NordicCNC's build log

[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]

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.

[NordicCnc]

Okay I now have a dilemma.

The price difference between 400W and 750W Delta servo motors are only about 100€ each, so total of 400€ price difference. This means that I would get 2 times the torque if deciding to go for 750W servos. Anyway are there any possible drawbacks with these huge servos other than more space requirement and somewhat more expensive? Larger pulley diameters would be needed due to 19mm shafts instead of 14mm shafts.

Also would 400W servos have enough torque to spin 2020 ballscrew with a 2:1 ratio? That would give me a speed of 30m/min. Same case with 750W servos, but those would for sure have enough if not too much available torque.

Also do I need that kind of speed for anything? Machine working area is approx 1200x1000mm anyway. Perhaps 15m/min (achieved with 2010 ballscrews) would be more than enough.

I need help. Please advise!

Some info that might be useful:

• Z-axis weight: 27kg (1605 ballscrew, 2:1 ratio)
• X-axis weight: 60kg (2020 or 2010 ballscrew, 2:1 ratio)
• Y-axis weight (gantry): 120kg (dual motor drive, 2020 or 2010 ballscrew, 2:1 ratio)

[JAZZCNC]

400W with a 2:1 on 10mm pitch will be fine. The ratio will double the torque and Like you say you won't need more than 15mtr/min, in fact, you could go 3:1 or 2.5:1 and still have plenty of speed.

Save the money and put the 400 into better ball screws.!

[NordicCnc]

400W with a 2:1 on 10mm pitch will be fine. The ratio will double the torque and Like you say you won't need more than 15mtr/min, in fact, you could go 3:1 or 2.5:1 and still have plenty of speed.

Save the money and put the 400 into better ball screws.!

Thanks JAZZ. I am now waiting for a quote from DMM Technology for 400W servo motors. Their servo motors looks really good and the manual/software as well!

The ballscrews that I was planning to get arw C7 rolled ballscrews from BSTmotion. I guess the next step would be either:
1. C7 rolled, with double ballnut
2. C5 ground, with single ballnut
3. C5 ground, with double ballnut

I think that Fred doesn't offer C5 ballscrews so I am mot sure where to buy those from!

Edit: I looked into it and I will probable have a go at double ballnuts. I may need to increase the ballscrew lengths to maintain the same working area, but it will be well worth!

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