Anyone have a free Checkering pattern?

[Shane Tietz]

No, these are CNC turned. I've been doing it for 3 years now and am pretty much self taught. This has been my one problem since the beginning lol.

[David Somers]

Shane,

Everyone is correct here. Your circumference needs to be the circumference of what you are lasing to, not the mandrel going through the piece. Your method of calculating is fine, but you were measuring the wrong thing.

The other issue confusing you is what Mike Null described. Your rotary is not working on the same plane as the laser. That is showing up in the start of a spiral in your pattern.

The problem with that type of pattern is that getting it spot on is going to require a really accurate circumference, and a rotary that is spot on level with the focal plane of the laser and rotating perpendicular to the axis of the laser as well. Otherwise you will get that spiral starting.

You might ask how I know this since I don't have a laser yet? <grin> I spent a ton of time with the local Epilog rep talking about this since it was one thing I was hoping to do. He explained the issues carefully and said you had to be prepared to fuss extensively with it to get a decent result....and expect a fair number of failures. He was not encouraging this kind of full circumference use for a production environment. His solution to it was to work with a broken pattern. So instead of a complete band of cross hatching you might have blocks of cross hatching going around the item. Then a touch of misalignment or a sloppy measurement is not going to affect you as noticeably. He did think you could probably get good enough to regularly have a simple line go around the circumference and meet decently, but for a pattern to match up correctly in all ways on the circumference repeatedly was going to take some cosmic karmic alignments that would be highly unlikely.

And this doesnt take into account the fact that you are working with wood, which is pretty dynamic due to it being a very live material. I run into this when I do hollow christmas ornaments and small lidded objects on my lathe. A piece that fit beautifully today might fit loosely the following day, and be too tight 3 days later. Using a stabilized wood can help some and at least reduce that one variable for you.

Dave

[Shane Tietz]

Thanks for all the info David. Well it started out with 4 simple lines. I did it with raster first and it was taking too long to see how it hit. I swapped to vector and ran quick lines and just adjusted as I seen fit till I got it straight. Of course, I have to engrave the other logos and stuff too, so I always have to move my rotary and stuff lol. Would there be a good way to get a 3D checkering effect with one pass? I know on wood you can only do it so slow and powerful till it's all burnt up, but we also do acrylic, which is what the call is made of in the pic I posted. I have 2 Mini 18 30Ws, what would the settings have to be to achieve the 3D effect in a single pass, or is it even possible?

[David Somers]

Hey Shane!

I am afraid I can't help you with settings. Others will have to chime in. Like I said earlier, I haven't bought a laser yet.

Would Epilog have a list of settings for that since you have 2 Epi's in hand? The numbers would be ball park only of course, but likely to be a bit closer to correct than from any of us with other brands.

When I finally do a laser I do hope to try and work out a decent process for what you are trying to do. A decent engraving around a circumference that meets, and while not production, I would like it to be repeatable. My thought was to take time to develop something that would hold the rotary in a way that was accurately lined up to the XY and Z axis of the machine, and be easily repeatable. Otherwise you will be dinking with it each and every time. And in your case, its seems like you might be interested in running batches. So if you could rig a work hold for the rotary that facilitated your level of production that would help. Main thing though is to be able to mount the rotary accurately and fairly quickly each time.

Then your main worry is being able to measure that circumference accurately enough to make the pattern meet. Or, develop a pattern you like that is more forgiving.

May take some serious fussing. But a worthy challenge for what you are doing.

Dave

[Shane Tietz]

Epilog has the standard settings for types of material. They really don't go into 3D stuff lol. This won't be so much for production, just some limited run custom stuff.

[Niklas Bjornestal]

I dont know how the rotary device works on epilog lasers, but on gcc's lasers it's very easy to get the pattern to meet.
You just specify the diameter in the print driver and tell CorelDRAW to get page size from printer. You doesnt even need the diameter to be very exact since the page will always be a complete "circle" around the object.

[Shane Tietz]

That's all I thought you had to do on here too lol.

[Konrad Birchfield]

Is there anyway to put a small emblem or design where the two ends would meet and just stop the band short of the sides of the emblem? But this wouldn't solve the issue with repeatability.

[AL Ursich]

If I was doing this I would make a thin ruler in Corel and tilt it slighlt. I would apply blue painters tape to the call and run the file and at the overlap point look at the reading and go back and make your checkering that same length in corel. The tilt so you can read the side by side line up point and not burn double on the same line.

[Bill Cunningham]

would take another tack.. If you have a logo for your calls, I would keep a space between the ends of the checkering and insert my logo there. Then, if the ends don't match up no one but you would really notice. You have, your checkering, you have your logo, and no one will look at the ends unless they are totally weirdly ended.

[Robert Walters]

ALIGNMENT

The ends aren't aligned due to something not being parallel to each other.

Either the Y-Axis movement of the laser is like "/" or "\" to some degree instead of "|".

In corel, draw a 10" x 10" hairline square, black stroke, no fill, center, then vector engrave it.

A----B
|    |
|    |
C----D

When measured with a ruler, the distance between AD and BC should be the exact same.

Just in case your alignment is off on the long end of X-Axis,
move the 10" square close to the far end of the X-Axis travel and try again.

What you are trying to determine is if something on your machine isn't aligned properly and is actuality producing something like this even if it's not visible to the naked eye:

   A----B
  /    /
 /    /
C----D

If so, the distance of BC will be greater than AD, and you'll need to make the proper adjustments.

This includes:
1. the X and Y axis of the machine itself.
2. the placement of the rotary fixture in the machine.
3. the squareness of the rotary fixture, and
4. the object's alignment in the rotary fixture.


OVERLAP

If you are seeing overlap, your graphic is greater than the circumference of the object.

If you are engraving on (what you believe to be) a 2" diameter wooden dowel:
The circumference would be 6.28", so your graphic needs to be that as well.

To get the circumference, multiply the diameter by 3.14159 (pi)



REPEATING PATTERN

Even when adding a repeating pattern to an object, where the ends meet may not align aesthetically.

for example, if you have this repeating pattern: "/--/--/--/--/--", when you get to the end where they meet
you might end up with: "/--/--/--/--/--/-/-/-/-/-/-/-/-/-/-/--/--/--/--/--".


What you could do is add a "hallmark" or "maker's mark" of sorts.
Maybe your hallmark is something like this: ' SMC ' (note the spaces) and is 1/2" long/wide.


Change your repeating pattern to: "-/--/--/--/--/-"
and tack on you hallmark to one end, and you get: "-/--/--/--/--/- SMC ".

Once engraved on a round object, would look something like this:
"...-/--/--/--/--/--/--/--/--/--/- SMC -/--/--/--/--/--/--/--/--/--/-..."


So your repeating pattern would need to be:
6.28" (object's circumference) - 0.5" (hallmark) = 5.78" or less

and you no longer have to deal with a pattern aligning up properly end-to-end and still have a nice look to it.


If the ascii art doesn't come thru properly, blame lack of proper <PRE> tags and evil css =)

[Bruce Dorworth]

I would first try and cut/raster a single line all the way around and see if this lines up. It looks to me like something is not quite straight.

That is just my take on the it, hope this helps,
Bruce

[Brian R Cain]

I would first try and cut/raster a single line all the way around and see if this lines up. It looks to me like something is not quite straight.

That is just my take on the it, hope this helps,
Bruce

I think that's a sensible idea. I would vector it myself to save time, also making the vector at a slight angle, say half a degree, so you can see where the start and stop points are in the event of overshoot.

Some years ago I had the task of marking an encoder on F1 wheel bearing casings. The marks had to go around the complete circumference and be equally spaced and identical in size. I got there in the end, but it took several failed attempts to discover where the error in the start and end points was coming in. Although I had set everything up correctly and had a precision part to work with, there seemed to be a slight difference in how the laser driver was interpreting the info it received from Corel. Just a few thou made it work or not. The resolution was to measure the error accurately and adjust the graphic to compensate.

[Shane Tietz]

Thank you for the very in depth answer Robert! I'll give this stuff a try when I get caught up on the weekend orders.

[Bruce Dorworth]

For that mater you could burn a dot, go all the way around the cylinder and do another dot.

Bruce