help with a 4' by 9' cnc build

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25-12-2009
soyeb

help with a 4' by 9' cnc build

Hi All

Starting on a new project for a 4' x 9' cnc machine. Before i buy all the parts i would like to ask what is the best motor size to go for on this size project?? Also can anyone recommend a nema 23 or any other kit which will include all the electronics which i need?? I have seen some ranging from 22, to 40kg but i do not understand what this means. Thanks in advance :smile:
25-12-2009
irving2008

Re: help with a 4' by 9' cnc build

Quote:

Originally Posted by soyeb

Hi All

Starting on a new project for a 4' x 9' cnc machine. Before i buy all the parts i would like to ask what is the best motor size to go for on this size project?? Also can anyone recommend a nema 23 or any other kit which will include all the electronics which i need?? I have seen some ranging from 22, to 40kg but i do not understand what this means. Thanks in advance :smile:

Soyeb,

Welcome. 4' x 9' is a monster machine and one you can spend a lot of money getting nowhere on. Start by deciding and designing the basic structure, dont worry about motor or electronics at this stage. No one can really recommend a motor or drive electronics without knowing a lot more about the machine and its purpose, all they can do is give you their own experiences.

The key issues you will need to deal with are what sort of things you will be making with a machine this size. You have some major tradeoffs betwen speed and cost here. If most of your work could be done on a 4' x 4' or 4' x 6' machine you need to carefully consider the reasons for going to 9'. Similarly are you thinking of production runs or one-offs? Is time to complete (and therefore speed of operation) a critical factor? What sort of accuracies are you looking for and what sort of materials will you be cutting?

All of these factors will influence the overall design, what drive mechanisms (screw, belt, chain, rack, etc.) would be possible and what construction techniques can be used.

Get some ideas together, sketch some drawings, post them here and get feedback.

Good luck!
26-12-2009
soyeb

Re: help with a 4' by 9' cnc build

What i am looking for is a variation of sign manufacturing and cotinuous production of items. from very large to small. I am looking for reasonable cost but at the same time something which is fast as what i can get. I have done some research and would like to follow the plans off www.buildyourcnc.com. I have the actual make covered more or less and just need help with the electronics.

thanks a million :smile:
26-12-2009
irving2008

Re: help with a 4' by 9' cnc build

Quote:

Originally Posted by soyeb

What i am looking for is a variation of sign manufacturing and cotinuous production of items. from very large to small. I am looking for reasonable cost but at the same time something which is fast as what i can get. I have done some research and would like to follow the plans off www.buildyourcnc.com. I have the actual make covered more or less and just need help with the electronics.

thanks a million :smile:

OK, pleased to see you're not going for 9' long leadscrews! It just doesn't work (with sensible sized motors and screws) as he discovered...
27-12-2009
soyeb

Re: help with a 4' by 9' cnc build

Only problem i have is he is making a 2 x 4 foot machine while i want to make almost twice that size. what is going to be the best with regard to electronics for my machine or is there a chart or someone who has made a similar size??

thank you
28-12-2009
Lee Roberts

Re: help with a 4' by 9' cnc build

Soyeb, you know what you need ?

You need a [ame="http://www.mycncuk.com/forums/showthread.php?t=1524"]What size stepper motor do I need...?[/ame] tutorial !

:joker:
28-12-2009
irving2008

Re: help with a 4' by 9' cnc build

Quote:

Originally Posted by soyeb

Only problem i have is he is making a 2 x 4 foot machine while i want to make almost twice that size. what is going to be the best with regard to electronics for my machine or is there a chart or someone who has made a similar size??

thank you

If you hunt through his site you will find information on BlackToe, his 8' x 4' design using chain drive.

If you want to go with leadscrews you will need a ballscrew of 25mm diameter with fixed bearings at each end holding the screw in tension. With a 5mm pitch this will give you 1200mm/min (50ipm) cutting speed and 3200mm/min (125ipm) rapids (limited by screw whip) using an 8Nm NEMA34 stepper with decent drivers (50 or 60volt drives).

For the short, 4', axis a 16mm x 5mm ballscrew simply supported and a 2Nm motor would suffice.
31-12-2009
phooddaniel

Re: help with a 4' by 9' cnc build

Quote:

Originally Posted by irving2008

If you hunt through his site you will find information on BlackToe, his 8' x 4' design using chain drive.

If you want to go with leadscrews you will need a ballscrew of 25mm diameter with fixed bearings at each end holding the screw in tension. With a 5mm pitch this will give you 1200mm/min (50ipm) cutting speed and 3200mm/min (125ipm) rapids (limited by screw whip) using an 8Nm NEMA34 stepper with decent drivers (50 or 60volt drives).

For the short, 4', axis a 16mm x 5mm ballscrew simply supported and a 2Nm motor would suffice.

Quite correct. There have been some interesting ways to stop wild whipping of lead screws, but the expense and efforts are generally futile. Rack and pinion, timing belt and roller chain seem to be the best methods to move at long distances. I have tried with great success both the roller chain (at #40 size) and timing belt. My intension was to try to eliminate as much mechanical backlash as possible and these two really do the trick. Rack and pinion, although the best for the longest distances, can still exhibit some backlash due to the possibility of space between the two gears. Backlash is almost eliminated since the roller chain and the timing belt are both tensioned and the drive pulley/sprocket are fastened to the motor.

By the way, thanks for supporting the efforts over at buildyourcnc.com. This is my first post on this site.
31-12-2009
Lee Roberts

Re: help with a 4' by 9' cnc build

Welcome phooooo!
31-12-2009
irving2008

Re: help with a 4' by 9' cnc build

Quote:

Originally Posted by phooddaniel

Quite correct. There have been some interesting ways to stop wild whipping of lead screws, but the expense and efforts are generally futile. Rack and pinion, timing belt and roller chain seem to be the best methods to move at long distances. I have tried with great success both the roller chain (at #40 size) and timing belt. My intension was to try to eliminate as much mechanical backlash as possible and these two really do the trick. Rack and pinion, although the best for the longest distances, can still exhibit some backlash due to the possibility of space between the two gears. Backlash is almost eliminated since the roller chain and the timing belt are both tensioned and the drive pulley/sprocket are fastened to the motor.

By the way, thanks for supporting the efforts over at buildyourcnc.com. This is my first post on this site.

phooddaniel,

Welcome to MyCNCUK.

I note from your site you achieve 1500ipm rapids on BlackToe, thats pretty impressive!. What cutting speed do you generally recommend?

What size motors do you use for the X-axis to get these rapids and what is the gantry weight on your BlackToe design? Assuming you drive it from MACH3 can you say what acceleration values you have set up for cutting and rapids?