Hi everyone
Firstly totally new to the forum and have had a good look around before posting and all I can say is I have a lot to learn but looks like I am in the right place.
Now for my “current” issue, I have a K40 and I am trying unsuccessfully to cut though some small pieces of oak about 5mm thick but just does not seem to be working for me.
I have the speed around 15 - 30 and no matter how many passes I do it just does not cut through… I gave up at about 30 passes
Is what I am trying to do just not possible or is there something I am doing wrong?
Have you added air assist to your K40? Any other modifications?
I have added an air assist fan but that is the only thing I have added
What cutting power are you using, and how are you measuring it?
Cutting power I have tried between 60% - 80%, my K40 does not have the digital readout but has a know that I have marked 0% and 100% and then just guess the rest
Do you have an analog ammeter?
Yes though I did not know what it was called - i think this is usually hitting between 10 - 15 mA
How old is the tube?
Only about 4 months but run only 30 times
How are you cooling your laser tube?
Water pump using distilled water
Have you noticed any loss in cutting power in other jobs?
I have not tried cutting before trying to do this oak, was going to try it on ply tomorrow to see how that goes
What speed were you cutting at?
i have tried between 15 - 30
The machines are very sensitive to focal height, if your bed isn’t in quite the right place it will never be fine enough to cut the full 5mm. I saw a recommendation elsewhere to prop one end up slightly and cut a straight line right across, see if a particular height is working.
It’s a simple method. Lay material on the bed with one end propped up so that it is sitting at an angle to the cutting head. Like a ramp.
Etch a line(s) down the length of the material.
Look for the thinnest portion of the line.
This is the correct focal length. That is, the distance from the head that the object must be set to.
Measure the distance from the head to this point on the incline (ramp).
Make a gauge that is this length so that you can easily set the objects height from the head.
I’ve cut 6mm oak before and, based on your initial post, the thing that jumps out is the speed. For single pass cutting your speed will need to be around 5mm/s.
Also it is important that the bed height is set so that the focus point is halfway into the workpiece because of the beam divergence around the focal point.
I would not go above 60% on the power for any significant cutting time without a current meter to verify you aren’t exceeding 18ma on the tube. To preserve tube life it’s recommended to max at 16ma. When I still had the digital control on mine 55% gave me 16ma.
You said you are cooling with a bucket and distilled water. Are you adding frozen water bottles to cool the water?
To preserve tube life it’s recommended to keep the tube under 23C while running. Lower is better but usually we recommend around 18C at the low end due to condensation issues.
Thanks Ned - so ideally temp of the water is between 18C - 23C? It’s not a huge window but I will order a temp gauge today and do my best… i might have to add in bottles of hot water
You can go lower but you have to be careful of getting too much condensation on your tube. How low you can go before you get condensation will depend on your local dew point).
Of course you don’t want the water to freeze or it will crack the tube. If your machine will be exposed to freezing temps then would want to keep the pumping running continuous with an aquarium water heater in the bucket.
I use a couple of frozen 1/2L water bottles to chill my bucket. These will last me anywhere from 30-60 mins depending on how much cutting I’m doing. I actually have a stash of about 12 bottles in my freezer.
I have one on my laser tube but that just monitors the tube’s outer temp. That is not sufficient to protect the tube.
I have my main water temp sensor in the bucket. I would think that if the sensor is literally attached to the water tube vs the actual water stream that there would be a delay and error as to what the actual water temp is.
You can get 18B20s in stainless cans. I imagine one could use a T in the tubing and silicon to have the tip of the 18B20 just touching the water going through. They respond pretty fast. But I don’t know if the stainless is isolated from the 18B20 and if so to what voltage rating; I’d hate to kill a mainboard that way.