Hi all,

Been lurking around for about a month in the forum and decided in this last week to start jumping in. I'm a Mechanical Engineer / Electrical Engineer with a focus on rotating machine design. Recently I went from a 90% desk 10% lab/shop position to a 80% shop 20% desk position involving a lot of fast paced prototyping in agricultural robotics and fruit handling. The result is that I've reconnected with just how enjoyable it is to cut material and end up with what you need to use at the end. Don't get me wrong, the 3D printer farm is also pretty nifty, but I'm all about smallest functional form (optimized) and 3D printers rarely cut it for final versions with that goal in mind.

I've designed brushless and servo motors, frameless kits and fully housed custom solutions, as well as a couple of large (120-300kW) axial gap traction motors for EVs. Before motors I worked on custom continuously variable transmissions (belt and pulley type), as well as up-fitting class 3-8 utility vehicles and busses to plug-in hybrids before that was much of a thing.


I have an end machine design goal, but before I jump into that, I figured it would be great to cut my teeth on individual subsystems to get a better understanding of the specifics of CNC machine design. I have access to a manual and CNC lathe (linuxCNC), and a manual Bridgeport knee mill and a Matsuura VMC with a ridiculously extensive chain type tool changer. I also have access to a solid 36"x48" work area router, a plasma cutter, and various other shop tools. My employer actively encourages side projects (on our own time) and will front a small bit of cost in tooling and materials. I do also get paid well enough to front most of the cost of materials and parts myself.


My first project target here is to leverage my motor design background into a custom spindle. I'm looking into some novel active vibration management methods as well, but those will be beyond the scope of this particular build thread. I also may keep those proprietary (unless they don't work of course!).

My intent is not to make a full ATC spindle, but simply the drive motor part. I want to walk through the design process for both an induction motor and a permanent magnet motor, fully housed into a spindle motor. Any references for standard interfaces would be very helpful. Things such as common spindle holder size, connectors, etc.

For myself personally I'm looking at smallest viable product for cutting steels up to gear steels. Why? Well, again, I come from rotating machines and that means splines, case or through hardened surfaces, etc, often in <1" diameters and with <0.001" tolerances referenced to all datums. Yeesh. Yes, servo industry man, customers be like that. Also keep in mind that in a high performance motor, you might have a 0.010" nominal airgap, which you don't want to vary more than +/-25% from tolerances and also should never achieve contact under maximum loading conditions, with a factor of safety, while your working diameter is as large as 8". With stackups? You get the idea. Especially since unless you want to grind them, machining laminated stators is a risky proposition and they typically achieve between 0.002" and 0.005" profiles on the OD and ID, which already just ate your entire airgap for breakfast, worst case. YEAH.

Anyways, let's break down the separate projects and please give me feedback on the target performance I would need:

High Speed Machining Spindle (Minimum Specs for gear steels, such as 4342, and stainless such as 416)

RPM >=?rpm
Power >=?Watts (I see 2.2kW as a common rating, but how much do we actually NEED, at the tool?)
Assembly dimensions (for interface with the machine)
Connectors?

Induction Spindle: Simplicity and old school reliability
- Indexing? (Absolute Encoder/Resolver) or Non-Indexing?

PM Spindle: A servo and a gentlemen (unless you're metal)
- Indexing. DUH.

Coolant options?

I should mention I specialize in cooling motors a bit more aggressively than any spindle I've seen on the market... and I won't be violating any patents (because I'm on them )