El Beast - Initial design phase, comments and critique welcomed!

[Zeeflyboy]

Few comments:
- I do not understand why you are using AL profiles and AL plates, check stiffness...

Why alu profile, because it is available cut to length at sizes larger than I can handle myself with decent precision and also with ground surfaces from misumi. GFS (high rigidity) profiles are being used, they have substantially more mass than normal profiles.

Why alu plate, because I can process aluminium plate myself and I can buy it in ecocast form with a high flatness tolerance, again readily available. If I pay for every part of this machine to be made up in steel to high tolerances by someone else then I will not be able to afford it, even if the material itself is cheaper... which i'm not sure it is when you start talking about milled tooling plate.

- design of lower (x) rails is .... You need to grind both surfaces to get perfect parallelism, otherwise will linear bearings feel the load caused by angular displacement of both rails , put them on the top of the table, in same plane - much easier for DIY,

Both surfaces are ground...

- design of gantry (y) - it must be closed beam - it has no sense to do a "nice look" without functionality,

I don't understand what you mean here.

- side brackets, what is the method for setting the "true" right angles? Do you expect that everything will be machined within few microns? , y length tolerance stack is problematic anyway

That little mounting plate at the bottom of each side has an eccentric nut on one end and a DIN shoulder bolt at the other, which will allow the entire gantry to be trammed fore/aft, while the side arms and mount plates are both made from eco-cast plate which will have to sit flat to each other when bolted together. Further adjustment is available on the spindle mount for tramming left/right.

- foots: do you expect that desktop is planar?, machine must be stable,

On a machine this small I think adjustable feet are more trouble than it's worth. Better just to make sure you have a flat level surface for it to sit on... depending on what I can find I will either sit it on a granite block or pour a self levelling base block for it which will form the bottom of my enclosure.

Before design set the requirements i.e.
- max work space
- max space for machine
- max tooling dia
- material of machining
- define what you wish to do ( mirror surfaces, engraving...)

and the start with design.

regards

My design requirements were of course set out before I started to design it... the majority of what you list there was mentioned in the very first post. I'm not sure how you can even start designing a machine without knowing what you want it to do...


Thank you for the feedback but I do think there is a danger sometimes of losing sight of reality on this forum. For what is ultimately a small hobby desktop machine the rigidity of a 50x100mm GFS extrusion and 20/25mm alu plate is hardly going to be the limiting factor... This machine will be an order of magnitude more rigid and precise than my current one while expanding the work area, which is really all I'm after.