Jagged edge on acrylic

[david forte]

Hi all,
I have a Hugo made by hurricane lasers. (Chinese). Uses a reci tube.
I cut 1/4" acrylic on a regular basis and have always gotten nice smooth cuts. The jobs I do run for about 25 minutes. I use 5 speed and 87 power in Lasercut 5.3. I am getting very jagged edges now on the cuts. When I do a small test cut (2-5 min job). The cuts are smooth. When I do a large 25min job they are jagged. It seems as though the cuts at beginning of job are decent and then gets worse as time progresses.
Any ideas what could be causing this? My gut thinks the tube is going out? I went ahead and order a new tube and should get it in a week or so.
Thanks for any help!
Dave

[Michael Henriksen]

What kind of cooling do you have on the tube? Perhaps it is due to temperature increase? I find that power drops once you go much above 20C.

[david forte]

What kind of cooling do you have on the tube? Perhaps it is due to temperature increase? I find that power drops once you go much above 20C.

I have the Cw5200.

[Doug Fisher]

>>I use 5 speed and 87 power in Lasercut 5.3.<<

Have you ever tested "87 power" to make sure it is not over driving your tube and killing it? What is the mA reading at 87 power?

[david forte]

87 means power is 87%. I don't know off hand what the ma reading is, but I know it doesn't max out on the scale or anything. I've always made sure never to go past 90% in an effort to preserve the laser.
I am going to try a couple of engraving jobs tonight to see how those come out.

[Doug Fisher]

FWIW, with many Chinese lasers, setting power over 65-70% over-drives the tube past the manufacturer's recommended level and thus prematurely kills the tube. You can go on to the RECI site to get the mA specifications for your tube.

[david forte]

So your saying that the tube is bad/going bad?

[Michael Henriksen]

Have you checked the temp stays constant throughout the job?

[Doug Fisher]

I am pointing out that tube failure could be a possibility at this point if you have been over-driving it. I can't say for sure since so many variables are involved. More important, since you have bought a new tube I wanted to give you the precaution so you take the steps to make sure you minimize the chance of damage by over-driving it.

[Jerome Stanek]

FWIW, with many Chinese lasers, setting power over 65-70% over-drives the tube past the manufacturer's recommended level and thus prematurely kills the tube. You can go on to the RECI site to get the mA specifications for your tube.

My Chinese laser does not over power at 90% but that is the limit I keep it at 85% or less

[Kev Williams]

for reference--

My 80w Reci hit's a solid 28mA at 70% power as entered, that's as far as I'll take it when cutting. 65% usually, which is typically 26mA...

And those figures go down as the water temp goes up--

If you are overdriving the tube, it may be pulsing after running for several minutes

Best way to troubleshoot would be run a job (practice job if necessary) at 70% power and a bit slower and see if the jagged edge stops--

[Joseph Shawa]

Check the temp of your cone after you do the long jobs. If your beam is hitting the side of the cone it can heat up and warp and get worse as it heats.

[david forte]

Thanks everyone for the input. Last night I verified that the mA is not the issue. I even umber it down to speed of 3 and 50 power.
When it is cutting I am noticing what appears to be the laser pulsing sometimes when it shouldnt be, so hopefully changing the tube will fix it. The current tube is about 5 years s old.
I'll let you know if it's better after replacing.

[AL Ursich]

Any chance of a loose bearing on the rails?

[Clark Pace]

I normally dont go beyond 80 percent power

[Ray Scott]

It can be difficult to diagnose problems with a laser machine... Since the problems are occurring due to time in usage. It is a fact that the sealed glass laser tube will change performance efficiency as the laser tubes changes temperature.

1) what is your cooling system?

2) what is the water temperature at 5 minutes of usage?

3) what is the water temperature at 15 minutes of usage?

4) what is the temperature of the Laser Power Supply during these projects?

5) is the laser machine powered by 110VAC or 220VAC?


What is the condition of the lens and mirrors? I have experienced that glass dust and some oxidative on the mirrors can heat up and change the reflective properties of the mirror surface.

Can you please clarify the term "jagged edges". I think that most of us are assuming you mean the edge of the material that resembles the edge of a USA quarter. This is commonly called the "coin effect".
I have also seen the stepper motor heat up and the drive transistors not correctly do the micro-stepping. The result is that we don't get a diagonal line... We would see what looks like stair steps.


I hope that that my experience is of help to readers.

Thank You,

[John Noell]

Thanks Ray. Very helpful.

[david forte]

I replaced the tube and after struggling with realigning the mirrors, it appears to be cutting properly. So much so that I need to redetermine all my power settings since it seems to be engraving and cutting deeper now. I guess my old tube had lost quite a bit of power.
Thank you to everyone for the help and advice!