PDA

View Full Version : Used laser engraver addition



Bryan Rocker
10-19-2017, 12:40 AM
Finally brought home a laser engraver. No its not one of those nice brand spanking new Epilogs or even a Rabbit or a Trotec. Its a 5 year old Hurricane Hugo 60 watt machine that they were unable to get the laser to fire. After getting it home I found a few of the problems.

1. The 6" ducting hole was reduced to 3 or 4 inches which would explain why the inside of the machine looks like they were burning the wood or running the laser to high.
2. Extremely dirty inside.
3. For some reason the laser high power lead from the laser power supply to the laser was cut in 2 and twisted together. That one by itself scares me.

The only saving grace is a "0" hour 60 watt tube from lightsource.
The machine has a tremendous "z" and it did include the rotary attachment.

It will need a thorough cleaning before any real troubleshooting can start and maybe a new high power lead if I can't install a new end.

Mike Null
10-19-2017, 10:47 AM
Good luck on that project. Keep us posted.

I went to Fairborn High School and played a lot of games against Beavercreek.

Kev Williams
10-19-2017, 11:54 AM
FWIW, I reduced the 6" hole in my Triumph to 4" because the smaller hole speeds up the air flow, which puts the actual moving air closer to the table, and the smoke... Smoke evacuates faster. So the smaller exhaust on your machine may have been an attempt to cure the smoke residue problem rather than being the cause of it-

Bryan Rocker
10-20-2017, 4:57 PM
At this time I intend to stick with a 6" duct. My initial plans are to use an old 7" roof vent. I stopped by the local electronics dude and we were able to piece together the parts to make a resistor to test the laser. Oddly enough he didn't have a 50K ohm resister in his stash so we had to make one up.

Bryan Rocker
10-22-2017, 2:13 PM
Yesterday while digging into the machine and cleaning, lots of cleaning, I found the red Cathode wire spliced within maybe 5-10" of the laser tube. The connection was held together with a simple orange run of the mill wire nut. The other splice was just twisted together with no protection at all. I am looking at replacing the wire if possible and at the minimum taking it down to one splice. My thoughts on a splice would be the wires straight and meshed together with no points, soldered, heat shrink-ed, silicone rtv allowed to cure then several more layers of heat shrink. Does that sound like the correct way? I want to do this right since there are 30K volts going down in.

Jerome Stanek
10-22-2017, 3:17 PM
You may not be able to solder the wire to the tube most just twist and seal it there. you could damage the tube with to much heat.

Joseph Shawa
10-22-2017, 11:24 PM
Kev, I can visualize that the air flowing in the tube would be faster at the entry point, but surely you don't think it would evacuate air at a higher volume.

Kev Williams
10-23-2017, 2:14 PM
The increase in air speed creates more vacuum, which is more efficient at removing smoke than sheer air volume.

Think vacuum cleaners- the end of the small attachments hose will suck up MUCH more dirt from deeper within carpet fibers than the same air flow spread across a wide carpet cleaning head, simply because the deep dirt is drawn into the faster moving airflow. Getting a wide head to draw up an equal amount of dirt would require a much higher volume of airflow, which is why they use brushrolls ;)

--Also, the amount of air volume lost to a 4" hose from a 6" hose is minimal.

More realistic reference- I have a plastic blast gate on a 4" solid-flex vent pipe near my fiber. If I close the gate somewhat, the vent draws MUCH more smoke than it does full open...

Jerome Stanek
10-23-2017, 3:43 PM
The increase in air speed creates more vacuum, which is more efficient at removing smoke than sheer air volume.

Think vacuum cleaners- the end of the small attachments hose will suck up MUCH more dirt from deeper within carpet fibers than the same air flow spread across a wide carpet cleaning head, simply because the deep dirt is drawn into the faster moving airflow. Getting a wide head to draw up an equal amount of dirt would require a much higher volume of airflow, which is why they use brushrolls ;)

--Also, the amount of air volume lost to a 4" hose from a 6" hose is minimal.

More realistic reference- I have a plastic blast gate on a 4" solid-flex vent pipe near my fiber. If I close the gate somewhat, the vent draws MUCH more smoke than it does full open...

Moving air is all you are doing a bigger hose has less restriction and moves more air just like a hose if you have the same amount of water flowing through a large and small hose it takes more pressure to push it through the small hose to get the same amount out

Bert McMahan
10-23-2017, 4:53 PM
--Also, the amount of air volume lost to a 4" hose from a 6" hose is minimal.


That's HEAVILY dependent on the fan curves for your blower. A 6" duct has more than double the cross sectional area of a 4" duct. Your fan may be able to compensate somewhat with more backpressure, but it's absolutely not true across the board.

Joseph Shawa
10-24-2017, 10:30 AM
Kev, I think you are using a distorted understanding of the Bernouli principal.

Yes the speed near the tip of a vacuum cleaner attachment is going to produce higher air velocity but only at the tip.
Aren't we talking about the vent hole in the guts of the table? Not a vacuum tip near the head.
Regardless of the velocity of the air just as it leaves the table, the total amount of air would be less if it goes through any hole that is small enough to make it speed up....resistance to flow (smaller hole) results in a decrease in pressure in the vacuum tube. It might seem to compensate exactly by increasing air speed but it's just not true. It is not a straight line 1:1 equation. Visualize the results as the hole gets ever smaller. You could easily test this by measuring the volume of air flow at the exit end or even just the velocity.
In fact you can test this on a normal vacuum cleaner by listening to the sound of the motor as you block suction. The motor speeds up because there are less air molecules being pushed out by the fan blades. When the motor reaches max speed vacuum is also at a max but airflow is now zero.
One thing that may be useful about faster exit speed is that the increased air velocity at the intake end would minimize the amount of smoke and particulate settling on the edges of the smaller entry orifice but once inside the tube I promise the airflow, although a bit more turbulent, from there to the final exit will be slower in velocity.

Kev Williams
10-24-2017, 11:44 AM
sucking smoke out of a laser box ain't rocket surgery guys, it's a simple matter of the smoke being drawn to the airflow.

Fact: I have two HF blowers sucking air out of my Triumph, and I share one identical blower with my fiber and LS900... so essentially I have 4x airflow in the Triumph as the 900-- so with all this airflow science that I admittedly don't know much about, someone explain to me why it is that I have to wait nearly a full minute for smoke to completely evacuate from my Triumph, BUT, virtually ALL smoke in my LS900 is evacuated immediately as it's created, even with the door wide open! Why do you think this is? Because Gravograph designed their box to evacuate smoke extremely efficiently with minimal air flow. Part of this efficiency comes from using a 4" inlet rather than a 6" inlet, which would probably require a larger blower to draw the same amount of smoke. Who cares about airflow principles when they don't work in my real world? When I first got my fiber laser, I attached a 4" to 6" adapter to the vent line. The end of the vent was about 10" above and 6" to the right of the work table. I used the 6" pipe believing it would 'catch' more smoke, than a smaller pipe. Wrong-- most of the smoke drifted right past the large opening without being drawn in at all, but once I pulled the adapter off, which was about 10" long, the 4" pipe very visibly drew smoke from 6-8" away. I've found that be decreasing the opening size even more draws smoke faster, from even closer to the table. But the compromise is that the smaller the hole gets, even though it does pull smoke faster and from a bit farther away, less total smoke is drawn in, more smoke drifts away due to the narrower airflow path. So my happy medium is I close the gate about 1/4 to 1/3. So I have a slight issue with the speed near the tip of a vacuum cleaner attachment is going to produce higher air velocity but only at the tip, because the air that IS moving faster at the tip is coming from somewhere, and in my experience, from a fair distance in front of the tip, and that's the air the smoke will find :)

I'm not trying to argue aerodynamic or Bernouli principles because honesly, I know nothing about them. I'm just trying to suggest ways to increase smoke evacuation without increasing airflow, which is definitely doable based on my experiences.

Bryan Rocker
10-24-2017, 11:56 AM
My thoughts on this whole issue is the same principles that apply to dust collectors applies here. As I have been working on this machine I have found a number of potential issues to resolve.

1. The cathode wire to the power supply was to short so they just pig tailed a 12" or so piece of 12/14 awg wire to make up for the difference. Not happy with that at all.
2. The new laser tube that came with the machine, both the cathode and anode wires have no ends, gotta figure that one out, would like a mechanical connection. I managed to disassemble the old connector on one side. If I have to replace the wire to the power supply (cathode) I will have to run a new wire to the analog meter.
3. There does not appear to be a resistor at the 5V wire and I am not sure what size to use. I see some say to use a variable one.
4. During cleaning, OMG it was dirty, I found a small round piece of wood lodged between a limit switch and the rail. It may have been the problem all along.
5. For the ground on the back of the machine, do I just run a wire to the ground on my electrical system or to one of the outside grounding rods for the main fuse panel?
6. The new 80 watt power supply is twice as long and heavy as the old one. Not sure that's an issue.
7. I am thinking of putting a section of metal ducting from the suction port at table height and a connector at the back to easily disconnect it. The duct they connected with was "plastic" and had no clamps to hold it on.
8. For all the access doors, are there any issues with removing the dam key locks and putting rare earth magnets on them?


PS I hope this isn't too many questions.

Have a day blessed with the graces of God ;)

Rich Harman
10-24-2017, 12:36 PM
Because Gravograph designed their box to evacuate smoke extremely efficiently with minimal air flow. Part of this efficiency comes from using a 4" inlet rather than a 6" inlet, which would probably require a larger blower to draw the same amount of smoke.

I'm not going to argue your experiences, but I am confident that your reasoning is flawed - since it is in conflict with know physical properties. Restricting a duct will increase velocity but it will reduce efficiency and cfm. A larger inlet (and ducting) would not require a larger blower to draw the same cfm. Just the opposite, the same blower will evacuate more air with a larger duct and inlet. That is just physics.

Gravograph may very well have designed a better cabinet. I know my machine's designer has put zero effort into making it evacuate smoke efficiently - it is a box with a hole in it where you hook up a tube, lots of room for improvement there.



When I first got my fiber laser, I attached a 4" to 6" adapter to the vent line...

I agree, that scenario would not provide a benefit. You would need to replace the entire 4" line going to the blower with 6" to realize the increased efficiency.

Bill George
10-24-2017, 12:42 PM
Go to your local auto parts store and buy whatever length you need of high voltage spark plug wire, just make sure its copper core instead of carbon. You might need to find a older store or farm store as the new ones with the kids on the counter will not have a clue. The metal used for tube connection is not really able to be soldered, successfully. You can gob solder on but its not a good connection. Mechanical connections such as split bolt connectors, screw or the like sold at Home Depot for splicing wires will work. Do not over tighten.

If you have true 3 wire 120 volt outlets with a real ground wire attached to the U prong and the wire inside the machine from that 120 volt power cord is connected to metal or machine ground inside via the green wire that is all you need.

Rich Harman
10-24-2017, 12:54 PM
...I found the red Cathode wire spliced within maybe 5-10" of the laser tube.

Red cathode? Are you sure about that?

I spliced my anode wire (the red one that carries the high voltage) by soldering it and wrapping it neatly with a couple dozen layers of electrical tape. Then I fed the wire into a silicone tube.

I had spliced it previously with the same method except for the silicone tubing part, but it developed a pinhole and starting shorting to the frame. No, not where I spliced it but about six inches away. That is why it is now inside a silicone tube.

Bill George
10-24-2017, 2:28 PM
I'm not going to argue your experiences, but I am confident that your reasoning is flawed - since it is in conflict with know physical properties. Restricting a duct will increase velocity but it will reduce efficiency and cfm. A larger inlet (and ducting) would not require a larger blower to draw the same cfm. Just the opposite, the same blower will evacuate more air with a larger duct and inlet. That is just physics.

Gravograph may very well have designed a better cabinet. I know my machine's designer has put zero effort into making it evacuate smoke efficiently - it is a box with a hole in it where you hook up a tube, lots of room for improvement there.




I agree, that scenario would not provide a benefit. You would need to replace the entire 4" line going to the blower with 6" to realize the increased efficiency.

Actually high velocity air distribution systems exist, in older homes or a building where space for ductwork is extremely limited they use PCV or steel tubing about 2 inches in diameter to deliver the air to the rooms. The outlets or supply registers are usually installed in the corner of the room discharging the air, out of direct contact with the occupants. Its also common practice to reduce the inlets in exhaust systems to pull the air in rapidly and in a certain direction. After the reduced inlet the duct is the normal size for the calculated CfM.

Rich Harman
10-24-2017, 8:54 PM
Actually high velocity air distribution systems exist...

They do exist, and make some claims of higher efficiency due to better mixing of the air and longer run time, less temperature swings - among other things. They do not however claim to be more efficient at exchanging a volume of air than a standard larger duct system.

Bryan Rocker
10-25-2017, 11:39 AM
The wiring in my house is top notch, in 2009 we took it down to the studs and installed new to code wiring and installed insulation where there was none. For the laser I may add a dedicated circuit for it.

For the connector I have decided against soldering. I am disassembling the connectors on the old wire they cut off too see if I can salvage them. I managed to get the female apart fairly easily and will do the mail to day.

Joseph Shawa
10-30-2017, 10:54 AM
Kev, you said, " it's a simple matter of the smoke being drawn to the airflow. "

Actually the words you used are distracting you from understanding what we are arguing about.
Nothing is "drawn" . Air is PUSHED only. It is pushed away from the fan blades and the air in the tube is pushed (air pressure) and fills the void where the missing air by the blades of the fan was. This isn't just semantics. Air rushes into the box only because there is a void there.
Anyway, no need to further discuss. Just trying to discuss your increased efficiency.

Bill George
10-30-2017, 1:43 PM
Kev, you said, " it's a simple matter of the smoke being drawn to the airflow. "

Actually the words you used are distracting you from understanding what we are arguing about.
Nothing is "drawn" . Air is PUSHED only. It is pushed away from the fan blades and the air in the tube is pushed (air pressure) and fills the void where the missing air by the blades of the fan was. This isn't just semantics. Air rushes into the box only because there is a void there.
Anyway, no need to further discuss. Just trying to discuss your increased efficiency.

Huh? After well over 30 years in the HVAC/R trade and having taught it for 12 years afterwards, air flow and duct work design was part of that, I find your statement....

Joseph Shawa
10-31-2017, 6:05 PM
Enlightening? Never too late to learn. I find your lack of response....

Rich Harman
11-01-2017, 12:40 AM
Nothing is "drawn" . Air is PUSHED only.

That's true. Suction, centrifugal force, cold - those are all things that technically do not exist.

Kev Williams
11-01-2017, 4:26 PM
... for every action there's an equal and opposite reaction... True? If so, can you push something without pulling something? ;)

I found this answer online to the question 'is air pushed or pulled':


It is neither pushed or pulled really.

Molecules are assigned random movements (think brownian motion), and having a vacuum means a molecule is less likely to hit another one there. In the area of high pressure, they are more likely to hit each other. That means that if you do the calculation to how much ALL the molecules have moved they will naturally tend to move toward to the area of low pressure from the area of high pressure (until the pressure is equalized in which case as many molecules will go one direction as there are molecules going the other direction).

And about smoke:

Smoke is a collection of tiny solid, liquid and gas particles. Although smoke can contain hundreds of different chemicals and fumes, visible smoke is mostly carbon (soot), tar, oils and ash
with that, I'll say that while AIR- a gas- is being pushed by AP to fill a low pressure area, SMOKE- mostly a solid- is DRAWN to the low pressure area.

We can split hairs all day on this dumb subject. I'm not trying to break the laws of physics, gotta know 'em to break 'em... ALL I'm trying to say is, with a few changes, you most definitely CAN make your exhaust plumbing efficient enough to remove smoke from your laser box MANY times faster than it currently is, and do it with 1/2 the air volume you're currently - pushing ;) -- and you do it by creating a larger low pressure area...

Rich Harman
11-01-2017, 7:01 PM
ALL I'm trying to say is, with a few changes, you most definitely CAN make your exhaust plumbing efficient enough to remove smoke from your laser box MANY times faster than it currently is, and do it with 1/2 the air volume you're currently - pushing ;) -- and you do it by creating a larger low pressure area...

I mostly agree. A larger low pressure area is a larger diameter duct and larger inlet.

Both air and water are fluids. They behave in pretty much the same way, at least until the air starts getting compressed - which does not occur in the situations that we are talking about.

You cannot drain a sink faster by restricting the size of the drain. Maybe it is possible (I am skeptical) to remove some floating particles near the drain earlier if the drain is restricted which if true is what you are experiencing.

My machine, and all the Chinese machines I have seen, are just large boxes with lots of places for air to seep in. In order to remove the smoke effectively a very large volume of air exchange must occur. Most of the air removed from the box does not have smoke in it. Lots of air seeping in through the cracks and being "drawn" in from other areas of the machine. By the sheer volume of airflow the smoke is removed.

In a better designed machine I would expect the area where the smoke is to be a smaller volume than the entire interior of the machine. Most of the air movement should be coming across the table, not the entire interior of the machine.

You cannot aim "suction" like you can aim pressure. Have you ever tried to vacuum up a flying insect? If so you will have noticed that you have to get the vacuum nozzle much closer to the critter than you would have intuitively predicted.

Joseph Shawa
11-01-2017, 10:29 PM
I mostly agree. A larger low pressure area is a larger diameter duct and larger inlet.
.

You cannot aim "suction" like you can aim pressure. Have you ever tried to vacuum up a flying insect? If so you will have noticed that you have to get the vacuum nozzle much closer to the critter than you would have intuitively predicted.

Great example!

Bill George
11-02-2017, 10:20 AM
In a attempt to correct some of the mis-information posted here, first is terminology. Its Supply and Return or Exhaust air. Yes Return or Exhaust air can be directed or designed in such a way to effect air flow direction, its done everyday. Velocity does make a difference as to direction of the Supply and Return air. Designing for proper velocity is part of the job, just as important as Cfm.

In the real world we used ACCA materials and software, The Manual D was used for
ductwork design. Air Distribution Basics, the ACCA Manual T is another reference we used in the Classroom and Real world. Yes I have those and several more in my library and they can be purchased on their website if your interesting in learning.
I had well over 30 years of experience both working in the real world and then teaching HVAC/R in a classroom.
I also had the experience of working with some top notch mechanical engineers, and some we called armchair ones, the engineers who read in a book and then wrote the specs and designed the jobs…. That did not always work. I was one of the ones who had to go in, find the screw ups and get it fixed and running so they would get paid! For this I was paid very well, and I loved my job.

Bryan Rocker
11-02-2017, 10:46 AM
Yesterday I was getting ready to put the male/female red wire connectors on and I looked at the wire coming from the PSU and it had that silicone/rubber tubing on it to reduce arcing. Do I need to put that on the wire from the connector to the laser tube connection? Since I have to solder the pin on I don't want to proceed until I get it right. The connectors has turned into a real PITA since they cut off the ends when the pulled the laser tube. All the other connections are together and ready to go.

Bill George
11-02-2017, 11:03 AM
Brian, My HV wire has that clear tubing and it almost looks like the stuff used for air and water supply lines to the machine over the entire length. Not 100% sure its needed but its on.

Rich Harman
11-04-2017, 5:00 PM
In a attempt to correct some of the mis-information posted here, first is terminology. Its Supply and Return or Exhaust air. Yes Return or Exhaust air can be directed or designed in such a way to effect air flow direction, its done everyday.

Yes, of course it can. Having the return air vent in the middle of a room vs the corner of the room will significantly affect the airflow patterns. That is not the same as "aiming" the "suction". For example you cannot put the return in the middle of the room and "aim" it to the side to get the same effect as putting it in the corner. You also cannot restrict the return air and expect it to move more air through it, nor "pull" air from further away.

Rich Harman
11-04-2017, 5:03 PM
Yesterday I was getting ready to put the male/female red wire connectors on and I looked at the wire coming from the PSU and it had that silicone/rubber tubing on it to reduce arcing. Do I need to put that on the wire from the connector to the laser tube connection?

You probably don't need to, many machines do not have that extra layer of protection. However, I would strongly suggest that you do add it. It causes no harm and can save you from further problems.

Bill George
11-04-2017, 5:22 PM
Yes, of course it can. Having the return air vent in the middle of a room vs the corner of the room will significantly affect the airflow patterns. That is not the same as "aiming" the "suction". For example you cannot put the return in the middle of the room and "aim" it to the side to get the same effect as putting it in the corner. You also cannot restrict the return air and expect it to move more air through it, nor "pull" air from further away.

The restriction used to increase velocity in supply and return diffusers is not a significant loss. Done all the time, go to the ACCA website and do some reading as I suggested.

You do not depend on velocity to direct air flow in a room entirely for return air. The location of the returns either high or low and in the heating areas of the country the returns are located on the inside walls and supplies are designed to Sweep the outside walls with warm air. Supply diffusers are selected on air delivery or Cfm, Velocity is used to Throw the air in a certain pattern.


Good resource for those interested, check the Engineering data in the back of the catalog > http://www.hartandcooley.com/