CV blending feedrate moves into rapids and visa versa

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CV blending feedrate moves into rapids and visa versa

Postby stirling » Thu Sep 06, 2018 3:36 pm

I notice that CV blends feedrate moves into any following rapid and visa versa. Is this intentional?
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Re: CV blending feedrate moves into rapids and visa versa

Postby cncdrive » Fri Sep 07, 2018 1:38 pm

How would you expect the feedrate to change?
I mean your motors have to accelerate up to the rapid feedrate, it can't just jump from feedrate A to feedrate B without accelerating up or down. Your motors would loose steps otherwise if the software will not follow your acceleration settings and acceleration takes time, it does not happen in 0 time.
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Re: CV blending feedrate moves into rapids and visa versa

Postby stirling » Fri Sep 07, 2018 3:24 pm

cncdrive wrote:How would you expect the feedrate to change?


I'd expect a rapid/feedrate-move junction to be exact stop
I'd expect a feedrate-move/rapid junction to be exact stop
I'd expect a rapid/rapid junction to be exact stop.
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Re: CV blending feedrate moves into rapids and visa versa

Postby ger21 » Fri Sep 07, 2018 6:15 pm

I agree, but rapid to rapid shouldn't really make much difference?

Depending on your error tolerance setting, you may not see much difference though?
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Re: CV blending feedrate moves into rapids and visa versa

Postby stirling » Sun Sep 09, 2018 9:12 am

Well a couple of rapids navigating around a fixture could end in tears but that's not really the point. IMHO there are zero advantages to blending rapids in all three cases but several disadvantages so why do it?
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Re: CV blending feedrate moves into rapids and visa versa

Postby ger21 » Sun Sep 09, 2018 11:26 am

Didn't think of that.

However, I would think that the vast majority of people are using CV settings that would prevent that much deviation from the path? Typically much less than 1mm?

Not arguing with your point, just pointing out that UCCNC typically stays much closer to the commanded position then Mach3.
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