In this week’s blog, we take a look at how to monitor the efficiency of your Lightblades mirrors, and demonstrate the importance of doing so.
We have mentioned in the past about the effect of dirt on the optics and the detriment to performance – but what does that actually look like and how much does it really affect the cutting or engraving output?
There is a big benefit to cleaning the mirrors – beyond the obvious, as it will actually help you to save money.
We have seen customers convinced that their tube is exhausted and needs to be replaced. Symptoms are typically increased power and reduced speed to cut the materials.
When an engineer has attended site, the optics are normally the first point of call for any checks. Often on inspection the optics are coated or damaged and a good clean or, in the worst case – a new set of mirrors, has restored the output power at the nozzle to within a few percent of new.
Mirrors are around £20 each, whereas a new tube can range from £200 – £1,500 depending on power.
So; its important to keep an eye on the cleanliness of your optics. Last week, we took a look at the basics of cleaning the lens, this week we look at the mirrors.
The mirrors on the Lightblade are made from Molybdenum, it’s a pretty resilient material and far harder wearing than the lens’. As such, we put Acetone in the Optics Cleaning kit supplied with your Lightblade – please do not use this to clean the lens….(that’s what the IPA is for).
How to clean your Mirrors.
The mirror cleaning process is summarised below, before we get started you will need the following from the optics cleaning kit:
- Cotton Buds
- Lens tissue/Lens wipes (do not use tissue/loo roll/swabs etc – these might scratch or leave dust and debris on the mirror)
Cleaning the Mirrors:
- Dip a cotton bud in the Acetone.
- Gently (but not to gently) rub the Acetone onto the mirror face in a circular motion.
- Repeat, if necessary.
- Important – Acetone will leave a residue on the mirror as it dries, make sure you polish the mirror with the Lens wipe as the final step.
- Beam alignment check.
Hey Presto! Nice, clean, residue free mirrors that should be efficient in transmitting the beam from the tube to the nozzle.
A beam alignment is worth doing, as cleaning the mirrors may shift them in the housings and alter the beam path.
What do we mean by Mirror efficiency?
Many people take mirrors to be 100% efficient – this is actually not the case, you will loose energy, dissipated as heat or scattered light, every time the beam hits a mirror.
The mirrors on the Lightblade are >98% efficient, its just physics – unless you are in possession of a perpetual motion machine, you will always loose energy somewhere in the process (if you do have a perpetual motion machine – please feel free to get in touch, I have some great ideas).
There are 3 mirrors in the beam path, if you lose 2% at every mirror, it can have quite an effect:
- Tube output: 100W
- Mirror 1 (98% efficient): 100 x 0.98 = 98W
- Mirror 2 (98% efficient): 98 x 0.98 = 96W
- Mirror 3 (98% efficient): 96 x 0.98 = 94W
- Lens (98% efficient): 96 x 0.98 = 92W
That’s a drop of 8W from the tube to the nozzle on clean, new optics alone. This is part of the reason that Thinklaser use over spec tubes in the Lightblade range.
For example; our 80W machines use a 90W tube, so we know we are getting 80W at the nozzle. We also check this output and match machine to tube during the PDI process, so when your machine arrives you can be confident your machine is delivering the specified output at the nozzle.
But, how can you check this for yourself?
Enter the Dohickey
Thinklaser engineers are in possession of a Coherant power meter – these cost around £650 each but are very accurate and quick to test the beam output. A more cost effective and similarly effective system is the Dohicky (or laser power meter) at around £90.
This device can quickly tell you how much power is output from the tube and how much power is being lost at the mirrors by completing some simple calculations.
The calculation is as follows:
(Finish temperature – Start temperature) x 2 = Power output in W
I will leave it to the master himself to demonstrate the use of his Dohicky the laser power meter and the correct mirror cleaning process.
The test files are available here: https://we.tl/t-Ez0PeQeW2r
And with that, we hand you over to our tame super user;
Some say, that if he were to hold a laser cutting contest, it would be top secret and held on his private island, and that his Lightblade is actually called Bolo…… all we know is that he is called Russ.
Both the laser cleaning kit and the Dohicky are available through Thinklaser, please get in touch for more details on 01737 826902 or email us on firstname.lastname@example.org.