Vertical Feed rates in partially-vertical cuts

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JoshM
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Re: Vertical Feed rates in partially-vertical cuts

Postby JoshM » Sat Nov 25, 2017 11:58 pm

Y's are meant to be Z's in your PDF, no @chrisb?
berka
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Re: Vertical Feed rates in partially-vertical cuts

Postby berka » Sun Nov 26, 2017 12:01 am

Referring to your PDF drawings,
How about:
Vl = fx * Vx + fz * Vz
Where fx = X/L and fz = Z/L
This would eliminate the conditionals you deal with while deciding whether it is a steep or shallow ramp.
In the ramp extremes it degenerates to Vl = Vx or Vl = Vz.
chrisb
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Re: Vertical Feed rates in partially-vertical cuts

Postby chrisb » Sun Nov 26, 2017 12:09 am

JoshM wrote:
Sat Nov 25, 2017 11:58 pm
Y's are meant to be Z's in your PDF, no @chrisb?
Yes sure, I will correct it. My machine has Z and Y swapped and I made my hand notes in the XY plane, making a mistake when typesetting it. I will correct it and replace it in the original post (saves bandwidth).

In fact the length of the ramp is sqrt(x^2 + Y^2 + Z^2) and the horizontal distance is sqrt (x^2+y^2). I have omitted this because I had the feeling it rather obstructs things than clarifying. Should I add to the paper?
berka
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Re: Vertical Feed rates in partially-vertical cuts

Postby berka » Sun Nov 26, 2017 12:13 am

chrisb wrote:
Sun Nov 26, 2017 12:09 am
In fact the length of the ramp is sqrt(x^2 + Y^2 + Z^2) and the horizontal distance is sqrt (x^2+y^2). I have omitted this because I had the feeling it rather obstructs things than clarifying. Should I add to the paper?
Keep in mind also the possibility of an arc. I think what you're dealing with here is any horizontal distance traveled vs plunge.
chrisb
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Re: Vertical Feed rates in partially-vertical cuts

Postby chrisb » Sun Nov 26, 2017 12:22 am

Thanks for all the responses!
I changed the Y/Z-swap in the pdf and have a look at the rest tomorrow.
berka wrote:
Sun Nov 26, 2017 12:13 am
Keep in mind also the possibility of an arc. I think what you're dealing with here is any horizontal distance traveled vs plunge.
The thoughts hold only for G1 commands.
berka
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Re: Vertical Feed rates in partially-vertical cuts

Postby berka » Sun Nov 26, 2017 12:29 am

chrisb wrote:
Sun Nov 26, 2017 12:22 am
The thoughts hold only for G1 commands.
I have exactly the same issue with arcs too. E.g. helix drills are feeding too slowly.
This makes me think may be it should be possible to override feed rate as someone else pointed out. I just don't know how that could be done. On the helix drill example, each diameter would need a different override.
GeneFC
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Re: Vertical Feed rates in partially-vertical cuts

Postby GeneFC » Sun Nov 26, 2017 3:19 am

JoshM wrote:
Sat Nov 25, 2017 10:28 pm
Oh boy--it's on now :lol:

:lol: :lol: :lol: :lol: :lol:

Seriously, I would expect the coding is reasonably straightforward. What is difficult is the determining the best strategy. I experimented with ramp rates some time back, and I decided that I did not want the full horizontal feed rate. Others clearly have different needs.

I will retract any hint of disagreement in this thread. I can manually correct anything that does not work for my jobs.

Gene
mlampert
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Re: Vertical Feed rates in partially-vertical cuts

Postby mlampert » Sun Nov 26, 2017 6:39 am

what I'm hearing is that the feed rate of "non-vertical-or-horizontal" moves depends on the job?
As a feature request - do we need a "hybrid-feed-strategy"?
Min/Max/Algebraic?
chrisb
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Re: Vertical Feed rates in partially-vertical cuts

Postby chrisb » Sun Nov 26, 2017 10:40 am

berka wrote:
Sun Nov 26, 2017 12:01 am
Referring to your PDF drawings,
How about:
Vl = fx * Vx + fz * Vz
Where fx = X/L and fz = Z/L
This would eliminate the conditionals you deal with while deciding whether it is a steep or shallow ramp.
In the ramp extremes it degenerates to Vl = Vx or Vl = Vz.
It looks intriguing, however, it leads to speeds which are too high:

Take the example from my paper with X=8, Z=2, Vx=4, Vz=3.
Your formula yields Vl=4.6
If I project this on the X-direction I get 4.4, which is too much as 4 is the maximum.
chrisb
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Re: Vertical Feed rates in partially-vertical cuts

Postby chrisb » Sun Nov 26, 2017 10:46 am

mlampert wrote:
Sun Nov 26, 2017 6:39 am
what I'm hearing is that the feed rate of "non-vertical-or-horizontal" moves depends on the job?
As a feature request - do we need a "hybrid-feed-strategy"?
Min/Max/Algebraic?
I am with GeneFC: manual override is sufficient. It might not lead to the maximum possible speed, but the user can use common rules of thumb as herbk has indicated.

It might be sensible to create a feature request anyway so it will not be forgotten if in the far future we will optimize speeds.

The technique presented for G1 commands can be extended to helix ramping. I will think about it and report back.