difference. I will try it again with the other lens because it definitely gave me more burning power. I'm glad I have allot of extra birch plywood to burn up.

Thanks. Jeff

[Tweakie]

Hi Guys,

Has anyone tried to laser a simple grey-scale, rather than colours, just to check how many shades are reproducible on wood ??

Tweakie.

[JJWMACHINECO]

From what I understand, the PVC software is made to interpret colors into depths of cut, but coverts it to grey-scale first. I don't know how it would convert that grey-scale into a grey-scale for the depths of cut, but I will try it.

[JJWMACHINECO]

OK, this is how it burned. I ran this at .0145 full depth and 40IPM with a .007" step over. At .8v-1V about Z-.0015 from zero volts on my setup is where the laser starts burning the wood. It looks like the first 4 and the last 3 had no real change in shades. I suspect because of the grey-scale to grey-scale conversion. I did not notice any voltage change in the first 4, but 5-6-7-8-9 did and no change from 9 through 11.

[dlgabry]

Here's another grayscale with a smooth transition from white to black to try out. I'm not in the shop right now, but I'll give it a try tonight if I get a chance.
Dave

[Tweakie]

Hi Guys,

Thanks for taking the time to try this, I am most grateful.

My CO2 laser is a bit like a bull in a china shop when it comes to wood and does not have the fine degree of control you are able to achieve with a diode.
The maximum number of ‘easily distinguishable’ shades I have been able to achieve on wood is 5 with an all time maximum of 7 (including white) with an unknown type of veneer.

I am attempting to collect as much data as possible before writing the software for the step / direction controlled PWM generator and your input is extremely valuable in this respect.

Thanks again.

Tweakie.

[JJWMACHINECO]

Tweakie,

there are so many variables, like feed-rates, step overs, tool call out, size of the burning beam, size of the image your engraving, how the image is processed or enhanced, where you set zero based on the power of your laser, full watts of the laser and the type of wood your engraving on.

I received my laser power meter yesterday and now I should be able to focus the lens somewhat better then before based on it's maximum wattage output power. Before I was trying to focus it down (the best I could visibly see) to the smallest dot possible on a black anodized piece of aluminum. I can only assume the smaller the dot, the more full watts, detail and intensity you will be able to get out of the laser. Also it should be more responsive to the change in the inputted voltages to the analog modulation to visibly see the difference in shades too.

I believe the best way to do the grey-scale test with my laser and with the PVC software is, redo the 256 color pallet again with more refinements and I will post the results later today. I will scan in the image and post it instead of taking a picture so it does not loose as much detail.

Jeff

[Tweakie]

Thanks Jeff, I look forward to seeing the results.

I suspect that PVC does actually convert the colour information to grey-scale before calculating the depth information form the pixel value but I have yet to be enlightened.

Tweakie.

[JJWMACHINECO]

OK, here is the Grey-Scale of the 256 color pallet again. I scanned it to grey-scale instead of posting pictures of brown-scale so you can see the differences in the shades. Did Auto Adjust and a slight boss on it this time like I have been doing with the photos. Made white transparent and ran it .0145" depth at 40IPM with .01" stepover. Started Z zero .0018" from where the encoder jumped to 5V and set retract at .0015".

How many different shades can you count?