1.7*0.74*0.4m Mill / Router building...

[Jonathan]

Jonathan what have you used on your Y axis, I can't quite make it out

Which part in particular?
It uses an RM1610 ballcrew, 3Nm stepper motor...nothing unusual.

[deannos]

Which part in particular?
It uses an RM1610 ballcrew, 3Nm stepper motor...nothing unusual.

Your gantry in particular, is it ali box section

[Jonathan]

Your gantry in particular, is it ali box section

Yep:

I went to a small local metals supplier and picked up a meter of 80x3mm aluminium box section for the Y rails to mount on

It's mounted with 20mm aluminium plate milled to fit in both ends. It's adequate, but I would advise using something a bit stronger. Since the rails are on both sides of the box section it had to be aluminium since the width of steel box section is not accurate enough. Extrusion is a good option, but quite expensive.

[Jonathan]

Forgot to say in the previous post...
Around the edge of the aluminium bed I've put 3x2", 1/4" thick aluminium angle. This acts as a barrier for the coolant, so to ensure it seals I put a strip of 1.5mm thick neoprene under each piece. I used my metal cutting bandsaw to cut the 45° angles, but the finish from this although not bad for a bandsaw, is still quite rough.



Bit of an unusual set-up on the lathe so I videoed it:



(Something wrong with the sound on the past two videos)

[olalofberg]

Hello, looks like you've got a fine machine there Jonathan! Good work, It inspired me to go the way with the bed-box-gantry type mill, if I get started with one on my own.
Usage: pcb, wood, plastic engraving, possibly some easy metals, maybe 3d printing?, 3d scanning? Bigger polystyrene works. I like the idea of the adjustable bed height for different jobs. I already have three industrial dc motors+encoders and two ballscrews I was planning to use. I was thinking of a machine capable of moving 800*700*300mm.
A couple of questions came to mind:


1. Where do you get all parts? Is there a standard online place with good prices/service? Guides, ballscrew, bearings. Saw that Hong kong was mentioned.
2. I was thinking of moving the gantry with two rotating ballscrews and one motor. Long
gearbelt to sync the screws and have the motor directly on one screw. Whats your thought about this? I think I'm ok with a 1/10 or 1/20 mm milling accuracy. (I don't think I can build the complete works with greater tolerance)

Cheers

/Ola

[Jonathan]

Usage: pcb, wood, plastic engraving, possibly some easy metals, maybe 3d printing?, 3d scanning? Bigger polystyrene works.

So just about everything!

800*700*300mm.

That size is very manageable, although you will have to make it quite strong to make good use of the large Z-travel. Are you sure you need that much? I guess it's for the 'bigger polystyrene works', in which case since you will use an adjustable height bed, the required rigidity is lower.

Where do you get all parts? Is there a standard online place with good prices/service? Guides, ballscrew, bearings.

The nearest you'll find to a cheap standard online place is the seller linearmotionbearings2008 on eBay. Many people on this forum have used him, myself included, and been pleased with the products and service. It works out cheaper to get the spindle from other eBay sellers, or even better ali-express.

I was thinking of moving the gantry with two rotating ballscrews and one motor. Long
gearbelt to sync the screws and have the motor directly on one screw. Whats your thought about this?

6 of one half a dozen..
If you use two motors the available torque is greater, so you should get higher acceleration and top speed, however it will work out a bit more expensive than one motor and a long belt. I don't consider one motor stalling and the gantry racking a valid concern since if your machine is tuned properly, and you shouldn't be running it if it isn't, then that should never happen. On my machine I had little choice since with the current gantry design it's impractical to route a timing belt to link both rotating nuts.

I think I'm ok with a 1/10 or 1/20 mm milling accuracy.

Not difficult.

In other news, I have made and installed the drain for the router bed so I've been cutting with flood coolant. I fount that one corner of the machine is ever so slightly lower than the rest, so I put the drain in that corner so the coolant flows. A week later I discovered the reason for this corner being lower - there's a crack in the floor and it's sunk down!

The drain is fairly basic, just two parts I made on the lathe to hold some fine mesh, which is easily replaced:



After running for some time:



Video of cutting with flood coolant:

[Jonathan]

I finally had chance to drill the array of M8 holes for clamping in my router bed. Here's the result:



I used a carbide drill since the spindle speed required for a 6.8mm HSS drill is too low for the spindle to have enough torque to cut efficiently, if at all. I ran the drill at 9500rpm and 840mm/min with flood coolant, which according to the manufacturer's recommendations is quite conservative, but still plenty fast enough. I didn't see any point pushing it harder as that would only increase wear on the spindle bearings.

Here's a video showing the process. Possibly the most repetitive video I've uploaded to youtube so far...


The Z-axis motor, not surprisingly, got pretty toasty but other than that it went well. I had to move the bed out to reach the whole length, so it's currently 360mm from the normal position. Just need to make the router cut a drain in it, then I'll put it back.