Laser issue

[Dalton Calford]

Hi Everyone,

I solved my last issue with the laser not firing due to code - it was a door sensor and my own lack of knowledge as to what will and will not shut down the laser.

My current issue is a new one.

The laser will not fire, even when pressing the test button on the power supply.

The power supply is on.

Everything appears correct, but, I am getting arcing to the frame.

This did not occur last weekend when I was working on it.

It was firing fine and I was able to setup the mirrors, but today, it made a cracking sound when it was set to fire (from code or test button).

I immediately powered down and performed a visual inspection.

I started isolating the laser and performing tests - giving it its own power plug vs running through the circuit board, disconnecting the control wire from the circuit board etc.

Each step I heard a crackle when pressing the test button.

Finally I opened up the whole back end to see what was going on and that is when I discovered the arcing.

This is very strange as it was working fine.

Does anyone one know why the tube would arc from the red (back) end?

The distance to the frame is about 2".

Would this be a power supply or tube issue?

[Steve Baker]

There should be a big cylindrical chunk of acrylic that covers the end of
the laser tube where the red high-voltage wire attaches. If that's
missing, the crazy-high voltages can throw a spark for several inches.

At the other end of the wire, it should be permanently fixed to the power
supply - so there shouldn't be any arcing at that end. The only other
possibility is if you have a small nick in the wire itself.

-- Steve

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-- Steve

[Jondale Stratton]

What Steve said.  The only time I've seen arcing is when the wire on the output side came loose from running to a ground.

It's also possible if the tube is damaged enough as well.

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[Dalton Calford]

Like I said in my first email, laser was working, now it does not.   No mechanical/physical changes made to the system.

After contacting a few people with lasers the basic response was

Tubes dead, and shortly to follow will be your power supply if you allow it to arc like that.

That arc is 22,000 volts, if the loop is across your heart on way to ground it will kill you.
Most laser tubes when they eventually die act this way.

The feedback has to do with CO2 - Laser tubes do not store well and they have a maximum life even if they are just sitting there.

I noted that Coletech does not recommend storing laser tubes and purchasing them as need as they will loose CO2 containment over time.

So, time for a new tube.   Coletech projects mid July for delivery.

Does anyone have a direct link to the exact tube we use in the saur?   I am learning as I go on this and I lost my original link from when I purchased and now I am seeing different tubes with the same rating for different prices and I don't want to make a mistake in the purchase.

best regards

Dalton

 

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[Steve Baker]

Well, certainly you can't let it arc. That's bad for just about everything.

For the quick shots you were doing with the button on the power supply,
you might not have noticed it...but for sure that has to be fixed before
you can move on.

1) It'll trash any electronics it hits - or any electronics
connected to any wire that gets in the way.
2) It's easily able to kill you.

A VERY important thing to know is that even after you physically
disconnect the 110v supply from the power supply, it retains enough charge
to produce a decent arc and kill you - so be sure to wait a long time
after disconnecting it - or ground the output - BEFORE you start working
on it!

I doubt that the arcing caused the tube to die - but it could have wrecked
something else in it's path.

Tubes last for years - I have one that's 3 years old that's working just
fine...I don't buy it that yours *JUST* failed if it was firing using the

button on the power supply.

When the CO2 starts to leak out or gets contaminated, the power output of
the laser slowly drops - but it doesn't abruptly stop working - so I don't
buy the "It's an old tube" argument if it was firing OK just a few days
ago.

Much more likely is that the power supply got damaged - the older style
ones that most of us have are easily damaged - but can often be fixed with
a couple of tricks. However, we have very little information about the
newer kind with the LCD display...we don't know how robust they are - or
how to fix them when they break.

A good rule for "repair-by-replacement" is to replace the cheapest part
first - and that's the power supply. So don't replace the tube until
you're 100% sure the power supply isn't at fault.

If you *really* need a new tube (and I very much doubt it) - then I
generally just search for "100w RECI laser" or "120w RECI laser" on
EBay...most of the chinese and US suppliers advertise there.

The prices do vary considerably - but so do the shipping costs - when you
add together the price plus shipping - they are all within a few tens of
dollars of each other on price!

You should be paying around $1000 (maybe as little as $900 - maybe as much
as $1200 depending on...whatever). Sometimes you find a US supplier who
can get them to you faster.

The tubes are described variously as 100 watt and 120 watt - but that
seems to depend only on whether they are talking about peak power or
sustainable power. We're only interested in sustainable...which is likely
to be 100w even on a "120w" tube! Higher power tubes are out there too -
but they don't fit inside the lasersaurs' case.

But honestly - I'd replace the power supply first...and if it were me, I'd
try to get one of the older ones that don't have the LCD display...we just
have a TON more experience with them as a group. The newer ones *MAY* be
better quality - but we don't know. Certainly the extra features of the
newer type seem to be more trouble than they're worth. The lasersaur
electronics already handle every fault condition that the new power supply
handles...so why complicate things?

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[Dalton Calford]

Hi Steve,

I would have noticed the arcing from my earlier tests - I noticed it immediately when it began.

I do not believe the arcing killed the tube, but the death of the tube started the arcing - the response I have had on different cnc laser forums has been quite consistent - the arcing on that end of the tube is caused by a lack of CO2 inside the tube itself.    My problem is that I underestimate the work involved and overestimated my free time to work on the system - the tube is about two years old, but only fired for a day.

It is not the age that causes issues, nor the use.  From what has been described to me, it is storage.    If I had the tube in operation all that time, it may still be in good working order.     My using the laser for a day and then not touching it for two weeks to start again, may have just been enough to push a borderline unit past it's breaking point (speculation on my part).   I did try a separate power supply as I ordered one a few months back in anticipation of a power supply failure (this I learned from the forums).    I bought the original non-lcd power supply as I did not know if it would work properly with the version of saur I purchased.   I am very cautious in this as I am learning each step of the way and I would prefer to ask vs assume.

The electronics all work fine, I can run the machine without the laser and it operates correctly.   I wanted to buy new sensors and circuit board as I had purchased them all pre-assembled, but  I found that the circuit board did not transmit the 5V to the Beagle board properly and I have found 3 sensors that refuse to work properly - I have one that always signals that it is near to it's magnet while I have two that always signal they are not near.  

I was quite pleased to see the same plug for open, worked for closed.   I had assumed the plugs from the wiring diagram would just be for a single state instead of working for both states (I had a bad sensor on the Right X axis which always signalled that a limit was hit, while I had a top Y sensor which never triggered so homing was difficult until fixed.   The door sensor was the last issue, but I had hoped that it was not the item stopping the laser from firing).    As I had not wired them up, nor had I worked on the code, I had some difficulty figuring out some issues.

I am the type of person who does not fiddle with a design or codebase until I have it working as originally envisioned or else I would have spotted some of this earlier.

With my experience of the build, I have noted a few things that would be of benefit to new users.

1. On the web interface, a tab/page that indicates the state of all limit switches, the chiller etc.   A simple open/closed or yes/no would aid in diagnostics vs plugging and unplugging various limit switches with the limit patch cable.
2. A beam combiner/laser indicator as part of the build.
3. Moving the electronics to the side vs the back of the machine - effectively separating the laser and its power supply from the control circuity.   Perhaps an electrical control box that attaches to the side.
4. A hinged/door back section to extract the laser from the top vs bringing it in from the side.
5. Optional framing bom/design for legs to make the entire system standalone vs needing to build a table for it.
6. Air flow venting as part of the base design. 
7. Photos of the various parts to go along with the 3D representation and cad drawings - Many days I spent going over various items that where confusing from the renderings and drawings, but became very obvious once you see it in real life or an image.

Also, I noticed that Coletech is selling linear rail systems with mirrors/motors/focusing heads etc., perhaps a pre-done solution would ease build time, reliability and costs?   If we can keep the saur controls with their mechanics, we may be in a good situation.

Thanks for the name and link for the Tube.  I will order one this coming week.

best regards

Dalton

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[Steve Baker]

I *REALLY* find it hard to believe that storing the tube without using it
degrades it any faster than using it over the same period of time...or
that a degraded tube would cause arcing...or that your tube has
degraded....or that arcing could have killed your tube. None of those
things fit with my experience with RECI tubes - or with what I've seen
from other Lasersaur owners with the same tubes - or with my general
understanding of the underlying mechanisms of tube degradation.

As I understand it, the mechanism behind tube degradation is that the CO2
inside the laser needs to be really pure - and if it's not, you get a loss
of power. The cheap chinese laser tubes are pre-filled with pure CO2 and
sealed in the factory. But since the seal isn't 100% perfect and perhaps
some of the components inside do a bit of out-gassing, the tube gradually
degrades over time...in part because of age - and in part because of
usage.

I don't see how running it versus leaving it on the shelf would DECREASE
the amount of pollution of the CO2?!? That makes no sense.

I *do* see that running it causes it to gradually lose power, because I've
done just that over several tubes. Our home business has two lasersaurs
and they both run for 2,000 to 3,000 hours per year - we've been in
business since 2012...so I've seen a LOT of laser tubes. We keep spares
on hand and some of those sat on the shelf for a year or two before we
started using them. I have tubes that I've owned for around 3 years now -
and they're still working perfectly.

And what happens is *precisely* what RECI say will happen. The more you
run it at full power, the shorter it's life will be. It says that right
there in the manual! They claim you'll get 10,000 hours out of a tube -
but that's assuming that you're mostly running them at low power. When
you hammer them at full power most of the time, they start to degrade at
about 2,000 hours and they're pretty much down to half of their original
power after maybe 3,000 hours of heavy useage. You can see a brownish
tinge around the electrodes as they age from heavy use. Tubes that have
been in storage for a year look as clear and clean as the day they were
delivered.

Given all of that - I could certainly understand that tubes would degrade
slowly in storage and FASTER in active use - but the other way around
makes no sense.

I also don't see how polluted CO2 could cause the arcing...I've had
several tubes gradually "wear out" from a few thousand hours of use - and
the power output just slowly degrades without the tube ever "dying". I've
certainly never seen any arcing due to a severely worn out tube.

On the other hand, we've had multiple people on this mailing list who
reporting seeing arcing - and in every case, they'd either not connected
the wires up right, had small nicks in the insulation - or (in at least
two cases) they'd left off the acrylic end-cap on the laser tube thinking
it was just some unimportant packaging piece(!). Don't take my word for
it - look back through our archives.

I don't recall the final outcome in those cases - but I don't *think* that
arcing damaged the laser tube. I don't see how it could really...I mean
how does the tube "know" that arcing is going on? All it sees is power
supply variations - and that's what it's designed to do while you're
cutting.

Plus, your "aging" hypothesis doesn't hang with the fact that the laser
DID fire when you used the test button on the power supply a couple of
days ago...if it was working just a few days ago - then what is the
mechanism for it suddenly not working AT ALL today? Even worn-out tubes
with polluted CO2 will fire at the 100% setting - they'll just produce
maybe 50 watts instead of 100 to 120 watts.

What you're saying here just doesn't in any way tie up with what I've seen
in years of working with Lasersaur - or in the thousands of messages from
other lasersaur owners that I've read.

I don't know where you're getting your information - but it certainly
doesn't fit with anything I've seen over about 15,000 hours of laser
cutting with these exact laser tubes! I *could* be wrong about this - I
learn new stuff here all the time - but if this is true then it's entirely
new information that I've never seen anywhere before.

That's why I'm so deeply skeptical at this point!

In your situation - I truly wouldn't spend another $1000 on a new tube
until I was very *VERY* certain that it isn't something else.

My bet is still on wiring or power supply issues. If you have one of the
older power supplies - then I suggest you use that one...at least until we
figure out what all of your problems are.

> 1. On the web interface, a tab/page that indicates the state of all

> limit switches, the chiller etc. A simple open/closed or yes/no would
> aid
> in diagnostics vs plugging and unplugging various limit switches with
> the
> limit patch cable.

> 2. A beam combiner/laser indicator as part of the build.
> 3. Moving the electronics to the side vs the back of the machine -

> effectively separating the laser and its power supply from the control
> circuity. Perhaps an electrical control box that attaches to the
> side.

> 4. A hinged/door back section to extract the laser from the top vs

> bringing it in from the side.

> 5. Optional framing bom/design for legs to make the entire system

> standalone vs needing to build a table for it.

> 6. Air flow venting as part of the base design.
> 7. Photos of the various parts to go along with the 3D representation

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[j. eric townsend]

On 6/20/16 12:32, Dalton Calford wrote:

> I do not believe the arcing killed the tube, but the death of the tube
> started the arcing - the response I have had on different cnc laser

Get a strong flashlight and maybe a magnifying glass and look for cracks
in the tube around the cooling nozzles. We had a RECI die in the first
few days of operation and discovered the crack in the tube during
triage. Of course we couldn't prove it was like that out of the box
and that we didn't fracture something during installation. We asked
nicely and got a replacement tube (split the shipping cost) after
destroying our tube and sending them a photo of the label on broken glass.

--
J. Eric Townsend, IDSA
design <http://www.allartburns.org>
hacking <http://www.flatline.net>
consulting <http://www.functionalprototype.com>