Engraving on Rubber for Stamps HELP!

[wendy]

We have the 6840 and love it - we really, really want to introduce rubber stamps to our range - we are having real problems lasering the rubber with very uneven results - one line the cut will be good, the next line very shallow and not clean - any advise would be appreciated, anyone successfully lasering rubber?...and urgently because we have the opportunity of a large order...that we really, really want to be able to do.

[Spooky]

Hi Wendy,

What speeds and feeds are you using?

What type of rubber?

What power tube has the machine got fitted in it?

Whats the water temperature like? (water Vs ambient temp)?

Sorry for the direct questions but most of the above can make quite a difference :@)

best wishes

Dave

[wendy]

Hi Speedy - here is as much information as I can think of -
Lamp size 60W
Feed - sorry please could you explain what this is?
Speeds - have used 400 @ 80% down to 120 @ 100% and all combinations in between. 120 @100% repeated twice and still not getting clarity and also get a very poor background cutout....that is in bi-directional. Also have tried 85 speed 100 power 1 direction - reasonable result but left all sorts of high curved lines...it appears as though it is not missing one line but very random misses.
Rubber - we are using SLR 100 2.3mm.
We have a big problem making a cut deeper than 0.5mm - have tried various combinations of speed and power also have used grade engrave - this gives slightly more depth, but more of a blurred image. Also as an aside 1/2 way through engraving the section in the middle of the engraving area rises, probably heat build up. The residue does not get blown away only the very fine stuff and only sometimes larger chunks of the rubber. When cutting the rubber have used a speed of 16 x power 100 twice and this does not cut through fully. Just so that you are aware...on mdf or wood we get fantastic results.
Room temperature 20º - no heating just normal room temperature - we will purchase a thermometer this morning for the water container - it feels slightly warmer than tap water when it comes out of the tap (if that helps in the interim). Thank you for coming in on this one and any other information you need please just ask.

[Daven]

I would be inclined to drop the power to around 60% and speed 80mm/s and then go up in power increments of 5% until you are happy with the depth. Go for a scan gap (DPI) of around 0.05080. As Dave said the water temp can help a lot, if you can keep it in the range of 14-20 degrees that will help (a chiller is worth thinking about if you are running the machine for long periods).

I found engraving rubber meant cleaning the optics and extractor a lot more often so may be worth checking if you havn't done so already. The dust that comes off is most likely causing your problems as it is blocking the power from the beam so slow and gentle may be a solution, better air assist will also help I would imagine.

Best

Dave

[Spooky]

Hi Wendy,

Sorry, a legacy from my days as an engineer (feeds applies to machine tools) it means the same as speed

Heat is the problem, too much power like Dave says, I'd drop to probably 60% or less (start at 40) 60% of 60 watts is quite a lot.

Daves already mentioned the rest of it, air assist, clean lens's etc

Use grade engrave all the time for rubber stamps, that's what it's designed for, it provides a tapered depth so fine details don't snap off.

give that a go and see what happens

best wishes

Dave

[wendy]

Hi - now have water temperature it is 20...same as the room temperature. Hope that helps.

[wendy]

whoops - had not read your replies when I gave temperature....testing now....thanks for your great input will let you know how it goes.

[wendy]

Hi - we have worked through your suggestions and are now getting a cleaner cut but still not the depth - definitely think we need to upgrade the blower, any suggestions?

[Spooky]

Hiya Wendy,

A more powerful blower may makes things worse not better, it's about clearing the cut away and the additional airflow *may* just blow more of the crud back down on to the surface.

It can help if you reverse the cut action from front to back rather than back to front, pretty easy to do but means changing the machine settings.

As they stand the machines extract from the back with any stuff that is burned away being dragged back over the completed work, by reversing the cut it always drags over the material that has not been cut. (I had to do it on some markers I made)

Air pressure is the "God" of woodcutting but not always a great help on plastics.

Leave it with me for a couple of hours and I'll see what I can do on mine with some laser rubber.

best wishes

Dave

[wendy]

Hi Dave & Speedy - for your information - we have tried 60% at 80 and then up in 5% increases - 75% gives a better result but still does not have depth and there are still the random lines (not horizontal - they angle and arc) - the cut away is still very messy looking, (like rhino skin). We kept the water temperature at approx 14º (putting ice in the water). Also for information at a speed of 14 @ 80% it still does not cut through the rubber to cut out the stamp shape. We already run the machine front to back - from front of table (nearest to me) working to the back of the table - this is how it came set up...and the debris appears to be being blown towards me and away from the next line of work. Hope this helps with your experiments...which are deeply appreciated. Thanks Wendy