So if i read this correctly what I hear you saying even the physical head travel speed would be the same …the vertical lpi could be half the travel distance so the total time could doubled…
Both machines I have used and all the pictures I have seen have a bow in the lid highest in the center between front and back.
With an unrestricted exhaust there is a negative pressure inside the machine, so every crack in the case and lid are sucking air in. In the case of an exhaust restriction smoke can be pushed out of the cracks.
It took me a couple of months to nail it, but I finally sealed all of the leaks in my 30’ exhaust run and it is odorless now.
I used standard 4" vent pipe, and had to use silicone to seal all the connections, edge seams and especially the elbows which leak badly.
I would recommend a screw type hose clamp and that aluminum tape for the vent connection to the machine. Also, installing the booster as close to the end of the run as possible is best because everything downstream of the booster is under pressure. If it is at the end every potential leak is pulling air in instead of blowing smoke out.
Regarding the speed, the mass of the head is much more than just a mirror and lens like many commercial machines that fly around. I think there is a limit to how fast you can yank that head around. That’s just my speculation.
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I thought the bow was on the sides, not the lid itself. I haven’t taken a straight edge to mine though.
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If you’re using too high of an LPI, you’re drastically increasing your print time. There are other posts that go into discussions around LPI for different materials, but it seems that one of the things that we should all consider in our projects is whether or not very high LPI is truly required. For instance, there are cases where increased LPI could decrease clarity in engraves because too much material gets burned away.
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You are right, I just checked. I guess I assumed the lid was tempered with a slight camber for structure.
Wow. There’s a first time for everything 
Now if only my wife would say that to me…
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Thanks for the recommendation @JimSocks. I ordered one. I also find that cracking the side door (Glowforge is in the mudroom for now), allows for extra intake air. Think about what happens with a vacuum when you put your hand over the end. Exhaust fans work best when they have someplace to pull from.
Very True. Good point. Every single seam needs to be attended to. I was really happy with the aluminum tape I used for this. I’d never used it before this and it does a great job.
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Hmm. If my fan is a lower CFM, will that be a bad thing? I think the one I ordered doesn’t measure up to those numbers…
I’ll double check my machine levelness when I get home tonight to see if that’s the issue with the lid. That would be awesome if that’s all it is, though I’ve already checked that once and thought it was spot-on.
The speed issue that caught me off-guard has everything to do with the head movement speed. I’ve been operating on Epilog Helix machines for years, and as mentioned above, those carriages only contain a mirror, lens, and air assist tube basically. The laser head on those machines easily moves 4x faster from side to side- at relatively lightning speed compared to the GF.
While LPI might shorten times if lowered, it’s really the head movement speed that really took me by surprise.
I agree- the GF head is much bulkier and only held by magnets, so there is surely some physics limitations there when it comes to how fast you can whip it back and forth. All I’m saying is, it was a complete surprise to me how slow that limitation turned out to be. To be honest, I hadn’t even thought about the possibility it would be different than what I am used to until the moment I saw it move.
Yeah, it surprised me when I got the PRU in the spring. Not an issue if you’re coming from a cheap chinese laser (K40 type) but larger robust ones like the Redsail or Epilogs, etc are much faster. The ipm speeds of the GF vs the 1000mm/sec of other machines is enormous. But I have less re-work and the workflow is smoother so that helps the total time to project completion. It is still net slower though and that has to be factored into any production planning.
Isn’t the Epilog Helix also over double the price of the GF Pro (even with the newer pricing)?
Oh yeah. Speed costs in lasers as in cars, planes and boats 
But anyone who has used a CNC is happy with laser speeds - even GF laser speed.
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The buyers conundrum exists everywhere.
Quality.
Speed.
Price.
Pick 2.
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yup, and my $30k universal at work is faster, too. but for 1/15th of the price…
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This and the fact that I don’t have to worry about runout or deflection of the bit is very nice.
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i found that it wasn’t so much putting a level on the lid and making sure the lid was at perfect level. my desk is fairly level. but what i did was look at the front corner of the GF that seemed a little lower than the lid in that corner. i put a tiny shim under that foot and the lid became level with the top. that seemed to help.
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Yes, level is not as important as flat. Few of our surfaces are dead flat. Since I had received the pre-release it had the right front corner of the lid sitting up about 1/32" from fully seated. Moving the machine from its ‘flat’ perch to a ‘flat’ table for cleaning the exhaust fan grill resulted in a rub in the fit of the lid on one side.
When I put it back, I repositioned the machine about an inch further to the right from where it had been. Not only did the lid rub go away, but the lid closed full seated on both sides.
With that lesson taken, when the new machine came, I took the time to position it so the lid operation and fit were right.
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Definitely – the helix is double the price for sure. I’m not saying that a machine which is half the price is unacceptable to be so much slower, I am only illustrating that I did not expect it to be.
As I said above – I hadn’t really read anything that prepared me for the realization of its actual speed when I saw it for the first time.
I had just ASSUMED that all laser carriage speeds were created equal, which looking back is obviously a silly assumption. All I’ve ever known is Epilog, so I didn’t even realize consciously that I had made that assumption, it just automatically wasn’t a factor in my expectations. Since I had that expectation already rooted in my subconscious (built through year after year after year of seeing the exact same carriage speed capabilities) – you can bet it threw me for a loop when I saw it for the first time and my “laser carriage speed world view” was brought instantly to a crumbling ruin.
And I am certainly not aiming to be Negative Nancy either. There is plenty to love about this machine! I have a few issues I would like to fix (smoke, front door fit), a few I would like to see fixed in the future (accuracy, maybe a handy driver), and really just one that I’m sure will never change – which is the slow carriage speed.
That one thing IS pretty significant and caught me completely off guard, but on the whole it is still awesome to have a machine this capable in my very own home for the price point that I picked it up at.
I am excited to get home and monkey with the levelness and exhaust sections based on advice given so far!
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This is an important point.
The GF fan can’t exhaust air unless there is a way for replacement air to get into the room. You might have to crack a window in another room to allow makeup air.
If you have an open wood-burning fireplace or stove, be aware that the GF exhaust can cause backdrafting, same as a bathroom fan.
I would focus on sealing all leaks in the GF exhaust system and providing makeup air before doing anything to seal up gaps in the GF case - they are needed to allow air in, to carry away the smoke.
Don’t recall who first suggested big zip-lock bags or plastic bins to store left-over material, or the product until you have time to clean it, but for me that has made the biggest difference in cutting down the smell in the room.
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very true. and also far more compact than the more industrial versions. we have a brand new (literally weeks old) 75w universal laser in my office. i would not have been able to get that thing up the stairs and into my office, let alone put it on a desk.
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