How I move around my heavy DIY CNC

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That's very interesting. I've just re-built my own machine onto a base with castors and in spite of checking the alignment of rails and ballscrews I have had to reduce the max speed from 9.0m/min to 7.8m/min after a couple of stalls. I had not thought that a small amount of rocking of the whole machine would have a negative effect on it's operation but may have to think again.

I think many people assume that if the CNC is resting on four locked, industry quality, heavy duty castors then everything is fine. I did that assumption as well when I built my machine. My settings were OK and worked well, but after a while I thought I wanted to test how my machine would behave resting on the floor, so I removed the castors. By doing this, the machine suddenly became much more quiet, vibration and shaking stopped, I could increase the speed, acceleration and the overall accuracy also increased, got better results. I think I made this video some time after lowering it to the floor about four years ago:



While it may not be a masterpiece, and there are faster machines out there, it definitely shows that there is no shaking, except my own hand shaking with the camera in it.

It is actually logical that if the machine is shaking during work then something must be wrong, and that something definitely will have a negative impact. It is impossible to quantify how negative, and what will be worse, but one thing is sure, it is NOT beneficial to the quality, even if you can overcome the stalling issues by reducing the speeds, but that's not all, the machine will still continue shaking and that is not something we want, after all, a small shake of that huge Z mass can still cause issues, maybe not missing steps, but definitely leaving some unwanted marks.

Please note, that when my machine was on castors, the castors I used are not the ones you see in the pictures above. The ones I used were larger and wider, each were specified for 200kg and were really industry quality, not cheap eBay things. That was one reason why I did not expect any problems, but it is clear that they are not meant to be used on these sort of rapidly, and erratically moving machines with heavy Z spindles. Maybe that's why we never see any industry made CNC resting on castors only. They all stand firmly on the floor below.

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This project is finished. Yesterday I swapped out the PSU to a more powerful one and released the last part of my video series about it.



The new PSU was necessary because the current use was too high for the 7A PSU I initially chose to use. I was not sure about how much current is needed, and was a bit naive, thought that since my CNC is far below of the maximum load, I would need far less than the maximum current, but that seems to be the case only for "normal" operation, which is starting from zero load, i.e. when the linear actuators are fully up and the castors are dangling. From there I could drive the actuators to full extension, but if I stopped before, I could not restart. When the CNC was resting on the castors I could not restart to push the CNC further up, because the load to start from that position was just too much for the 7A PSU so the PSU just stalled, no movement. In that situation I had to lower the machine completely and restart from there. This I though was not very safe. Imagine if my toe gets caught under one of the CNC feet and there is no way to change direction, meaning I have to lower the CNC fully on my toe before lifting it up again... not good for my future... so I changed to the 82A 12V PSU I have and with that it can be stopped, restarted or instantly swap direction any time I want to.

Anyway, I am now ready, it works well and no regrets, would do it again if I had to. Yes, it is over-engineered, but it was fun and I really like this solution to a fairly simple problem. It's really cool in my opinion and hope it inspired a few people, so thumbs up for me.