Startup Issues

[Martin Reynolds]

I use a three-step process.

Scan original into Corel, and cut and paste from Corel into Turbocad
Construct Turbocad master using bitmap as a guide
Save as DXF, and read back into Corel

My experience with Corel is the same as yours. It is designed for artistic drawing, not technical drawing. So things that are easy in CAD are hard in Corel, and vice versa.

[Richard Rumancik]

An open path is is a big no no in most of the work I do. Evidently, it doesn't matter much if you get close enough in Corel.

Well, it does matter if you want to fill it, or trim/intersect it with another shape. Then you want a closed shape.

I spent a couple of hours trying to draw a circle, then add a few nodes, and break part of it off, close the path, and extract the subpath. . . . Again, I am sure there is an easy way to do it, but I couldn't find it

David, try this. Suppose you want to draw "half a pie". Draw a circle. You will see it has one node. Convert the circle to curves by using Arrange ->convert to curves. Then you will see 4 nodes 90 degrees apart. Click on one node with the node edit (shape) tool or right-click. Either way, find and click "break apart". Then go to the opposite node and do the same thing.

The next thing to do is Arrange ->break curve apart. Now you will have two semi-circles. Delete one of them. You are left with an open semi-circle. Click Arrange->close path -> close path with straight lines. You should have half a pie.

Does this help at all?

By the way - if you have a shape and you are trying to close it, you may need to join coincident nodes back together. For example, go back to the point where you had two separate semi-circles. Let's suppose you wanted to reverse the process. You select both halves, and click Arrange->Combine. Then select one pair of overlapping nodes (using a window selection of the shape tool) and click "Join two nodes". Do the same on the other side. Now you are back to a closed circle. (The simple test is that if it will fill, it is closed properly.)

[David Brasfield]

It's obviously not something tech support can answer, it's an engineering issue. I've said it before, I think Epilog's tech support is excellent, but the next level up from tech support, they fall way short. The next level up needs to be as customer oriented as their tech support is.

I don't know anything other than what Barb has written, and the recent comments made to her (publicly) by Peck.

I do know that Epilog clearly states the CFM/Static pressure requirements for the box. I also know that the little "1hp" blower provided by my rep may actually move 914 CFM as spec'd in the manual that came with it, but I also know that there is no way that motor/rotor combination is going to move that much air unless it is spinning itself to the point of self-destruction, with no ductwork whatsoever connected to it. Therefore, the CFM rating without some corresponding ADDITIONAL specifications is absolutely useless, and benefits ONLY the manufacturer(of the MOTOR/BLOWER), and amplifies issues that shouldn't have to be solved by Epilog, other than in training their reps not to buy blowers without complete specifications which MATCH OR EXCEED Epilogs stated requirements.

Even so, my understanding is that Barb outsourced her exhaust system to a third party. That introduces yet another layer of potential confusion.

My concern, which may be proven to be unfounded, is that since her blower is "loud", possibly indicating the motor type is "universal", and if so that it might be way too small for the job, regardless of the manufacturer's (motor) rated claims of horsepower, CFM and static pressure.

That would leave both Barb and the Epilog people in a state of confusion.

David

[David Brasfield]

I use a three-step process.

Scan original into Corel, and cut and paste from Corel into Turbocad
Construct Turbocad master using bitmap as a guide
Save as DXF, and read back into Corel

My experience with Corel is the same as yours. It is designed for artistic drawing, not technical drawing. So things that are easy in CAD are hard in Corel, and vice versa.

Hi, Martin.

I was hoping to avoid moving files back and forth, but I may have no choice. I am going to stick with it for a while and see if I can adapt to some reasonable facsimile of productivity with X3.

Thanks,
David

[David Brasfield]

Well, it does matter if you want to fill it, or trim/intersect it with another shape. Then you want a closed shape.



David, try this. Suppose you want to draw "half a pie". Draw a circle. You will see it has one node. Convert the circle to curves by using Arrange ->convert to curves. Then you will see 4 nodes 90 degrees apart. Click on one node with the node edit (shape) tool or right-click. Either way, find and click "break apart". Then go to the opposite node and do the same thing.

The next thing to do is Arrange ->break curve apart. Now you will have two semi-circles. Delete one of them. You are left with an open semi-circle. Click Arrange->close path -> close path with straight lines. You should have half a pie.

Does this help at all?

By the way - if you have a shape and you are trying to close it, you may need to join coincident nodes back together. For example, go back to the point where you had two separate semi-circles. Let's suppose you wanted to reverse the process. You select both halves, and click Arrange->Combine. Then select one pair of overlapping nodes (using a window selection of the shape tool) and click "Join two nodes". Do the same on the other side. Now you are back to a closed circle. (The simple test is that if it will fill, it is closed properly.)

In all honesty, I thought that I was following the procedure much as you defined it, even closing the path, then selecting it for extraction. It would highlight in red, but the extract path function was never available.

You are right, of course, about needing closed paths for fills.

I spent some time on the Corel website last night, and I am going to apply all the patches for X3 even though it is supposed to be up to date. It is still doing some bizarre things. Like leaving the font menu in the center of the screen when I am not in text mode

If nothing else, I will wipe it and do a re-install. There is no telling what I have done to it during my learning curve. If I can get it to do basics, then I will be happy.

I will also follow your example above verbatim this evening and let you know the results.

Thanks for your time.
David

[Richard Rumancik]

I do know that Epilog clearly states the CFM/Static pressure requirements for the box. . . . the CFM rating without some corresponding ADDITIONAL specifications is absolutely useless . . .

You are right, you need an airflow/static pressure curve of the blower; plus knowing duct sizes, lengths, number or elbows, and exhaust method of the actual installation will also be relevant. What happened in Barb's case if I recall correctly is roughly this: Epilog accidently put the wrong requirement of 400 cfm (@6") in the spec. Barb's contractor doubled the number and gave her a 800 cfm blower (@6"). Then Epilog adjusted the spec requirement to 800 or 900 (not sure of the exact number.) Which put her in "marginal" territory.

My concern, which may be proven to be unfounded, is that since her blower is "loud", possibly indicating the motor type is "universal", and if so that it might be way too small for the job, regardless of the manufacturer's (motor) rated claims of horsepower, CFM and static pressure.

She had (still has?) a Peerless PW-12 which is a 3hp 3500 rpm blower which is probably way more blower than 90% of the people on this forum. It uses an induction motor. I looked at the spec and it looked like a pretty decent industrial blower to me. It is no Harbour Freight dust collector.

A 3 hp motor on the roof running 3500 rpm WILL make some noise. Plus it depends on how well it is mounted. So the noise does not indicate a cheap blower.

[David Brasfield]

You are right, you need an airflow/static pressure curve of the blower; plus knowing duct sizes, lengths, number or elbows, and exhaust method of the actual installation will also be relevant. What happened in Barb's case if I recall correctly is roughly this: Epilog accidently put the wrong requirement of 400 cfm (@6") in the spec. Barb's contractor doubled the number and gave her a 800 cfm blower (@6"). Then Epilog adjusted the spec requirement to 800 or 900 (not sure of the exact number.) Which put her in "marginal" territory.


She had (still has?) a Peerless PW-12 which is a 3hp 3500 rpm blower which is probably way more blower than 90% of the people on this forum. It uses an induction motor. I looked at the spec and it looked like a pretty decent industrial blower to me. It is no Harbour Freight dust collector.

A 3 hp motor on the roof running 3500 rpm WILL make some noise. Plus it depends on how well it is mounted. So the noise does not indicate a cheap blower.

Hi, Richard.

I looked at the specs for the Peerless. and it is 842 CFM @ 6 inches, which considering any restrictions in the ductwork, and those figures move down substantially. Even with no static pressure, the blower was at 1185 CFM. A decent blower for a 3HP vacuum system should be able to pull 2000+ CFM, and at least 20 inches max pressure. Epilog states 800 CFM @ 6 inches for the 9000 series as a minimum.

I looked at the construction of the Peerless as well.

The construction of "blowers" designed for dust systems is a bit different, and result in some better numbers for the intended application. If you change the perception from one of "exhausting the enclosure" to one of a large volume vacuum, then I believe the solution becomes more obvious.

I should have my new system hooked up next week. Then I can say for sure that there is an inexpensive solution to her needs. My approach is to use a blower from a medium volume vacuum system with specs of 1500 CFM @9.6 inches static pressure, that uses about 2 horsepower, and is quiet at 65db. I also have a very short path between the laser and the exhaust wall.

Have a look at http://en.wikipedia.org/wiki/Static_pressure and scroll down to the "Static pressure in fluid dynamics" section. The issue is complex to say the least, and taking Epilog at its word for their minimum requirements, and multiplying by a factor of 1.5 would be a good place to start for an adequate exhaust system under average installed conditions in my opinion, especially considering the size of the cabinet.


David

[Mike Mackenzie]

David,

I am very curious on which blower you are going to be using please keep us posted on the model and mfg.

[Richard Rumancik]

A decent blower for a 3HP vacuum system should be able to pull 2000+ CFM, and at least 20 inches max pressure.

My approach is to use a blower from a medium volume vacuum system with specs of 1500 CFM @9.6 inches static pressure, that uses about 2 horsepower, and is quiet at 65db.

David, I am curious as well . . . I have looked at a lot of blower specs and I just don't know how you can get this performance with 2 hp. Do you mind revealing the manufacturer/part number?

Many dust collector blowers are poorly defined by the manufacturers; I find that the industrial exhaust fans are typically spec'd much more thoroughly. I have yet to find an actual performance curve for a dust collector unit. Some specifications don't even address static pressure.

To get 1500 CFM and 9.6" using a Peerless branded unit (which are spec'd as suitable for exhaust systems) you would need over 7.5 hp (it is actually off the chart). Something is not right if a dust collector can hit the same performance point with only 2 hp.

You seem to be suggesting that the Peerless-style pressure blower might not be ideal for laser exhaust systems but in my experience these types of blowers are commonly used for exhaust systems. Dust extractors are similar to exhaust blowers but not identical; for dust collecting you have to maintain a certain air velocity to move particles. But for a laser this is much less of a requirement as it is mainly smoke and gasses from combustion. Can you elaborate as to why you feel a centrifugal pressure blower is not as suitable as a dust collector?

The requirement to have the blower sitting very close to the laser is not practical for everybody, often due to space and/or noise constraints. I have my blower in a garage attic which moves the noise well away from the work area and enables me to exhaust at a high elevation. I certainly would not want it on the other side of my wall due to noise.

[David Brasfield]

I figured I would stir up some controversy. Not intentional.

Like I said earlier, the approach is what I looked at. High volume vacuum systems will move more air at higher static pressures than a system designed for exhaust. A look at the air distribution inside the cabinet of the the 9000 series cabinet "screams" vacuum to me (in my little engineer brain), rather than smooth flow exhaust.

Well designed vacuum blowers don't incorporate straight fins on the impeller. They are typically designed more "screw like", and can move more air under greater pressure. It is an efficiency issue.

Think about it this way. If an aircraft propeller had no pitch, and was flat, it would produce no lift, and not move the aircraft. Many aircraft have variable pitch systems which are adjustable for the greatest efficiency at a given speed/horsepower ratio.

Blowers with straight fins work by creating a pressure difference between the two openings. While that works, with a modest bit of additional engineering, that process can be made much more efficient. That usually increases cost, however. With the influx of China made copies of what would otherwise be some more costly technology, the better blowers are out there, and cheap.

Have a look at the impellers on the peerless systems. Then have a look at some designs on the major dust/chip handling systems.

The really good "blowers" will appear to work in reverse of the standard side fed(intake) blowers, being end fed and exhausting out the side as in many "cyclone" systems.

I'm not trying to stir anything up. I will be glad to provide part numbers and photos when my system is up and if it stands up to the test.

As for published specs, I don't really take anyone's specs at face value. Sears tells me it can get 6.5 horsepower from a shop vac powered by 120 volts at 12 amps. That folks, would be a true miracle. In a perfect world, that would equate to about 1.9 horsepower. Add in design and electrical/motor inefficiencies, and real world output would be about 1.5 - give or take.

David

[David Brasfield]

I am out of butt for the evening, but I though this was a rather straight forward treatise of some of the issues of air handling.

http://www.dmr-hvac.com/Downloads%20...%20Paradox.pdf

" The Static Pressure Paradox
An important consideration during fan selection"

I'm sure there are better links. I will find more later.

David

[Richard Rumancik]

I figured I would stir up some controversy. Not intentional.

Not for me either - some of us are just hoping for a "Eureka" as a few members have struggled with exhaust problems in the past.

I want to ensure nobody breaks any laws of conservation of energy on this forum - but I think that 1500 CFM @9.6 inches static pressure using 2 hp is running over 100% static efficiency . . . so maybe they have mis-spec'd their unit in some way.

Like I said earlier, the approach is what I looked at. High volume vacuum systems will move more air at higher static pressures than a system designed for exhaust. Well designed vacuum blowers don't incorporate straight fins on the impeller.

Not sure about this - the Peerless for example is called a pressure blower but what leaves the exhaust has to come from somewhere; they could have called it a vacuum blower I suppose.

Blowers with straight fins work by creating a pressure difference between the two openings. . . .
Have a look at the impellers on the peerless systems. Then have a look at some designs on the major dust/chip handling systems.

Straight radial fins are kind of a middle compromise I think. You can go forward curved blades for high flow, low pressure or backward curved for high pressure low flow. But we want both - high pressure and high flow. Seems like a radial blade falls somewhat in the middle. Each type has certain advantages to efficiency, handling of particulates etc as well. In our case there are minimal solid particulates (no sawdust.) These wheels are usually cast (not sheetmetal like a furnace blower) and making a curved blade casting is really not more expensive than straight. The selection is based on what you want the blower to do. It's all tradeoffs.

The really good "blowers" will appear to work in reverse of the standard side fed(intake) blowers, being end fed and exhausting out the side as in many "cyclone" systems.

I haven't seen this type. Everything I have seen has the suction coincident with the center of rotation of the wheel. But I guess I have only looked at conventional centrifugal systems.

Still interested in what you come up with . . .

[David Brasfield]

Not for me either - some of us are just hoping for a "Eureka" as a few members have struggled with exhaust problems in the past.

I want to ensure nobody breaks any laws of conservation of energy on this forum - but I think that 1500 CFM @9.6 inches static pressure using 2 hp is running over 100% static efficiency . . . so maybe they have mis-spec'd their unit in some way.

Yep, I figured around 1350 instead of 1500, but like I said, I don't take any manufacturer at their word

Not sure about this - the Peerless for example is called a pressure blower but what leaves the exhaust has to come from somewhere; they could have called it a vacuum blower I suppose.

I think that they aim at low restriction minimum negative pressure on the inlet side. That is a great approach to blow things, or even a good idea for large (mostly open) area exhaust systems. I have experience with some massive ones. The biggest one I ever dealt with was an exhaust system for a huge melted tar rectangular tank used in making roofing felt. As I recall, it was about 70 feet long and 10 or so feet wide.

Straight radial fins are kind of a middle compromise I think. You can go forward curved blades for high flow, low pressure or backward curved for high pressure low flow. But we want both - high pressure and high flow. Seems like a radial blade falls somewhat in the middle. Each type has certain advantages to efficiency, handling of particulates etc as well. In our case there are minimal solid particulates (no sawdust.) These wheels are usually cast (not sheetmetal like a furnace blower) and making a curved blade casting is really not more expensive than straight. The selection is based on what you want the blower to do. It's all tradeoffs.

I agree, again, my sense of things is in thinking of the laser enclosure as just that, instead of something like a ventilation hood. That makes my little mind want to treat it as an enclosed vessel that will experience lowered pressure when exhausted. Hence my proclivity toward using a system more geared toward vacuum, regardless of whether or not debris and particulates are involved. Higher static pressure differentials and higher flow.

I haven't seen this type. Everything I have seen has the suction coincident with the center of rotation of the wheel. But I guess I have only looked at conventional centrifugal systems.

Well, I have a link with some drawings of different systems and impeller designs, which I can't find right now (of course). I will get it to you.

Still interested in what you come up with . . .

Basicly, my "gamble" is simple. A vacuum specific "blower" simply because the exhaust side of the blower represents the least part of the problem since there are no filters, only ductwork induced restrictions (if any). Time will tell. I do know that I will solve the issue, and I won't go broke doing it

David

[David Brasfield]

Hi, folks.

Still can't find my comparison links, but here are some picks of a Grizzly impeller and one from Oneida.

David

[David Brasfield]

Hi, folks.

Still can't find my comparison links, but here are some picks of a Grizzly impeller and one from Oneida.

David

I have had the new blower for a couple of days, but just now unpacked it. It sure enough has a 2HP induction motor, and a nice steel impeller very similar to the Grizzly picture I posted (didn't really want to spend the bucks on an Oneida quality blower, even though I already own one).

It has a 6 inch inlet, but they were nice enough to provide a 4x4x6 inch "Y" that directly attaches to the inlet, so in the spirit of experimentation, I am going to leave my system temporarily choked down to 4 inches on the ports, and additionally choke down the exhaust side to 4 inches.

I am doing this in hopes of simulating Barb's dilemma, and seeing if this will help her out. I will vector cut some 1/2 - 3/4 inch material so that I can make lots of smoke.

I still have to wire up another 220 circuit, but I should get to that tomorrow. I will have pictures soon.

All the best,
David