The Gantry is attached!

Now the fourth axis finally looks at home on the CNC plate.  The new gantry sides are almost 100mm taller than the old ones and share a similar shape. While the gantry was off the machine was a good time to attach the new Z-Axis which gains a similar amount of Z travel. Final adjustment of where the spindle sits in its holder are still needed but it makes sense for the cutting edge to be fairly high up when the Z-Axis is fully retracted as shown.

After a day of great success early on a day of great problem solving arrived before the attachment was possible. The day of great success involved testing the two new sides to see if or how well they attached to the mount points at the base of the machine. These holes in the gantry were hand marked, drilled, and tapped so there was some good chance that they were off target enough to not work well. But those all went fine.

The second success was mounting the Z-Axis to the existing points on the gantry. I had in the back of my mind the thought that one side (the three holes on the bottom of the mount) to line up and attach fine but the top holes to be out of alignment. Both of these plates, seen in horizontal in the image above, were made by CNC so the holes should be where I intended. Though these plates were both mounted to the Z-Axis and the bottom plate goes right through to the lower steel bracket so the alignment might not have been 100%. I registered both plates to the smooth side of the spindle backing plate so the alignment in that axis should have been ok. To great surprise and joy the top holes also aligned perfectly and the second phase fell into place.

It was only when putting the new sides onto the gantry that interesting things started to happen. I will have a new blog post on that part soon and likely a video of the problems and solutions for that part. One thing I will say now is that it helps to have washers, bolts, and spare skate bearings on hand for this process depending on how you have designed your far side gantry upright.

CNC Z Axis with 150mm or more of travel

Many of the hobby priced CNC machines have limited Z Axis movement. This coupled with limited clearance on the gantry force a limited number of options for work fixtures. For example, it is very unlikely that there will be clearance for a vice on the cutting bed of a cheap machine.

I started tinkering around with a Z Axis assembly which offers around 150mm of travel. The assembly also uses bearing blocks that should help overcome the tensions that drilling and cutting can offer.

The assembly is designed to be as thin as possible. The spindle mount is a little wider which allows easy bolting onto the spindle mount plate which attaches to these bearings and drive nut. The width of the assembly is important because it will limit the travel in the Y axis if it can interact with the gantry in any way.

Construction is mainly done in 1/4 and 1/2 inch 6061 alloy. The black bracket at the bottom is steel. This seemed like a reasonable choice since that bracket was going to be key to holding the weight and attachment to the gantry.

The Z axis shown above needs to be combined with a gantry height extension when attaching to a hobby CNC to be really effective. Using a longer travel Z axis like this would allow higher gantries which combined allow for easier fixturing and also pave the way for a 4/5th axis to fit under the cutter.