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Discussion Starter · #1 ·
My new Comet is up and running!:smile: Here's a few pics of the base I built, the machine, and first (succesful:laugh2:) cuts. Took some experimentation to get the CAM setup figured out.

Need to spend some more CAD time now to make some more models ready to cut.
 

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Looking great! First photos I've seen of their new design. Very curious why they have the open triangle on the gantry risers.
Looks like they've also upgraded the steppers they are using. Thanks for posting those photos.

4D
 

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Congrats Brian! Are those cuts with a drag knife? That is not something I have tried. Looks good!

You may need to add some diagonal bracing, and I hope those are locking casters because once the machine is going at full speed you may be surprised at how much it wants to move!

I look forward to seeing what you make with your new tool (not toy!).
 

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Mike
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Looking great! First photos I've seen of their new design. Very curious why they have the open triangle on the gantry risers.
Looks like they've also upgraded the steppers they are using. Thanks for posting those photos.

4D
I'm with you 4D, what is that little triangle cutout for? If it is not for mounting something then it looks like a finger trapping problem. I would not think it would be for weight reduction.

Looks like the steppers are the Nema 23 570 oz dual shaft motors. They don't have specs listed for them so you can't compare them to the Green Nema 23 420 0z steppers.
 

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Mike
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Brian congratulations on your first steps into the CNC world. Looks like you'll catch on pretty quick. Looking forward to see how far you push limits.
 

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The only answer that pops into my mind for those triangular cutouts is to give them a place to hook into when lifting the CNC with an overhead crane. With the gantry parked in the center of the machine those points might be very close to the center of gravity. An easier lift (than 2 or more men) of an assembled machine to drop it into the shipping crate.

4D
 

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4D I would think that that would put undo stress on the Y axis gantry rails. I know several companies stress that when moving their machines not to use the gantry to lift the CNC use the frame only.
 

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When the bed of a CNC is cast iron (like the multicam that lives in my college fabrication lab) then of course you wouldn't want to pick it up by the hooking onto the gantry sides. The aluminum extrusions used by probotix, short on the Comet, reinforced by the linear rail, aren't going to flex under the weight of the machine itself. If they did then they would already be sagging as the gantry bears down and the side beams are only supported up on their ends. Right below that triangle the side plate bolts into two bearing blocks that ride on the linear rail which is bolted into the frame. When I moved my Meteor from my garage into the basement room where it now resides, I removed the MDF bed, stood in the middle, and lifted the whole CNC by the center of the side rails. Nothing flexed then.

So until @probotix reveals the real reason for those cutouts, I'll stand by my guess. They do show up here every now and then so maybe we'll get an answer. It can't be just for looks.

4D
 

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Discussion Starter · #13 ·
The parts pictured are for a profile model airplane, made of dollar store foam board. Cuts were done with a 1/16" downcut end mill. I am interested in the drag knife setups for this material, though the end mill seems to do a good job with just a little fuzz on the backside. Upping the feed incrementally. Started around 40 ipm, up to 75, and will bump it up again on the next test.

Looking to cut some balsa, basswood and ply once I'm comfortable with the whole process. And, I would like to also use it for some furniture type projects.

On the topic of the base table, it does twist a little bit (@1/16" corner to corner) depending where on my uneven floor it sits. For the simple 2d contours this hasn't caused an issue. So far it hasn't moved around on the casters, we'll see what happens as I increase the feed more. I may get rid of the casters anyway,in favor of some larger fixed wheels on one end and a single drop foot on the other end. The idea being that with only 3 contact points, floor surface won't rack the table. The outer posts will still be there just off the floor slightly.

On the gantry riser cutouts, I have no idea. Maybe just to provide a visual cue to the new design?? I would say I wouldn't have put them there just because more material means more rigidity, but the machine seems plenty solid, so I'm not worried.

Brian
 
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