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Direct drive spindle. No gears. No belt?

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drum maker22/01/2021 10:07:32
17 forum posts

browsing the Amadeal site earlier, they have an E2 mill for sale that they describe as direct drive, no Belt, No Gears

i searched this site & several others but cant find any further info on this type of machine, i have become so used to one or the other.

anyone know about these? the pros & con's?

thanks

Ady122/01/2021 10:19:25
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I presume they have a sacrificial pin or some such weak point if something goes wrong

If they don't then the cutter or the motor or the spindle nose becomes the sacrificial weak point

I suppose this approach means less losses and more power for doing the jobt

Edited By Ady1 on 22/01/2021 10:23:05

John Haine22/01/2021 10:23:18
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Simple in principle, just attach a chuck to the motor spindle and beef up the bearings. Use a variable speed drive, such as a 3-phase induction motor with a VFD, or indeed a standard brushless motor (which is 3 phase but not an induction type). The late great John Stevenson described a partial conversion of a Myford VMB for CNC, where he mounted a modern powerful 3 phase induction motor with a new end cap incorporating upgraded bearings and a new shaft with (I think) integral ER taper into the moving mill head.

Especially appropriate with CNC where the modern approach is to use smaller cutters running at high speed, so the reduction in power with speed is mitigated. Less so if you decide you want to use a big face cutter and take large cuts at low speed. One of the problems would be that mill manufactures probably buy off the shelf motors for standard machines, whereas for direct drive they will have to be (or ought to be!) specials with better bearings, more rigid frames, and non-standard spindles. Either the motor will be more expensive (especially if it needs replacing), or compromised.

Ady122/01/2021 10:35:18
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Does look a lot like a CNC development that is being tried out in the retail market

One big disadvantage is you're stuck with that type of motor forever, nothing else fits the system

At least with a belt drive you can use a different motor in 20 years or if they suddenly become difficult to source and replace you can cobble in a 1HP alternative

Edited By Ady1 on 22/01/2021 10:36:14

JasonB22/01/2021 10:38:24
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No more details on the Weiss site either just the same as on Amadeal plus a larger E3 version.

More likely to have an electronic overload that cuts the power if the load is to high.

Would need a fancy hollow motor shaft to allow the drawbar through, maybe even internally splined so the quill can work or the motor moves up and down with the quill.

Then again it could be marketing hype playing with words as it does not have the typical two stage speed ranges that other hobby machines have obtained by belts or gears. Just having one direct belt to the spindle.

Ady122/01/2021 10:41:11
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Posted by JasonB on 22/01/2021 10:38:24:

No more details on the Weiss site either just the same as on Amadeal plus a larger E3 version.

Would need a fancy hollow motor shaft to allow the drawbar through, maybe even internally splined so the quill can work or the motor moves up and down with the quill.

Sounds a bit scary to me...

drum maker22/01/2021 10:46:35
17 forum posts
Posted by JasonB on 22/01/2021 10:38:24:

No more details on the Weiss site either just the same as on Amadeal plus a larger E3 version.

More likely to have an electronic overload that cuts the power if the load is to high.

Would need a fancy hollow motor shaft to allow the drawbar through, maybe even internally splined so the quill can work or the motor moves up and down with the quill.

Then again it could be marketing hype playing with words as it does not have the typical two stage speed ranges that other hobby machines have obtained by belts or gears. Just having one direct belt to the spindle.

yeah i Checked the Weiss site too

Hugh from Amadeal has replied to my gentle probing

"The motor is located directly over the spindle hence doing away with gearing or belts and pulleys. Being a brushless motor there is good torque throughout the speed range."

so it does not sound like hype.

John Haine22/01/2021 11:28:57
3663 forum posts
206 photos

From the picture on the Amadeal site the motor clearly moves with the head. If you had an ER fitting (taper and closer thread) on the end of the spindle you wouldn't necessarily need a through hole. But yes it won't be a standard motor shaft. In JS' conversion he pressed the original spindle out of the rotor of a new 3 ph induction motor and made a new one, presumably with a through hole if needed. The motor end cap was replaced by a substantial new one machined from Aluminium IIRC to take new upgraded bearings. If it's a decent induction motor I don't see why it should ever need replacing provided the VFD has reasonable protection circuitry. And you could easily vary the speed from 6000 rpm or more with an appropriate 2 pole stator and rotor running at 100+ Hz, down to maybe 10 Hz or less. Flux vector control to maintain low speed torque, separate cooling fan to keep the winding temperature down. Sounds a good approach to me. After all people fit water cooled direct drive spindles (see recent thread here).

drum maker22/01/2021 19:19:21
17 forum posts

great info & thoughts on this guys, I'm very tempted to give one a go & be the Guinea pig as no one seems to have first hand experience of these.

JasonB22/01/2021 19:49:15
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John, while the motor will indeed move with the head, what do you think they have done with the quill? Motor moving within the head as quill is lowered or some form of splined arrangement so motor is fixed within the head and quill slides within it?

Must be hollow as they do R8 and MT3 versions so a drawbar would be needed and suspect that is what the little flap at the front lets you get access to.

DM if you do get one please keep us updated with how it's put together.

JasonB22/01/2021 20:25:20
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John Haine22/01/2021 20:26:40
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I didn't notice the quill! Obviously don't have courage of their convictions. Maybe the handle move the whole head?

drum maker22/01/2021 20:27:54
17 forum posts
Posted by JasonB on 22/01/2021 20:25:20:

ohhh more info, how did you acquire that?

drum maker22/01/2021 20:31:21
17 forum posts
Posted by JasonB on 22/01/2021 19:49:15:

DM if you do get one please keep us updated with how it's put together.

i will, I'm still edging towards it, I'm just paying off a powered hacksaw & a recent wood work bandsaw purchase and then i should have the funds spare to take the plunge.

JasonB22/01/2021 20:36:26
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Part way down the page, looks quite nice

Whole head more likely moved by the handwheel at top side of the column.

 

Edited By JasonB on 22/01/2021 20:39:30

drum maker22/01/2021 20:42:52
17 forum posts
Posted by JasonB on 22/01/2021 20:36:26:

Part way down the page, looks quite nice

Whole head more likely moved by the handwheel at top side of the column.

Edited By JasonB on 22/01/2021 20:39:30

Brilliant, will take a look.

Ady123/01/2021 13:49:51
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Posted by JasonB on 22/01/2021 20:36:26:

Whole head more likely moved by the handwheel at top side of the column.

I have a cheap aldi bench drill which does just that and its brilliant

Setting up a job is really fast and I love using it, wished it was a mill

hmmm The plot thickens...

mgnbuk23/01/2021 14:26:22
930 forum posts
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I would guess that Weiss use a lot of motors, so it would not be difficult to get their motor manufacturer to make a "bespoke" motor with a hollow shaft with an internal spline or drive key in place of the standard shaft. Even if it cost a bit more for the special motor, it would probably be more than paid for by savings from the removal of other drive components & assembly time reductions. So while it is "direct drive" to the spindle drive shaft, it is not a "motor spindle unit".

I have only come across "motor spindle units" on aerospace aluminuim routers - these were squirrel cage motors especially built for the task, with heavy duty frames, high precision bearings & ISO 40 taper spindles run from inverters. During the rebuild of one such machine (3 spindle Marwin Max-e-trace) we upgraded the bearings to allow an increased speed (12,000 rpm IIRC - the limit of the bearings) and replace manual drawbars with hydraulic units (new spindles). The ISO 40 tooling was manufactured with the carbide cutters machined integral with the tool shank for maximum rigidity. One of the reasons for the upgrade to hydraulic clamping was to get a positive tool ejection, as the tools got so hot in use that they tended to stick in the spindle - the operators wore welders gloves to change tools. Spindle bearings lasted around 10 months of 24/7 operation.

Several motor manufactures supply "kit motors" for machine tool use - basically a hollow permanant magnet rotor & a cartridge stator unit. The rotor is shrink fitted to the machine spindle & the stator unit is placed in the headstock casting, with the usual high precision bearings in the headstock end caps. Both air & liquid cooled versions are made. Expensive toys !

Nigel B.

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