Re: [CAD_CAM_EDM_DRO] CNC'ing a Mini Mill

Hi!

Hi!
This is not right on the nail but good to know, here is how to count the ~rpm and the ~feed for a mill.

rpm = 20*1000 / pii * D
mm/min = rpm * pii * tooth feed (to be sate use .05mm to start with)

A gross value for HSS is 20 m/min, so with your 25mm 2 flute? (tooth) HSS the rpm would be ~250 rpm and the table feed ~25 mm/min.

Regards Ese

>
>
> jharnedy@... wrote:
>
> >Am converting a Chinese MiniMill circa 250KG, with round column on Z. Plan
> is to convert the X (stroke 405mm) and Y (Stroke 200mm) first. End use
> would be on plastic, wood, al alloy, brass and mild steel. My "max
> cutting
> conditions" would be 2 flute HSS end mill 25mm dia at 750mm per min
> with a
> 2mm depth of cut, what would be the load generated?
> >
> >
> You are kidding yourself! I think a Bridgeport Series II would be
> humming VERY loudly
> and maybe dancing across the shop floor at this load. My calculator
> indicates this will
> absorb 4 Hp in mildest steel, and almost a full HP in aluminum. You
> don't indicate
> your RPM for this, so I can't calculate chip load or linear force
> generated, but I'd guess
> it would approach half a ton. I can tell you with absolute certainty
> that I've never gotten
> within 10% of this cutting rate (2.4 In^3 / min) on my Bridgeport.
>
> >Have some new bipolar stepper motors Sanyo Denki 103 H8223-5011, Nema 34,
> 200 steps, 7.2 V, 2 A/ph, 3.6 ohms/ph, inductance 32.5mH/ph, holding
> torque
> 6.85 Nm, which hopefully i can use. With the lead screws being T24-2.5mm
> and the motor hooked direct (1:1) the theoritical resolution will be
> 0.0125mm / step.
> >
> >
> You'll never handle your desired cutting forces with these motors, but
> then, your
> machine can't handle that, anyway.
>
> >My targets are cutting at 750mm/min which when hooked up directly (1:1)
> would be 1000pps with a torque value of 4.6 Nm from data sheet and for
> rapids 2250mm/min equates to 3000pps and torque value of 1.4Nm.
> >
> >Am a little worried that the high inductance will slow the reaction of the
> control process.
> >
> Reaction of the control process? There is no "control process" used
> with most stepper
> motors, as they are used "open loop", without position feedback.
> 7.2 V,
> 2 A/phase
> motors do sound like they have high inductance, but at only 1000
> steps/sec, that shouldn't
> be a big problem.
>
> Jon
>
>
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