Re: [CAD_CAM_EDM_DRO] Re: Servomotors & Minimill - do these need speed reduction or not?

turbulatordude <davemucha@...> wrote:
--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers
wrote:

> The low rapid rate and general lack of torque at high speed seems

to be the case with steppers. I'm wondering why anyone would opt to
use them. The drives are much more expensive, alot more difficult to
configure. Heating problems compared to servos etc. I've just noticed
alot of posts with questions regarding steppers and I'm just confused
why anyone would use them. There seems to be an abundance of used
servos around. One person one here mentioned that "the steppers on
his small mini-lathe produced enough heat to fry eggs"

>
> Ron

Becasue steppers are so dang easy to use.

:::::They are? They weren't easy for me.

Also, because most people do not know where the 'abundance or
servo's' are

::::::Ebay, and from what I understand you can use any DC brushed motor as a servo by simply adding an encoder. i.e. small automotive or lawnmower starter motor used, very cheap. Silicon Salvage has tons of them. Google "standard DC motor as servo"

and/or don't want to get involved with encoders as there
are not a lot of cheap encoders around.

:::::US digital under 40 bucks a piece

Steppers offer the power at cutting speeds so in that way, are ideal
for home-brew.

::::::And no torque for rapiding. When I asked Microkinetics about driving the knee for Z on my Bridgeport with their stepper they never would give me a straight answer. Someone suggested gas springs to assist the knee, I guess they thought I was retrofitting a toyota hatchback.

Stepper drivers are easy to make, find or buy.

::::::My understanding is that "Chopper drives" are very complex and L/R drives dont work for machine tools. DC servo drives are much simpler by comparison. And cheaper

There are a few complete stepper packages for small machines that
sell for under $200.00

:::::I guess alot of it depends what you are expecting from your retrofit, size and how much it will be used

I don't know of any servo packages that are that low cost.

Dave



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