NordicCNC's build log

[NordicCnc]

So machine design is now what I consider 99% completed so that I can start ordering parts. Since none replied on the ballscrew change I've decided to do the following:

- Keep the 2:1 ratio
- Change Y- and X-axis ballscrews to 2020
- Keep the Z-axis ballscrews as 1605
- No belt tensioners
- Double Y-axis motors will be used


I will put together a shopping list for all components so that I can get as much as possible in one order without missing anything. The final piece of design was to find a good location for the Y-axis home/limit switch. Cable chains I will fit later and wont add those to the 3D at all. Please ignore that the screw is not in the center of the limit switch. I will lathe and mill some custom screws but I could not care to design those yet.



Final assembly!



Some things still bugging me is the 120x80 for the gantry. I hope that those will not be too weak for machining aluminium with the ATC spindle. I am still consider changing to 160x80. JAZZ, if you read this, I remember that you wrote somewhere that for larger machines you use the 160x80 for the L-shape gantry. Since my gantry is 1200mm wide and I am using an ATC spindle, would it be wise to go for 160x80 anyway?

[joe.ninety]

Can I just ask what the benefit is of using blocks of profile to sit the gantry profile on, as indicated in the picture?



It seems because of this you were forced to place the bottom linear rail on the front, thereby pushing the spindle further away from the gantry. I'd always though that the idea is to try and keep the centre of gravity of the spindle as close as possible to the bearing blocks the gantry rides on.

This is not in anyway meant to be a criticism, but just me trying to understand if this design means there are benefits to it that outweigh the spindle being pushed further outward.

Cheers

[mekanik]

As a rule you ideally want the spindle IN the same envelope as your X axis bearings, i would make the distance between these bearings further apart.

[JAZZCNC]

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.!

Exhibit: A

Can I just ask what the benefit is of using blocks of profile to sit the gantry profile on, as indicated in the picture?

It seems because of this you were forced to place the bottom linear rail on the front, thereby pushing the spindle further away from the gantry. I'd always though that the idea is to try and keep the centre of gravity of the spindle as close as possible to the bearing blocks the gantry rides on.

This is not in anyway meant to be a criticism, but just me trying to understand if this design means there are benefits to it that outweigh the spindle being pushed further outward.

Cheers

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.

As a rule you ideally want the spindle IN the same envelope as your X axis bearings, i would make the distance between these bearings further apart.

[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

[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]

As a rule you ideally want the spindle IN the same envelope as your X axis bearings, i would make the distance between these bearings further apart.

Can you explain what you mean? I am not sure I follow.

Edit: I think you meant the spacing between the Y-axis bearings? Doing this would also decrease the Y-axis travel. I also want to be able to machine dovetails at the end of the table, so overtravel is a must!

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[mekanik]

I was working on the assumption X was your Base and Y your Gantry, Dean is the go to man for advice and if he says it's OK just crack on.
Regards
Mike

[NordicCnc]

I was working on the assumption X was your Base and Y your Gantry, Dean is the go to man for advice and if he says it's OK just crack on.
Regards
Mike

I see! My design is defined with Y-axis on the base frame, X-axis on the gantry and then Z-axis on the spindle. Anyway thanks for checking in!