So, this is how my CNC looked like a few weeks ago.
I built this a few years ago and use it mainly for plastics and PCB, but also mill aluminium pretty well on it, so for my needs the machine is definitely good enough. From the start I kept track of the weight, but as time went by, the machine got heavier and heavier after all the modifications I constantly make. I knew it was more than 100kg, but not more exactly. The other day I managed to check it more precisely by placing two ordinary bathroom scales under it, just for fun, to check the exact weight. One showed 60kg, the other showed 65kg, so now I know that the total weight was 125kg, which explains why it was more and more difficult to move it around. I noticed this “problem” some months ago when I moved to another, larger room in my house. This is the way I had to do it:
I had to lower the round black feet on all four corners to lift the machine, remove the wooden blocks the machine normally resting on, raising the black plastic feet to lower the machine on the four castors, move it to the new place, lift it again, place the wooden blocks under it and lower the machine on those. It was a complicated operation, which actually put me off from doing any improvements and modifications, so I decided to do something about it.
What I did was, I ordered four linear actuators, installed castors on them and installed on the four feet.
After installing the actuators, my CNC looks like this.
Each linear actuator can lift 152kg, so I knew I had good margin. The only thing I am not that happy about is that they extend to three different lengths, only two are the same, but in this application that is not critical.
I made a control box with some relays, a switch and three LEDs to control the actuators.
Of course, simplest would have been to use a 3-way two pole switch, but I had no such thing in my boxes and drawers. I had however more than enough relays to make it, so I went for a relay based solution.
The box isn’t as nice as I wished for, but it does what I wanted it to do. This was the first time I made this sort of engraving, so it’s OK for now, but I will make a new box top with better polished surface another time. Now it is easy to move my machine around, just flipping a switch and that lifts the machine with the wooden blocks permanently attached under it’s feet. No more crawling on floor for a simple move.
Anyway, the subject of moving around heavy machines is often discussed, also if CNC can be permanently on castors or should rest with better stability. Initially, my CNC was on large, heavy duty castors placed under it´s four feet (not like you see in the top picture), but even though each had a lock, preventing rolling, the CNC was shaking because of the rubber wheels and the fact that they are wheels. So my conclusion was that castors are good for moving the machine, but using it resting on castors is not a good idea at all. I considered fixing it the wall, but then I concluded that it will shake the walls and it would be better to let it rest on wooden blocks on my floor. Under the teak parquet I have concrete floor, so there is no floor vibration, and the CNC is resting firmly on the soft-ish wooden blocks, which are soft enough to dampen the machine vibration, but hard enough to provide very good stability. Actually, my CNC works much better, with higher speed, acceleration and accuracy than it had when it was resting on castors.
I feel that my solution with the linear actuators can be used on many other machines as well, and is not adding much to the price of those 400kg + machines, so I don’t understand why we don’t see any of those. I have seen people building hydraulic systems, which may be needed to machines which are REALLY heavy, but for the few hundreds of kg our machines weight, I think a pure electric linear actuator is more than enough, simple to implement and can lift quite a lot. Even if a machine weights more than 600kg, it is possible to use the type of cheap actuators I am using, but of course, it may need more than four. In general, I think it is a good idea to leave some margin, personally I’d feel comfortable to use it up to 400kg, which would leave a 200kg in that case.
In short, I don’t think it is a good idea to build CNC which rests only on castors, it is much better to lower the castors when the machine needs to be moved.