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Profile photo of John PatersonJohn Paterson
Post count: 8
#7887 |

I am near to the end of the build of my MPCNC.
I have finished the basic frame, legs and gantry.
But I still have to print one rigid joiner and that will complete the middle assembly.
Then I will measure & print the Z motor support and tool holders.

I decided, early on, to go for stainless steel tubes despite the additional expense.
(I couldn’t find the original galvanised steel conduit in the UK where I live and because I reckoned stainless would last longer and be resistant to rust).
But I chose 1 inch diam tubes, and only discovered, after delivery, that Ryan’s design would not accommodate that diameter!
So, having committed myself, I realised I would have to modify the design to cater for 1 inch tubes.
The main change (apart from inserting triads of bearings circling a one-inch diam tube section) was to split most of the monolithic parts, like middle_ends, into two parts.
The idea was to insert/remove shims as required to adjust the ‘grip’ of the bearings on the tubes.
My redesign removed a small amount of plastic from each mating face so as to allow for closing down the size if needed.
Also, I planned to make the single bearing bolt hole into a slight slot, so I could shim that bearing in/out.
So, I could move the two Y bearings closer or further away form the tube by flat shims between the new joints in my split middle_ends, and slide the single bearing in/out by putting curved shims around its bolt.

Did it work?
Yes. When first assembled it was a loose fit. I just shimmed until the fit was correct for each part of the assembly.
It took most of a day but was straightforward.

Thanks very much, Ryan, for a really original design and thanks for being so generous by making it open-source.
I am really enjoying the build and the technical hurdles I introduced and am looking forward to adding the electronics very soon.
Thanks for the cable kit and the drag knife; it all arrived safely. (postage was a killer though!)

I have attached a photo of my middle_assembly with dark lines in places to try to show the joins I have mentioned.