Homemade CNC

[cangaroo]

So I am designing a simple CNC Mill/Router just for an easy side project. I have it modeled but I am wondering what would be an acceptable THREADED rod to use to drive my axis. I realize that the BEST solution would be a BALL SCREW but those are super expensive. Right now I am thinking 3/8 - 16.

Any input would be appreciated!!
Thanks,

 

[JohnRBaker]

I would consider using an Acme Thread instead of a normal screw thread for something like this, particularly if you're looking for smooth and consistent motion considering that there could be significant thrust load on the 'knuckle' if this is to be the primary feed screw.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

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To an Engineer, the glass is twice as big as it needs to be.

 

[CorBlimeyLimey]

http://buildyourcnc.com/CNCMachineMechanicalParts.aspx

Loads of info in the 'net.

 

[bithkits]

I agree completely with John:

A screw thread ("V" or Whitworth etc...) has a tendency to bind, whereas the ACME thread promotes sliding even under load.

Adriaan.
I am a Mechatronics Engineer from South Africa.

http://www.martin-electronics.co.za

 

[bigTomHanks]

Goto a junk yard and get yourself a few screw jacks. They have decent acme screws and can be picked up for a few bucks each.

 

[dik]

Can you use a double nut to take up the slack? with one snugged against the other and the thread... this might minimise movement.

Dik

 

[CastMetal]

Dik,
Anti backlash nuts are made specifically for these applications (low cost/precision lead screws) and essentially function like two nuts with a spring between them. Not as good as a ballscrew still, but effective. Available here from Nordex

http://www.antibacklashnut.com/

Comprehension is not understanding. Understanding is not wisdom. And it is wisdom that gives us the ability to apply what we know, to our real world situations

 

[MintJulep]

How accurate do you think you really need to be?

A timing belt may very well be capable of the accuracy necessary, at much lower cost.

 

[cangaroo]

Thanks!! From reading this I will probably go with an ACME precision Rod. I don't really need tight tolerances but if I can might as well do it right the first time.

 

[MiketheEngineer]

How about scouting around E-bay and buying a used one!! You know it probably works(test it) and will save you a ton of time and money??

 

[cangaroo]

I'm in it for the fun , I just want to build something cheap too.

 

[Metalfixer]

Try this Forum

http://www.cnczone.com/

 

[moltenmetal]

What are you planning for the interface to a CAD program?

 

[KENAT]

"What are you planning for the interface to a CAD program? "

A machinist?

I mean the OP never claimed CAD/CAM or similar terms.

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(probably not aimed specifically at you)
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[cangaroo]

I am just in charge of the mechanical part. My buddy has sourced all the stepper motors and motor controllers required to manipulate the CNC. I just need to get it work.

 

[FeX32]

Check out

https://sdp-si.com/eStore/

I have used some components from them before. Seems ideal for a home project as you describe.

I would also love to have my own personal CNC Milling machine. Here is one on the American market

http://www.taigtools.com/cmill.html

For sure, I will get or build one some day . Good luck with yours.


Fe (IronX32)

 

[ThomasUtley]

Having recently completed my first 3-axis CNC router, go with the ACME lead screws. They're not that expensive to buy in lengths up to 6', and there are multiple sources of supply for adapters between your input shafts and the lead screw, whether of the single-start or multi-start variety. Note that I did not say adapters between your steppers and your leads crews--you always want to include some kind of thrust bearing between your steppers and the loads they're driving.

All that said, the main thing is to just get it working. After that you can use each new iteration of your machine to fabricate ever-more accurate components for the next!

Have fun...there's nothing like the first time you cut a part on your very own CNC!

Take care,

Tom