Fixed gantry build-newbie tuesday

Hello all!

I am currently in the process of designing my CNC machine to be desktop compatible(if that makes sense).

I'll try to update this with a few pictures/screenshots every day so i can get some good feedback for free!

So the build is going to be a fixed gantry with a moving bed. I decied to go this way because of 2 reasons:
1) when building a DIY machine and for the first time - less moving parts
2) since i want to cut aluminium and rack-pinion is too expensive currently its simpler to make a moving bed(just X axis).

Personally i have 2 questions to the wider audience:

1) can belt systems be used successfully to cut aluminium(and not some commie aluminium. proper 6082 T6 aluminium)?
2) is 10mm aluminium plates as the main construction material overkill or just about right?

Thanks!

Quote:

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Originally Posted by ahtopahtel

1) can belt systems be used successfully to cut aluminium(and not some commie aluminium. proper 6082 T6 aluminium)?
2) is 10mm aluminium plates as the main construction material overkill or just about right?

Thanks!

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1) Dont know about the belts, but why not use acme or ballscrews?
2) Depends on size, support and many other factors. Show us what you have so far. (drawings etc)

What does rack and pinion have to do with the decision of moving bed vs gantry?

Boom - The idea is to ask if belts would work or not. i just find the belt systems to be slightly better. When it comes to moving bed vs gantry, i've seen moving gantrys with pinion and ballscrews - pinion is much more precise and reliable(i've seen big machines though, 3m+). ACME or ballscrews are the next logical choice after belts.
Drawings(or rather screenshots, no drawings yet) coming in 3-4 hours.

I will not use belts for cutting alli. If you are talking about hobby grade components, I will definitely use ballscrew, or rack if it's a very long span.

"or ballscrews are the next logical choice after belts."

I would say it's the other way around. After adding gearboxes and what not on the belt system you will not save much if anything.

What size metal do you need to cut?

Hey everybody.

I got infected with a nasty virus, had some green stuff coming out etc.

Anyways - I had some time to think about things and this is what i came up with:
Acme threads
Linear rails and open pillow blocks
Aluminium plates from alu 8082 T6

The next thing i need to deduce is what kind of motor to use. I've leaned towards a nema23 with 1.8 NM of hold torque.

Spindle will be custom built and not a problem.

I promise some pictures by the end of the day :). And thanks boomslang - good points.

T

Hello all.

I now had some time to add elements and looking for some feedbacks.

Namely: how should i take care of the z-axis?

Feed back would be appreciated on all things :)

What are the dimensions of the machine and rails?

I would put the bearing blocks on the bed as far apart on each rail as possible, it will help with binding and racking. Without dimensions (as I've asked ;) ) it's hard to help.

On Z, I will put the bearing blocks on Y and the rails on the moving part of the Z axis (hope that makes sense). That way the bearing support stays close to the work surface.

The unsupported shaft will flex too much to cut aluminum. Most find that they flex too much to cut wood.

Hey guys.

Dimensions are added as a picture.
The rails i selected were 20mm. If i switch it up to supported rails, would that deliver a more satisfactory result?

Hi Ahtopahtel,
You don’t need a screw that long, try something like in the picture, you still get the travel needed but to half the price.
http://i27.photobucket.com/albums/c1...iff/s1-016.jpg

Or maybe like this.

http://i27.photobucket.com/albums/c1...iff/s1-017.jpg

I think you some bracing is needed as well. Attached file show 6063 t6 1000mmx250mm 10mm thick. 10kg load on the centre block will deflect it 0.31mm... just to give some idea of what you are dealing with.

http://i20.photobucket.com/albums/b2...Strain10kg.jpg

Hey guys, thanks for the feedback!

There will be bracing, since the deflection would be to great indeed.

A very interesting idea on how to shorten the ballscrew, i'll give it a good think and see if i can somehow change the moving bed.

boomslang-can you do a simple drawing about your suggestion, i'm embarrassed to say i dont quite grasp the concept?

also a very important note, i decided to downsize the machine quite alot: the aim is to get 250mm for X-axis, 200mm Y-axis and 150mm for Z-axis. 2 reasons= the materials i get my hands on is that size and also i can create a more stable/rigid machine.

tonight updated system(smaller and supports included).