Newbie question on rigidity
 

Hi all,

For years I have wanted to own or build a CNC controlled mill or router. The MechMate seems to be targeted at woodworking although I think with careful revision it could do soft metals such bronze or aluminum. What I would like is not a big routing area such as 4' X 8' but something more manageable for a small shop such as 2' X 3'. And machining wood does not interest me so much, except maybe for creating casting patterns. I would like to mill or route aluminum and bronze for immediately usable parts, and machinable wax for casting patterns.

I think that if I were to build a sturdy example of MechMate on a smaller scale I might even be able to machine steel in a moderate sort of way. Biggest issue I see for that is spindle speed and bearing quality of the spindle in order to sustain the higher loads. In this case the frame of the machine must be exceptionally rigid, but I think that is possible using heavy wall tubing and accurate jigging for the welds.

Anyway, have any of you gone this way before? What torque values for the steppers might be needed and what pitch ball-screws as well? Just casting about for some ideas here. Geco parts seem to be one way to go. I think the offerings of steppers from Zapp seem too weak, but Zapp does offer good deals on linear components. Please feel free to chip in on this, I welcome any and all opinions. Thanks.

Randy

Hello and welcome
There have been people that have machined steel but it is not really recommended for the reasons you mentioned but with light cuts and many passes it is possible.
Aluminium and other softer metals are now considered to be easy to machine with many people having positive experiences.
Lubrication is a topic that has not been decided on as yet some thinking it is essential others have had good results with a cooling "gun" that blasts ice cold air at the tool bit preventing the aluminium from melting to the bit.

If you really want a small envelope and metals, you can probably better spend your money modifying a mill. Poke around hossmachine for some ideas.

The sweet spot for the MechMate design starts at about 16 square feet (2x8, 4x4, 3x6, etc) working with wood and plastic sheet goods that tolerate flex in the cutter at non-trivial cutting depths and speeds. Aluminum sneaks into this category when handled in multiple passes. Steel is in 'you can get away with it, sometimes' territory.

Ball screws are not relevant to the MechMate design - it is a rack and pinion machine.

I guess the first question is what do you think your going to be making and is this for production type setting? Yes the MM can cut aluminum and steel. Is it the right job to produce 8,000 circles in 1/4 aluminum with a spindle. Probably not but a plasma cutter would complete the job in no time and be more cost effective in the end.

I do take aluminium jobs occasionally, it is PITA when lubricants get soaked up on my vacuum table top board. BTW compress air isn't enuf to cool the bit in my part of the world.

You are asking too much of the design right up front.
Move on to something that has your requirements in the headline not the byline.

Regards
Ross