Am I heading in the right direction?....

[EddyCurrent]

Regards ballscrews then I wouldn't use 16mm diameter for the long axis because in my experience it's just a bit too long. Now you can get 10mm pitch in 20mm Diameter then your much better using them over 16mm at this length. The difference in performance is neglible and your far less likely to get whip so often can go faster than 16mm screws that whip.!

Yes, sorry about that, I overlooked the length, I was still thinking about my own build.

[JAZZCNC]

Yes, sorry about that, I overlooked the length, I was still thinking about my own build.

Wasn't having ago at you Eddy because he is on the edge of being able to use 16mm just IME 20mm are better at this length and the higher inertia doesn't have a big negative affect compared to if they whip.!

[Lloyd]

DONT use 25mm ballscrews this is a BIG mistake.? The inertia from 25mm screws is too much for nema 23/4 motors and you'll end up with a very slow under performing machine. Like wise if you go with nema34 Motors then unless you use expensive high voltage drives you'll have underperforming machine due to the slower speed of the motors.

I'm considering investing quite some money into the machine - as I'll be using it for some work I do... So I don't mind kitting it out with good quality motors...

that said, it would be good to see anyone's idea of what percentage of your budget you' should allocate to which part of the machine... e.g. 15% on base structure, 35% xyz hard wear 50% on power, control, motors etc....

So you get the best out for your buck..

any takers?

anyway, I'll take your advice regarding the brackets, positioning, and screws, - but this could change should I decide to invest in more expensive digital drivers?

thanks again for the comments

[JAZZCNC]

anyway, I'll take your advice regarding the brackets, positioning, and screws, - but this could change should I decide to invest in more expensive digital drivers?

You don't have to take my advice and by all means go for the larger screws etc but you will regret I guarantee you that.!!

Your doing the classic BIGGER IS BETTER approach and that's a sure fire way to waste money and build an under performing machine. Digital drives won't make any differance if they are sized wrong and mismatched to screws.
Even with the stuff I suggested I recommend you use Digital drives but this as nothing to do with giving more power but more to do with being smoother running and resonance handling capabiltys.

[Lloyd]

You don't have to take my advice and by all means go for the larger screws etc but you will regret I guarantee you that.!!

Your doing the classic BIGGER IS BETTER approach and that's a sure fire way to waste money and build an under performing machine. Digital drives won't make any differance if they are sized wrong and mismatched to screws.
Even with the stuff I suggested I recommend you use Digital drives but this as nothing to do with giving more power but more to do with being smoother running and resonance handling capabiltys.

I understand what you're saying- I have received advice saying I should get large screws on my X,Y and Z and I should get 800w digital drives... But here, collaborative experience dictates otherwise...

as for the bigger is better approach; no, I just want a good solid reliable machine and I'm willing to invest the time and effort in researching the best equipment - you guys seem to know what you're talking about, and I'm just trying to understand the reasoning behind, which for all intents and purposes you've so far done well to justify.

My general philosophy when it comes to building stuff is to keep it simple and functional, I hate things that are over engineered unnecessarily.

So with the machine, I would like to use only the best possible parts for the required cutting area and material.

based on what you've told me (and off the top of my head)

profiled rails are best on all axis.
20mm ball screws on x, 16mm on y and z.
the ball nuts should be reinforced more than I have.
the position should be better placed, to avoid chips and being knocked
i should use digital drives correctly sized and I should not get poor motors with high inductance. (Have to get the maths out for the lads!!!!)
the bed should be adjustable, so when I cut alu, I should be as close to the y gantry as possible.
to help reduce resonance, I should use pullies this will also enable me to adjust ratios...
pitch on the ball screws should be 10mm on x and y and 5mm on z...
And dont waste money - unless I really want to ;)

did I miss anything?

[EddyCurrent]

did I miss anything?

Yes, you mostly just listed the mechanical items.

the PC to machine interface
breakout board / spindle speed control
Emergency stop / limits / homing switch strategies
the rest of the electrical stuff like power supplies, what voltage to use, amps required ?
the spindle and cooling system if water cooled
the variable frequency drive
type of wiring to use
cable drag chain
fan assisted cooling of control panel
software to use, Mach3, Linux, other ?
material and construction of bed surface.

must be something I've missed now ?

[EddyCurrent]

. . . it would be good to see anyone's idea of what percentage of your budget you' should allocate to which part of the machine... e.g. 15% on base structure, 35% xyz hard wear 50% on power, control, motors etc....

For my machine http://www.mycncuk.com/forums/gantry...eady-eddy.html the breakdown was roughly this;

mechanical £1600
electrical £1500
spindle + vfd £1000

I've listed the spindle/vfd seperate bacause most people here seem to buy the Chinese 2.2kw model but I went for an Elte spindle and ABB vfd.