Is the rule of thumb for the Sphinx machine that the standard OpenBuild lead screws are 40 to 50mm longer than the c-beam length of the axis it's installed on? Such that if the X-axis c-beam is 503mm the lead screw should be about 543mm in length?

 

Thanks...I did get hand wheels that I can use to manually adjust the gantry positions...and in reality I see that if the screws extend out longer they don't affect anything functionally. I have been looking at a build that was created in solidworks. I should have thought about verifying the length in the model.

So far my only gripe is a few of the wheel assemblies do not spin freely and a few others have a gritty feel while spinning the wheels. And yes I made sure I installed the spacer inbetween the bearings.

 

OK...what's the secret to getting the bearing out so I can flip it around?

 

Can I get some clarity on what level of accuracy you have gotten with this machine? thanks!

 

Not to speak about someone else's machine, but I can tell you about mine which is a Sphinx design as well.

I can achieve accuracy of greater than 0.05mm consistently.

Here are what I feel are the keys to this:
1) Step tuning - Tuning the steps/mm to ensure accuracy. I find the best way to do this is to cut 2x2 blocks, and measure and adjust accordingly.
2) Backlash (Nuts) - Need to ensure that backlash has been eliminated. I run dual anti-backlash nuts.
3) Backlash (Collars) - I determined another source of backlash was the collars on the lead screws. Unless you ensure a flat spot for the set screw, the collar will sit slightly cocked, and not fully engaging the end bearing, and therefore introducing backlash into the system. I corrected this with clamping lock collars.

 

dual anti-backlash nut

I get 3 - makes sense, but can you detail out 2 for me a bit more?

 

There is some adjustment to the anti backlash nuts. Therefore you need to adjust them properly based on feel/tension.

 

Because of the wheel and bearing materials I thought that an attempt at disassembly of the wheels would damage either the wheel or bearings however I actually was able to get one of the larger ones disassembled. Sure enough upon closer inspection I found that the outer race on both bearings was recessed on one side and flush on the other so installing the bearings with the recessed outer races and consequently protruding inner races towards the center of the wheel. That was the shim between the two bearings contacts only the inner races.

It seems to me that I don't remember hearing or reading anything relating to this in the build guide or the YouTube build videos. Perhaps OpenBuilds should include at least a note pertaining to the orientation of the bearings in the assembly process.

 

Hi @Michael.M

Nice build! I would like to build the same machine as you and I have a quick question for you ?

What is the length of the Cbeam you used for the Z axis for your build ?

Thanks !

 

I think I made mine 280mm. Yep...when I got home I measured 280mm.

 

Even though I made sure all the beams for the frame and the axis were cut exactly to the dimensions I planned for the X axis distance between plates is greater than it theoretically should be. My X axis is planned to be 600mm so I cut the c-beam to 603mm. I guess some tweaking is required.

 

Thanks for the information !

 

Michael, which shielded cable did you use for the spindle? Thanks.

 

Did you find a way to incorporate linear rails yet with custom plates?

 

Yes i am, i have most parts laying around from other builds so wanted a good way to use it.

 

Can you give us a copy of your template for modifying the x-axis stand off plate?