laser cutting at an angle

[project41]

Hi i an new to the forum and am looking for a bit of help.
I has a HPC6030 laser cutter which i have just fitted a new tube into.
I have been cutting and engraving acrylic making sample with no problem, or at least thats what i thought.

on closer inspection the cut line that the laser produces is at an angle by a couple of degrees from the top to the bottom of the material making the bottom slightly wider.
I first thought that the mounting at the cutter head was at an angle and causing the problem but on further inspection i have noticed that the angle is the same all the way round the cut piece making the base slightly wider than the top.

This may seem like a minor issue but i am working on some fine scale moulds for a client using a hard etch to burn away the material and the same thing happens there making the mould worthless as the cut line needs to be vertical.

Can anyone point me in the right direction on what the cause might be.

To add some info to this, i am not running the laser tube at max power, i have checked the alignment as per the HPC videos and it seems to be good all across the cutting area, it is a new tube and car a water cooler unit from HPC so runs at between 18-20 degrees so is not getting hot.

As far as i know i am setting the focus up correctly with the distance block from the material to the top of the carriage but i am not sure, can someone clarify the correct focus procedure and distance for me as well.

This is the first major problem i have come across and i need to rectify it if i am going to make moulds.

basically as an exaggeration the laser seems to be cutting a v shape cut live from the top of the material to the bottom \, the bottom being wider if this makes sense.

i look forward to any reply and hope to contribute to this forum in the near future when i get a bit more experience.

Thanks

[Daven]

What thickness of material are you using?
This is normal for lasers and is to do with the depth of field - have a read of Spookies info here.

You could do a ramp test which Tweakie has explained which may help. You also may find turning the lens over gives you a deeper DOF, this is a bit subjective but it won't do any harm to try.

Other than that another lens with a longer depth of field is worth looking into.

Hope this helps

Best

Dave

[Spooky]

Nature of the beast sadly, you have a total straight line length equal to the depth of field in a laser beam.In the case of a 2 inch focal length this is about 1.8mm total.Outside of this the beam will converge / diverge making the cut tapered.

Acrylic is a little better as it works as a form of wave guide allowing thicker cuts to be straight. The non polarised beam also doesn't help. The only real way round it is by beam contouring (adding extra lens's) but the kind of kit that requires is expensive (more than an average machine costs)

best wishes

Dave

[project41]

Thanks Dave for that info and it explains a lot particularly with my photographic background.
The info you have guided me to is great. I am going to start with the focal length because the angle of the cut is around 15 degrees so looks like it could be set to the wrong focal length. The first thing i am thinking is that i am using the focal length block incorrectly.

do you know what the focal length should be for the old style LS3060 and where it is taken from, my machine looks like the current HPC Laser LS3040.

I am thinking that the problem is more likely to be user error than a technical problem with the machine.

I look forward to the reply and thanks for the information so far.

Gary

[Spooky]

Hiya Gary,

Focal length gauges are great and a fast way to get things close. Most lens's have a variation in focal length though so running the ramp test Dave linked above is the only way to get it dead on. From there a vernier or height gauge can be set for future use. A lens *can* be 1mm either way out from it's given focal length in some cases so even setting from the back of the actual lens isn't a sure fire way to be dead accurate.

I still keep meaning to get a digital scale fitted to mine but time constraints mean it hasn't been done yet.

best wishes

Dave

ps: A photographic background will help a lot with lasers.