Cutting Power

[Robert Edington]

Hello,
I'm new to lasers. I just got mine a week ago. I bought some 3mm ply to use. I am waiting on my mAmp meter to come in. I don't have a business. I just do this for fun with the grandkids. I've cut a few things, mainly those thunder laser plans. I do not go over 50% power for cutting.

Should I expect a clean cut at 50% at 25mms from my 50 watt chinese laser? I had to "pop" out half of the tiny pieces from one of the intricate boxes I made.

I plan to try one of the thuder laser toys next. It doesn't have as small pieces.

Should I consider two passes?

I might add, I put a piece of 3/4" plywood on my table. Then I put some small wooden sticks on top of the plywood and then the 3mm ply for cutting on top. The pattern of the box was engraved in the plywood, yet the pieces had to be "popped" out from the backside with a dental tool.

RP

[Tim Mellor]

After midnight here but I think last time I ran non Laser grade 3mm ply I think was running more like 13-14mm/sec at around 65% on my 40W.

Set up a basic 50x50mm (or 2"x2" if you must ) square. Keep the power at your 50% as it is more than safe and then run a series of tests coming down in speeds. I suspect you won't start getting a clean cut unti you are 16-18mm/s but that is a guess. If I am doing a new material or different thickness I run through a similar procedure and then write on the sample in Texta what worked.

Currently I have a box of cut and engraved bits with scribble on them but it really needs to be put on a database or be added into Lightburn when I fit the new board to my Laser. Even though it is not a proper system it works for me at this stage.

Rule one of improving stuff change only one variable at a time, inspect it tweak and test it again Most important of all is Record the results for later!

[sebastien laforet]

depending of your power supply, 50% means exactly nothing! the only real useful value is the mA than you read on the mAmp meter.

also, your laser is supposed te be 50W, so it is optimistic to fully cut at 25mm/s even at max power. instead of 2 passes, it is better to go slower and fully cut in one pass.

at 50%, you may already be "too much" and destroying your tube!

i strongly advise you to NOT use a plywood as your support material, look at all the horror stories of machines burned!!! use only non flammable material for your cutting table (steel or aluminium)!!!

[Gene Uselman]

I agree with Sebastien- my 130w would be overdriven at 50%.

[Robert Edington]

The label on my tube is covered up by the clamp. I'm not going to disturb the mount by opening the clamp. I'm afraid I'd mess up the alignment. When I get my mAmp meter, how can I determine the "working" amperage?
RP

[Robert Edington]

I have watched Russ's video about the dept of burn test on the thick acrylic. But I didn't know if you needed the tested wattage off the label on the tube, or if the test was adequate.

RP

[Jeffrey Aley]

I might add, I put a piece of 3/4" plywood on my table. Then I put some small wooden sticks on top of the plywood and then the 3mm ply for cutting on top. The pattern of the box was engraved in the plywood, yet the pieces had to be "popped" out from the backside with a dental tool.

RP

That's an interesting thing. Plywood can be frustrating to cut if it's not made for lasering. There could be internal voids or internal plugs or excess glue that causes the cut to not go through in certain areas. And of course you can't tell where those areas are until after your cut is done.

Perhaps that's why you're getting all the way through and marking the underlying plywood (as someone said - change to a non-flammable material!).

We make a big deal about "not overdriving the tube", probably because they're expensive. One way to tell if you're getting into that "overdriven" range is when you increase the % power but the cut depth does not improve. I think Russ has a video clearly showing % power vs depth of cut, and you can see where his tube saturates. You could reproduce that experiment for your laser and tube to guess your max power.

[Jeffrey Aley]

The label on my tube is covered up by the clamp. I'm not going to disturb the mount by opening the clamp. I'm afraid I'd mess up the alignment. When I get my mAmp meter, how can I determine the "working" amperage?
RP

Well, you could guess.

I'm serious - I'd bet that most "50W" tubes that are 1.0m long have very similar specs. So measure the length (and diameter) of the tube (with the power OFF, please), and compare it against new tubes you could buy on the internet.

For example, Lightobject sells a 45W (50W peak) SPT tube with the following specs:
Power: Rated 40W~45W (50W peak)
Triggering Voltage: 20KV
Operating Voltage: 15KV
Current: 18mA max. Recommended 16mA
Length: 1000mm/ 39.4"
Diameter: 50mm/ 2"
Water Cooling required
Water temperature: 20~25'C(68-77F)
Warranty: 6 months

They also sell a Tongli tube with the same Current specs.

[Willy Ivy]

I cut 3mm ply with my 60w at 20mm speed and 67% power (which is 20ma).
You really need to have the ma meter installed before you do too much more of anything other than engraving.
You are already doing more with your machine in a week than many of us did in several months. Is the gantry square with the rails? Are the mirrors properly aligned? Is the bed square to the laser head? The list goes on. The Chinese guy that built this machine does not care if all this is correct, only that he got paid to throw it all together. It is up to you to do the job that he did not do. All of this and more are important unless you just want to settle for what you have. It takes a lot of testing and a LOT of material to figure out exactly what your machine does. Any changes you make will alter the results and your testing will start over but at least you will have an understanding of how it is affected.
Please, please DO NOT use plywood as a pin bed. I do not think this can be stressed enough. Take it from some of us that have been there and done that. We have helped pave the way so that you guys with all this extra knowledge of this forum and youtube do not suffer some of the pains and countless hours we have shared to help you.
I will post this pic again just as a reminder. I think the topic was "Be Careful"