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View Full Version : Comparison between mechanical designs of cnc machines



ammaratef45
17-07-2016, 06:33 PM
Hello All, I want to start developing my own CNC machine and I found different designs in the internet.
I want to know how to choose the best design and why should every design be better in some field.
I want to read more about this and need your help
Thanks

Lee Roberts
17-07-2016, 10:10 PM
Post the designs your considering as options?

What is your chosen field?

.Me

ammaratef45
18-07-2016, 12:10 AM
Post the designs your considering as options?

What is your chosen field?

.Me

I need comparison to choose, My field is Computer and Control
Sorry if i didn't understand your question well

Lee Roberts
18-07-2016, 01:06 PM
I need comparison to choose, My field is Computer and Control
Sorry if i didn't understand your question well

Np, you said you found designs on the Internet? Share/post these designs for us to review ?

What materials do you want to cut with your new machine?

Do you want help choosing a machine or just advice on the structure of a machine?

.Me

routercnc
18-07-2016, 06:56 PM
Each machine is designed to cut different types and sizes of materials. For example:

1) Engraving small objects -
Type: Fixed gantry, moving bed
Movement: Ballscrew, Leadscrew, or direct belt
Feedrate: Low
Stiffness: Low
Rails: Supported round
Accuracy: Low

2) Large wood or plastic sheets -
Type: Moving gantry with side legs
Movement: Ballscrew, or more likely rack & pinion (size and feed makes ballscrews less desired)
Feedrate: High (to cut properly and prevent burning)
Stiffness: Medium
Rails: Supported round, or profile rail
Accuracy: Medium

3) Large aluminium parts-
Type: Moving gantry with raised X-axis (no side legs on gantry)
Movement: Ballscrews
Feedrate: Medium
Stiffness: High
Rails: Profile rail
Accuracy: Fairly high

4) Small aluminium/steel parts -
Type: Fixed gantry, moving bed
Movement: Ballscrews
Feedrate: Medium
Stiffness: Very high
Rails: Profile Rail
Accuracy: High
(or convert a milling machine to CNC)

You can argue the details for the above but the point is that depending on what you want to cut, how big it is, etc. it will have conflicting requirements. That is why there are so many different machines out there. If you use a machine to cut a different part to which it was designed it will either be slow, dull the cutter, or not give the accuracy you need.

As Lee says, tell us the sizes and materials you want to cut and that will help narrow down the best options.

ammaratef45
18-07-2016, 09:17 PM
Each machine is designed to cut different types and sizes of materials. For example:

1) Engraving small objects -
Type: Fixed gantry, moving bed
Movement: Ballscrew, Leadscrew, or direct belt
Feedrate: Low
Stiffness: Low
Rails: Supported round
Accuracy: Low

2) Large wood or plastic sheets -
Type: Moving gantry with side legs
Movement: Ballscrew, or more likely rack & pinion (size and feed makes ballscrews less desired)
Feedrate: High (to cut properly and prevent burning)
Stiffness: Medium
Rails: Supported round, or profile rail
Accuracy: Medium

3) Large aluminium parts-
Type: Moving gantry with raised X-axis (no side legs on gantry)
Movement: Ballscrews
Feedrate: Medium
Stiffness: High
Rails: Profile rail
Accuracy: Fairly high

4) Small aluminium/steel parts -
Type: Fixed gantry, moving bed
Movement: Ballscrews
Feedrate: Medium
Stiffness: Very high
Rails: Profile Rail
Accuracy: High
(or convert a milling machine to CNC)

You can argue the details for the above but the point is that depending on what you want to cut, how big it is, etc. it will have conflicting requirements. That is why there are so many different machines out there. If you use a machine to cut a different part to which it was designed it will either be slow, dull the cutter, or not give the accuracy you need.

As Lee says, tell us the sizes and materials you want to cut and that will help narrow down the best options.

Great that help me start, I will come back to you guys if I had been stuck again

Boyan Silyavski
19-07-2016, 11:48 PM
Tell us what you will use it for, cause there are many hybrid designs and variations also. Apart from that you will have to understand that machine frame, motor and driver choice, linear movement parts are inter dependent and must be chosen at the same time. Not build frame then choose motors...