Strange Trotec Problem - Help!

[Glen Monaghan]

Well, they feel the same thickness to my mark 1 fingers and both are supposed to be 3mm. While the new stuff measures more like .117" than the old stuff's .118", that's not enough to explain the differences. I'm going to try the burn test on a scrap of the old stuff because I think it may have been some sort of extruded rather than the cast it was supposed to be.

[Dan Hintz]

I'm going to try the burn test on a scrap of the old stuff because I think it may have been some sort of extruded rather than the cast it was supposed to be.

That's the likely answer, I just wanted to cover all bases (and measuring is a simple, non-destructive test).

[Jiten Patel]

Hi All,

Back up and running. Nice shiny new tube. Old one war putting out 67 watts after 7 months of moderate use....not good. New tube is putting out 86.

Thanks to all for the replies regarding mirror acrylic. I am cutting it from the back and it is only 3mm. No matter what settings I try, I can never get the pieces to fall out. Maybe this is to do with the intricate patterns. I occasionally get this with cast too, but they fall out much easier (still need weaning which is not ideal). The ideal situation is I lift the piece off the bed and ta-da, everything has already fallen out.

Paul, thank you for your suggestion, unfortunately, we do not have another compressor as the lasers are the only heavy machinery we run.

[David Somers]

I am curious. Is there a way to visually tell the difference between cast and extruded acrylic?

Dave

[Paul Phillips]

David, this might answer your questions, short answer is no, not visually but there are tests you can do.
http://www.sawmillcreek.org/showthre...truded-acrylic

Jit, it might be something to look into in the future, you should be able to put together a small compressor system for a few hundred dollars and it will allow you some more flexibility in your cutting.

[Glen Monaghan]

Jit, something I did to help with removing small, intricate shapes being cut from a finished piece is to add additional cross cuts so that the cutouts are smaller and generally convex. For example, if you were cutting out an hour-glass shape from your finished piece, the hour glass would tend to get hung up in the opening and be relatively difficult to clear out. So, add a small cross cut at each end of the hour-glass shape's middle stem, creating a separate "bulb" shape on each end and the short, straight, center piece. The little extra time required for the additional cuts is much less than would it would take to worry out the entire hour glass shape; those three smaller pieces will come out a lot easier and faster than the entire hour glass shape. Also, when a cutout does try to weld itself back to the finished piece, those extra cuts make it easier to pop the cutout bits free without so much risk of breaking the finished design.

[Mike Null]

Dave

There are a couple of ways. As somebody else mentioned cast acrylic engraves to a frosty white while the extruded engraving is almost clear just showing the laser mark. Extruded is unsuitable for engraving in my opinion.

All the cast acrylic I've purchased has a paper protective cover front and back while extruded has always had a plastic covering.

[Donna Hawk]

We usually used 10 for our correction value on our Trotec Speedy 500 when cutting. We were never able to get a suitable answer for significant 'overshoot' on raster engravings - slowing it down helped, but there was always an overshoot that made the finished engraving look 'fuzzy'. I'm curious - do you notice 'faceting' on curves when you use Job Control? it was great for a lot of applications, but curves were always a series of straight lines (however small) rather than a true curve. Anything that had to have a good curve got cut in iCut.

Hi Guys,

I've spent about a half-hour session with Trotec's excellent UK support and the problem is now 'fixed' - well, there is a solution (!)
They don't know why it has started but have had this issue reported by a few others.

Relatively quick fix:
Upgrade to new firmware 10.10 necessary.

As already noted by some of you guys, the laser as it slows or accelerates adjusts power to compensate.
In Material Settings - each setting has a drop-down at the end of the line. I've looked in here but not touched. See attached picture

The Correction value needs to be tweaked. Apparently, earlier versions of the firmware recognised values in here for cutting but not engraving.

It represents a minimum value that the laser power drops to and is a percentage of the laser power.

Recommended settings around 10%-25% - need to be played around with for EACH MATERIAL (which is a bit of a pain to have to go through everything)
As I found that cutting was also affected when I was cutting stencils over the weekend, I guess I may have to tweak all those too!

The idea is to set power & speed normally. Then adjust this correction value to bring the faded edges in to the same engraving depth as the centre (if that makes sense)

I have briefly tried it and at 30% the edges are definitely more deeply engraved that the middle now.. so it works!

Many thanks to all who gave advice.

Kind Regards
Tony





Attachment 280279

[Michael Reilly]

Yes, I knew it was correction, but if that version of the software wasn't going to listen to the setting, it wouldn't have mattered.

Correction is essentially a power minimum. When the head slows down to prepare to change direction, it has to taper off the power to maintain the same depth. But if it tapers in a linear fashion, some materials (anodized for instance) require a minimum amount of power before they mark at all, so they will experience problems. This setting is basically a threshold. What I never could really figure out is whether the value is an absolute minimum (20=20% power) or whether it was a percentage it can vary (20 = 0.20x100% power = 80% power minimum). I mostly just left it at 20.

What Donna is mentioning is something else that was a much bigger problem for us, but it doesn't sound like what you're seeing.

Michael

[Kev Williams]

I am curious. Is there a way to visually tell the difference between cast and extruded acrylic?

Dave

Maybe not so much visually, but- Extruded acrylic is MUCH softer than cast. If you smack a piece of cast with a screwdriver handle, it will have a hard, 'solid', resonant sound. Smack a piece of extruded and it goes "thud".

The other way to test is, you can indent extruded acrylic with a screwdriver tip (for example), cast acrylic will chip or crack, but you can't put a dent in it (unless it's very warm or hot)...

>disclaimer< -- Lexan can act like either, it's harder than extruded but it can be dented. Best giveaway to lexan is it has a blue tint. (usually)

[David Somers]

Thanks Paul, Mike and Kev! I will tuck that info away for later use.

Dave