Flying Gantry Build Diary

After much deliberation, I have decided to have a go at building four fully-supported ball-bearing slides to create a closed-table flying gantry cnc router machine. I have also taken the decision to build in metric.

The dimensions chosen are based on what would fit on my workbench and that would give a reasonable work area. I wrote a spreadsheet to calculate the required wood/metal sizes I would need for any given work area required.
The dimensions I chose were 300mm x 600mm. This give an overall base of about 650x800 with an estimated height of around 400mm.

I have cut and routed most of the wood required, but made the faux-pas of ordering 12mm guide rails and routing 1/2" slots in the guide rail supports!

For the sake of another £10, I have generated a cutting sheet from a stock 18mm MDF 1200x600 sheet and will be going to the DIY tomorrow to buy a sheet and get the whole lot cut down to workable sizes (I estimate 11 cuts).

I will route the necessary pieces using a 12mm square router bit, and then separate the smaller parts using my bandsaw.

Good luck with your build Geoff, dont forget to post your pics !

As usual, what you say you are going to do at the weekend never happens!

I have cut/drilled and tapped the ali right-angle material for one side of one slide. Although accuracy is paramount, I have been unable to get better than about 0.5mm accurracy when drilling/tapping for the 22mm bearings. It will be interesting to see what problems I find when trying to assemble the slide with this sort of error.

The main immediate problem with the design is that I can't see how the slide guide rods are held in place. I will probably go with a ply plate on the inside of each slide-endplate. I will also use this plate to mount limit switches. It will, of course, reduce the working area of the slide.

Well, I've had the wood cut at B&Q, and found that the operator has used the wrong side of the blade to make measurements. The upshot of this is that all the dimensions are 2mm less than my requirements!

I didn't think much of this until I tried making up a Y slide, and found that the base is too narrow - by about 2mm!

Anyway, apart from this, I am having a problem I was dreading when fitting the second guide rod/support to the slide. I used epoxy glue to give the guides an even bed to sit in, and the upshot is that the supports have warped (just a little). I have glued one rod/support to the base and am now trying to fit the second.

However hard I try, I cannot get the 8 bearing runners to stay tight against the guides across the full travel of the slide. How difficult can it be?

I know I need to check squareness, but is there anything else I should do? I have heard about having to "shim" the runners?

Unless this is solved neatly, I think I may have chosen the wrong design based on my abilities. I hope not as I have £70 worth of 12mm guide rods...

(posted on yahoo too)

I have tried and tried to sucessfully build the slides for a flying gantry router, but with no joy.

I seem to be unable to get all eight bearings on the block assembly to keep in contact with guide rods over the whole travel.
An error of 0.5mm can magnify to several mm over the whole travel. This problem is compounded by the fact that this alignment error happens on two axes.

Am I missing something? Has anyone successfully build a slide, and if so, how did you overcome these problems. If you pre-loaded the blocks, how did you do this and with what materials?
I also noticed that MDF warps when glues are used.

I may have to return to the original design as it seems to address all these kind alignment problems...
Question is can I create one using 12mm guide rods, and where can I get the 12mm brass bearings ?

Geoff.

I have had some positive responses on the Rockcliff forums, so I will have to persevere...
I will start again. 1st up will be a single Y slide.

sounds interesting..you building this from plans?
robby

God time flys !, i have some of the bronze bushings in my ebay shop Geoff !

I think hes building the rockcliff machine Robby, let me know if you need that link to them.