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View Full Version : Connecting a pattern on a round object with the rotary



Matt Dunn
03-08-2013, 10:21 AM
Ok, I have an Epilog Mini 30W with the rotary attachment. I'm engraving on duck calls, and the circumference varies on different points on my call barrel. I have a customer wanting me to engrave a cross hatch pattern all around it. How will I be able to pull this off where I can have the lines connecting back into itself?

Dan Hintz
03-08-2013, 10:42 AM
There is no simple solution, but it is possible... the more complicated the surface, the more complicated the adjustment needed. I posted a solution in a thread several years back, so see if you can find it in a search... it had to do with drinking glasses that had a taper to them.

In a nutshell, you need to prewarp the pattern in the opposite direction as the surface... wider diameters get stretched vertically more than smaller diameters.

Joe Hillmann
03-08-2013, 10:53 AM
With a Universal laser and rotary it is fairly easy. You just make sure your page size height in corel is 3.14 times whatever you tell the laser the diameter of your part is and it will wrap all the way around stretching the areas that are wider and shrinking the areas that are narrower automatically. On an epilog style I would start by making the drawing 3.14 times as tall as the diameter (measured carefully) that sits on the drive wheels of the rotary. Also on the epilog style rotary you may have to worry about slipping between the part and the rotary.

Dan Hintz
03-08-2013, 11:09 AM
Joe,

That makes the pattern meet, but it doesn't keep the pattern consistent. Checkering will show small diamonds at small diameter portions, and wide diamonds at large diameters. If you want a consistent pattern, you need to pre-warp.

Matt Dunn
03-08-2013, 11:22 AM
I normally wouldn't even have thought to do this, but he had asked another call companies' engraver and he turned em down, so I figured I would step up and try it. I'm gonna look for your write up. I assume the easiest way would be to do a post script fill with squares for the pattern? I was thinking of measuring each section with calipers for my circumference then warping it from there.

Joe Hillmann
03-08-2013, 11:24 AM
You are right. My method only makes the design meet at the start and finish and it will be distorted based on the change in diameter over the part. But on anything other than a simple taper it is beyond me on how to get the diamonds all the same size and meet up.

Matt Dunn
03-08-2013, 11:30 AM
It actually is a fairly simple taper also I might add, if that helps.

Chuck Stone
03-08-2013, 12:22 PM
I think the hard part is going to be making sure that the pattern will
continue without a seam. That's just trial and error.

Make your file height to match the diameter x pi (as mentioned .. 3.14)
Place your pattern. THEN make the canvas size twice the height, leaving the
pattern at the top. Place a guide line at the bottom of the top file.
Copy it and paste the file below and you'll see how it will
match up at the join. The very top of your file must match (exactly) the
very bottom of the file. You can see this where the bottom of the top file
meets up with the top of the bottom file. If they don't match up, get rid
of the bottom file and start manipulating until it meets up seamlessly.
Then delete the bottom file, change back to your exact size of the top
file and save.

That sounded much more confusing than it really is.

It will also work without pre-warping as Dan suggested, but then your
image will be warped according to the taper. (ie. your diamonds will
get smaller as the taper gets narrow, but they will still line up.)
Better to pre-warp before you start sizing/placing.

Matt Dunn
03-08-2013, 1:15 PM
Ok, I think I get what you're saying, but where should i measure my circumference, at the widest area or at the thinnest or does it matter?

Matt Dunn
03-08-2013, 1:18 PM
Oh ya, the customer already has a logo on the call and I will somehow magically make this pattern so it won't engrave through the existing logo...

Joe Hillmann
03-08-2013, 2:07 PM
If you have a universal I would suggest averaging the diameters and use that. If you have an epilog you need to use the diameter EXACTLY where it rests on the drive wheels.

Matt Dunn
03-08-2013, 2:30 PM
well the part actually fits on a 5/8" dowel which sits on the rollers

Joe Hillmann
03-08-2013, 2:39 PM
Then 5/8" is the size you need. I would suggest building a jig so it isn't sitting on such a small diameter. If the the diameter of the dowel is smaller than the part any imperfections will be magnified. If the dowel is larger than the part any imperfections will be reduced and if the dowel and part are the same size any imperfections will stay the same size. Also just because it is a 5/8" dowel doesn't mean it is actually 5/8". Measure it with a caliper or micrometer. Every .001" you are off on measuring the dowel will cause a .00314 x call diameter/dowel diameter overlap or gap in your engraving. (All of this only applies to epilog style rotaries).

Dan Hintz
03-08-2013, 2:47 PM
Then 5/8" is the size you need. I would suggest building a jig so it isn't sitting on such a small diameter. If the the diameter of the dowel is smaller than the part any imperfections will be magnified. If the dowel is larger than the part any imperfections will be reduced and if the dowel and part are the same size any imperfections will stay the same size. Also just because it is a 5/8" dowel doesn't mean it is actually 5/8". Measure it with a caliper or micrometer. Every .001" you are off on measuring the dowel will cause a .00314 x call diameter/dowel diameter overlap or gap in your engraving. (All of this only applies to epilog style rotaries).

All good advice...

Joe Hillmann
03-08-2013, 3:08 PM
I don't want to discourage you but is it possible your customer would be willing to have it so the the checkering doesn't go all the way around? Maybe do four ovals with a 1/8" inch gap between them. That way where the pattern comes back together if you are a bit off it doesn't matter? The more I think about it the more difficult it becomes. Although I am assuming you are only doing one call. If the customer wants many of them done and you can ruin one or two in testing then I would suggest building a jig that fits over the 5/8 dowel that is close to the average diameter, or slightly larger, of the call.

Matt Dunn
03-08-2013, 3:47 PM
Well we use a dowel because I engrave hundreds of calls a day on the rotary and our inside diameter is 5/8". So you're saying I should use 0.625x3.14=1.9625 to get my height? I'd really like to do it all around like he is wanting, just for the fact the other company flat out said NO we won't do it, I'd at least wanna try before I try a different route. Yes, it is for 1 call only, but I have several of the same ones to use as setup parts.

Joe Hillmann
03-08-2013, 4:01 PM
Well we use a dowel because I engrave hundreds of calls a day on the rotary and our inside diameter is 5/8". So you're saying I should use 0.625x3.14=1.9625 to get my height? I'd really like to do it all around like he is wanting, just for the fact the other company flat out said NO we won't do it, I'd at least wanna try before I try a different route. Yes, it is for 1 call only, but I have several of the same ones to use as setup parts.


Assuming the dowel is actually .625 (did you measure it with a caliper?)then yes 1.9625 is the number you want to use when you send it to the laser.

Although first I would draw it out full using the call diameter x 3.14 What it looks like on screen is what it will look like on the call. Once you have what you want shrink the height down so it is 1.9625 but leave the width as is. On screen it will look very distorted. Send it to the laser using as many horizontal lines per inch as possible and probably 75% more power than you would normally use on a flat piece(the rotary will stretch it back out again so the power and lines per inch will also be stretched out over a larger area).

For the first run I would suggest using blue tape and a very low power to see how it comes together at the end. If it works take the tape off and run it again. If it doesn't work put new tape on and try it again. That way you are less likely to screw up the call.

Matt Dunn
03-08-2013, 4:20 PM
Well the dowel isn't exactly because it's wood and it isn't perfectly round and smooth, but I still used 1.925 anyway just to see how close it would come. It came fairly close and overlapped a little bit and an off angle. The way the barrel is shaped, the diamonds weren't too bad off in size from top to bottom. Should I have the rotary at it's lowest level to get it evenly lined up?

Chuck Stone
03-08-2013, 6:54 PM
Oh ya, the customer already has a logo on the call and I will somehow magically make this pattern so it won't engrave through the existing logo...

ah.. didn't know this part.
I'd walk away. (and I'm not one to back down from
a challenge like this)

Dee Gallo
03-08-2013, 8:56 PM
ah.. didn't know this part.
I'd walk away. (and I'm not one to back down from
a challenge like this)

Oh come on Chuck, that does not sound like you! hahaha! Why couldn't he just temporarily cover the logo with some heavy foil to block the design?

Chuck Stone
03-08-2013, 11:58 PM
Oh come on Chuck, that does not sound like you! hahaha! Why couldn't he just temporarily cover the logo with some heavy foil to block the design?

I'm not so worried about eating into the log as I am finding that the placement
isn't exact enough and leaves too much or not enough space to one side.
I'm positive the customer would want it replaced.. and it would turn out to be
something handmade by a 104 yr old craftsman sitting high atop a mountain and
it's #1 of 2 .. special edition .. and the other one is owned by the pope or something.
Rotary machines are notoriously finicky about placement. It would be easy to see
where to place your item if it were 3 feet in diameter. But you can't see .25 or .5 on
a pen tube or a duck call.. so it's almost impossible to get things in the right position.
Better to do everything in one shot.

I have to refuse any rotary work that is already marked in some way.
Brides often send me wine glasses that say "Bride" and "Groom" on
them. I tell them I'll use a new glass and I'll PUT the words on it. But
I just can't match up the positioning with any confidence.

Shane Tietz
03-09-2013, 8:09 AM
Ok my actually account finally got verified, I was having to use Matt Dunn's account yesterday. Sorry, but I'm not the walk away type, especially when I haven't even spent more than 2 hours on it, and in those 2 hours I almost have it dialed in. The reason I'm doing the job is because our biggest rival company shot him down without even attempting it, which is something I just don't think is right. I was thinking of forming a piece of foil to the logo, just gotta make sure it stays. I've got the basic pattern mocked up on tape, just have to dial it in exact, it's off my an extremely small amount which is probably due to the dowel not being an exact diameter.

Chuck Stone
03-09-2013, 8:48 AM
if you're going to attempt this, I'd suggest several dry runs with a dummy.
No need to cover the logo.. in fact, you'll want to be able to see it.
Not sure which rotary style you have, but you'll want to find some way
to mark wheels, points, discs .. whatever you have.. as accurately as you
can. Mark the base of the part, too. Clean all rubber parts well first.

I would do dry run while noting the starting position of the wheels or discs
as well as your part. Then I would do a second one. And a third. Then I would
restart your machine and do another dry run after not having touched anything.
The starting and engraving positions may (or may not) surprise you,
but they will give you info you need to do this successfully.
You'll keep fine tuning your positions till you're satisfied and then run it.

To be clear.. I would take on a challenge like this ONLY if the duck call were mine.
I know it can be done. I also think it isn't worth the risk,

Chad Fitzgerald
03-09-2013, 9:55 AM
Just an idea, and very rough design but. Could you create a "line" where the diamonds meet? i think that would help with consistancy. dont know if that would be ok with customer but and idea. either have it centered on the logo or on the backside opposite the logo? Kinda like the drawing, if that makes any sense.
256491

Shane Tietz
03-09-2013, 10:44 AM
Ill post a picture of it Monday when I get back to the shop so y'all can see what I have so far. The customer knows the risk involved, and he said take my time, if I can't do it let him know, but as close as it is now, it shouldn't be a problem.