They do vary a little. Just had mine out of the spindle mount anyway as I'm investigating dynamic balancing and it's slightly different to that drawing. The main body is 80mm diameter for 200mm, then 11mm more at 68mm diameter, then the chuck protrudes by 39mm. When a tool is installed you need to add about 8mm to the length to account for the collet nut. It shouldn't make much difference to the Z-axis design...
The Following User Says Thank You to Jonathan For This Useful Post:
If strapped for cash you can buy a straight shank ER collet chuck and a couple of bearings on ebay for very little, then add whatever motor you can turn up. If you want to cut aluminium or steel, rather than vapourise it, 2-3000 rpm is good.
http://www.mycncuk.com/forums/diy-pr...le-design.html). Prior to seeing that I was struggling to work out how to do the collet and spindle. I was totally unaware of the ER spindles! I probably have a suitable motor somewhere in my Dad's shed.
Thank you very much for the suggestion.
Just found this on eBay @ Tousdiamants Diamond milling machine W12 collet spindle ( schaublin aciera sixis | eBay
Attachment 6512 Already @ £82!!! an unknown quantity, so not going to buy it. However this idea seems is very much do-able.
The link I posted earlier is using an RC plane motor, These are very very grunty for their tiny size, but are still in the 10s of thousand rpm range.
A quick look at "typical" 1/4HP (180W) single phase motor on ebay gave me 220mm dia (way too big to be practical) and is as heavy as a very heavy thing. Not after massive depths of cut as max material thickness I envisage in Ally is 30mm* and maybe 2mm (maybe 5mm) in steel.
*First job will be single piece motor mounts when I can trust myself and the machine!
A 24v 200w electric scooter motor:
e scooter electric 24v 200w Motor belt drive escooter | eBay
It has a what seems like a "too good to be true" new price of just £26 on eBay and from the size of the wires is relatively diddy. It gives 2700rpm, which is in the right ballpark now! Presumably these are man enough, they lug humans around!
Main concern is with Duty Cycle, any thoughts?
ER20 Long shank collet roughly £20
2 x 6004 2RS Bearings £10
Scooter motor £30
24V 10A Power supply roughly £30
Some pulleys & a belt say £30 all in (Might even have some suitable somewhere in Dad's shed
Might have material for holding bearings and making motor mounts
Downside, simply cos I wanted to do this myself...
Would need someone to do the machining for me.
With stepped pulleys, I guess wiring the motor direct to Power Supply with a switch and a link to the machine E-Stop would be fine.
£120 say £150 tops, definately do-able, especially as it would be close to "best practice" for metal.
Obviously collets to get as well, but since it's ER20 only 1 set needed if I go 2.2kW WC eventually.
Any ideas for a 240v motor, minimum power and so on?
or is the Scooter motor idea viable? Bearing in mind Steppers are also often run this way!
I'd look for a DC tread mill motor far more powerfull with good duty cycles.!
The Following User Says Thank You to JAZZCNC For This Useful Post:
What an excellent idea Jazz
Plenty on eBay for <£30 I can rob power supplys, motor & speed control from a complete machine!
Gonna check Freecycle to!
After some more reading and some hard thinking, here is the Mk2 machine (progress so far):
Went back to the drawing board completly, re-assessed the space and scaled the machine to what I think I can get away with, rather than basing the machine on the A3ish size previously.
Ive used 5mm Wall Steel RHS as that should be good for the tapped threads to hold down the rails.
Bottom Cross members: 120x60x870
X Rail Supports: 120x80x900 with 900mm SBR25 Supported Rails
Ballscrew Supports: 80x40x220
RM1605 Ballscrews on all Axissss.
Gantry "Feet": 80x40x200 5mm Wall Steel RHS with 2 x SBR25 Bearing Blocks
Gantry Cross Member: 80x80x870 with 2 x 700mm SBR25 Supported Rails, top and bottom.
Y Axis Ballscrew Supports: 10mm Thick Steel plate
Z Axis Plates: 12mm Thick Steel plate
Z Axis Rails: SBR25 Support rails 300mm long
That makes travel roughly X=780, Y=480, Z=100
Y & Z are driven by 2:1 Belt drives, for the X Axis, I am considering a single belt, 3 pulleys and 2 idler bearings also at 2:1 reduction
That's a 2.2kW watercooled spindle on the Z, though I'm also looking at the Treadmill motor option for low rpms. Just waiting for a suitable treadmill motor to appear on eBay!
Problem with this machine is I'll have to "borrow" a mates workshop to build the frame and pay someone to make some of the other components as they go beyond my skills and equipment, ho hum, not the original plan, but I'd like to build just 1 machine and have it last me.
As you can (probably) see in the image, the Spindle comes outside the X Axis, I have left this as it gives me good travel over the steel box which I plan to use for a base for machining metals.
Most likely welded construction, though bolts still hold some appeal for maintaining a "I built it myself" perspective...
... Just noticed I will have to bolt on the Y axis leadscrew/motor mounts, otherwise I can't get the leadscrew in!
Last edited by BikerAfloat; 16-08-2012 at 11:06 AM. Reason: Added comment on need for some bolts