Buying a CO2 laser cutter – how much power do you really need?

Laser cutters are usually defined by their working area in (mm or inches) and rated power (in watts). While picking working area is pretty straightforward (for most people), deciding on wattage is a different story. This is where variables like tube type, brand, materials and few others come into play. All this makes it hard for people who are just looking to get started with laser cutters to figure out how powerful machines they need to get.

A general rule of thumb is 10W per 1 mm of acrylic for cutting. For most people who are looking for a multi-use laser cutter recommended power for CO2 laser with a glass tube is 80W because it’s considered a sweet spot for both cutting and engraving.

Now, there are obviously ways to cut thicker materials with less powerful lasers (slowing down speed, multiple passes etc.), this rule is just to get a general idea about what you will need. To figure out exactly how many watts is needed for your specific case, there are a couple of questions you need to ask yourself first.

Application – engraving or cutting

Depending on the whether you are looking to use your machine predominantly for cutting or engraving the power requirements will vary.
When it comes to cutting its quite simple: higher is better. More power will allow you to cut through thicker materials in a single pass while also allowing you to increase speed on thinner ones and reduce working time required to complete the job.
But when it comes to engraving it’s a different story.
Laser tubes of different wattage have different firing thresholds – a minimum power at which a proper laser beam is formed. For example, a 40W tube will fire at 3% power while 80W tube will fire at 9%. You can compensate this by increasing speed but only to a certain point.  Also, wider tubes will produce wider beams which will result in a bigger dot size which will have an effect on the resolution of your engraved pictures. All this means that on higher powered tubes you can sometimes struggle to get low enough power and small spot size to get that fine detail engraving.
So if high quality engraving is something you are looking to produce, then look for the lower rated (power wise) machines.

Tube type – DC or RF

While we are on the topic of spot size and engraving quality it’s also worth mentioning that the type of laser tube will also have an effect on engraving. There are 2 types of tubes used in CO2 lasers:

  • DC(direct current) glass tubes and
  • RF(radio frequency alternating current) metal/ceramic tubes
RF Tube
RF tube
DC tube

They operate differently. Glass tubes provide a constant (or slow pulsing) beam while RF tubes pulse the beam at a high frequency, which is why you can see rough edges on clear acrylic cut with RF tube powered laser cutters. Compared to glass tubes, RF tubes produce much smaller sized dots. This can help with cutting, because the same amount of power is focused in the smaller point so RF tube might be able to cut thicker material compared to glass tube of the same wattage.
Smaller dots size also means you can get higher resolution when trying to engrave photos for example. RF tubes have faster switching time (time to react to power changes) meaning that you can engrave at higher speed that with CO2 tubes. The downside to RF tubes is the price. For the price of one 40W RF tube you can get five 100W glass tubes. Plus, the RF tubes are usually fitted in expensive brand name machines like Epilog and Trotec so the initial cost for getting an RF tube laser is quite high.

Tube manufacturer – reputable or unknown brand

Depending on who produced the specific laser tube in your machine you might get mixed results, especially if you buy cheaper Chinese made laser cutters. To save costs they buy tubes from low brand (cheep) glass tube manufacturer. These tubes are usually advertised by their peak output power which is always higher than their actual working power. This means that you will buy an 80W rated machine with a tube that can actually produce up to 60-65W of power. Easy way to find out approximate power of your tube is to measure its physical size and compare it with the table below. If you want to find out exactly how many watts your laser tube is outputting you will need to invest in a power meter (calorimeter).

Power (W)40506080100130
Length (mm)85010001200160014501650
Diameter (mm)505060608080
CO2 laser tube power vs speed table

RF tubes don’t have this problem but are (as already pointed out) significantly more expensive. EFR and (especially) RECI are some of the most reputable brands, but be careful with RECI since there are lots of copies or fake RECI tubes. Original RECI tubes have scannable QR  code and a serial number you can use to check if your tube is actually made by RECI.

Budget

Last (or maybe it should have been first) thing to consider is your budget. Higher wattage laser tubes costs more, but (as mentioned before) that’s only about 10% of what RF tubes of the same wattage costs. But that’s not all. CO2 tubes of higher wattage are physically bigger (see table above) and are usually built into machines with larger working area. So, for example, an 80W tube will come in a housing that provides working area of 500×700 mm, while 40W tubes are built into lasers with 300×400 mm working area (if its and actual 40w tube, not an  200×300 mm 30W K40). As you can probably imagine, bigger working area = more materials used = more expensive machine. And it’s not linear. For example, Laser cutter equipped with 80W tube can cost 3 to 5 times more than a 40W laser cutter.

Conclusion

Choosing appropriate power for you laser cutter is important and can save you some money (in the short or long run). Hopefully now you have a better idea of what to look for when you pick your laser cutter.