Nova Plus Ramp Test and setting Autofocus Height for best engraving results

Preface: This article will cover the steps to perform a ramp test to be able to set the autofocus height and the length of the manual focus tool. For this procedure, it is assumed that you are already connected to the machine and ready to run. This article was written with screenshots from Lightburn 2.0.5, if you are using a different version then your screens may look different.

Tools and Materials that you will need:

1.5mm Allen Wrench

Manual Focus Tool

Lightburn installed and configured to connect

Consistent Material (MDF as an example)

Before you begin:

Let's start at your computer that is connected to your Nova Plus and take a backup of your Machine Settings.

In Lightburn, goto Laser Tools>Machine Settings  (will be under Edit>Machine settings if you are on older versions of Lightburn)

Then use the "Save to File " button to save a copy in your desired location ( save the file with _Original attached to the name).   Do not close out the machine settings window, it will be used in the first step of the process of doing the ramp test.

A Bit more info on settings that can be backed up with Lightburn:

Backing Up Machine and LightBurn Settings

The Process:

Follow these steps in order. Each step assumes that the previous step was completed.

Step 1: Reset the Focal Length

In Lightburn Machine settings....

Scroll down until you find the value for "Focal Distance". Take note of your current value, write it down. Set the value to 0.00mm and then use the "Write" button to send the change to the controller.

Scroll down until you find the value for "Home Offset (mm)" under the Z axis settings (Down in the Vendor settings section). Take note of your current value, write it down. Set the value to 3.00mm and then use the "Write" button to send the change to the controller. Click the OK button to close out the Machine Settings window.

Step 2: Enable Z Moves in Lightburn

We need to enable Z moves so that the honeycomb table position can be changed on the fly for the ramp test.

In Lightburn, select the icon that is a Wrench and Screwdriver, highlighted below.

The Device Settings Prompt will open up and you will need to set the following to Green under the Z Control section

-Enable Z Axis

-Relative Z moves only

-Optimize Z moves

Step 3: Do a Coarse Ramp Test

 Lets go back to the laser machine. and perform Autofocus to the surface of your test aterial, the lens will be a little closer now that the Focus Distance is set to 0.00mm in the machine settings.

Here is how:

First, jog your laser head using the Laser control screen buttons so that the red dot pointer is over the top of your material.

Like so:

Set the Origin:

Then select the Auto Focus option from the Menu

The machine will raise the material to the Auto Focus position with a 3.00mm offset which for a Nova Plus that will leave jus a small space between the material and laser head tip.

Then, back at your computer, set Lightburn to "User Origin" with the "Top Left radio button" selected as the  assigned relative location.

Open the Focus Test Tool in Lightburn from the Laser Tools menu

Configure the test as shown below for the Start and EndZ and steps. You may need your own settings for Speed, Max Power and Min power.

Preview the test:

Frame the Focus Test Job from the Focus Tool Prompt in Lightburn and verify that the Frame is on your material. If you are not over your material either jog the head and set a new origin or move the material to the work area. Be sure to stay away from the edges of your honeycomb try to work in the center of the bed for this test.

Start the Focus Tool job using the Start button in the Lightburn Focus Tool Prompt:

Before you start the job, be prepared to watch the Z Honeycomb bed move and understand that it is normal If the laser looks like it may crash, be ready on the Estop button. 

Observe the results. The Finest line value will be used for the next step for the Fine Ramp Test.

In this example, the 3.8 and 4.0 reading look similar and the best, we will use 3.9 as the median value for the next test.

Step 4: Do a Fine Ramp Test

Using 3.9mm for this example as the median value, the test was set up as shown below, with a target range of 3.4mm to 4.4mm and 20 steps still.

Preview:

Note that LB does not show the .05mm between steps, looks like the same number repeats but it should be 3.5mm then 3.55mm then 3.6mm and so on.

Before you run this Focal Test, be sure to set your new origin (or move the material) and frame the job to verify it is on the material and not overlapping the previous test.

Run the job as before and observe the results:

In this case, 3.9mm looks to be the most crisp and will be used as the Focal Distance for the 2.5" lens on this machine.

Step 5: Set the new Focal Distance

In Lightburn, goto Edit>Machine Settings and scroll down to find the Focal Distance setting which should be at 0.00mm. Type in the new value, in this case 3.9mm, and use the "Write" button to send them to the laser machine. Do not close out the "Machine Settings" screen just yet.

Step 6: Backup New Machine Settings

Press the "Read" button and then the "Save to File" Button to save a copy to your computer (add something to the end of the file to differentiate it from the previously saved Original)

Step 7: Disable Z moves

In Lightburn, select the icon that is a Wrench and Screwdriver, highlighted below.

The Device Settings Prompt will open up and you will need to set the following to Red under the Z Control section

-Enable Z Axis

-Optimize Z moves

-Relative Z Moves Only

Step 8: Set the manual focus tool

Place the material under the laser head and Auto Focus the Laser head. Place the manual Focus Tool on the Laser head as shown to check the distance:

As you can see, this manual focus tool is way off.

If you need to adjust, remove the focus tool from the head and use the 1.5mm Allen wrench to loosen the set screw on the Manual Focus Tool Shaft.

Reinstall the Manual Focus Tool and let the shaft rest on the material and then tighten the set screw to lock the shaft in place

 

Machine Setting for Focal Distance Vs Home Offset:

If you run into the case where Focal Distance would need to be negative, you can adjust the value of Home Offset down and carry that adjustment over to the Focal Distance. The two settings work in conjunction to give the total distance away from the Laser Head Tip. If you remove distance from one, add it to the other and then make your final correction so that Focal Distance is a value greater than or equal to 0.

A picture may better help explain. In this example, the values were 5.0mm for Home Offset and 1.7mm for focal distance for a total of 6.7mm. The values could be split to 3mm for home offset and 3.7 mm for Focal distance. Then, when a ramp test is completed, the new focal distance can be set.

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