[IanFiTheDwarf]

Hi guys,

Until two years ago I had access to a well-equipped machine shop at work but I took a new job and am now missing all the toys. I have a small lathe and really want a mill but they are so expensive for anything decent so I have decided to build a router table.
I’m mostly wanting to machine fiberglass and aluminium, I need a work area of at least 300mm x 300mm (12” x 12”) for a project I’m working on at the moment but a bit more would be handy. I am thinking of aiming for about 450-500mm by at least 600mm.
The construction will be as follows

Bed: welded 50mm steel box section
Rails: SBR20, 20mm round supported rails and bearing blocks
RM1605 ballscrews
The gantry I would prefer to be aluminium but I might go for steel box section to save cash and time as I have the steel and tools to knock it up in an afternoon.

The decision I have to make is whether to go for one or two ballscrews on the “X” axis. I don’t have a lot of cash so a single ballscrew will be cheaper as it saves me a stepper and driver as well but if I go for the two can I get away with cheaper steppers and drivers?
I was thinking of using 4 NEMA23 27 oz-in steppers with a cheap 3A 4 channel driver which will be cheap but can always be upgraded in the future

Am I on the right lines?

Cheers
Ian

[pippin88]

That will do for a cheap build, but very seriously consider stretching your budget a bit.

I will never do a central screw design again, dual drive is much better. You avoid racking, and you can support the table properly at any point. The round rails (SBR) allow a lot of racking.

If you can stretch to linear profile bearings (square rails) then do. They are sooooooooooooooooooooooooooooooooooooooooooooooooo much better. BST Automation on aliexpress have great prices on Hiwin gear. There are plenty of other sellers (some cheaper by a bit) but I've had experience with BST and others on CNCZone have also.

I hope 27 oz-in was a typo? You want low inductance steppers. There are no good cheap drivers that I'm aware of. A Gecko G540 is a great investment and super easy to get going.

I favour steel if you have the tools to use it, but it is not flat enough without milling or epoxy or similar. It's debatable whether alu extrusion will be, but all these things are luck of the draw and depend on what you consider flat.

[wizard]

Hi guys,

Until two years ago I had access to a well-equipped machine shop at work but I took a new job and am now missing all the toys. I have a small lathe and really want a mill but they are so expensive for anything decent so I have decided to build a router table.
I’m mostly wanting to machine fiberglass and aluminium, I need a work area of at least 300mm x 300mm (12” x 12”) for a project I’m working on at the moment but a bit more would be handy. I am thinking of aiming for about 450-500mm by at least 600mm.

For a small machine you should seriously consider a fixed gantry moving table design. It is far easier to get a stiff machine wth modest materials and you don't have issues keeping the gantry square.

The construction will be as follows

Bed: welded 50mm steel box section

Not bad for a gantry of this size, though it may make more sense to go to a larger beam for the gantry.

Rails: SBR20, 20mm round supported rails and bearing blocks
RM1605 ballscrews

Round rails are bad for a starter machine but in your case you may seriously want to consider profile rails. Why? Because your focus on fiberglass and aluminum you will want a stiffer machine. Thankfully in a small machine the cost differential isn't huge and hitting EBay bargains is easier.

The gantry I would prefer to be aluminium but I might go for steel box section to save cash and time as I have the steel and tools to knock it up in an afternoon.

Unless you are very very far from the developed world you are far better off buying steel tubing in the sizes you need. As for aluminum in this structure I wouldn't go that route myself. For one aluminum is just plain expensive. If you weld it it weakens dramatically and drilling and tapping the stuff is problematic. With steel, if the wall thickness is such that it will hold screw threads, you will have far less screwing around.

The decision I have to make is whether to go for one or two ballscrews on the “X” axis. I don’t have a lot of cash so a single ballscrew will be cheaper as it saves me a stepper and driver as well but if I go for the two can I get away with cheaper steppers and drivers?

A moving table design would not need two ball screws. The table itself would need to be longer than your desired working area but that isn't a bad thing at all, especially if you want to mount a fourth axis or other fixturing.

I was thinking of using 4 NEMA23 27 oz-in steppers with a cheap 3A 4 channel driver which will be cheap but can always be upgraded in the future

You want something a little bigger than 27 oz-in. As for a driver buy something decent to begin with. By the way think about that control panel, if you expect to upgrade over time it is far easier to do so in a roomy control panel.

Am I on the right lines?

Cheers
Ian

With a small machine you have far more design options that can lead to a machine that performs decently. I'd explore the various machines seen in these forums and around the net.

You seem to have a good handle on what you want out of the machine. The trick is to find the most economical design that fits the budget.

[IanFiTheDwarf]

Hi guys, thanks for your comments.

The steppers should have been 270 oz-in not 27, I will look into the linear bearings and square rails.

I was thinking about mounting the rails on a length of milled or even ground flat bar about 80x10mm bolted on the side of the frame. This would let me to shim it out and I could make adjustable stops to align it vertically.

I want to stick with the moving gantry rather than a moving bed to keep the mill as compact as possible.

That package of steppers and controller is about four times the price of what I was looking at so I think I will need to ggo for the cheap option for now and I can always upgrade later if I need to. I want to put most of my cash into the mechanical parts which will be hard to upgrade later.

Thanks again
Ian

[IanFiTheDwarf]

well I've been pricing up the parts for my router and the square rails will add about £250 to the cost, the Gecko drivers will add another £150 which would definitely take the build well out of my budget.

I'm going to scan eBay for the next week or two for cheap square rails before I commit but if nothing comes u it will have to be the round rails.

I have decided to go for 100x50x4mm steel box section for the bed as below

Attachment 266096


And this is my plan for levelling the rails

[louieatienza]

With the small table size, you might be better off moving the table instead of the gantry, then it qould be feasible to use one leadscrew to move it.