Re: Custom Spindle (Custom Motor!), Very Gradual Progress Planned
Originally Posted by
StrawberryBoi
Hi all,
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)
For cutting 4xxx and 4xx series steels, with modern cutters you are able to run in the 200 to 800 SFM range. Cutter diameter and other cutting parameters are pretty much dictated by your machine, mostly the mass of the machine. (for the purposes of this discussion I'll use pounds as the imperial unit of mass, and yes I know this is not correct)
Spindle power and machine mass are closely related, you need a machine frame that is capable of resisting what ever cutting forces you apply. You could eventually accomplish the same part using Dremel tool as a spindle as you could with the Matsuura VMC, but using the Dremel would take a lot longer because of less HP. On the other hand the machine with the Dremel spindle could be a lot less massive. Using modern cutters, spindle power and machine rigidity are the limiting factors, the cutters will take just about any amount of power you can provide to them.
The standard BP knee mill with a 2J2 head is about 2300 lbs., 2HP, and will reasonably cut with a 1/2'' dia endmill in steel, has an R-8 spindle. About 4200 RPM max. My BP clone is a larger frame, but the same 2J2 style head, 3500 lbs., 3 HP, with a BT30 spindle, same RPM range as a BP. Will reasonably cut with a 1/2'' end mill in steel. Not really much gain there, but I can push it a bit harder than a standard BP because of the larger frame. Spindle power is not the limiting factor, machine rigidity is. I rarely run at greater than 70% spindle load.
Then we move up to my Haas TM-2P. This is a VMC, bed mill design, about 5500 lbs., 7.5 HP (servo?) spindle, 6000 RPM max, and wish we had the 8000 RPM spindle option. It will generally run parts about 4X as fast as my BP clone. A much more rigid design and will comfortably handle 5/8'' endmills in steel. #40 spindle. We generally run it at 70 to 80% spindle load. This is still a lightweight machine.
Maybe 10,000 RPM max
Power >=?Watts (I see 2.2kW as a common rating, but how much do we actually NEED, at the tool?)
The answer is: It depends. The machine needs to be massive enough to resist the cutting forces. More mass and rigidity allows higher HP. Higher HP allows higher Material Removal Rates (MRR).
Assembly dimensions (for interface with the machine)
There is really no standard. Buy the spindle and match the mounting.
I assume you mean tool holders. R-8 is standard for BP type machines. #30 is OK up to about 4HP, #40 is standard for 5 to 10 HP, and #50 above that. These holders come in several flavors; CAT, NMTB, and a few others.
Induction Spindle: Simplicity and old school reliability
- Indexing? (Absolute Encoder/Resolver) or Non-Indexing?
You normally need indexing for use with many ATC systems to align the spindle dogs that engage with the tool holder.
PM Spindle: A servo and a gentlemen (unless you're metal)
- Indexing. DUH.
Nice to have. I just replaced the 5.5kW induction motor with a 7.5kW servo on my lathe so I could have spindle indexing capability.
High pressure flood coolant is normally the best for most operations, but requires a full enclosure of the work area. Coolant does three things, cools the tool, lubricates the tool, and maybe most importantly blasts the chips out of the cutting area so you are not recutting the chips. For lighter duty applications, spray mist coolant works, and is a lot less messy.
I'll try to be more specific as you have further questions later on in this process, but for now this is a general overview.
Jim Dawson
Sandy, Oregon, USA