Over sized/over engineered spindle Z-axis

I am in the early stages of building a “proper CNC” style Z-axis and spindle sled, ie: I have all the pieces of the puzzle, now I just need to work it out.

I would appreciate any thoughts on this setup.

I am using SBR12 supported linear rails with SFU1204 zero backlash lead screw set and the smallest ER20 air cooled spindle I could find.

I choose a spindle for the speed control offered by VFD to avoid chip loading/bit burning issues. I selected ER20 so that I have a larger range of router bits to choose from as have found ER11 limiting on the desktop 6040 machine I cut my teeth on.

So far it remains to be seen if this is a good idea or not as it’s going to take a bit of engineering to make it work.

What the Ebay listing doesn’t tell you is that the spindle is heavy, ~5kg, and the weight is in the upper 2/3 of the body. I am concerned that by the time you have a bit in the spindle you could be looking at a total length of 250mm with a 5kg lump between 100-250mm away from the sled will causing a tendancy to tip away from the work piece with the cantilevered weight, I suspect i may have to raise the ring height away from the sled to counter for this.

Pieces of the puzzle:
SBR12 rails: https://www.ebay.com.au/itm/302815884241
SFU1204 set: https://www.ebay.com.au/itm/132406400223
Spindle: https://www.ebay.com.au/itm/323248037332
Spindle mount: https://www.ebay.com.au/itm/222777650347
VFD: https://www.ebay.com.au/itm/121224071334

I’m also building a uni-strut frame which is another work in progress.

1 Like

Not sure what your thinking of cutting but I doubt you need a 2.5Kw spindle

The reason I say this is you wont be able to plunge or travel at a speed that will put the kinds of loads on the spindle that will need that level of power.

To put it another way your going to use a spindle that is roughly equivalent to a 5 - 7.5Kw router.
Id suggest you start with a 500-800W unit with a 1.5Kw unit Max

Im putting together a 1.5Kw unit now but that is because I had one spare. If I was to buy one Id get a 500W unit. Now I have a 3.5Kw unit on my big table (not Maslow) but that is able to load the spindle up with a much higher travel rate and a fixed gantry

Take a read of this thread as I post a lot of info on this and the bits needed

Also from the links it appears you are in OZ, not sure where, Im on the Sunshine Coast

what kind of bigger bits do you need? Not sure maslow even works well with bigger bits? If anything the smaller the diameter of the bit, the less material the machine has to cut through

something like this might let you use 1/2" big bits in a smaller collett. Probably not recommended though because it will be rather long and prone to vibration

I 100% agree, I recently used a 3” long 1/2” 3 flute bit in my Maslow that has a gantry style sled. And I found I couldn’t get the bit far enough into the Maslow so that the spindle is as close as possible to the cutting surface as possible and I tore through 2 of my 3d printed spindle holders. (I like them because I would rather those break than something more expensive, it is kind of my mechanical fuse)

Thanks for the feedback, I am aware that a 3hp spindle is overkill, especially given that it will mostly only be used for V carving, pocketing and profile cutting. Regardless of the spindle I wanted a lead screw Z-axis.

I may have gotten a little carried away on spindle purchase because it was only “a little more” to be honest I never considered the weight until I had it in hand.

If it becomes too hard to manage the weight I will take your advice and grab one of the 500w spindles.

If it doesn’t work I’ll have a 3hp spindle to use on a future project on my to do list.

Has anyone else noticed these to do lists never seem to get any shorter.

Yes I am in Australia, I’m in the Shoalhaven, NSW.

[Here](DEWALT DW618 2-1/4 HP Electronic Variable-Speed Fixed-Base Router https://www.amazon.com/dp/B00006JKXB/ref=cm_sw_r_cp_api_FYVABb84B0EB4) is a link to the router I use, it is probably over kill too but I liked it because of the variable speed down to 8,000 (which is less than the ridgid) and then here is a picture of my sled to give you an idea.

I think if you make it sturdy enough you should be fine, you may just need to get creative with weight etc. if you look around you can see ideal weight for sleds and how to center of gravity them. (If you have not already)