Wednesday, April 20, 2011

CNC mania

At this stage I have the CNC up and running. Not flawlessly mind you!
So I'd better try to catch up with myself!
After getting the supported rails mounted on the machine base, I got going on the gantry.
I put it together roughly first just to get a feel for what it would be like with the weight of the z axis. It moved very easily. A great relief!. My last machine used bronze bushes in place of bearings. They contributed a large amount of friction as far as I could feel. Though my alignments may have been off.
This is the bottom of the gantry sides. I drilled and tapped for M8 bolts.

One point to mention here is that the end you can see was finished on my trusty Aldi router table!

First I cut the Al. plate1mm or so too long. I then made a clamping jig. This consisted of two pieces of flat Al. bar 15mm*5mm or so. These were bolted to each other "squeezing" the plate in between. With a set square it is easy to fix them at 90 degrees.(good enough anyway!)
I used M6 gutter bolts to hold it together.(Low profile heads)
Now, there is a slot in the top of the router table to allow the use of an adjustable angle attachment. This slot was 6mm deep and 15mm wide. In there went the bottom of the clamping jig.
So with a few passes and adjustments, I got my nice square finish which you see above.

This is the Zaxis. The Aluminium I used was from my local friendly scrap dealer. God bless him!

Believe it or not, the12mm Alu plate I'm using came from a bird house! Now that's over engineering!
I think this axis is fairly self explanatory.
The clamp for the router is held in place with 3 M8 bolts.
In this picture I haven't put in the lead screw yet. As it stands I'm just using M8 threaded bar. I
may up grade at some point.

I cut a bit of excess Al. off the to edge of the gantry. To save weight, and to make it "more workman like"!

The top hole here is 20mm and the bottom 22mm(this is to allow adjustability, more on that later). I didn't have a 22mm drill bit so I ended up using the 120 degree V router bit as a drill bit to widen the hole to 22mm! It worked a charm!

*I learned how to drill holes "properly" a few years ago. I would urge anyone to learn the real
method and get them right and accurate every time. It is time consuming, especially if you have loads of holes to drill but it is worth it.*

Measure, scribe, spike point with scribe, centre punch.(double check)
Then: Clamp, align with a pointed tool in drill chuck, replace with centering drill. Drill it. Drill with pilot drill bit (3mm, or so), go ahead with the big bit. Up to 6mm/ or 8mm if your drill press is nice and ridged. Then step up gradually. There's more tricks too!

Here are some bearing blocks: