Luthier CNC

[Clive S]

3kW air-cooled spindle. Mainly decided on due to the K2 machine. I'm reluctant to use water-cooled as don't want the faff of pumps and water near my dried woods - after VFD control I'm also running out of capacity on the basic parallel port breakout board. I'm a bit worried about the noise - I use handheld routers a lot - I hope that an air-cooled spindle will be a lot more quiet - does anyone have any experience with one?
- For weight, I rely mainly on extrusions, using plates only where necessary. All plates are 15mm thickness. Machine size is kept as small as possible.

Air cooled spindles are generally very noisy. Not sure why you think the water cooled ones are going to put water all over the place as they are fed with 6mm tubing and the pump and water container can be anywhere off the machine. They are also quiet .

Re the plates I would use 20mm and if you don't want to machine it use cast as that will be flatter.

Have you checked out if any of the bolts clash with each other ie on the bearing blocks for Z and Y

[bluesking]

Air cooled spindles are generally very noisy. Not sure why you think the water cooled ones are going to put water all over the place as they are fed with 6mm tubing and the pump and water container can be anywhere off the machine. They are also quiet .

Re the plates I would use 20mm and if you don't want to machine it use cast as that will be flatter.

Have you checked out if any of the bolts clash with each other ie on the bearing blocks for Z and Y

Thanks Clive,

Point taken re the air-cooled spindle. Water cooling seemed like one extra thing to worry about but perhaps the noise issue will make it worth it. I spent some time with a local CNC machine today which was using the Kress 1050 spindle - air cooled. Whilst not particularly loud (certainly compared to a router) it could certainly have been quieter. I don't see many people using 3kw water-cooled spindles, nor that many places to buy - I wonder why?

Re the plates, what if I used 20mm just on the gantry sides? That seems to be the critical point - surely the z-axis won't matter too much (if anything, the thicker plates will move the spindle further away, creating more torque on the gantry?). Another idea I had was just to bolt some extrusion vertically to the 15mm gantry sides to stiffen them up a bit.

I was going to buy my plates from here: https://www.aluminiumwarehouse.co.uk...e-cut-to-order
I can't see cast here - is there somewhere I can go to specifically buy cast aluminium?

Also I see 2 alloys - 5083 & 6082T6 - but I don't know the difference and which is best for machining. Biggest machining job I really want to take on is drilling holes on my drill press and tapping them.

[Voicecoil]

If I were you I'd stick with 15mm (or even 12mm) on the gantry sides and add some reinforcement ribs (say 40mm tall) all the way up along the edges (40x15mm flat bar for instance) - if you do the sums it works out much stronger than thicker flat plate. Aluminium Warehouse are not bad for plate, even if not the cheapest and having had a slightly checkered history with some of us on here, at the moment they are giving good service, cutting plate VERY square and generally 1...2mm oversize: to select the cast stuff click on "grade" and select the bottom item from the drop down box.
If it were me I'd also be adding some plates top and bottom of your bed frame members to form like a "sandwich" structure and tie it all together in X and Y - though I can see that might have some weight problems for you.

[bluesking]

If I were you I'd stick with 15mm (or even 12mm) on the gantry sides and add some reinforcement ribs (say 40mm tall) all the way up along the edges (40x15mm flat bar for instance) - if you do the sums it works out much stronger than thicker flat plate.

That was my feeling too - If I can spread the cross sectional area of those gantry sides that would be better than basically just adding more mass. I was just going to bolt some 45x45 extrusions to the outside of the plates. Easy to align and not a lot of extra weight.

Aluminium Warehouse are not bad for plate, even if not the cheapest and having had a slightly checkered history with some of us on here, at the moment they are giving good service, cutting plate VERY square and generally 1...2mm oversize: to select the cast stuff click on "grade" and select the bottom item from the drop down box.

Very useful information - I didn't expect the cuts to be oversize - hell, when I have bought pre-cut sheet wood/mdf I expect much better than that! May not prove to be that critical though if I can at least drill all the holes accurately relative to each other. Even if the measurements are out, maybe they will be consistently so, such that two pieces of the same spec are the same size, even if its not the right size!

I do have a table saw and maybe if I buy the right blade I may have to take the plate cutting into my own hands - but I'm a little concerned about cutting it square enough - its not a precision table saw by any means! I'm scared enough of the table saw when cutting hardwood - don't know what to expect with aluminium!

If it were me I'd also be adding some plates top and bottom of your bed frame members to form like a "sandwich" structure and tie it all together in X and Y - though I can see that might have some weight problems for you.

Yes, I may just plonk a single plate on top. I was going to use a couple of layers of 18mm MDF here but might make the lower one of them aluminium. Putting one below the frame will mean some redesign and yet more gantry height plus hinder what little access I have to the drive mechanism - I'm already worried about how I'm going to retension the pulley belt under there.

[Voicecoil]

I do have a table saw and maybe if I buy the right blade I may have to take the plate cutting into my own hands - but I'm a little concerned about cutting it square enough - its not a precision table saw by any means! I'm scared enough of the table saw when cutting hardwood - don't know what to expect with aluminium!

Cast plate cuts quite nicely with the appropriate blade if you keep it lubricated (WD40 works OK) - just take it steady. Provided your saw is rigid enough you can do quite good work if you spend the time to get it set up square.

[bluesking]

Cast plate cuts quite nicely with the appropriate blade if you keep it lubricated (WD40 works OK) - just take it steady. Provided your saw is rigid enough you can do quite good work if you spend the time to get it set up square.

I've gone through the design with a fine tooth comb and it seems there is only one plate where the dimensions are critical. If any of the other plates are cut a mil or two oversize it won't make any difference.

Also, costings show that I would pay more for uncut plate of adequate size than I would pay getting aluminium warehouse to cut everything for me.

I'll probably just go with the precut cast plate.

I've given up on a plate for the tabletop - aside from the weight - it'll cost rather a lot. A piece of well attached MDF will suffice I think.

[A_Camera]

I do have a table saw and maybe if I buy the right blade I may have to take the plate cutting into my own hands - but I'm a little concerned about cutting it square enough - its not a precision table saw by any means! I'm scared enough of the table saw when cutting hardwood - don't know what to expect with aluminium!

Cutting aluminium on a table saw is no big deal. I have a Bosch GTS 10 J and with the Bosch blade made for cutting aluminium, it cuts aluminium like butter. Squaring the saw took some effort, but now it is square enough for this type of work. It is though messy to cut aluminium, so a shop vac is a must.

[bluesking]

I don't see many people using 3kw water-cooled spindles, nor that many places to buy - I wonder why?

Just to attempt to answer my own question - it seems not many people are using 3kw spindles full stop.

From what I can tell, a 2.2kw ran off the common huanyang VFD is often rated around the 8A level for current draw - this means you can plug it into a normal mains socket without worries (assuming you use and appropriate fuse).

The 3kw spindles I'm looking at, when run from an appropriate VFD will likely draw in the region of 18A. You're not going to find a mains socket fuse for this type of current. Still, the ring circuit from your consumer unit will probably allow currents up to 30A, so providing you can get beyond the mains plug you might be fine. One thing worth noting is that 13A fuses may not actually be designed to blow until 20A (go figure....) so it may be possible to get away with it (that's what I read here https://www.pat-testing-training.net...cteristics.php).

[A_Camera]

I spent some time with a local CNC machine today which was using the Kress 1050 spindle - air cooled. Whilst not particularly loud (certainly compared to a router) it could certainly have been quieter.

Don't worry about the noise generated by air cooled spindles. It only makes a difference if you will be cutting air. ...and you'll be surprised how quiet an air cooled brushless spindle is compared to the Kress or a router...

I have been using air cooled spindle for some years now, though it is only 1.5kW, but it is that noisy before cutting starts. If it must be replaced I'll buy another air cooled spindle, that's for sure.

[bluesking]

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