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Discussion Starter #1
Last weekend I started another CNC router CAD model and finished it up last night. My goal on this one was to keep the overall width to a minimum by tucking the Y ballscrews in as close to the frame as possible. I think this would be a reasonably rigid machine, within the limitations of aluminum extrusions, and not difficult to build once machined parts are in hand. The model was created with Fusion 360 and all major dimensions are driven by user parameters. Those include X Ballscrew Length, Y Ballscrew Length, Z Ballscrew Length and Gantry clearance height. Change any one of those and the model adjusts to reflect the new dimensions.

Specifications:

Size - Parameter Driven
Extrusions - 80/20inc. 40 Series. All extrusions are 80mm x 40mm
Aluminum Plates - 5/8" for all except the front end plates which are 1"
X & Y Profile Rails - 20mm
Z Profile Rails - 15mm
X & Y Ballscrews - 20mm
Z Ballscrew - 16mm
Stepper Motors - Drawn with NEMA 23 ClearPath Servos but mounts will also accept NEMA 34 Stepper Motors
 

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When are you going to start building it?

I do not want to critique, but I do have some suggestions for you to consider if you are actually planning to build a CNC like this in the future. They are things I thought about and designed into my machine (which is by no means perfect). They are just things that made sense to me. But only if you are interested, this looks like a nice clean design that would work well.
 

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Very nice work, Ed! You are so far ahead of me in Fusion 360 it's not even funny. Great job and a good design.

Except for ease of access to the Y servos (or steppers) could they go on the back to get them out of the way in the front?

David
 

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Thats really sharp lookin Ed

Can the motors be on the backside or??
I think I'd get hung up on them or they'll be a good place to hang me hat.
 

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Discussion Starter #5
Very nice work, Ed! You are so far ahead of me in Fusion 360 it's not even funny. Great job and a good design.

Except for ease of access to the Y servos (or steppers) could they go on the back to get them out of the way in the front?

David
Thanks for the comments, David. The last couple of designs I did had the steppers in the back and this one could easily be swapped. Unless I screwed up somewhere along the line, there is only one joint connecting the entire gantry to the right side rail car spacer, so deleting that joint and spinning the gantry 180 degrees would put them in the back. My thinking was the router could be placed closer to a shop wall in this configuration and the couplers would be easier to get to if they needed to be checked. If the steppers end up hanging out over the edge of a table, I can see where it could be a problem this way.

Ed
 

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Discussion Starter #6
When are you going to start building it?

I do not want to critique, but I do have some suggestions for you to consider if you are actually planning to build a CNC like this in the future. They are things I thought about and designed into my machine (which is by no means perfect). They are just things that made sense to me. But only if you are interested, this looks like a nice clean design that would work well.
I don't know if or when I might build this one. I currently have a Probotix Asteroid which is serving the purpose right now (particularly after replacing the Z assembly), so it may be a while. When I do decide to replace the Probotix, this one might be the way I go. I'm always open to critique and/or suggestions, so please, let me know what you have in mind.

Ed
 

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Discussion Starter #7
Thats really sharp lookin Ed

Can the motors be on the backside or??
I think I'd get hung up on them or they'll be a good place to hang me hat.
Yes, that would be an easy change to the design. Thanks for the comments.

Ed
 

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I thought about it being able to set closer to a wall but then I also thought about those times when a board needs to hang over the end or you need access to that end and realized placing it against a wall has some drawbacks. Same thing with placing one side against a wall. I can get to about 90% of ours, 100% if I move a small stand, and have used every bit of that many times.

Good job - again!

David
 

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Suggestion # 1 Design for maintainability.

There are various parts of the machine that will need periodic maintenance, including the bearing assemblies for the linear rails. Visualize how much of the machine needs to be disassembled to access any of your bearing assemblies to clean, lubricate or replace them. This will need to be done at some point in time.

On my machine, I can remove the 4 screws on any bearing block and slide it off the end of the rail. Please excuse the state of my machine, I just disassembled and moved my machine from my old shop to a small shed on my new property. It is not fully recommissioned.

Y-axis: (my longest axis the way I am currently configured)
IMG_0328.jpg

X-axis (along the gantry axis)
IMG_0330.jpg

Z-axis
IMG_0329.jpg

And yes, there are hard stops on each axis that prevent the any of the moving parts from sliding off accidentally.

Your design shows profile rails, the blocks on those usually have grease nipples, so that eliminates the need to remove them for lubrication, which helps, but they are all trapped on each end of the linear rail by structure, and quite a bit appears to be involved to remove one.
 

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That is a beautiful beast you've imagined HDvideo. My only reservation about the gantry bridge is that all those open spaces will fill up with sawdust/chips and be a pain to suck clean.

4D
 

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Suggestion # 1 Design for maintainability.
My take? If you have to disassemble any part of your machine to maintain it, it's a bad design, or uses the wrong components.


You certainly want access to be able to grease your ballscrews and linear rails. If you grease them regularly, they should run fine for years, or even decades.

Round rails are not a very good choice in a dusty environment, as they don't seal nearly as well as profile rails and bearings.



My only suggestion would be to ,make the gantry beam one large extrusion. What you have now will not have good torsional rigidity, and will twist fairly easily. I'd recommend a single 80x160 extrusion. It does change the design, as you'll need to raise the rails to get ballscrew clearance. But you'll have a more rigid machine.
 

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Discussion Starter #13
My take? If you have to disassemble any part of your machine to maintain it, it's a bad design, or uses the wrong components.
You and Richard both make good points about maintainability and I agree maintenance should not require more disassembly than necessary. To say it's a "bad design" if "any part" has to be disassembled might go a little too far. lol Y axis end plates with the floating bearings come off with 5 bolts, providing access to the Y bearing blocks and four bolts hold the gantry beams to the riser. Removing those and manually moving the riser forward or aft provides access to all X axis bearings. Z axis rails are open at the bottom so not a problem there. Clearly not as easy as your design, Richard, but something I think I could live with.

My only suggestion would be to ,make the gantry beam one large extrusion. What you have now will not have good torsional rigidity, and will twist fairly easily. I'd recommend a single 80x160 extrusion. It does change the design, as you'll need to raise the rails to get ballscrew clearance. But you'll have a more rigid machine.
I do consider this particular gantry configuration the weakest element of this design. The past two or three designs I've drawn used 80x160 extrusions for the gantry, one even used them for the Y frame rails, so for this one I wanted to do something different. The 1/8" steel plate connecting the two extrusions is there to provide additional rigidity, but still wouldn't be as good as one larger extrusion. I like this design for its simplicity and compactness, but if/when I actually build one, I'll probably go with the larger single gantry beam.

Thank you all for your comments and suggestions! I do appreciate it.

Ed
 

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I wasn't saying that your design was bad. I was saying that no machine should need to be taken apart for regular maintenance.
 

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Discussion Starter #15
I wasn't saying that your design was bad. I was saying that no machine should need to be taken apart for regular maintenance.
Any comment I made referred to things you said, not things you didn't say. BTW, love your 2017 Screenset. You've managed to make a very good program (UCCNC) even better. Thanks!
 

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I'll stand by my statement. :grin:

I'm working on an update to the screenset to support all the new UCCNC features, but it'll be a few more months. Glad you like it.
 
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