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S curve
« on: November 04, 2019, 01:17:00 AM »
we use the mach system in chines cnc
its work very good  ,and we improve ... so now i can say we almost can reach the Europa big brand(in wood cnc field)
but in one parameter i sill far back  ,it the acceleration deceleration while G1(working in the material)
if i try change to be close to that machines  ,i start get very bad working at the start ,end of working
so we add M function that change accl dccl in gcode ,so when move on G0 for example for drilling  ,we increase
...
but in G1 we need go very very low accll (les then 10000 mm/sec2)
as i try learn about that problem  ,i see that solution may be with the s curve
is some one meet that problem before? have an ide how mange it with mach4?
thanks
* i thought about simple solution that i can divice the movment in my pp and change acc dccl in the g code  ,but in this case  i can make it in some steps not smooth like s curve






9
Re: S curve
« Reply #1 on: November 04, 2019, 01:19:03 AM »
Re: S curve
« Reply #2 on: November 18, 2019, 08:40:36 PM »
its strange no any one here refer this question,most here are retrofit old Europe or USA  cnc that in there original controller for sure
have that option ,and no one mat that problem? even if cant solve but...
thanks
yaakov
Re: S curve
« Reply #3 on: November 19, 2019, 01:48:20 AM »
Hi,

Quote
its strange no any one here refer this question

That's not quite correct, at the time that Mach4 was being planned and talked about the possibility of including
a third order planner was discussed and experimented with. Historic now ....but:

https://www.machsupport.com/forum/index.php?board=83.0

Enjoy...all 142 posts of it!!

Craig
My wife left with my best friend...
     and I miss him!
Re: S curve
« Reply #4 on: November 19, 2019, 02:07:00 AM »
i not talk about cv
i talk about acceleration deceleration
its have maybi at the end some share points ,but its something else
please take alook at the  link i put its explain about this s curve
thanks
Re: S curve
« Reply #5 on: November 19, 2019, 02:21:26 AM »
Hi,
I'm well aware of what an S curve controller looks like. Its called third order because of the cubic term in the motion equation,
per the sample extracted from your link (attached).

If you read Arts explanation the Tempest Planner is a third order planner with 'extra bits'.

I believe the upshot was that the developers of Mach4, Art at that time had already sold to NFS, saw Arts work as interesting
but were more focused on producing a working CNC solution and the complication presented by a third order planner would
only delay that. The third order planner was never adopted by NFS.

Smurph has from time to time mentioned that he would like to revisit that decision. Now that mach4 is very definitely a working
CNC solution the intellectual investment in upgrading to a third order planner might be very welcome indeed.

Craig
My wife left with my best friend...
     and I miss him!
Re: S curve
« Reply #6 on: November 19, 2019, 02:33:02 AM »
Thanks alot for that answer ,i can wait
Re: S curve
« Reply #7 on: November 19, 2019, 09:18:15 AM »
As an engineer who focuses on motion control and robotics in my day job, reading through Art's write-up on Tempest really made me smile. He has a wonderful knack for being able to get his stream of consciousness thrown onto a page and make it enjoyable to read. Motion control is wonderfully complex.

I could definitely see benefits for many in including a higher order motion planner within Mach, in particular the ability to specify a maximum path deviation during movement blending, rather than just CV.

Thanks for sharing that link Craig, it was enjoyable to go through.
Re: S curve
« Reply #8 on: November 19, 2019, 11:23:07 PM »
mcardoso
do you think if i as temporary solution,ill dived the end,stop path in mine post processor
(the software that create the tool path its mine ,so can do inside as i need)to several small segmets
and change the speed for each segment ,do you think can help?
second option divied to not many segment ,but change the accl dcll in this segment(in mach we use m function to change acc dccl)
thanks
yaakov
Re: S curve
« Reply #9 on: November 20, 2019, 12:33:56 AM »
Yaakov,

I will admit that I am not 100% sure what your are attempting to accomplish, however I will try to provide information the best that I can.

First off, I think you really need to evaluate if S curve motion planning is something that you absolutely need, if it is just a nice feature, or just something you’re interested in but don’t need. Mach 3/4 is currently not offering S curve motion planning and I wouldn’t bank on it being changed anytime soon (although I don’t work for NFS, so I don’t know what they are actively working on :) ). If you absolutely need higher order motion planning, there are many products on the market that can offer this, although I do not know of any at the price point of Mach 4. If it isn’t absolutely necessary for you then I wouldn’t try to go down the rabbit hole. Maybe there are other, possibly more elegant and cost effective, solutions for your needs.

With all that being said, there is no reason that you can’t manage your Gcode to adjust feedrates to simulate the motion generated by higher order motion planners. Many fancy CAM suites offer features like feedrate reduction into corners and high non-rapid feedrates when the software knows you are cutting air. You might be able to set up your CAM to segment all your Gcode with variable feedrates. But again, why? That seems like a lot of work and your issues might be more easily solved in other ways.

My opinion is to leave the purchased software packages to work as they are intended to.

Can you elaborate on what is driving your interest in S curve motion?