I would suggest you do a test run on some material scraps to find the precise focus point of your laser and then insert the focus point 2mm into your 4mm acrylic. This is important because then you can cut properly through the material and to keep the cut as straight as possible. By experimenting, you will find a power / speed combination that best suits your machine. Unfortunately, you can not just take over some finished values from other K40 users, there are no two lasers that are identical. But you can use, for example, my values to start from. Once I have found the right values that are reproducible, I make a test item and hang it on my test wall. It’s nice to just be able to see what it looked like and you can also keep an eye on your laser tube and find out when the tube is about to retire.
Picture no.2 is my updated version of my test subjects, with mA