Keeping beam tight?

[Programmergeek]

I am a proud owner of a 3w blue burner does great with in 5' but then the dot gets about 2mm wide and 4mm high and it will not burn. How can I correct this is it just a poor lens? It has a focuser an it is focused. I know I have seen some people use magnifying glasses, I have not tired that. My other lasers seem to hold a better round beam but are lower wattage, this one kind of makes a rectangle.

 

[Speedy78]

Its a multimode diode. Short of using a FAC that s what you will get. What are you burning outside of 5 feet?

 

[Programmergeek]

I have a rope in a tree about 40' up I would love to melt off, much easer than climbing. Even if I have to do it one minute at a time and wait a min or two to cool. It is thin was holding something up but I don't want the kids to play on it and don't like the way it looks. I also may try some old fireworks that I prefer not to be near. It is more of a interest question as well.

 

[Leodahsan]

Its the divergence (read about it). Its dictated by the diode too, not by the lens alone.

Single mode diodes have better divergence.

edit:
You're better off throwing something at the rope than using a laser to cut it... :thinking:

 

[Shakenawake]

A 3W could easily ignite the rope before it's cut through, you don't want that to happen in a tree me thinks

 

[CDBEAM777]

See the " Tridentis " post under the 445 section. An " Optically Corrected" 445 LD is demonstrated. It is possible....but it is a demanding build.

CDBEAM=======>

 

[Pi R Squared]

I am a proud owner of a 3w blue burner does great with in 5' but then the dot gets about 2mm wide and 4mm high and it will not burn. How can I correct this is it just a poor lens? It has a focuser an it is focused. I know I have seen some people use magnifying glasses, I have not tired that. My other lasers seem to hold a better round beam but are lower wattage, this one kind of makes a rectangle.

This doesn't sound right. What kind of laser is this and what lens are you using? If its really 3w it should burn just fine at much more than 5 feet. Either its not focusing very well or your getting a power drop not much after the laser is turned on.

 

[ZRaffleticket]

You'd be so sadly surprised that its really not that effective past five feet.

 

[hwang21]

Really? :thinking: how can that be?

Especially if it's a focusable laser...

 

[cheech226]

I am a proud owner of a 3w blue burner does great with in 5' but then the dot gets about 2mm wide and 4mm high and it will not burn. How can I correct this is it just a poor lens? It has a focuser an it is focused. I know I have seen some people use magnifying glasses, I have not tired that. My other lasers seem to hold a better round beam but are lower wattage, this one kind of makes a rectangle.

The lens is the stock lens of the diode. Although it allows higher power one pays for this with increased divergence. A 3 element lens will give better beam specs but with less power output. At 40' you won't be burning anything with either lens unless you refocus with a magnifying lens close to the target.