Used laser engraver addition

[Bryan Rocker]

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]

Good luck on that project. Keep us posted.

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

[Kev Williams]

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]

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]

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]

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.

[Rich Harman]

...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.

[Joseph Shawa]

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]

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]

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]

--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]

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]

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.

[Rich Harman]

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]

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.