Hi That-Jim,

I have been looking at your build and I am currently starting my own build of a similar nature.
Apolgies for quoting metric, are you using 4080 C beam extrusion.
If so, what size of ball screw and nut did you use as I am struggling to find ball screw flange nut that will fit in the 40mm space of the extrusion.

Thanks - WoodKnot

 

Thanks JIm -
I thought i may get away with a thicker ball screw than that?

However, now i have seen the simplicity of the nut, i may still be able to use my 16mm screws and get something machined up in the UK?

Thanks

Steve

 

What would be the benefit in utilizing ball screws instead of lead for this machine? Speed, accuracy, etc...? Would the cost and labor justify the change?

 

Speed/acceleration, mostly. much lower friction for a given level of backlash. Can run smaller motors because less power is lost as friction. Price isn't that much different any more, ball screws got really cheap.

Backlash can be just as substantial as lead screws though; DFU nuts are required to get almost-zero-backlash operation, which is particularly important if you're using a control that doesn't provide even basic single-value backlash compensation, like grbl. So that costs more. Some vendors offer "anti-backlash" screws which is where the nut's been emptied and repacked with slightly oversize balls, which take up more room between the two channels and allow for less "slop". They do help, but they're not magic.

Accuracy/precision is largely the same as lead screws; "C7" doesn't really mean anything, once you've actually mapped screws you see that the true pitch varies wildly as you move along the screw, which is almost certainly the case for any rolled screw, leadscrews included. Ground screws (ball- or lead-) cost serious money though; you could build an entire machine for the price of a couple of ground screws. There are happy mediums, of course, C5, C3, etc. You get meaningful precision guarantees then.

If you're unsure, want to use off-the-shelf OpenBuilds type products more or less as-intended, and don't want to deal with any additional work combating backlash, lead screw is probably the way to go. If you want significantly higher performance, the possibility of far higher rigidity and power put into the tool instead of the machine (12mm and 16mm screws are enormous compared to 8mm), and are willing to build your machine to the specifications required to actually use that additional performance without simply bending your machine frame, then ballscrews are awesome.

 

Thank you both for the responses. I currently have a lead 1515 but I'm looking to downsize the footprint. I'm leaning towards modifying it similar to this setup and still utilizing my blackbox and other parts.

 

Brilliant build, Thank you.
Would it work if I were to make it bigger, using 1000mm C-Beam Extrusions? I'm worried about the deflection of the gantry by the weight of the spindle and Z-Axis

 

Thank you, I'll do some more research on it.

 

Great Build, very well executed! I have the same plate set and have finally gotten back to finishing it after a long, long hiatus.

I have a few questions if you dont mind:

1) What length are you using for the 2060 extrusions that make up the base? I just used 474 (500mm - 13mm*2 for the mgn12 rails/blocks on each end) Just wanted to confirm my thinking is correct.

2) On that note, what dimensions are you using for your mdf spoilerboard?

3) Also if you could share the STLs for your 3d printed induction sensor mounts and your printed drag chain bracket, that would be awesome

Much Appreciated and again, great build

 

I am going to try a 600x600 build. Would 640mm lead screw’s be long enough? Also, if I were to use Chris’s 11inch plates, do the z pieces need to be longer?

 

You would need about 30mm to satisfy the build, so I'd say 640 is enough though you'll have about 10mm more but I'd say it won't hurt, good luck Chris's 11inch plates cause I don't know about that.

 

If I actually complete a working machine, I now know what my 1st aluminum project will be. That is a great looking z.

 

This build looks awesome and will be the inspiration for my first cnc build. One question I have is that looking at the pics it looks like your base frame is different than the sphinx 55 frame. Am I seeing correctly that there is only a piece of 2060 front and back of the machine? Another question not specific to this build is, how do folks cut multiple lengths of extrusion precisely say I want 3 lengths at 800mm how can cut and have precision accuracy in length and squareness. Thanks.

 

Thanks. One other question I have: on the original sphinx build the x axis is 3mm longer than the width of the frame. Is that correct? Why is this necessary? Are spacers used and provided with Chris’ plates, and what is the reason the frame can’t just be narrower?

 

If I use a stock length extrusion for the x (1000mm) could the frame just be 26mm narrower than that since the parts of the frame that run parallel to the x axis are the ones that get cut to a custom length anyway?

 

Thanks that actual clears up a lot of confusion for me.