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Discussion Starter #1
Don't take this the wrong way.... I love the CNCs made by Probotix. We have a Meteor where I work though which has always been reliable... except when precision of detail alignment or dimension has been a critical factor.

I've lately been perplexed more than usual on why joinery cuts on my vertical clamping jig have been misaligned. Over the Thanksgiving break (9 days when no students were on campus) I decided to get to the bottom of the mystery.

With squares and precision measuring rules I went at this old Meteor. My findings surprised me, but do explain why so often over the last several years I've been dissatisfied by the results of a cut.

1. The Z axis assembly was not square to the frame or X/Y travel plane. Tilted back roughly 2 degrees.
2. The gantry wasn't parallel to the front/back frame members. Approx. 1/16" back on the right side compared to the left side.

The gantry alignment is set when homing. Limit switches on the right and left hit a triangular bracket screwed to the bottom of the side frame members. In this meteor the bracket on the right was 1/16" farther back than the one on the left. A relatively easy fix, but also should have been easy to set right at the factory.

The only way I can see to square the Z axis assembly is to rotate the gantry beam. Two bolts on each side hold the beam to the vertical side plates. These bolts go through holes in the side plates with no obvious slop in the fit. The solution I see is to remove the two front bolts, ream out the holes they went through, crank the whole beam/Z axis forward until plumb then insert and tighten those two bolts.

I also have a Meteor in my home shop, and it does not suffer the same flaws this work machine does. My Z axis is plumb. My gantry runs parallel to my front frame rail.

My point here is to check any new machine for plumb and square. In most cases flaws found can be corrected, and the accuracy of your work will increase.

4D
 

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Is there a chance the gantry amd machine got tweaked a little as a student had the router forced against a piece of wood or something, putting to much strain on the gantry as it was trying to move ?
 

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Discussion Starter #3
Our college went through a remodel that took essentially 3 years. The CNCs went through 4 moves as we were first kicked out of our original shop are so asbestos was removed and that area was turned into a large lecture room. We moved into a basement area in the old building first. Then a move to a temporary wearhouse while we waited for a temporary metal shop building to be erected near the temporary classroom building, then finally back into our new shop space. It is quite possible the Probotix CNCs were lifted by a crane using straps around the gantry which may have twisted the gantry. I personally didn't witness how they were moved any of the 4 times.

I've had the Z axis come down on immovable clamps a few times, which certainly puts unusual forces on the Z axis assembly and gantry. On inspection though I can't see any way things could have been rotated or twisted to a new position and stayed there, as I can't see any bent/damaged parts in the assembly. There is also no apparent way to adjust the rotation of the Z assembly around the beam, or the rotation of the beam itself relative to the side brackets.

4D
 

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I know you're glad to have it all lined up and like it should be.

Our Saturn gantry was out of square by about 1/8". Someone suggested I use homing to square the gantry but I would never want to do that. I'd rather have the gantry mechanically square than to force it square with electronics. And the Saturn is so rigid I doubt it could even be pulled square by the electronics. So now it's square, the gantry glides easily along the linear rails, and it cuts as it should. But it was out for the first year I ran it because I didn't realize it was out. When I fixed it all sorts of things I cut in the past began working much, much better.

David
 

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It is a good idea to check the alignment of your machine at least every 6 months just to make sure something hasn't changed. Just a little wear in parts will affect the alignment and quality of projects. It also lets you know when parts are failing before something major happens.

In the last year I have been getting questions on how to align the Y axis to the X axis on the Next Wave Automation CNC Shark machines. They should be aligned before they leave the factory as far as I'm concerned. When I tell them what they have to go through a couple have said they contacted Next Wave Automation customer service about the problem and they told them the same thing about aligning the machine. They were hoping there would be an easy fix but you have to remove the bed so you can get to the Y axis mount to the gantry, make adjustments then reinstall the bed and recheck alignment. Then repeat if it is still off a little.

I have considered making aftermarket upgrade kits that would allow you to make easier adjustments for aligning their CNC's but I'm trying to get away from their machines and problems just like this.

I do maintenance calls on their machines and this is one problem I will not address, too involved and time-consuming to quote a price because of what you have to do to re-align and check to make sure everything is correct.
 

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I bolted mine together, wired it up and started cutting. I either got lucky or my old eyes are too bad to see the misalignment issues. Someday I will run the cncrp alignment tests and adjust if necessary but for now I'm pretty happy being lucky or blind. 🙂
 

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Discussion Starter #7
We have an old NextWave Automation Shark HD in the same room as our Nebula and Meteor from Probotix. It was our first CNC, and was heavily used until the Meteor showed up. The plastic Z axis design of the Shark has so much flex that I've essentially stopped using that machine. We just ordered a Comet from Probotix (10% off sale right now) to take its place, and the Shark will be sold. My little CNC room will now be a Probotix-only room. As they've raised and stiffened the gantry of their designs, the little Comet should now do all that the Shark was used for (extra Z height) and with my angle jig in it should do all the complicated joinery I cut as well. I'll mount it on a taller base to handle the vertical joinery cuts on long(er) stretchers and furniture panels.

The Comet will be thoroughly inspected for square and plumb once it arrives.
4D
 

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Discussion Starter #8
Today we received our new Probotix Comet. Uncrated, set up temporary on a workbench to mount the Z axis stepper and install the Y axis limit switches. A quick check of the Z axis shows it isn't 90 degrees to the bed. It appears the cantilevered weight has racked the whole gantry beam a couple of degrees forward.

We aren't quite sure how to remedy this. It was freezing cold today and the CNC parts were icy cold, so I'm going to let it acclimate to the warm shop overnight before final judgement and photos to send to Probotix. It may be possible that the bitter cold "shrank" the gantry risers which caused them to twist a bit based on how they are mounted/restricted by bearings and beam.

I'll admit I do like the improvements they've done to stiffen up the gantry/Z axis. The added Z travel will come in very handy.

4D
 

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Right now Probotix has a 4 day sale starting --- 20% off.
 
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True that is John. Very tempted to buy something.... anything from them just to save that 20%! Of course I don't actually need anything they have, but ...~!
 

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Discussion Starter #12
You are going to post photos, right?

David
Yep. On their new riser design the 4 bolts that hold the gantry beam have washers under them. I'm thinking the holes beneath the bolt heads may be slightly oversized, in which case loosening them all may permit squaring up the assembly before tightening them all down.

4D
 

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Discussion Starter #14
Yesterday I rechecked the Z axis and now that the machine parts have warmed up the out of squareness has reduced down to almost nothing. Still a small fraction of a degree off, but less than what I found our old meteor was off. Once the router we bought for it comes in I'll check again.

The 10% and now 20% off sales that Probotix has been running makes me curious. Perhaps they made a big investment in extrusion and other parts to get a price break and now are encouraging sales to reduce the space all that stuff takes up. Not complaining mind you. Just curious.
 

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Heck of a sale for anyone wanting a Probotix machine! I just sent a quote in for a Meteor for work as they were looking for a "spare" machine. That would make 7 Probotix machines I have set up for a specific operation.
We'd love to see a photo of all those machines, assuming it's permissible to do so.

David
 

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4D

I heard they're moving to Atlanta and are trying to get rid of as much stuff as possible so they have less to move. No facts - just what a little birdee said.
 
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Discussion Starter #17
I've got a sister who lives in Atlanta, and every even numbered year there is a woodworking trade show that sponsors a furniture design competition for college students that I attend occasionally. I may have to visit their factory next time I'm down there.

4D
 

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The only way I can see to square the Z axis assembly is to rotate the gantry beam. Two bolts on each side hold the beam to the vertical side plates. These bolts go through holes in the side plates with no obvious slop in the fit. The solution I see is to remove the two front bolts, ream out the holes they went through, crank the whole beam/Z axis forward until plumb then insert and tighten those two bolts.
4D
If I understand your issue, would it be possible to shim the router mount rather than try to rotate the gantry beam? If your machine is like mine, they use four Delrin or similar spacers between the router mount and Z-Plate. Maybe an adjustment to those spacers would solve your problem.

Ed
 

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Discussion Starter #19
If I understand your issue, would it be possible to shim the router mount rather than try to rotate the gantry beam? Ed
The router mount is flush/square to back plate, the plate is parallel to the guide rails. The guide rails run through bearings that are mounted on a bracket that surrounds the gantry beam. Shimming just the router mount would still have the router coming down a fraction of a degree off vertical. Only rotating the gantry beam would allow straightening the guide rails to vertical relative to the bed frame.

The CNC is a Probotix GX25x25 (formally called a Comet) https://www.probotix.com/CNC-ROUTERS/CNC-ROUTER-GX2525-COMET, and although they haven't updated the photos to reflect the latest changes to their designs, the Z axis is essentially the same design.

4D
 

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The router mount is flush/square to back plate, the plate is parallel to the guide rails. The guide rails run through bearings that are mounted on a bracket that surrounds the gantry beam. Shimming just the router mount would still have the router coming down a fraction of a degree off vertical.

4D
I have the Asteroid model and see what you are talking about. Would it be possible to shim either the top or bottom of the bearing to make the Z guide rails perpendicular to the bed? On mine, I've go so much slop in those bearings that being off a little is the least of my worries. lol

BTW, I've created a complete CAD drawing of the Asteroid in Fusion 360. I'd be happy to share it with any members here that are interested.

Ed
 

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