First CNC machine

[kev]

Hi everyone,
this is my first post, basically im building a cnc machine for my college project,
so far this is what i have got and made,






Its made from 45x90x1000mm aluminium profile,
i have used igus drylin linear bearings and rails
and thats about it really.

its about 1090mm x 965mm and i should be able to get a cut area of around 800mm2.

im planning on keeping the y axis as close down to the x axis as possible, and then making a long z axis so it will cut below its frame so i can raise it up if needed and cut bigger things.

i will be using 2 steppers on the x axis with the screws running along the top of the rails.

but now im a bit stuck on where to go from here, im trying to design it on autocad but its not going to well.

so suggestions are much welcome

Thanks.

O and how do u keep the pictures big? they look realy small on this post?

[Tom]

Hi Kev,

Looks good so far - should be nice and rigid with those large alu sections.
You have an interesting concept with the Z reaching to cut below the frame, do you have any sketches?

Next you need to decide where to put your y axis gantries, and how to mount your leadscrews and steppers.

When does your college project finish - a deadline is healthy! I wish CNCs were around when I was at college! :) (actually they were, but you fed code to them on punched card, not usb keys!)

Keep it up and keep us posted!

[irving2008]

Welcome Kev...

Rather than insert your pictures inline using the IMG tags, attach them using the 'manage attachments' button below the edit box... this will put thumbnails in the post and will auto-enlarge them on mouseover.

[kev]

Looks good so far - should be nice and rigid with those large alu sections.
You have an interesting concept with the Z reaching to cut below the frame, do you have any sketches?

yea its pretty solid, bit of a pain using the connectors tho.

with the z axis i got the idea from here

basically its going to be used for sign making but if i want to put something tall inside it then i can raise the machine up on a stand im going to make, thats why im planning on having no obstructions in the cutting area.

i will post up some autocad drawings that i have made so far tomorrow.

with the y axis im thinking of using some more rail, perhaps mounted on the top and bottom of another piece of alu box section. or perhaps top and side.

My deadline is around june time.

[kev]

Hi,
right just made some stuff up on autocad,
im not sure how heavy the z axis will be tho as it uses a lot of 10mm plate.
Any thoughts?
thanks

[irving2008]

Hi,
right just made some stuff up on autocad,
im not sure how heavy the z axis will be tho as it uses a lot of 10mm plate.
Any thoughts?
thanks

thats easy... work out the total surface area of the 10mm plate used in square millimetres (just work it for each piece then add them all together), multiply the result by the plate thickness (10) and multiply by 0.00275 will give the weight in kg. (weight of aluminium is 2750kg per cubic metre)

[Ross77]

Hi Kev.

just 1 observation. Are you only using one rail on the y axis? if so then the 250mm travel + the distance to the rail + the length of the cutting tool will put quite a bit of force on it!

Good luck with the build.

[kev]

Hi Kev.

just 1 observation. Are you only using one rail on the y axis? if so then the 250mm travel + the distance to the rail + the length of the cutting tool will put quite a bit of force on it!

Good luck with the build.

hi, no i was thinking of using one rail on the top and one one of the bottom, tho im going to redesign the z axis so that the motor is not so high up, possibly mount it on the other side of the alu profile, offset the weight a bit. im also thinking of keeping the linear bearings fixed and letting the rails move up and down on the z axis instead, this should keep 250mm of 12mm aluminium sheet fairly rigid.

Its hard designing things , might just order lots of bits and make it up as i go haha

[Ross77]

Sorry didnt notice the label tag was dog legged through the lower one.

Good idea to fix the blocks and let the rails move up and down on the z axis. Are they 4 way equal loading? Thats how I'm going to do it on mine. I would allow for a least a 1/3 of the rail to be held in the blocks. So for a 250mm travel you would need 375mm rails.

If its just for sign making then do you need so much travel? Why dont you just use the stand idea but have different size collars to rise it up in increments. Some people have also used multiple mounting heights on the z axis plate to allow for the cutting tool, might be worth looking at.

Its hard designing things , might just order lots of bits and make it up as i go haha

Yes but isnt that the fun part.

[kev]

Sorry didnt notice the label tag was dog legged through the lower one.

Good idea to fix the blocks and let the rails move up and down on the z axis. Are they 4 way equal loading? Thats how I'm going to do it on mine. I would allow for a least a 1/3 of the rail to be held in the blocks. So for a 250mm travel you would need 375mm rails.

If its just for sign making then do you need so much travel? Why dont you just use the stand idea but have different size collars to rise it up in increments. Some people have also used multiple mounting heights on the z axis plate to allow for the cutting tool, might be worth looking at.


Yes but isnt that the fun part.

Yes i think the bearings are 4 way equal loading, they are adjustable as well, theres a close up picture of one in my gallery.

It is supposed to be for sign making and would actually only require about 10mm of z travel but i want to cut big things inside of it lol, i might not go for 250mm of z travel i think i will test it first, see how much flex there is.

I have ordered some 45x45mm box section and some more rails so i think i might try the make it up approach until i come up with some good ideas.