What tolerance can you hold? and what can 40W laser cut?

[SRT Mike]

Specifically for cutting 1/16" (0.062") acrylic (tinted).

Can one of the small 40W chinese lasers cut this material?

Could a 40W chinese laser cut 1/8" (0.125") acrylic?


And what tolerances can you expect to be able to repeatably get? I am putting together a metal housing that will have a drop-in acrylic lens. It would be preferable of the lens were 0.062" thick meterial.

I need to figure out the tolerances so I will know if I have to adjust my housing. And I am curious about the cutting capability of a Chinese 40W laser because I was thinking of buying one to try it out

[SkipW]

Originally Posted by SRT Mike Specifically for cutting 1/16" (0.062") acrylic (tinted). Can one of the small 40W chinese lasers cut this material? Could a 40W chinese laser cut 1/8" (0.125") acrylic? And what tolerances can you expect to be able to repeatably get? I am putting together a metal housing that will have a drop-in acrylic lens. It would be preferable of the lens were 0.062" thick meterial. I need to figure out the tolerances so I will know if I have to adjust my housing. And I am curious about the cutting capability of a Chinese 40W laser because I was thinking of buying one to try it out

Hi Mike,

I know a 40w will cut 1/16" acrylic without any problem. It would probably cut 1/8" also.

As far as accuracy and repeatability, I think that depends on the machine and the manufacturer. You would have to check the specs if they are available, or try to find someone who has the same machine you are looking at.

One thing with mine (and most all Chinese lasers I think), the laser cuts right on the vector line so if you wanted to cut out say a 3.000" circle it would come out around .010 smaller. You just have to allow for that in the vector drawing, like making the circle size 3.010 to start with.

Sorry I can't be of more help.

Skip

[SRT Mike]

Originally Posted by SkipW Hi Mike, I know a 40w will cut 1/16" acrylic without any problem. It would probably cut 1/8" also. As far as accuracy and repeatability, I think that depends on the machine and the manufacturer. You would have to check the specs if they are available, or try to find someone who has the same machine you are looking at. One thing with mine (and most all Chinese lasers I think), the laser cuts right on the vector line so if you wanted to cut out say a 3.000" circle it would come out around .010 smaller. You just have to allow for that in the vector drawing, like making the circle size 3.010 to start with. Sorry I can't be of more help. Skip

Thanks for the info Skip.

I know the manufacturers specify a positioning accuracy of usually 0.01mm which is very tight, but I was curious - lets say you cut a 3.010" circle so that you end up with a 3.000" circle. Let's say you measure one and it's dead on 3.000". Then lets say you cut 100 of them... of course there will be some slight variance, but I wonder if it's thousandths of an inch or tens of thousandths?

If the machine can hold 5 or even 10 thousandths, then it would be fine for our application. I need to cut a window for a display - about 3" long and 1.5" high out of 1/16" acrylic. I'm machining the housing so I just don't want one to be really loose and the next one too big to fit, etc

Do you know how close 2 lines can be together before the piece between them melts? For example, lets say you are cutting out a letter "A". You leave a little tab of plastic so that the center of the "A" doesn't fall out. Of course you want that tab to be as small as possible so it doesn't show. How narrow can that tab be before it would be un-cuttable? Could it be 1/32" wide in 1/16" thick acrylic? Or thicker? Thinner?

Part of the cutting I need to do is for a keypad for an electronics device... so there will be cut-outs for buttons and logos and stuff. I don't want to put any of the cuts too close to one another and have the laser guy say "oh I can't cut this" and then have to go back and redesign the part

[DaveDoesIT]

Originally Posted by SRT Mike Let's say you measure one and it's dead on 3.000". Then lets say you cut 100 of them... of course there will be some slight variance, but I wonder if it's thousandths of an inch or tens of thousandths?

Hi Mike,

First off I do not have a Chinese laser I have a 25W US made one and yesterday I was cutting a lot of 1/8" acrylic and wondered the same thing about repeatability while standing waiting for the sheet to be cut. Coincidently I was cutting 3", but square. Round cuts would be much more dependent on the following paragraph content.

There are several variables that will affect the repeatability. First will be the alignment and construction quality of the mechanical parts as in how much free play is in the system. The next thing would be stepper motor resolution and if you had encoders or some form of positioning feed back to the system. Encoders can be used optionally on stepper motors, but they are mandatory for servo motors.

Steppers are instructed to go so many steps and then the system assumes they are there. Encoders tell the system when they have reached a spot so they are moved until that point is reached. I doubt the Chinese lasers are using encoders unless they are also using servo motors which are faster but more complex to build.

OK, back to the 3" squares. I didn't bother making the vector path oversize I just needed them all the same size when cut. So I got a slightly off-square rectangle, probably Corel caused that. I had 2.991" x 2.986" Individual length variation over 50 squares measuring all 4 sides was 0.003" and mostly down as in 2.991" became 2.988" etc.

I had to do two passes to cut through each one, hope that helps.

Dave

[SRT Mike]

Originally Posted by DaveDoesIT Hi Mike, First off I do not have a Chinese laser I have a 25W US made one and yesterday I was cutting a lot of 1/8" acrylic and wondered the same thing about repeatability while standing waiting for the sheet to be cut. Coincidently I was cutting 3", but square. Round cuts would be much more dependent on the following paragraph content. There are several variables that will affect the repeatability. First will be the alignment and construction quality of the mechanical parts as in how much free play is in the system. The next thing would be stepper motor resolution and if you had encoders or some form of positioning feed back to the system. Encoders can be used optionally on stepper motors, but they are mandatory for servo motors. Steppers are instructed to go so many steps and then the system assumes they are there. Encoders tell the system when they have reached a spot so they are moved until that point is reached. I doubt the Chinese lasers are using encoders unless they are also using servo motors which are faster but more complex to build. OK, back to the 3" squares. I didn't bother making the vector path oversize I just needed them all the same size when cut. So I got a slightly off-square rectangle, probably Corel caused that. I had 2.991" x 2.986" Individual length variation over 50 squares measuring all 4 sides was 0.003" and mostly down as in 2.991" became 2.988" etc. I had to do two passes to cut through each one, hope that helps. Dave

Great info Dave, thanks much. That is exactly what I was after.

I am going to outsource production of the parts, I think... I just figured a cheap $1,500 chinese laser may be a neat tool to have for rapid prototypes (since we already do the machining in house).

Dave, since you are obviously an experienced laser guy, do you have any idea how thin a piece of acrylic you can leave after a cut? I mean like I mentioned in the above post about leaving a tab so that the center of a letter doesn't fall out.

[DaveDoesIT]

Originally Posted by SRT Mike do you have any idea how thin a piece of acrylic you can leave after a cut? I mean like I mentioned in the above post about leaving a tab so that the center of a letter doesn't fall out.

Hi Mike,

I am a former Mechanical Engineer so this stuff is like breathing to me. I have no idea how small a link could be, pretty much anything you wanted. Since I need 2 passes to cut 1/8" the link could be half thickness too. The dot size of my laser is 0.006" so I could pretty much leave anything you wanted. The important thing would be how clean is the break when you did pull it apart if that is what you want.

PM me and I will give you an email address if you wanted to attach a DXF to cut a sample. Don't use the email address for this group as I never check it. Not even sure I remember the password now.

Dave

[LaserImage]

I have a 30 watt GCC/LaserPro machine and cut up to 1/4" all day long, in one pass. I have cut 1/2" as well, but the settings were full power and .1% speed.

I don't know why the other poster had to run two passes on 1/8", something must be wrong with his laser.

The repeatability on my laser is within a thou or two at the most - it does use servos for x and y and a stepper for z.

Gary

[DaveDoesIT]

Originally Posted by LaserImage I don't know why the other poster had to run two passes on 1/8", something must be wrong with his laser.

Hi Gary,

Well probably a couple of reasons, my Synrad 25 Watt tube was made in 1992 and still working fine so maybe it is not putting out a full 25W.

The slowest speed I can get is 1% and not .1% so my cut speed is 10-times faster than yours and at two passes to cut, that makes it 5-times faster.

I am guessing there is nothing wrong with my laser. What's wrong with yours? I just hit the "repeat" button on the front panel and off it goes for the second pass, so maybe just 4-times faster.

Dave

[LaserImage]

Originally Posted by DaveDoesIT Hi Gary, Well probably a couple of reasons, my Synrad 25 Watt tube was made in 1992 and still working fine so maybe it is not putting out a full 25W. The slowest speed I can get is 1% and not .1% so my cut speed is 10-times faster than yours and at two passes to cut, that makes it 5-times faster. I am guessing there is nothing wrong with my laser. What's wrong with yours? I just hit the "repeat" button on the front panel and off it goes for the second pass, so maybe just 4-times faster. Dave

Well, a 16 year old tube that is working is indeed a miracle! You are probably putting out 10-15 watts, based on your cutting speed. I can cut 1/8" at 100% power and 15% speed in one pass, and that's with 30 watts! It would be worth looking into a replacement tube, you'd be amazed at how fast things will go with more power!

Gary

[DaveDoesIT]

Originally Posted by LaserImage Well, a 16 year old tube that is working is indeed a miracle!

Hi Gary,

I am retired and this is a machine I resurrected from dead. I only got it because they thought the laser was also dead. When I got the laser working I called the friend that gave it to me asking if he wanted it back but he (his company) had already bought a new machine so I lucked out.
It is an old ex production bare frame that did all it's work in the middle 3" square of the table so the rest of it is great shape.

Since all it cost was a few hundred hours of my time and some dedicated electronics I had to design and build, I doubt I will be replacing the laser when it really dies. I have no idea how many Watts it is putting out but will make a cut using real figures and see how that compares to yours. The slowest speed I can do is 1cm/second.

I just use it now to make a few extra bucks to my income.

Dave

[fogassa]

Hi Mike,
I've a 40w chinese laser and I can cut up 5/16" in one pass but speed is darn slow.
0.1" acrylic at full power and 15"/min.
0.125 Acrylic full power at 11"/min.
If you want a usefull laser for bussines get 100w+.

Fogassa