I have a 5x5 PRO machine equipped with a recessed 4th axis, which I can currently mount at the front of the machine. My CNC also features a full-surface vacuum table. Initially, I designed the setup so I could remove the front section of the vacuum table to install the 4th axis when needed. However, I rarely use the 4th axis because removing the vacuum table and reinstalling it often causes me to lose Z-axis accuracy.
I’m now considering redesigning my vacuum table to make better use of the 4th axis. My idea is to relocate the rotary axis to the back of the machine and mount it permanently. The center of the rotary axis would align with the maximum Y position of the spindle. This setup would place part of the rotary module over an area of the machine that isn’t typically usable anyway.
Does this approach make sense? Are there any potential limitations or challenges with such a configuration?
I use my rotary axis A LOT and this is how I have it set up. I put a vertical table at the front of the machine, so the rotary had to go in the back.
After using it this way for a year, I’d say the only drawback is slightly more limited access to the headstock. When the spindle is over the headstock, you really can’t get at the headstock from the back because of the cable track on the back of the gantry. So, you need to lean over the table in front of the headstock. This is only an issue (for me) when I want to see how a V-bit aligns with a bit in the headstock (visually confirming that WCS position). Most of the time I put a piece on the headstock from the back of the machine with the gantry moved to mid-table.
I had the same problem. My maching is only a 4x4, and I didn’t want to commit to a 100% permanent rotary, but I also didn’t want to go through the procedure of re-calibrating the whole thing with those jack screws each time I re-installed.
So I installed shims and alignment pins so I could just unbolt it and lift it out, and then when I put it back, there isn’t anything to adjust.
You can see the details at about the 42 minute mark in this video:
Thank you, that’s an excellent point since I don’t have easy access to the back of the machine—I usually work from the front or the sides. I also have a vertical table mounted at the front.
That said, I think I can manage this setup since I don’t anticipate using the rotary axis frequently. But then again, you never know!
I hadn’t considered that—there are definitely some interesting use cases for it. However, I think I’ll keep things simple for now and focus on using my 4th axis a bit more without sacrificing too much of my vacuum table surface area
I came across your video during my initial research and was actually inspired by it to create a similar mechanism with the puzzle-like assembly between the front and back sections. While your setup works really well for a spoilboard, it’s a bit less ideal for a vacuum table. My main concern is maintaining Z-axis accuracy for the vacuum table, as I prefer not to surface it—doing so would gradually reduce the height of the gasket channels over time. Today, I’m loosing Z accuracy every time I remove / put back the front part of my table.
The green area is the vacuum portion of the table (4’ by 8’, in four zones). The six inches to either side is non-vacuum area with T-track (currently). This sometimes has evenly spaced 22mm dog holes next to the track. It is surfaced to the same Z height as the vacuum table.
In front of the vacuum section is an area for vertical table (not currently installed).
The rotary is recess mounted. The position is to allow the spindle to cover 100% of the material that would it (and rotate). The empty space between the vacuum table section and the rail just before the rotary is wasted. Future iterations would make use of this.
That’s exactly the setup I have—I left 10 cm at the front for a vertical table and added T-tracks on the left and right sides of the table. My CNC is smaller, so I try to make the most of the remaining vacuum surface. I mostly work on small objects or furniture pieces and rarely on full plywood sheets, so that setup works for me.
From all the feedback, I’ve decided to go with a permanently mounted rotary axis at the back of the table. It might not be the easiest configuration for loading and unloading materials, but I’m prepared to work around that.
