Build Thread- RomanLini's "M60" precision plastics mill

[RomanLini]

"M" for mill (as it's not really a router), and "60" for the 60 degree tilt.

Specs;
Excellent cutting precision and good performance cutting aluminium (hopefully).
Z travel 60 to 65mm
Y (table) travel 205mm
X travel 280 to 400mm (see comments below)


My original machine;
http://www.cnczone.com/forums/cnc_wo...ll_router.html
has performed very well and this new design is extremely similar but with some important...

Differences from my first machine;

1. It is on a 60 degree tilt, which allows gravity extraction of chips, as the machine will generally be used for plastic and aluminium cutting both generating large heavy chips I prefer this to vacuum chip extraction. An air blower nozzle will probably be used to complement the gravity chip extraction. The 60 degree tilt also allows excellent loading and visibility for a small desktop based machine.

2. It will allow mist or flood coolant to be used. The 60 degree tilt forces fast coolant runoff, and the job is held high and relatively dry allowing good loading with all the mess contained below.

3. It is much more rigid than my first machine which is made from 10mm aluminium plate. This machine has a smaller frame made from much thicker 20mm and 16mm aluminium plate, and 30mm epoxy granite slabs. This rigidity should allow production machining of aluminium, and also improves precision of tiny machined parts.

4. The vertical nature of the mill means all the moving parts are up high, so unlike my first (flat) machine this will suit being in a box where the bottom of the box can fill up with chips and again suits unsupervised production work.

Similarities to my first machine;

1. I will use the Igus plastic teflon linear bearings again. This machine is a "mill" in that the linear bearings are packed fairly tight, and give absolutely zero slop (and uses slower movement speeds). The plastic bearings are also rated for millions of cycles, and much higher loads than ball bearings, AND they are rated for dirty environments (they push chips out of the bearings and are fine with coolant).

2. I will make custom plastic leadnuts again, and again make solid couplings to the stepper motors. The plastic leadnuts are tight on the leadscrews giving zero backlash and averaging any "point errors" from any single point on the rolled screws. The solid stepper couplings mean no backlash and the ability for very small microstep movement to translate perfectly to linear movement for tiny precision parts cutting. My last machine showed how well that worked
(for my cutting needs) and there is no need to change it!

3. Again the bulk of the machine is made from flat plate, drilled and tapped as needed. This gives great geometry and makes a very rigid machine, and it also suits the Igus linear bearings which are very "flat". The whole machine is like flat slabs of metal sliding over each other which allows good rigidity and reduces any "bad" leverage to an absolute minimum.

4. It will use the same NSK rolled ballscrews 12mm diameter and 8mm lead, I still have some screw length left over from my first build. Stepper resolution is 400 steps/mm (0.0025mm or 0.000098").

5. Like my first machine this one will use 6v 2A unipolar steppers and SLAmStepper drivers, with a PSU adjusted somewhere around 32v which I found was the sweet spot for very low resonance and best precision cutting. Top speed again will be about 80mm/sec (190 IPM) which is fine for a precise mill with small travel distances.

[RomanLini]

This is the side view of the machine showing basic layout. The side plates are planned to be CNC cut out of Epoxy Granite kitchen counter top. I might even use solid CNC cut Granite, depending what the kitchen guy quotes.



The moving table slides up and down at the 60 degree angle and is on the right. On the left is the "gantry" which is almost horizontal (30 degrees off horizontal).

The granite side plates have a "throat" cutout that allows stock up to 150mm wide to fit in the throat so unlimited length stock can be machined. This might be good for machining items out of aluminium bar extrusion for example.

[RomanLini]

I have bought the aluminium (which is 5083 marine grade) from a local scrapmetal yard that gets cutoffs of new aluminium plate from local manufacturers. This worked out much cheaper than buying new plate cut to size, and for similar money allowed me to use larger and thicker plates.

Although some pieces need cleaning up on the Bridgeport.

The main backplate of the machine is 20mm thick aluminium plate, sandwiched between the two Granite side plates.



Originally my design was for a cutting area roughly 250x200mm, but when I found the nice piece of 16mm plate in 570mm length I decided not to cut it shorter, so leaving the gantry long at 570mm. It looks a bit funky but allows a longer X cut at 400mm not 250mm, and does not reduce the rigidity of the machine in it's original design spec cut size of X 250mm (which is now about X 275mm).

The longer gantry plate also moves the spindle further out of the way allowing easier loading of the work on the moving table.



The shape I designed for the Granite side plates allows the machine to simply be tilted back to sit flat, so on some jobs it can run unlimited length stock mounted horizontally.

At this point all I have done is buy the plate aluminium (27 kilograms of it!) and make some final decisions on the machine size and the sizes the plates need to be finished to.

Most of the decisions are made now (which is always the hardest part of a design!) so the work part begins.

Spindle choice is still unknown but the design currently allows for about 70mm diameter spindle so that includes a small router or 800W VFD spindle or most likely will be a ER16 collet spindle, belt pulleys and some quiet motor choice about 300W.

[Fish4Fun]

RomanLini,

What a fascinating design! I look very forward to watching your progress. In production settings I have seen CNC mills turned 90 degrees, but had not given any consideration as to why, now I feel like an idiot for not grasping the obvious.

Cheers,

Fish

[aarggh]

What a great design! I've been thinking of making a 90 degree beefy machine purely for machining aluminium, but a versatile one like this that can tilt, and lay flat is terrific! So simple but brilliant!

I've been wondering for a while though, does the effect of gravity help with the cutting force more when it's tilted compared to 90 degree, or does it make no appreciable difference at all?

I'm also with you on the gravity chip compared to extraction, after my festo extractor died while machining some aluminium that somehow punched through the multiple filters, and looks like it shorted the field/armature :-(

cheers,
Ian

[RomanLini]

Fish4fun- Hi, thanks for the nice words and for watching! It will not be a fast build as I have some commercial design work taking up much of my time, but hopefully I should have it built over the next couple of months.

Aarggh- Thanks too!

As for the 60 degree angle I chose it over 90 degree for a number of reasons;
1. When the machine is sitting on a bench it allows great viewing when you stand in front of it. It points right at your face. And good enough viewing from across the room.
2. Loading work material in is much easier on 60" especially in a jig etc.
3. 60 degree table means the gantry is at 30 degrees so chips and mess also drop off the gantry. If the table was vertical 90 degrees the gantry would be flat and get covered in mess.
4. 60 degree means slightly less force to "lift" the weight of the table and workpiece when Y moves.
5. The moving parts and electric motors etc are higher up on a 60 degree machine, hopefully well above fluids and metal chips.
I did mess with a 45 degree design but it was ugly, would not extract chips as well and would give poor visibility of the work from across the room. The 60 degrees seems pretty optimal and is a crude standard I guess if I had to pick an angle.

[louieatienza]

Pretty wild design! Will be watching...

[epineh]

I am in as well to see how you go, right now the footy is on so I will get back to read all the details a bit later

Cheers.

Russell.

[aarggh]

Originally Posted by epineh I am in as well to see how you go, right now the footy is on so I will get back to read all the details a bit later Cheers. Russell.

Go Pies!

[epineh]

Originally Posted by aarggh Go Pies!

Lol, well I was thinking the other footy, go Bronco's...ah well...

[Mountaincraft]

Nice.. Subscribed...

[RomanLini]

Thanks guys, it will be great to have you along for the ride!

I'm itching to get started on it. I've been busy with a high tech controller brain for a motorcycle engine dyno, it's the second one I've built for a friend who makes drag racing engines. The good point (and relevance!) is that it earns me some "Bridgeport time" on his machines to get some of these larger slabs of metal nice and square for this M60 build.

He's also got a surface grinder but doesn't like to put aluminium on it, but fortunately I can face the 5083 aluminium pretty good on the bridgeport with the power feed.