Large Scale Central

Laser Cutter Install Log

Modeling Technical Modeling
#41

Todd Brody said:

I see where these ebay laser cutters use water and chillers to keep the laser tube cool. But on the Epilog I use, I see no water attachments or chillers being used. When I turn it on (just one power switch on the unit) the fans come on, but I see nothing more for cooling. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-undecided.gif)

Todd All GLASS CO2 laser tubes are water cooled… Metal rebuildable/rechargable laser tubes under 100 Watts or less as I recall are air and or fan cooled in cabinent machines. Larger equipment is yet another story. The glass tubes typically have less than a half life of the metal tube lasers. Either works as good as the latter, cost and life expectancy are the variables.

Michael

#42

Ok, here’s a better diagram… can’t let that reversed fan stay… Also added the duct dampers.

[I edited this diagram out, since it’s misleading due to later discoveries]

#43

What Rooster said…

Its plausible that your air moving solution will in fact not work as desired IMO. Your system as deployed will introduce a notable increase to inlet static air pressure.

Todd makes a good point, yet HVAC systems utilize a similar air path concept, BUT with a different type of blower.

You might consider mocking up air change system to evaluate its short comings or not.

Can you take a picture of your centrifugal fans blade, it could be of several different types; i.e., forward curve, backward curve, radial or airfoil. I’d guess its likely a radial fan blade. Some are better suited than others for specific design criteria.

Michael

#44

Michael,

Your system as deployed will introduce a notable increase to inlet static air pressure.

Yes it will, hence my stated concerns about the inlet louvers on the cutter and the fan motor potentially burning up under the load. I will probably need to open those louvers up.

You might consider mocking up air change system to evaluate its short comings or not.

That will come when I make the window box, and change the euro plug out on the fan.

Can you take a picture of your centrifugal fans blade, it could be of several different types; i.e., forward curve, backward curve, radial or airfoil. I’d guess its likely a radial fan blade. Some are better suited than others for specific design criteria.

I don’t feel like taking it apart for a photo, but the blades are slightly backward-curved. Yes, blades are shaped for numerous criteria, including moving dust and other materials. But the cutter manufacturer supplied this fan, for this purpose and configuration, so I’m going to use it in that fashion.

As far as “screwing around” goes, and I received that as a joke from Rooster, I believe my initial post made it clear that this would take quite a while. There are a lot of things to figure out, and I appreciate the helpful opinions. I do build work on the weekends, and snag time here and there during the week for planning, purchasing the components and materials, and sometimes writing about the effort.

[edit: I guess I was a little cranky yesterday when I wrote all that, sorry Michael.]

#45

Cliff,

Some additional comments base on my research into a laser as well. First, make your exhaust system a down draft system, drawing the fume/particles away from the optics. This has been recommended by all the commercial vendors I have spoken with.

Second, make sure the exhaust volume is larger by about 20% than the make up volume to assure the fume/particles travel away from the optics.

Depending on your location and relativity to neighbors, you may also want to put a water mist scrubber on the exhaust (to minimize fume from plastics of any nature). AND BE CERTAIN TO NEVER CUT PVC OF ANY KIND! The resultant fume contains chlorine gas which besides being toxic, will quickly corrode your laser cutter.

Being as you mentioned you are using a fluid cooled laser, if there is not one provided, install a flow switch to assure that there is liquid flow. May cost a few dollars up front, but will be cheap insurance to keeping the laser tube in good shape.

Another tip I received from two of the vendors I spoke to is … etching (pulsed laser output) will shorten the life time of the laser by as much as 50% depending on the quality of the laser tube purchased. This included both of the vendor’s products as well, it was a ‘generic’ warning.

FWIW…Bob C.

#46

Why doesn’t the pictures show up that you are posting?..

#47

Thanks Travis, that’s puzzling though… I just opened it in IE [and Chrome], and yep, they don’t show up. I’ll work on it, thanks again.

[later] Not showing up… I checked the links in the inspection box, and they seem ok. I re-inserted one (the panorama from Sunday, showing the crate on the hill), and compared it via inspection to one that wasn’t working, and I couldn’t see any difference in address or format. Maybe someone can help me out here?

#48

Hi Bob, thanks for your comments.

Some additional comments base on my research into a laser as well. First, make your exhaust system a down draft system, drawing the fume/particles away from the optics. This has been recommended by all the commercial vendors I have spoken with.

I had to check, but the cutter’s exhaust post is below the cutting table level.

Second, make sure the exhaust volume is larger by about 20% than the make up volume to assure the fume/particles travel away from the optics.

I’m not sure how to check that. However, there is clearly a vacuum drawn by the exhaust fan, and its aperture is far larger than inlet louver area.

Depending on your location and relativity to neighbors, you may also want to put a water mist scrubber on the exhaust (to minimize fume from plastics of any nature). AND BE CERTAIN TO NEVER CUT PVC OF ANY KIND! The resultant fume contains chlorine gas which besides being toxic, will quickly corrode your laser cutter.

Understood. The warnings re. PVC I’ve heard many times. Neighbors are not near the exhaust area.

Being as you mentioned you are using a fluid cooled laser, if there is not one provided, install a flow switch to assure that there is liquid flow. May cost a few dollars up front, but will be cheap insurance to keeping the laser tube in good shape.

That’s a good idea, I agree, flow is critical. The chiller I’m getting has an alarm output (for temp I think), not sure for flow. I’ll have to look into that. Once I get the vent thing squared away, the cooling circuit is next.

Another tip I received from two of the vendors I spoke to is … etching (pulsed laser output) will shorten the life time of the laser by as much as 50% depending on the quality of the laser tube purchased. This included both of the vendor’s products as well, it was a ‘generic’ warning.

Wow, that’s a bummer. Have to look into that as well.

Thanks for all those Bob.

Cliff

#49

Back to ventilation. I replaced the power cord on the fan with a US-style plug, plugged it in with and without hoses, and took power readings using a “Kill-a-Watt” meter.

Without any hoses, the fan pulls 960W / 8.3A @ 124V. I know, that doesn’t quite add up, but that’s what the meter kept saying. My main observation was that this is far higher than the 550W @ 110V printed on the label.

I then installed the hoses per the instructions, one from the cutter’s exhaust port to the fan, the other from the fan to nowhere. I bent the bent the hoses to roughly represent the number of total bends I had in mind, and plugged it in. There was no difference in the power readings, which surprised me.

The big surprise though was that the makeup air is coming into the cabinet everywhere, not only (or even mainly) through the inlet louvers. There are 7 doors on the unit, and I belatedly noticed that the main lid has a lot of open slots in it. With the fan on, I walked around the thing with a lighter, and saw that air was entering via all the door seams, and only somewhat more through the louvers. But the biggest makeup air intake area is on the front the the main door, through all those slots.

I could seal up those doors, but not the slots in the lid. As Bob pointed out, the flow should go downward, and these slots permit that (unlike the louvers down on the side). And there’s no way to capture those slots under an intake plenum with a hose attached, because the lid needs to easily open.

So… there’s zero point in plumbing a makeup air line to the louvers on the side, or anywhere else. The makeup air will just have to come from the house, and we’ll have to run the heater more in the winter while cutting. Bummer.

The good news is that:

  1. The lighter’s flame showed flow toward the cabinet all around, meaning that the fumes have a good chance of being minimal.
  2. I won’t need to bother with inlet filters and screens; the window unit just got much simpler.
  3. There was no noticeable amp increase with the hoses attached.

Back to the drawing board,

Cliff

#50

oops

#51

Cliff

The amp draw on a centrifugal fan goes down as resistance to airflow is increased. So try restricting the exhaust and check again. A hand held tachometer to note RPM will also tell the tale.

Michael

#52

Well, I have to wonder how much “indoor” air you will be venting outside. After all, we agree that it will not be running constantly. So an hour or 2 of indoor air vented outside would require the furnace to run how much more? Enough to fret over?

#53

Cliff

The amp draw on a centrifugal fan goes down as resistance to airflow is increased.

Michael that is only true for a forward curved fan. Radial and backward curved fans do not act the same way. A backward curved fan is known as a ‘non-overloading’ fan for that reason.

Actually Cliff, if you take a piece of cardboard and start slowly covering the inlet side of the fan (if the fan has two inlets cover the one with out the motor) and listen to the air flow. If the air flow increases and the speed increases, amperage on the motor will go down as the fan will be operating at a higher efficiency. I will try to get a picture of my shop blower I made from a standard house air handler fan, which is a forward curved fan.

However, from your description of the results of testing, I would tend to believe you have a backward curved fan. A picture of the fan would be worth a thousand words. One of the reasons there are two types is complicated but a simple explanation is that a forward curved fan will give a larger volume of air flow for a given fan size than will a backward curved fan, but a backward curved fan is far more forgiving in duct flow resistances than is a forward curved fan.

Now that I have totally confused you …

Bob C.

#54

Bob is correct in the part , if you decrease the air intake on a backward incline fan the amp load will decrease, because less air results in less load.

Static pressure will increase slightly but BI fans do not increase load, like radial fans as they load up or higher staic pressure.

Radial fans or straight bladed fans, amp load, will increase with increased static pressure, or restrictions.

IMHO you are over thinking a simple task here, hook it up and lets start cutting. down draft only is beneficial in a vector mode, not

in raster mode. You will probably cut more vector, down draft and pulling horizontal will be needed, Is your vector table a honeycomb

type table or a pin type table. My large machine has a solid table with hold up pins for vectoring, but it is solid resulting in horizontal smoke

removal. Our small units are honey combed, which benefits in vector mode only.

Your makeup air will be close to the same as your clothes dryer.

Have fun

#55

Thanks guys, I appreciate your continued help.

Michael and Bob, though I appreciate the technical insights, I’ll have to make do with the fan I have. Having said that, I’ve worked to reduce the disruption / cV / delta-P wherever I can.

The misc. bits are on order. And here is the hose layout.

I hope the pics show up. In spite of my close attention to the process, the earlier ones are no longer doing so (even on my machine).

I’ll be working all weekend, but hope to get to this construction the next weekend.

David and Dennis, thanks for affirming that the loss of heat through makeup air is no big deal. Or not enough of a big deal to worry about it any more than I have. I’m calling that box checked.

Cliff

[edit] After making these figures I found that I could take out the insulated glass window pane and replace it with 1/2" or 3/4" lexan (with a hole in it), leaving most of the window clear.

#56

Here’s how the fan box is looking.

Hose plugged in:

Hose stowed.

Need to add the feed thru for the power cord still.

===>Cliffy

#57

Looks great Cliff, waiting to see your products

Dennis

#58

Thanks Dennis. Me too!! (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Next weekend I hope to do the power outlet & chiller install.

If anyone might be interested, here’s a few comments about the fan (or blower) box. I started with a used Suncast deck box, 73 gal version because I wanted the extra storage room. I’ve had this and one more Suncast box for years, and they do a great job keeping the moisture out.

The vents are 6" Lasco plastic dryer vents, and I had to to trim the bezels top and bottom for them to fit. There’s a nice flat surface though, all around the round tube part, and that’s where I sealed them with silicone. The square bezels are cosmetic. After cutting the holes in the box and applying the silicone I screwed the louvers on with #6 pan head screws.

The hose that came with the cutter has a molded end that fits snugly inside the Lasco vent. I bought a 25’ length of 6" vinyl hose for the connection between vent and fan inlet, and also for the line inside the house. As shown in one pic, I converted the top vent flap to a full door that drops down when the hose is pulled out. Those flaps have flimsy plastic hinge pins, so when that breaks, I’ll replace the door flap with something more stout, like a sheet of rubber with a hanger wire for a hinge pin.

The fan is screwed to a couple of treated 2x6’s which are screwed to the box from outside. This is to distribute the weight of the fan and also the reaction force when it’s on, and not depend on the plastic box bottom.

===>Cliffy

#59

Today I installed the power line to the outdoor fan, consisting of:

  • tie-in to a nearby receptacle near the laser cutter

  • new wall switch, ditto

  • 1/2" hole drilled through the concrete wall

  • new outlet box, GFCI and extended plastic cover

Nothing much to put up a photo of, just a boring outlet and switch, so I won’t bother.

After that, I began testing the chiller unit, but it’s not working as expected. I had to send the first one back, due to it’s being the wrong voltage & hertz. Not sure what’s going on with this one, but I’m working with the vendor to get some answers.

===>Cliffy

#60

Cliff

Are you saying they sent you a 50 cycle/Hertz unit? If so, was that a “What we have here, is a failure to communicate”. That little Chinese person did not get the memo all US imports are 60 HERTZ

Dennis