First Rule

Number 1 rule of Laser is to always use

the least amount of power that you can

get away with

The more power you use the more

issues you are going to have

For example if you are engraving plastic

and you use to much power your

material warps and in some cases stains

Second Rule

Never believe what the manufacturers

says is the proper power and speed.

There are so many materials it is hard

for them to give you proper values

Everyone is different. What you like is

not necessary what they like

Too much power can destroy an

image

Dot Gain – Printing

It is defined as the increase in the diameter of a halftone dot during the prepress and printing processes. Total dot gain is the difference between the dot size on the film negative and the corresponding printed dot size. For example, a dot pattern that covers 30% of the image area on film, but covers 50% when printed, is said to show a total dot gain of 20%

Dot Gain Causes in Printing

Dot gain is caused by ink spreading around halftone dots. Several factors can contribute to the increase in halftone dot area. Different paper types have different ink absorption rates; uncoated papers can absorb more ink than coated ones, and thus can show more gain. As printing pressure can squeeze the ink out of its dot shape causing gain, ink viscosity is a contributing factor with coated papers; higher viscosity inks can resist the pressure better. Halftone dots can also be surrounded by a small circumference of ink, in an effect called "rimming". Each halftone dot has a microscopic relief, and ink will fall off the edge before being eliminated entirely by the fountain solution (in the case of offset printing).

Dot Gain on a Laser

All materials you laser will create a

certain amount of dot gain.

As the laser burns a spot size the laser

dot becomes bigger and bigger.

The more power you apply the wider the

dot

Dot Gain on a Laser

The wider the dot the more dots start to

run into each other

The more dots that run into each other

the more our material starts to look a big

“blob”

Black Granite – to much power

To Much Power 40 power 100

speed

100 Speed 30 power

100 power 20 speed

100 speed 12 power

Zoomed in on the final

image

Laser Dot on anodized

metal

Notice how round the spot is

this is because of the optics

that are created by the

collimator

Lasered Dot on Metal

Testing our material

When you are starting to use a different

material you should be trying to

establish an ideal power and speed.

Here is how I typically do it.

First of all draw a black square as

per figure 1 in CorelDraw.

Send the job to your laser with settings

that should give you a good burn. For

example if I was doing laser plastic and I

had a 35 watt machine I would use a

speed of 100 percent and a power of 40.

Figure 2 shows the settings in my driver.

Driver setup – notice I am 400

DPI

You can adjust your speed

You can adjust your power

With the job at the laser machine place your material in the bed and focus out for the material.

Next press the start button and let the machine start to engrave.

With the machine engraving press the “power” button now press the down arrow button on your machine. This will decrease the power of the machine. Keep watching the black square on your machine until the machine stops penetrating the top layer. Note: you could press the stop button and open the lid to check the engraving.

Once you have reached the point where you stop penetrating the top layer start increasing the power again via the up arrow on the machine.

Sample material engraved

I tend to increase the power maybe 3 percent past where you are engraving out the entire area. I like to increase the power a bit more because you will have a little lose of power across the whole bed of the laser. For a lot of lasers the top left hand corner represents not only the starting position of the laser but also the closest distance to the actual laser source. As you move away from the left hand corner you will typically experience a drop in power. Adding a few extra percentage points to your laser power will help in combating any power drops you may have.

Look at your machine and jot down the power (or speed) that you are left with. Next go back to your print driver and open it up. Select the arrow located beside the configuration tab as per figure 3 and select “Save as”.

Save the settings

You will be taken into an explorer dialogue box as per figure 4. I have a folder created called “Laser Settings”. It is good practice to make sure that you save all your settings in one directory so that they are easy to find. Note: If you want you can also save the power and speed savings with the CorelDraw job. Go to FILE | SAVE and open the “Options” tab as per figure 5. Located at the bottom you can place in notes about the job. You will notice that I have placed in a number of variables about the job.

Give the File a Name

Save the File in CorelDraw -

XP

Save the File in CorelDraw – Win

7

Another way of adjusting your

figuring out your power and speed

Load up the settings as per

your job

Here is the test file on Glass

using Thermark

Here is a test piece using

Thermark on ceramic tile

Color Mapping

The one important feature of a lot of laser drivers is the ability to color map.

For example color mapping allows us to run a certain color and assign a power and speed to that color. Thus when we run a job we can have objects that can be engraved at different power and speeds

This is important as we may need one power for certain (finer) objects and another power for those (coarse) objects

Controlling Engraving order

The other important feature of color mapping is that we can speed certain jobs such as columns that would be a lot slower if we did a full bed engrave.

We all know that engraving across the table is the fastest way however if there is a lot of white space in between objects than we can have a lot of time that is wasted moving to the next engraving object

It is better than to place each set of objects into a column as per the next slide

Things to remember when you

are lasering

Am I doing photographs

Do I have fine text

Do I have bold text

Do I have a combination of objects that are fine and bold

How fine does my power (speed) need to be

Do I need to color map

What material am I lasering on