Reverse Engraving - double sided tape before or after

[Ian Wilson (AUST)]

Hi Creekers,

I'm quoting on 200 off 90 x 60mm Approx (4" x 2"") Reversed engraved, colour filled signs for school interior. Job specifies Double sided tape on back.

Just tried engraving the back of a Black Rowmark 1.8mm Reverse with backing tape....took 4 -5 passes with my Epilog 35 watt and once I colour filled you could see black residue/ dust in the white fill. 100 pw 60 sp.

Should I use a sheet with out the double sided tape and tape after colour filled? My fear is this may be very time consuming.

Is the Colour Cast Acrylics any easier to use? Ie Less dust residue?

As always, your help is appreciated.

Kind regards,

Ian.

[Richard Rumancik]

I think you are on the wrong track by trying to laser through the tape. You really want to laser on the clear material and apply the tape afterward. Especially if it is taking that many passes - it won't make you any money.

When you reverse engrave it is not uncommon to get some contamination in the letters and it may take some experimenting to get the settings and air assist such that it lasers to your satisfaction. Sometimes lasering bottom to top may help to reduce particles getting embedded into the clear rastering. But you are not the only one who has had this problem.

Once you get that part working you need to develop the color fill procedure. If it is a single color that might be really simple (flood fill and wipe excess). Or you may find that you can just paint the entire reverse surface. Otherwise it may mean selective masking for each color.

Does the customer require the tape to extend 100% over the back? If not, you might just be able to buy PSA in rolls, cut to appropriate length and apply manually. Yes, it would take some time. If you need it to cover 100% then you would need to have oversize tape and then trim with an Xacto knife. Maybe someone has developed a procedure to use the laser to trim the tape but that would take some "R&D" (fiddling) to get it to work. If the tape sticks out at all it will look bad and collect dust.

I suppose another option would be to raster the text on the reverse, but not cut out the shapes. Then color fill the whole sheet and apply tape. Finally, cut the tags apart (from front or back, whatever leaves the best edge.) But of course you would need to use some registration marks/tooling holes to get your sheet back into the laser in the correct position, so that the outline is registered properly to the text.

[Scott Shepherd]

ColorCast is not easier to use and it might not work for your application. The problem is that the acrylic is cast acrylic, so when you engrave it, it frosts. When you color fill something that is frosted, you don't always get the color you hoped for when looking at it from the front.

I've done a lot of reverse engraving over the years and it's one of the more difficult things in engraving to get dialed in and repeatable, in my opinion. It's notorious for banding and the techniques to minimize that take some effort to work through.

I agree with Richard, I would never ever engrave through tape or adhesive on reverse engravable plastic.

[Mike Null]

I agree with Steve and Richard. When you color fill cast acrylic from the back it will appear to be muted. You can try to engrave out of focus to clear it up but that doesn't always work.

[Richard Rumancik]

Even the Rowmark reverse-engravable material does not transmit the color really well - I find that as the rastering leaves a rather rough surface in the text it seems to diffuse the light. In any even you can't get vibrant colors with reverse engravable in my experience. So anything that frosts will be worse.

If you are using only white fill, the problem is not that bad as white will probably come through okay. With colors you need to pay close attention to settings and focus to get the smoothest rastering possible so the color transmits through.

[Martin Boekers]

JDS and other sell marbled acrylic sheets, when you get these they come with a double-sided "tape" sheet.
This sheet is bright white on one side and adhesive on the back. You adhere the white side to the side of
the acrylic that you engraved, the other side of the sheet/tape has a release liner that protects the adhesive.
The purpose of this is the white makes the engraving more "brilliant" per say. You can see what I mean by setting
your engraved piece over a dark background, then try it over a white one.

Not sure if JDS sell these seperate or not. Someone here may know where to get the sheets alone.

[Mike Null]

You may have better luck getting a true fill color by using extruded acrylic.

[Ross Moshinsky]

Front engrave whatever you want. Color fill. Stick a piece of acrylic on top. Use fancy hardware to make it look right. Reverse engraving and color filling is over-rated. Looks good when photographed and viewed from afar but when you get up close and actually try to read the sign, it leaves a lot to be desired.

I'd look into vinyl, printing, sublimation, or silk screening if my method above doesn't work. Using a boarder or something along those lines can mask the use of adhesive on a translucent or transparent medium.

[Scott Shepherd]

Not much beats taking clear extruded acrylic, painted the back, then engraving through the paint and filling. That's about the best, clearest option I've ever managed to do. Plus it's easy and cheap.

[Mike Null]

Front engraving will permit truer colors but by no means does it look better and in this case it wouldn't meet spec.

[John Noell]

Not much beats taking clear extruded acrylic, painted the back, then engraving through the paint and filling. That's about the best, clearest option I've ever managed to do. Plus it's easy and cheap.Even if it takes three passes for three colors the labor is not too bad and the result looks pretty sharp. The final layer of black on the back hides what you use to mount it.240964

[Ian Wilson (AUST)]

Thank you all...looks like I have some experimenting to do.......one more question. With the clear acrylic option, if I spray the back, then engrave the back and colour fill...wont the engraved area be frosty? Also do I have concerns about the adhesive sticking to the paint on the back?

Many Thanks...Ian

[Scott Shepherd]

Thank you all...looks like I have some experimenting to do.......one more question. With the clear acrylic option, if I spray the back, then engrave the back and colour fill...wont the engraved area be frosty? Also do I have concerns about the adhesive sticking to the paint on the back?

Many Thanks...Ian

Ian, if you use extruded acrylic, not cast acrylic, the engraving will be clear. If you use cast acrylic, the engraving will be frosty. You don't want to blast through the paint and cut deep into the acrylic, you just want to cut through the paint and expose the clear again. No, the tape will stick to the paint just fine. I've been doing that for quite some time (years) and I've never once had a single failure and I see my old signs all the time, they are still there, still holding up just fine.