Need Help!- Starting off a cnc project!

[ely862me]

Hello guys!
I m sooo newbie but I i try to get this machine done!
I m no engineer or mechanic but i think i can go along with this construction.
What i would like is a milling machine for wood,polystyrene(generally easy stuff) but i wouldn t mind to mill some aluminum,and to drill holes in steel . The milling range will be 1000mmx1500mm .
I will be cheap,very cheap: the main frame will be made by welded rectangular profiles(50mmx30mm) and the rest by mdf.(20mm tick)(but i want your advice regarding the combination of these two).
The axis will slide on regular bearings on aluminum angles as shown in the pictures. Please let me know what u think about precision on this system!
I would like to use trapezoidal screws(or ball screws but they re a lot more expensive ) . The screws and the motors aren t drawn yet but u figure out where they ll be placed.
Now i ve guestimate (without any calculation) that i will need like 9Nm stepper motors . Please let me know if i m right,or what kind of motors i should use.
I havent thought yet on the electronic part but i have a brother who knows a bit about this kind of stuff and he will help me around.


Thank you very much in advance!

[ely862me]

C'mon guys,i came here hoping that is the best place to come,is that hard to tell ur opinion about this?
The y axis assembly will weight like 20- 25 kg.

Thank you!

[ger21]

I don't think you'll have anywhere near enough rigidity to drill steel. And the gantry will have a bit of flex in it.

I meant to reply last night, but I fell asleep.

[analogman]

Originally Posted by ely862me C'mon guys,i came here hoping that is the best place to come,is that hard to tell ur opinion about this?

Oh the guilt, the shame.... we must learn to improve our customer service response time! Get to it people! We must work the weekends!

Ok, so enough of the sarcasm. All I wonder: why design from afresh when there are so many proven designs for this type of machine? Joes CNC?

[Drools]

I have seen some fantastic builds done with 80/20 and cncrouterparts rails. If I had to do it all over again I would use their R&P system with larger types of 8020 in some places. I went the angle and skate bearing the first time and quickly upgraded to Nate's carriages.

[crane550]

I would second that last comment.

David Steele at Solsylva.com has some great plans. I built his 25x25 and am pretty happy with it so far. Also check out the open source designs menu. You can build a sick machine with a few cncrouterparts.com components.

As a general rule, simplicity is efficiency. It is also reliability. That what I really like about most of the open source machines in that section. Modular is also very attractive. If I were to do it again, (which I actually will when I build machine #2) I would start there.

If your wanting to learn about CNC and try to find your way around, I would go with the Solsylva plans.

A few design consideration of your model:

1. How do you plan on taking the slop out of your linear mechanisms? You don't seem to have any sort of tensioning devices built in.

2. Carriage seems to be a lot taller then you would need. Ideally you want to have as little distance as possible between your point of pressure (i.e. the tip of the router blade) and your trucks. Realizing of course that some is necessary, unless you want no Z travel. I would probably try to make your gantry more level with your X rails, and your router more level with the carriage.

This is of course all contingent on what your needs are.

[ely862me]

Thank you so far ,guys,i ll document myself again and maybe rethink the plans.
Sorry if somehow i bothered some of you!
Gerry in which way will flex the y axis ,in z axis direction?

Cheers!

[cyclestart]

Originally Posted by ely862me I will be cheap,very cheap:

So sourcing as much stuff local as possible. Shipping can can really add up fast. Just throwing that in for people who might not notice you're in Romania

The axis will slide on regular bearings on aluminum angles

Why aluminum ? Minor detail but it caught my eye.

Better to build something and be disappointed than over plan and build nothing. Not to say you are not being offered some good alternatives to the existing design. People who have been here a while are on builds 2, 3, 4(?). A few others post pages of solid works drawings and disappear having built nothing. It's an addictive hobby and I recommend staying far away My own router ? Nothing you want to copy lol.

[Chi-Emily]

i donnot know if i understanding your meaning for my english is not very well, i know where you should put your motors and ball screws(i never see a trapezoidal screws, for we use ball screw),and even the electronic part. your draft looks like ours very much, so if you want to know my opinion about the motor and screw ones please send me a letter and i will give you my draft about that. sh-emily@hotmail.com

[florins]

Hi ely,

That's a good start, there are some small problems, but is better to start with something and correct that, than not start at all. I agree with most of the other comments, and it's true that there are some well proven designs on the web. However, why shouldn't be possible that two years from now to say that one of the proven designs is yours? Every good design started as ideea in somebody's mind .

Just a comment, I didn't see if somebody comented on this already: the slide for the Z axis seems to me very narrow, and this will translate in very big moments (and deflection) from the side load of the spindle. You should try to make all the carriages as wide and long as it is practically possible, in order to avoid big rotational momentum, and to obtain smallest possible deflection and vibration. Same applies to the other too axes, too. I would widen the X carriage and be sure that I have a way to compensate for the wood dimensional changes and for the parallelism of the guides.

Last, do not use aluminium for guides (aluminium is good as structure, but use steel for guides), unless you are just trying to make a not functional model .

Otherwise, all should work in my opinion.

Good luck, keep us posted!

Florin

[Chi-Emily]

Hi Florins:
"However, why shouldn't be possible that two years from now to say that one of the proven designs is yours? Every good design started as ideea in somebody's mind " I like this saying very much. so, good luck, and hope one day I can see your name and designs on the internet and everybody say "great" to it. Best wishes to you my friend.


Emily

[ely862me]

First of all i want to say that i live in Romania and i want to use the materials i have in here(except ,maybe, the steppers and some electronics).

crane550

1. How do you plan on taking the slop out of your linear mechanisms? You don't seem to have any sort of tensioning devices built in. 2. Carriage seems to be a lot taller then you would need. Ideally you want to have as little distance as possible between your point of pressure (i.e. the tip of the router blade) and your trucks. Realizing of course that some is necessary, unless you want no Z travel. I would probably try to make your gantry more level with your X rails, and your router more level with the carriage.

1. I have something in mind ,but,i usually find on place solutions.
2.I really need it that high,for i have very deep 3d surfaces to mill(the material used for those will be soft :wood,polystyrene ,clay,etc).
Maybe i could make the main table or the spindle support to have two levels.

cyclestart- Good to know!

Why aluminum ? Minor detail but it caught my eye.

My main reason will be rust.I ve seen a cnc build kind of this way and he used aluminum angle.Now i know is kind of a soft metal,and u have right,it s better to use steel angle(and i can paint the surface which is not in contact with the bearings).

Chi-Emily - I know where to put the screws and steppers(u can see some cross marks where the center point of the screws will be). I don t know what power will be required for the motors to do the job i want(mainly wood,and if possible some aluminum).

florins

Just a comment, I didn't see if somebody comented on this already: the slide for the Z axis seems to me very narrow, and this will translate in very big moments (and deflection) from the side load of the spindle. You should try to make all the carriages as wide and long as it is practically possible, in order to avoid big rotational momentum, and to obtain smallest possible deflection and vibration. Same applies to the other too axes, too. I would widen the X carriage and be sure that I have a way to compensate for the wood dimensional changes and for the parallelism of the guides.

I also thought about this but the larger it is the expensive will be.Anyway for the z axis i think i ll change the sliding system with something more accurate.

Thank you all!
Soon some updates!(I hope)