powercoated flasks, MY settings

[Kev Williams]

I'm one to advise 'less is more' quite often when lasering--

I just ran off a big 30oz 'SIC' yucky green flask, it turned out nice (as usual) and thought I'd share some pics and settings...

First, unless the coating is thin or isn't actually powdercoat, I ALWAYS run powdercoated flasks in 2 passes, I've found, with my machines, trying to get them done in one pass just doesn't work. As to 'less is more', this is a pic where I stopped halfway thru the 2nd pass. Note that the first pass almost reached bare metal, but didn't...
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Closeup, shows the 2nd pass cleaned it off perfectly. And there's no sticky left behind. However, that's partly a function of this color, some colors aren't so friendly ;)
And note the engraved edge, shows the thickness of the coating, this is pretty typical, not thin at all, but not too thick either...
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This is a 'size reference' pic, this is a big cup, and that's quite a bit of real estate engraved...
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My settings, although hard to read, so I'll translate :)
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Speed: 38% (of 80ips) - Power: 100% (30 watts)
DPI res: 380 (which is this machine's "400")
and most important, the clock: 1:58, which is per pass, so both passes took less than 4 minutes total for a fair amount of engraving. Not bad!

I've found that higher DPI is counterproductive, as is slowing the machine down, to attempt one pass runs, what I get is more initial coating removed, but with a lot of goo left behind, more than can be wiped off with DA or acetone. And that goo is harder to remove by laser than the base coating. My theory is, my light 'just enough' passes are causing the coating to better vaporize, for whatever reason. More power seems to overheat it...? Depending on the cups and coatings, I'll vary my speeds between 38 and 30%, and DPI between 380 and 300. I never go slower than 30%, or go into 500 or 600 DPI territory. And I get very good results with only 30 watts, definitely fits the "less" part :D

[Doug Fisher]

Thanks for sharing, Kev!

You don't use any air assist, correct?

[Kev Williams]

hardly ever use air assist, especially during raster engraving. Usually the only time I use air is in the Triumph when cutting stuff or engraving bamboo cutting boards or leather. It's not for 'assisting' the laser, I use air simply for moving smoke away from the lens and stopping flareups. My air 'nozzle' is just the end of a piece of 1/8" tube, and it's about 2" above the work, about even with the edge of the lens (I don't use a cone either)... using the diaphragm pump that came with the machine, it blows a lot of air but at low pressure.

[Trey Tull]

I run two passes, at a lower power, on ever cup I do. I think it looks better and is easier not having to deal with that goo that one pass leaves. Thanks for sharing!

[Chris Costello]

I agree. I definitely get a better "burn" result running two passes, my problem is that my second pass never lines up exactly with my first. It's close, but not close enough.
I'm using an Epilog mini 24 with the rotary attachment that came with it. I'm burning Polar Camel mugs that I get from JDS. Any suggestions for getting the second pass to line up perfectly?

[Doug Fisher]

If that is the four wheel type of rotary like I remember, have you filled small ziplock bags with sand that you put inside the tumbler to weight it down? Have you changed the speed of the machine so that does not spin the tumbler very fast when moving between sections of graphics and when it homes back to the origin? Those moves are often when the item is most likely to slip on the wheels/rollers.

[Chris Costello]

Doug, thanks for your reply. I have not tried the sandbags, as this rotary has a spring loaded wheel clip that holds down the inside lip of the tumbler, but I will still try that when I run my next tumbler job.
I would really like to know how to slow down the travel speed over the non-lasered sections of the graphic though. I don't see any options for this in the advanced section of the print driver.
Does anyone know if this is possible running an epilog driver using corel? If so, how?

[Doug Fisher]

Mine isn't an Epilog, so I can't help. Give Epilog a call. Fast customer support is one of the reasons they charged you $$ for that machine. :)

[Chris Costello]

Thanks Doug,
I did call Epilog. Unfortunately the travel speeds are not changeable. I did add some weight to tumbler, and it seems a little better. Still not spot on though. I would much rather burn away in two passes, versus one pass and then wipe/scrub with acetone, so I'm going to keep playing with it. Might try to burn the tiniest reference mark to use to re-orient before the second pass. If I have success I will post what I've done.

[Doug Fisher]

Ok, I was hoping for you sake that the Epilog had a default speed like on Ruida controlled machines. For those with Ruida controllers who are reading this and might not know, you can go to the control panel on the laser and program that speed OR you can set the speed in the list of rotary options within the RDWorks software settings.

[Glen Monaghan]

Thanks Doug,
Might try to burn the tiniest reference mark to use to re-orient before the second pass.
Maybe you could stick a bit of masking tape on as a marker rather than burning a spot in the PC. For precision, you could set up a laser pointer in a fixed position so that the pointer beam hits a specific spot on a manufacturer's mark or product logo on the cup (or just use a piece of tape as already mentioned), and then make sure the beam is back on that reference spot again before the second pass. Of course, if the reference spot is at top along the lasering line when you "home" the rotary, you could just use the built-in red dot pointer to verify, but a separate laser pointer would allow lots of flexibility in selecting the reference location and position relative to home.

[Kev Williams]

I found a pic of an Epy driver online, I notice it has the option of engraving top-down or bottom-up---does yours have this option?

If YES, then try this: first, force the image or text you're engraving against the top of the page/working area. If you get an 'output doesn't fit on media' or similar error, lower the layout .005", that should fix that problem...

Now you're ready for pass one, which you want to engrave bottom up. This way, the abrupt movement of the rotary will occur before any engraving takes place. And when it's done, the rotary will be 'home', and shouldn't make any further movements, at all...

Now engrave pass two, TOP-DOWN...

The net result should be, no rotary movement at the end of pass one, and no movement at the beginning of pass two, should equal a very close if not perfect alignment of the 2 passes :)

If you DON'T have a bottom-up option........ never mind ;)

[Makrel Johnson]

@Kev
Do you experience any inaccuracy when you do 2 passes? My Epilog rotary has proven to be accurate - as long as it's one pass. 2 and it's a gamble. I do check my math for the diameter and it still seems to not be repeatable.
I suspect the (for example, HydroFlask) rocks slightly sometimes during the rotation. I've considered using a rubber band of sorts to hold the piece down, sort of tying it to the assembly but the rollers are below the plane of the support bar...

[Gary Hair]

You will likely never get a hotdog roller to be accurate enough for two passes, the only way to be certain is a chuck style rotary. My Trotec rotary could do 100's of passes and not skip a beat, never going to happen with a roller.


@Kev
Do you experience any inaccuracy when you do 2 passes? My Epilog rotary has proven to be accurate - as long as it's one pass. 2 and it's a gamble. I do check my math for the diameter and it still seems to not be repeatable.
I suspect the (for example, HydroFlask) rocks slightly sometimes during the rotation. I've considered using a rubber band of sorts to hold the piece down, sort of tying it to the assembly but the rollers are below the plane of the support bar...

[Wilbur Harris]

You will likely never get a hotdog roller to be accurate enough for two passes, the only way to be certain is a chuck style rotary. My Trotec rotary could do 100's of passes and not skip a beat, never going to happen with a roller.

This is an absolute fact!! If you have a hot dog roller and you can't do it in a single pass...then you can't do it.

[Kev Williams]

concur with the above. I don't have a hot dog rotary, but I DO have a hot dog COOKER rotary, which I use(d) to keep Cermark mixed up (wore it out) -- as slow as it actually turned the bottles, the Cermark does stay mixed up. But the bottles wander all over the place :) --for repeatable engraving, the workpiece needs to be anchored to the drive...