engraving acrylic awards

[Abdul Baseer Hai]

Hi all
Need some pointers on engraving good quality clear acrylic awards. i have never done these before so any help would be appreciated e.g;
Should i mirror engrave?
Should i mask both sides?
I have a GCC 50 watt machine.
Any suggestions on settings?

and whatever other do's and don'ts i should know to get a good quality result
thanks
Abdul

[Joe Pelonio]

Those come in a variety of shapes. If you plan to do a bunch of them, trace the shape with a black sharpie, scan, and use to center the text.
Then when you go to engrave, some of the odd shaped ones are flat only on the base, so it may help to do it upside down so the flat part can be up against the 'x' rule, or even make a jig for the shape.

I think they look a lot better reverse engraved on the back side.

On my 45 watt I use 100% speed 50 pwr 400 dpi.

[Abdul Baseer Hai]

Hi Joe, Rodney and Mike (Miken)
Thank you all for the quick response.

The outline trace and scan is a wonderful idea. I have to do 24 items, oddly shaped, (diamond, star and slanted rectangle). They are expensive pieces and i cant afford to try a sample. It has to be right the first time. This customer will require these items every month so I have to put my best foot forward.
The outline trace, coupled with the centering option suggested by rodney sounds like a good mix if I want to do one item at a time.
For repetitive work, I may create the outline, repeat it in corel, vector it on coroplast board and walla!! i have a jig.

The supplier does not know whether the items are extruded or cast. I am assuming all of them would be cast, if not then do I have to paint fill? Any suggestions on this. I dont want a colored finish, just a frosy white.
Keep it coming folks.

Thanks again

Bachi

[Joe Pelonio]

They pretty much have to be cast. Cast means that molten plastic is either poured onto a sheet or into a mold. Extruded is soft plastic pulled into shape like taffy. I don't how they could do that with the award shapes.

[Mike Null]

Bachi:

If you're going to do these every month you should keep a months supply on hand just in case of problems. No color fill is necessary.

Following yours and Joe's idea. I used to take irregular items and lay them on a piece of aluminum to make the outline. Then I would use that as my jig every time.

[Rodne Gold]

Joe , A lot of em are made with sheet stock and not cast in a mould (Casting needs a long time in autoclaves under pressure and heat to "cure" , extruded doesnt and is thus a lot more expensive to produce in terms of time) and thus less than stellar acrylic is used. The problem with cast is that it is not possible to get very accurate thickness and tolerances are normally +- 10% so when thickness is critical , often extruded is used.

The fact it laser engraves frosty is no guarantee its cast , some extruded also does well in this regard (Like UHI etc) and often the pieces are intended to be sandblasted or screen printed where cast vs extruded makes no diff.
Even cast is prone to stress cracking , albeit not as badly as extruded. Any process that puts heat into acrylic like sawing , routering, flame polishing, diamond polishing and especially lasering will almost guarantee stress cracking when solvents are near or used on the item.
You can destress acrylic by leaving it in an oven at 70-80 degrees for 1 hour per mm of thickness.

[Mike Trenshaw]

Abdul -

Just a quick note that when we do something for the first time and we have no extras, we ALWAYS lay over 1/8" acrylic, run the job, then look for any conflicts like off center, too close to the edge etc. It is the cheapest insurance you can have for a $50.00 piece your cost.

We also do the trace and scan, but we turn around and use the trace to cut through cardboard material to use as a jig. Just do your layout within the trace, and then cut your cardboard. That way you know your art is where is should be in relation to the jig.

As far as the actual engraving goes, with our 30 watt ULS we run 100% pwr, 100% spd, but I run it twice. I've had problems in the past with scorching, so better to go slow. I also MUCH prefer engraving on the back side. The prismatic effect is awesome.

Hope this helps.

-Mike