New Machine Build- DIY CNC Mill

[joprinz]

Hi, With a lot of help from Guys out here, I have finally completed building my CNC Router So lemme begin by saying a BIG THANK YOU to all the guys here.

And now I'm trying to design a CNC Mill to work with aluminum and probably light steel. There is a lot of information on this site on various aspects of the machine design and I'm reading as much as I can. I have come up with a design which uses Hardened Steel Shafts and Linear bearings for Linear motion and Ball screws for driving.

Listed below is the spec I'm thinking of using.

• Machine axis are 2' x 2' x 6"
  
• Construction is welded steel for base and aluminum for z Axis.
  
• All Axis have 25mm Hardened Steel Shaft (2 on either sides of the axis) and each axis have 4 LM25 THK Linear bearings (Each shaft has 2 Linear Beaings).
  
• All Axis are driven by 20mm (5mm Pitch) Ballscrews and 400 oz.in Steppers.
  
• I'm planning to use a 1HP Spindle.

Now My question is... Will this machine be sufficient to mill Aluminum and light steel? Ofcourse I am sure the spec I have written is hardly sufficient to give an opinion with. But I was wondering if a sturdy CNC MILL can be made using the components mentioned above. Or will I be required to go for Bigger (Larger Dimension Shafts etc...) more stronger parts for Milling Metals?

Please Advice!

Thank You!

J

[Sieg]

Hi,

I think the linear bearings are bad. Unsupported shafts are going to flex, I dont care how thick they are. Use a linearmotion product which is supported over its entire length.

The ballscrews are good, exactly the same I am going to use in mine.
400 ozin steppers can work, depending on how fast you want your machine to be and how heavy your moving axis are.

The spindle I dont know yet, I am trying to find out aswell. I have my own topic about this. Looks like you are building the same machine I am! Same cutting area!

[LeeWay]

I will just say that for the cost of the shafts and bearings, I would go with something more traditional like linear slides and trucks. Cost would likely be close for either. Accuracy and rigidity are more easily achieved using those.
These are the weakest point I see in material selection so far.

That said, if they are fully supported rails, maybe they would work okay.

A design or drawing would be helpful too. Good parts are certainly a start, but how you use them could really make a big difference.

[joprinz]

Thank you for your replies.

I missed to mention that the shafts I am using are supported on a rail. The Shafts have tapped holes on one side and are mounted on a Rail and the Bearings are OPEN Type LM Bearings. I hope that would reduce/prevent Shaft Flexing.

however I have a couple of questions!

1: Is it Always a requirement to preload the Ballscrew Nut in order to reduce backlash??? or can I use the standard Ballscrew Nut that comes with the Ball Screw unmodified?

2: What should be the average cutting speed for a reasonably well made CNC Mill?

3: What cutting speed can be expected out of a machine with the above mentioned spec?

4: Is it Always required to use a liquid coolant while milling steel even if the Cutting speed are lower?

Please Advice.

Thank You,

J


PS: I'm trying to go with shafts coz I have a source where I can get a very good deal on Shafts and LM Bearings.

[joprinz]

Thanks Sieg, Lee

A quick update on my Mill Design Progress...
After your replies I did some serious research and have decided to go with Linear Guides instead of Shafts and bearings. However I have a new design Question now. Please check the topic link below.

GUIDE WAY QUESTION???

I have added a new thread as I think it was an entirely different discussion.

Please Advice!

Thank You.

Joe!