NordicCNC's build log

[joe.ninety]

Those block are used to increase the gantry clearance. I want to build machine out of aluminium profiles and the 200x80 profile for the Y-axis sides are not high enough.

Ok, in that context I understand. It's just in most designs I've seen there is simply a gap there... The desired height achieved by where on the gantry sides you bolt the cross-section (the main bit of profile that forms the gantry).
So in your design, the gantry cross section is supported by being both bolted to the side plates and also by sitting on other pieces of extrusion? Are the blocks underneath connected to the cross-section or does the cross-section simply sit atop them?

Cheers

[joe.ninety]

Ok well I'll answer this question seen as he's mostly following my design.!

It always makes me smile when I see comments like these because while the physics shows that what you are saying is the ideal location the reality is that it makes no difference to the machine and how it works.

To prove this point I'm going to give you a challenge.! . . . Industry demands the highest cut quality and performance, so logic dictates that they would follow the physics and optimum location very closely.?

So go find me a machine from the major manufacturers that place the spindle smack between the bearings.! . . . If you find one then I guarantee you'll have seen ten before it that don't.!! . .. In fact, you'll be lucky if you find any with spindle inside the bearings.!

You all need to stop worrying about the physics and virtual world so much and get building so you can realize just how little if at all, these affect a real-world machine.!


To answer you directly Joe, then to place the gantry further back to bring spindle into line with bearings would actually weaken the machine not make it stronger. To do what you suggest without getting into complex gantry side designs means using plates for gantry sides that can flex side to side and introduce vibrations at the tool.
I can tell you from building many different designs of router that the design he's using is the best possibly way to build a router without getting silly about.
Mike is correct in that having longer distance between the bearings is good but thats a trade off between travel and foot print of the machine. In the grand scheme again it makes very little difference.

Is it any wonder that us mere novices get totally confused by all this, as there seems to be loads of conflicting advice floating around in the ether and I'm not talking about just on here.

So there I was working on some supposed designs... Linear rails on back of spindle mount, carriages on z axis, and trying to have a design that keeps the spindle as close to the bearings as possible... Now I find out all that is unnecessary, or not as necessary as I'd been led to believe. But as you've given this design the seal of approval then I guess I'll just try and make mine more like this one, only smaller.

Cheers

[NordicCnc]

Ok, in that context I understand. It's just in most designs I've seen there is simply a gap there... The desired height achieved by where on the gantry sides you bolt the cross-section (the main bit of profile that forms the gantry).
So in your design, the gantry cross section is supported by being both bolted to the side plates and also by sitting on other pieces of extrusion? Are the blocks underneath connected to the cross-section or does the cross-section simply sit atop them?

Cheers

Yes, L-shape bolted together to the gantry sides. Screw clearance holes in the lower profile, threading into t-nuts in the upper profile. I also intend to use aluminium plates and shim them in the t-slot, to act as guides/stopper so that the gantry profiles doesn't move. The blocks underneath the L-shape also have holes and mounts to the lower profile.

Actually I am extremely glad that you commented on the design. It made me realize that I could further increase the stiffness while not compromising gantry clearance significantly!

I've now removed the 60mm high profiles from the gantry sides. Instead I've replaced the 20mm thick blocks underneath, with 40mm blocks. These are going to be machined so that the Z-axis can pass above the blocks. This effectively decreased height the gantry sides by 40mm, less parts, increase simplicity & accuracy while making the gantry stiffer.



However this means that I need to modify the table to compensate for the lost 40mm clearance.

In the current base frame, I've used 120x80 profiles bolted into the sides, consisting of 200x80 profiles. I have 2 alternatives I think:
1. Replace the 120x80 with 120x60 to gain 20mm clearance. Now I've only lost 20mm clearance.
2. Move the 120x80 underneath the 200x80 profiles (+40mm clearance) and bolt from the bottom. Add 20mm item profiles (wide version) as a "T-slot bed" (+/-0mm clearance).

I think I will go with option 2, which will make the bed stiffer also! The budget allows for it anyway.

[AndyUK]

Might be worth considering how you'll access some of these bolts.

Take for instance the front bearings on the gantry - does the rail being longer than needed foul adjusting those bolts? Does the servo on the back prevent access to the rear ones?

If you're trying to adjust the machine for gantry squareness, and you have to remove the servo between adjustments, that is going to get old fast.

I'm sure someone will be along shortly to tell you not to worry and to ignore this advice it'll all be fine... but hey, worth a thought.

[NordicCnc]

Might be worth considering how you'll access some of these bolts.

Take for instance the front bearings on the gantry - does the rail being longer than needed foul adjusting those bolts?

The rails are not longer than needed. The X-axis can travel all the way to the end actually. The clearance between the rail and the block is 30mm, so I am quite sure there will be enough room. I need to double check this.

Does the servo on the back prevent access to the rear ones?

If you're trying to adjust the machine for gantry squareness, and you have to remove the servo between adjustments, that is going to get old fast.

I will have to look into this as well, hehe.

Thank you for the heads up!

[Scustom]

Hi nordic
Why dont you consider doing bed insted of 200x80 similar what robocnc on youtube did?

[NordicCnc]

Hi nordic
Why dont you consider doing bed insted of 200x80 similar what robocnc on youtube did?

Hello! I am using 200x80 because it is very stiff. I could of course do it as you describe but I would be sacrificing stiffness. The base frame stiffness is key to a good machine! I also want to keep the part count as low as possible.

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[JAZZCNC]

Is it any wonder that us mere novices get totally confused by all this, as there seems to be loads of conflicting advice floating around in the ether and I'm not talking about just on here.

So there I was working on some supposed designs... Linear rails on back of spindle mount, carriages on z axis, and trying to have a design that keeps the spindle as close to the bearings as possible... Now I find out all that is unnecessary, or not as necessary as I'd been led to believe. But as you've given this design the seal of approval then I guess I'll just try and make mine more like this one, only smaller.

Cheers

Joe It's not really fair to hi-jack Nordics thread so let's do it on yours or start another asking this question if you want some guidance and I'll gladly come along and explain the differences etc.

[joe.ninety]

Joe It's not really fair to hi-jack Nordics thread so let's do it on yours or start another asking this question if you want some guidance and I'll gladly come along and explain the differences etc.

Sorry, that was never my intention. But in my defense, that was more of a statement of a bit of frustration than a question relating to my own design.

All my questions on this thread have, I think, been aimed at Nordic and his design. I will however be more mindful in the future.

Cheers

[NordicCnc]

Sorry, that was never my intention. But in my defense, that was more of a statement of a bit of frustration than a question relating to my own design.

All my questions on this thread have, I think, been aimed at Nordic and his design. I will however be more mindful in the future.

Cheers

Hey Joe,

Please don't worry about that. You are free to continue asking any questions you want in my build log. JAZZ was only being polite, since I have not mentioned anything about it. But now I have, so feel free to ask anything!

Also thanks to your questions about the bearing blocks and the standing profiles, I've come up with a much better design I think. I will post more about that later.