Gathering ideas for a new CNC router-mill thingy

[Davek0974]

I was looking at buying one of the 6040/3040 import routers but after reading many threads on them I think I can build a better unit myself. I have built two CNC plasma tables to-date, both successful and my last 1250x1250 is my main production machine now.

I went against the odds when designing it - everyone was leaning towards very large rigid gantries and heavy frames etc. I decided to use thinner 2mm box section throughout and gain rigidity only where needed by correct use of bracing and ribs etc.

The result was a 100% success and was even FEA tested with flying colours proof of the pudding is in the eating and it worked very well.

Now, after reading dozens of threads on building a mini router/mill for engraving and light work in alloys or wood etc, I saw a trend towards heavy builds again, some very heavy! Considering the average mill cutter is about 3mm for alloy work, maybe a little larger, and engraving tools are tiny I thought of applying my ideas to building one.

My want is for a general purpose machine - wood, alloy, plastic, engraving, carving, milling, envelope maybe 400mm x 500mm.

So, picture if you will, no box-section, use maybe 15mm x 150mm aluminium to make a shoe-box structure - 4 sides and a base (base can be thinner i think).

Mount 15mm HiWin rails to the tops of the long sides, 2 carriages on each side. Mount 1610 ballscrew on outer side of longer sides.

Make gantry base to span the opening, deep enough to take two carriages suitably far apart, drop plates down from ends to fix ballscrew nuts to - it would be an inverted U shape.

Build gantry as required from base up to hold Y axis and Z axis.

May even consider using steel plate throughout.


What do you all feel about that?

IMHO, i can't see enough counter-force coming from the small tools used in these machines to distort a 500mm x 150mm slab of aluminium by any amount that matters??

I have other ideas but this is the most radical so i thought i'd plant that one first

[jamesgates1000]

Even with smaller cutters if you want decent speeds and doc you will need rigidity. The heavy builds are to deal with vibration and resonance that the tool generates as it cuts.

[Davek0974]

Ok, i have the basic design sorted with the generous help of a forum member.

I have a nice lump of ground cast iron 18mm thick for a bed, what is the preferred method of fixturing - a matrix of holes or built-up T-slots??

This will be a multipurpose machine metal through to wood being used.

Any preferences???

[Davek0974]

Too much metal on the Z axis?

I have ordered a bit too much metal and linear rails for the front plate of my Z axis, the back plate is 320 tall but for some reason i ordered 400mm plate and rails for the front plate where the spindle mounts.

Should i leave the extra or cut it down to match the back?.

Is it generally a good thing to have maximum space between the linear carriages on the Z axis?
I had originally sketched around 30mm but after drawing it up fully it lookalike i can go to about 70-80mm apart.

[Clive S]

It might be a good idea to post up your sketches so that they can be commented on

[Davek0974]

Backplate attached, not shown but its 160mm wide, 20mm thick aluminium machined tooling plate, same for the front plate.



Blocks are HiWin HGH20CA narrow, screw is 1605.