Re: [CAD_CAM_EDM_DRO] Re: Sherline Spindle Pulse disk for threading

On Sat, 10 Nov 2007 11:02:38 -0500, you wrote:

>Multi-start is relatively easy with only an index pulse - the cutter
>hasn't started cutting when you're waiting for the next start to come
>around. The comment about the spindle slowing is the exact reason why
>threading with one pulse per rev "shouldn't work well".

But it does :)

>>In reality this is not a problem, inertia and the low cutting forces
>>involved in threading, shouldn't affect it.
>>
>>
>I'd rephrase that like so "if you don't have spindle feedback, then you
>need to use very light cuts to get acceptable threads". This is the
>same thing you have to do when using steppers instead of servos - you
>need to make sure that you never try to accelerate or move faster than
>the steppers can go in the worst case, because you won't see if there's
>a problem. In the threading case, you need to make sure that the cut
>depth you use is low enough that the spindle power and inertia will keep
>the speed constant enough for the thread quality you want. (that was a
>mouthful ;) )

That maybe so for low power spindles, I've 2HP, so it's more a case of
cut quality, maximum production and insert life for me.

Cutting forces aren't high when threading anyway, too much and you'll
bust the insert.

>>Mach does this by reading the index pulse, and adjusting the feed to
>>suit then locks those for that pass.
>>
>>
>I sure hope it keeps adjusting speed over the threading pass (more like
>"locks until it sees another index pulse").

Nope it doesn't, but it works.

I've cut thousands of threads over the years with Mach without a problem
:)


Steve Blackmore
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