I hear you on the 12mm, unfortunitly rails are hard to come by for a good price in the UK so its use what you can. Its because of the 12mm rails that the Y axis is using one rails on top and one below (trying to spread the load into the structure as much as possible). The Z is using 9mm rails! But these seem to be holding up very well without any noticable deflection.
It shouldn't be a big problem with the 9's and 12's as long as you're not going to cut harder stuff. The rails are holding for very high loads even though they are small, somehwere between 2 and 4 kN per wagon. Make sure to mount them as far as possible and it would work.
And hey, if they would break - then fix it!
Well, progress stalled for a little while as I am waiting on some aluminium sheet and box section.
Whilst I have been waiting I started to reconsider the usage requirements for this machine. I have decided that the working envelope is just to small for what I'd like to acheive (cutting acrylic for custom marine fish tank sumps, aluminium for 1/6 scale rc car parts and general wood work). 4' x 2' would allow me to cut 1/4 sections of full size standard sheets.
To this end I have purchased some more parts for the x axis and will use the parts from the old plan to increase the size of the y axis. The z axis carridge will remain the same but I have also sourced a very heavy duty 270mm rail that I may use to redesign the slide assembly (this rail is 42mm wide!!).
So whilst I'm waiting on the main parts shown below to arrive from Germany I will work on the y axis (as soon as my aluminium turns up).
I'll keep you updated!
Still waiting on my parts for the X axis but I have now started on the longer Y and revised Z.
The Y is using the same arrangement as before but is using the longer rails from the old X axis design, it is also using a "mount and play" ballscrew assembly form jimonchan on Ebay (excellent product, price and service).
The new Z is using a single heavy duty (43mm) IKO rail instead of the previous 2 9mm THK rails. I'm hoping that it should be stronger with less flex than the old design even though its only using one carridge. Nest steps are to make up the back plate of the Y axis and the ballnut attachement plate and then build the Y motor mount. Stay tuned!
More happening, slowly but surely.
The Z axis motor mount has now been made and tomorow I will hopefully finish the Z all together. To connect to the box section I have made a small aluminium block to slot into the end of the box section and allow everything to be bolted together.
on your z, it doesnt look like you have any thrust bearings and have the motor coupled directly to the ballscrew. this may work for a little while but the bearings in the motor are not meant to take thrust loads.
Very good point Jimbo, I had not considered that!
I will add a L plate to the bottom of the screw and bore a recess for a skate bearing (I know their not for thrust loads but it can be replaced easily).
I'll post some pics of this tomorrow.
I'm currently considering my last purchase which is the material for the X axis supports. The sides of the machine will be roughly 2 metres longwith a support at each end, the 1.8 metre rails will be bolted to the sides. I have a bunch of 2" x 2" X 10G and 1" x 4" x 10G box section so I'd like to use something that will match up with this well.
The options are:
1" x 4" X 10G box section (mounted vertically)
1/2" x 4" solid bar
2" x 2" solid Bar
The cheapest and simplest option is the box section, any opinions out there on the suitibility of these materials??