Here we go again . . . MK4

[routercnc]

Managed to cut another one out this morning:


Another trial fit showing both triangular supports:


Just 2 more to go for the other side.

Here is the current design for the Y/Z axis. You can see the tram plates (small grey rectangular plates) I mentioned earlier which will allow me to tram the spindle relative to the larger green bearing plates underneath.


Initially I will put the WC spindle in the main housing and drive it direct. It might stay this way depending on how much better it is than today.

But if not, the following pictures show the alternative full feature version. The parts will be made to accept either set up.

Main feature is a home made spindle (Tormach TTS drawbar style with R8 collets), driven by the WC spindle via a pulley with different ratios, plus the addition of powered drawbar.


Here is a rear view of the pulley drive from the WC spindle, which is connected via a sliding frame to allow the belt to be tensioned:


This view shows the Z axis with power draw bar. This will give a simple push button tool release. I don't have pneumatics in my workshop so this is electrically driven via a stepper, through a pulley reduction drive, and finally through a ballscrew. Quick calcs show this should have enough power/torque to overcome the pre-load on the belleville washers (part of the drawbar retainer) to release the tool. The whole PDB system floats on sliding bearings so that it squeezes the drawbar against the spindle shaft, rather than loading up the bearings.




Here is an underside picture showing the spindle which bolts in via the lower flange. It is also held in place with the clamps further up the main body, which are also used to hold the WC spindle in direct drive mode:


Here is a cutaway view of the spindle showing housing, bearings, draw bar and collet system. At the top you can see the pulleys for the drive and the belleville washers which hold the tool in place by pulling up the R8 collet, which in turn squeezes the 3/4" shaft of the tool holder. Google Tormach TTS for more info.

(The power drawbar assembly is not shown in this drawing)

Still some finessing to do (e.g. tube connecting AC bearings in nose to upper bearings not in correct alignment etc.), plus still have to convince myself that I am capable of machining the spindle in the correct steel (oversize by ~0.3mm), get it hardened, then grind the bearing journals and the R8 taper to all be parallel and aligned again as they will be distorted. I'll need to make a fixture for my lathe to hold a die grinder or some other idea.
This is the biggest part of the project, the most risky, and the main reason I may just stick with the direct drive set up. But the attraction of big torque boost, the ability to run larger cutters, and the quick tool change keeps me interested.