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Thread: Used laser engraver addition

  1. #16
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    Quote Originally Posted by Bryan Rocker View Post
    ...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.
    Shenhui 1440x850, 130 Watt Reci Z6

  2. #17
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    Quote Originally Posted by Rich Harman View Post
    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.
    Retired Guy- Central Iowa. , LightObject 40w CO2 Laser and Chiller, MakerGear M2 3D Printer. Fine Line Automation 4x4 CNC Router- Mach4 ESS

  3. #18
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    Quote Originally Posted by Bill George View Post
    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.
    Shenhui 1440x850, 130 Watt Reci Z6

  4. #19
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    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.

  5. #20
    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.
    Chinese 6040 by NiceCut. Originally 60 Watt upgraded to 150 Watt.....I thought I had pretty much every problem in the book of laser cutting. It turns out that there is a set of books.

  6. #21
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    Quote Originally Posted by Joseph Shawa View Post
    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....
    Retired Guy- Central Iowa. , LightObject 40w CO2 Laser and Chiller, MakerGear M2 3D Printer. Fine Line Automation 4x4 CNC Router- Mach4 ESS

  7. #22
    Enlightening? Never too late to learn. I find your lack of response....
    Chinese 6040 by NiceCut. Originally 60 Watt upgraded to 150 Watt.....I thought I had pretty much every problem in the book of laser cutting. It turns out that there is a set of books.

  8. #23
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    Quote Originally Posted by Joseph Shawa View Post
    Nothing is "drawn" . Air is PUSHED only.
    That's true. Suction, centrifugal force, cold - those are all things that technically do not exist.
    Shenhui 1440x850, 130 Watt Reci Z6

  9. #24
    ... 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...
    ========================================
    ELEVEN - rotary cutter tool machines
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    CASmate, Corel, Gravostyle


  10. #25
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    Quote Originally Posted by Kev Williams View Post
    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.
    Shenhui 1440x850, 130 Watt Reci Z6

  11. #26
    Quote Originally Posted by Rich Harman View Post
    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!
    Chinese 6040 by NiceCut. Originally 60 Watt upgraded to 150 Watt.....I thought I had pretty much every problem in the book of laser cutting. It turns out that there is a set of books.

  12. #27
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    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.
    Last edited by Bill George; 11-02-2017 at 1:24 PM.
    Retired Guy- Central Iowa. , LightObject 40w CO2 Laser and Chiller, MakerGear M2 3D Printer. Fine Line Automation 4x4 CNC Router- Mach4 ESS

  13. #28
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    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.

  14. #29
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    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.
    Retired Guy- Central Iowa. , LightObject 40w CO2 Laser and Chiller, MakerGear M2 3D Printer. Fine Line Automation 4x4 CNC Router- Mach4 ESS

  15. #30
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    Quote Originally Posted by Bill George View Post
    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.
    Shenhui 1440x850, 130 Watt Reci Z6

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