I am trying to explain how my old 40 watt 3040 ( just sold ) was able to cut so much quicker than my current spec 60 watt machines. For example 3mm laser ply that HPC say will cut at 30mm per sec on a 60 watt machine, does just that on my 60 watt machines. No problem there then. So why does my old 40 watt machine cut it perfectly at 50mm per sec ? This performance is consistent with acrylic, mdf and everything else.
The only difference I can spot is that the old machine has a 62mm focal length lens. If that really makes this much difference, is there one available for the 6090, and if so, why don't they fit them or where do I get one from ? Can there be any other explanation ?
Focal length and cutting performance
Re: Focal length and cutting performance
I found the same going from the 3020 to 3060 but not as much as 40w to 60w in the 3060. The power is lower over longer distance so you have to take that into account too 
This post from Dave (Spooky) may help -
As most people know when you place your material into the laser it needs to be set at the correct focal distance from the lasers final lens.
While we all know this is the case a few may not realise what the science is behind it.
What we first need to look at are the properties of the actual business end of your laser.
In the final section of the optical train there is a lens that reduces / focusses the beam down to a tiny spot, this tiny spot contains a great deal of power and energy, this is what cuts or engraves the material.
The lens itself will have a manufacturer stated "Focal Length", this "FL" is the distance from the rear face of the lens to it's best focussing point and is usually expressed in MM's. You may have seen lens's with figures of 50.8mm, 63.5mm, 75mm and above.For our purposes we will be looking at a focal length of 50mm as this is the standard fitted to just about all far eastern machines and indeed many western machines as well.
The next factor is the wavelength of the actual "light" produced by the laser, in the case of most home laser systems this is controlled by the excited CO2 tube giving a wavelength of 10 Microns or 0.01mm, physics prevents the beam being focussed to a smaller spot than the beams actual wavelength. So the absolute smallest "dot" you can get is 0.01mm irrespective of the actual lens set up.
Now we have an "Optimum Focal Length" of 50mm and a smallest possible focussed dot size of 0.01mm in a perfect world.
Sadly the world isn't perfect and manufacturing tolerances as well as machine design among other things mean the chances are our beam / lens isn't going to get anywhere near the wavelength of the laser being fired into it. Spherical Aberration, Dirt, Damage, etc will all increase the size of your final spot so in reality you're more likely to be looking at a final spot in the 0.3 to 0.5mm range.
Next we need to look at the "size" of the beam that is being supplied to or fired at that final lens. This can vary from tube to tube but most of the far eastern lasers work with a beam of around 6mm diameter (we won't get in to "beam expanders or power density right now).
When that beam strikes the final lens it does not taper straight to the point, it forms what is known as a "Gaussian Curve or Gaussian Bell" shape that can be seen in the picture below.The "bell" shape has two "sides" and as the beam passes the focal point it repeats the same curve but in a growing shape rather than a reducing shape.
For us to utilise the power of the beam our material should be placed as near as possible to this centre of the two curves (Noted below as "Center Of Field") and this will give us the focussed power we need.
Material placed too far from this optimum point will not have sufficient power directed at it to achieve any results past burning or scorching of the work.
Thankfully this "Center Of Field" position isn't as finite as you may think, in the past it was decided that measurement of the useful area of a laser beam should be a point between 1.4x the diameter of the spot in the positive direction and a point 1.4x diameter of the spot in the negative direction. The distance between these two points is called "Depth Of Field" of more commonly known as "DOF"
This magic number can be calculated using the following formula:
D = Diameter of input laser beam from tube.
F = Focal length of the lens we are using.
W = Wavelength of the laser tubes beam.
DOF = Useful depth of field for a given optical set up.
The equation goes as follows:
DOF = 2.5 x W x (F/D) squared.
This will tell you what useful depth you have for a given set up in a perfect world.
Kind Regards
Dave
This post from Dave (Spooky) may help -
As most people know when you place your material into the laser it needs to be set at the correct focal distance from the lasers final lens.
While we all know this is the case a few may not realise what the science is behind it.
What we first need to look at are the properties of the actual business end of your laser.
In the final section of the optical train there is a lens that reduces / focusses the beam down to a tiny spot, this tiny spot contains a great deal of power and energy, this is what cuts or engraves the material.
The lens itself will have a manufacturer stated "Focal Length", this "FL" is the distance from the rear face of the lens to it's best focussing point and is usually expressed in MM's. You may have seen lens's with figures of 50.8mm, 63.5mm, 75mm and above.For our purposes we will be looking at a focal length of 50mm as this is the standard fitted to just about all far eastern machines and indeed many western machines as well.
The next factor is the wavelength of the actual "light" produced by the laser, in the case of most home laser systems this is controlled by the excited CO2 tube giving a wavelength of 10 Microns or 0.01mm, physics prevents the beam being focussed to a smaller spot than the beams actual wavelength. So the absolute smallest "dot" you can get is 0.01mm irrespective of the actual lens set up.
Now we have an "Optimum Focal Length" of 50mm and a smallest possible focussed dot size of 0.01mm in a perfect world.
Sadly the world isn't perfect and manufacturing tolerances as well as machine design among other things mean the chances are our beam / lens isn't going to get anywhere near the wavelength of the laser being fired into it. Spherical Aberration, Dirt, Damage, etc will all increase the size of your final spot so in reality you're more likely to be looking at a final spot in the 0.3 to 0.5mm range.
Next we need to look at the "size" of the beam that is being supplied to or fired at that final lens. This can vary from tube to tube but most of the far eastern lasers work with a beam of around 6mm diameter (we won't get in to "beam expanders or power density right now).
When that beam strikes the final lens it does not taper straight to the point, it forms what is known as a "Gaussian Curve or Gaussian Bell" shape that can be seen in the picture below.The "bell" shape has two "sides" and as the beam passes the focal point it repeats the same curve but in a growing shape rather than a reducing shape.
For us to utilise the power of the beam our material should be placed as near as possible to this centre of the two curves (Noted below as "Center Of Field") and this will give us the focussed power we need.
Material placed too far from this optimum point will not have sufficient power directed at it to achieve any results past burning or scorching of the work.
Thankfully this "Center Of Field" position isn't as finite as you may think, in the past it was decided that measurement of the useful area of a laser beam should be a point between 1.4x the diameter of the spot in the positive direction and a point 1.4x diameter of the spot in the negative direction. The distance between these two points is called "Depth Of Field" of more commonly known as "DOF"
This magic number can be calculated using the following formula:
D = Diameter of input laser beam from tube.
F = Focal length of the lens we are using.
W = Wavelength of the laser tubes beam.
DOF = Useful depth of field for a given optical set up.
The equation goes as follows:
DOF = 2.5 x W x (F/D) squared.
This will tell you what useful depth you have for a given set up in a perfect world.
Kind Regards
Dave
Using two LS3060's and an ex 3020 user
Please note I am not employed by HPC, any advice or recomendations I give are based on my own experience and are not necessarily the same as HPC's. First point of contact on any hardware issues should be with HPC
Please note I am not employed by HPC, any advice or recomendations I give are based on my own experience and are not necessarily the same as HPC's. First point of contact on any hardware issues should be with HPC
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