Newbie needs some help before head explodes

[Louie Elbro]

Hello there even more questions ....
ok i set the laser at 80% and speed at 10mm , half the design has cut out and half has not .....
Im so close to nailing this , but dont know what i9m doing wrong
john

[Jeffrey Aley]

You probably know from your 3D printing experience that there are a million little things that can go wrong; lasers are similar in that regard.

Items to think about:
* Is the material you're cutting uniform in density? MDF usually is; plywood often is not. Since you're using MDF in this case, I'd assume there's no problem here.

* Is the laser beam focused on the material? Is it possible that the material is warped or of non-uniform thickness? Is the bed of the laser is not flat / planar with the laser head?

* Are the mirrors properly aligned? This is often the problem when the laser cuts at a particular part of the bed, but doesn't cut at a different part of the bed. The alignment has to be super-accurate. "Close enough" isn't.

* Is there a problem with the file? Have you set things up properly in RD Works (or LightBurn)?

* What's underneath the MDF you're trying to cut? Do you have a honeycomb bed, or a pin-bed, or is it just laying on a flat piece of sheet metal? When cutting through material, you want to have an air space below the material (and good air extraction to remove the smoke).

Best of luck!

-Jeff

[Pete Cyr]

1. Was the half that cut all the way through the first half of the path of travel of the laser head.
2. Can you cut through a piece of the same material now.

If yes to both question you have an overheating problem with the pwr supply or the tube.

[Louie Elbro]

Hello there , many thanks for the replies .
i have a honeycomb metal ' tray' underneath the MDF
In the simulation mode on RDworks , the fully cut through half was on the far left hand side -the laser starts top right ( sorry i know that sounds chinglish)
i put a spirit level on the bed and all four corners and middle appear to be level
I know theres no problem with the file as the gentleman who ran the business before me used to sell his designs , so i know they work , as for setting things up correctly in RD works , im going to assume i have (m i know assuming makes a ass out of you and me) , im really still learning -boy this learning curve is steep.
Im going to try cut this morning whilst its still reasonably cool , im thinking the extreme heat yesterday didnt help 120 degrees in the garage ( my workspace)

[Jeffrey Aley]

120 degrees in the garage? What specific model of chiller do you have? Some of these "chillers" are not chillers at all - they're just radiators (i.e. no compressor). If you do have an actual chiller, at what temperature is it set?

Experiment : try cutting just a portion of the design, but make sure it's a portion that is on the right side of the bed. This experiment will help to determine if it stops cutting because of the POSITION or if it's due to the TIME.

As far as the bed being level: it's nice that the bed is level with the planet Earth, but is the bed level relative to the X and Y axis? It's better to measure the gap between the nozzle and the bed at several different points to ensure it's consistent. I presume that when you checked for level, you checked also for flatness.

Don't worry - you'll find the culprit soon.

Best of luck,

-Jeff

[Louie Elbro]

Hi Jeff , thanks for the reply
Yes 120 degrees in the garage ! i have a CW-5000 industrial chiller its set at 25 degrees

As far as the bed being level: it's nice that the bed is level with the planet Earth, but is the bed level relative to the X and Y axis? It's better to measure the gap between the nozzle and the bed at several different points to ensure it's consistent. I presume that when you checked for level, you checked also for flatness.

LOL i appreciate your humour ! , however could you please explain how i would check for flatness .
please take pity on a mere newbie

This experiment will help to determine if it stops cutting because of the POSITION or if it's due to the TIME.
again please explain to me as if im a numpty (even though i am not)

I really do appreciate all the help and advice
John

[sebastien laforet]

LOL i appreciate your humour ! , however could you please explain how i would check for flatness .
please take pity on a mere newbie

you take a piece of whatever you want, for example a dice, a piece of scrap wood... you put it on a corner of the table, and you adjust the Z of you table so that the bottom of the nozzle is just touching the top of the piece.

you remove the piece by sliding it (not touching the Z!), move your laser head to another point of the table, and try and put the piece just under the nozzle.

it fits tightly? good. you can't put it? at this point your table is "too high". it fits largely and you have space between the piece and the nozzle : the table is too low.

try finding a pattern, for example the more you go to the right, the more the table is low.

once you have an idea of the "pattern" of incorrect levelness, you can try to adjust. either you unscrew/rescrew the table to its holder supports, or maybe you will have to add some piece of anything between the table and the honeycomb to add some millimeters where it lacks.

is some cases, the table is set on 4 screwballs axes, and a belt links everything --> you remove the belt, rotate the axes individually to adjust the level of each corner, then put the belt in place (trying not to botch your settings during the operation)

i have designed some (very crude) feet to adjust my honeycomb, that i 3D-printed, and it solved a lot of problems where i had incomplete cuts on some parts of the table.

https://www.tinkercad.com/things/fFwqXr134xM

[Jeffrey Aley]

Hi Jeff , thanks for the reply
Yes 120 degrees in the garage ! i have a CW-5000 industrial chiller its set at 25 degrees

As far as the bed being level: it's nice that the bed is level with the planet Earth, but is the bed level relative to the X and Y axis? It's better to measure the gap between the nozzle and the bed at several different points to ensure it's consistent. I presume that when you checked for level, you checked also for flatness.

LOL i appreciate your humour ! , however could you please explain how i would check for flatness .
please take pity on a mere newbie

This experiment will help to determine if it stops cutting because of the POSITION or if it's due to the TIME.
again please explain to me as if im a numpty (even though i am not)

Good - the CW-5000 is a true chiller. The lower-numbered CW's (CW-3000? I forget) are not. I presume that by 120 degrees in the garage, you mean 120 Farenheit. And by 25 degrees on the chiller, you mean 25 Celsius (25 Farenheit is WAY too cold).

Sebastien already described how to check the bed relative to the nozzle. The other thing in my comment was that I assume that when you put a spirit level on the bed, you noticed whether or not there were any high spots (the level rocked) or dips (there's a gap under the level).

Position vs Time: It is possible that you can't cut through at certain places on the bed (i.e. left rear quadrant). This would imply problems mechanically with that area (focus, mirror adjustment). On the other hand, perhaps the items at the left rear don't cut because they are always the last things in your test file. The laser is fine for the first X seconds, but after that, the power drops off. This implies a problem with thermals (tube heats up or power supply heats up).
How to test this hypothesis: change the order in which things are cut, relative to their location on the bed. Cut the left rear items FIRST instead of LAST. I think you mentioned your problem was the other way around (?), so in your case, cut the left-rear items LAST instead of FIRST.

[Louie Elbro]

Hello there , thankyou everyone so much for all your help ! I really am quite thankful .
And im sorry yet more questions , al;right so returned home from the first show got a few orders to fill and stock to replenish . So i fire up the cutter
and... i have no laser beam , i pressed the pulse button -nothing ...zip..nada . Does this mean the tube needs replacing ? is there a US supplier or must i go via China ? or am i doing something wrong ?
john