Experimental Z Axis
After trying to cut some Aluminium I decided that the 3 Axis machine really isn't rigid enough. I also received a great set of plans from John Klienbauer - if you are at all interested in home CNC you must have a look at his site (www.crankorgan.com) - the plans are great and gave me a lot to think about. I don't intend to actually build John's design more to use it as part of my own experiments. So having a couple of days to spare I decided to try and build a new Z Axis for the machine. If it works out I will also replace the X and Y axis which will hopefully give me a much more rigid setup.
The basic sizes of things I lifted from John's plans, however I decided to go with a tube based set of slides. The actual bearing is made from Acetal which I turned down in the lathe. The runners are Aluminium tube, I may switch to steel if I can find tube that is of the same side and which has a good smooth finish.
The bulk of the construction is made from 18mm mdf, bolted together with M6 bolts tapped directly into the mdf. The stepper motor mounts directly on the frame. I'm currently using a fixed coupling (I had one from previous experiments and the alignment is very good), but I will probably switch to a fuel pipe coupling when I rebuild it.
The aluminium tube is mounted in small mdf blocks which can be moved to help align things. The end of the m8 threaded rod is mounted in a skateboard bearing which is also held in place by an additional mdf block. The basic construction is complete and it works very well. Movement is smooth and there is hardly any flex. I'm now going to take it apart, clean up and finish the various parts and then paint the mdf.
New Y Axis
I enjoyed building the Z axis so much I've decided to revamp the entire machine. I'll use the new Z axis and below is a picture of the new Y axis.
I've made use of the "pipe plus bearings" design that John Klienbauer has used on many of his machines. It seems to work really well. I'll probably use something similar on the X axis. The other thing I've adopted from John's design is the adjustment blocks. Mine are in mdf rather than pvc but they seem to work really well. UPDATE on this PVC would have been much better than mdf. After a while the threads in the mdf fall apart, you can fix it with superglue but pvc would have been a better choice (sigh).
As you can see the actual "carriage" is much smaller than the table. Basically I don't have that much room so I thought I would try and "have my cake and eat it!". The design has a smaller area of approx 6" than is fully supported and a much larger area (10") that is only partially supported. The idea is that the smaller area can be used for heavy duty items (like PCBs) while the bigger area can be used when working on lighter items (like balsa). This way I get a smaller machine but can still do some operations on larger items. It will be interesting to see how it works out!
Construction basically took me one long day. Most of the time seemed to be spent tapping threads! Oh and adjustment seems to be nice and easy.... Lets hope it all works when we put it together. Next up is the X axis.....
New X Axis
Ok so here it is......
Yet another variant on the slides this time I've gone for "pipe plus bearings" but this time the bearings are mounted at 45 degrees and so they hold the z axis firmly in place. Building this part has been a little more difficult, but at least I found out that you can use a power screwdriver to tap m6 in mdf and that m4 bolts self tap!
The picture above shows how the parts all fit together. There is a back board still to fit which should make things a little more rigid but it is easier to set things up without it in place. If I build another I would probably make the sides a little larger to make them more rigid. I may have to add to them to stiffen them up.
I've finally got things painted (though the water based gloss paint seems to be taking a long time to harden up). The Dremel has been mounted and I've made a first pass at aligning things.
With the control software/hardware up and running time to start making some chips! Take a look at my cnc projects page for details of some of the things I have been using the machine for.
I've been using the machine for some time now and made a few changes. First off I built a new Dremel holder (using the machine), see my projects page for details. I've changed all of the "pipes" on my machine for steel rod seems to stiffen things up a little. After some use I noticed that the two mdf supports for the 45 degree bearings on the X axis had been moving a little. I've added some extra threaded rod between them to take some of the force. I've also added a new bed using slot wall board and built some new hold downs.