Wobblycogs CNC Mk1

[Wobblycogs]

Having realized that SBR20 rails are 45mm wide I scrapped the 80x40x4 box section in favour of 50x50x4. I've plugged the figures into the gantry stiffness calculator and if I understand it correctly I should be getting a maximum deflection of about 50um with a 30kg gantry (I assumed the maximum span was 750mm, it's actually more like 665mm) - I've not studied engineering though so I might be reading the spreadsheet completely incorrectly :-). Should I add another support to reduce the span further?

After seeing jon's design I've reduced the number of bed supports and thinned them down a bit, they are now 50x25x3mm. I needed to reduce the weight a little as this is going to be installed on an upstairs floor which already has a fair bit of weight on it. My calculations indicate the frame weighs about 85kg so far but that doesn't include the multitude of fixings and brackets I'm going to need.

To keep down the mess I've added 2mm aluminium sheet on the sides and ends. I plan on making the ends hinged so that I can work on longer pieces if needed. The bed is sacrificial a sheet of ply or mdf.

The length of the X-axis has been reduced slightly to 1480mm with the rails being 1450mm. This is so that I can hopefully get all for long rails out of a single 6000mm piece of box section and save a little money. The reduced cutting length on X doesn't worry me as I was only aiming for 1220mm.

I'm pretty happy with this design as I think it's something I can achieve. Any comments are, as always, very welcome.




P.S. Thanks to jcb121 for the sketchup models.