THC accel/decel

[cncdrive]

Terry,

No, it is not impossible to output a 1(t) step frequency change, actually it is very easy to do so.
Imagine that the frequency is zero and you simply start outputting for example 1000 Hz frequency, then the change in the frequency is immediate which means that the acceleration time is zero.

Reaching that velocity in 0 time is possible below the stepper motor's start/stop frequency limit, that is an advantage of stepper motors that they can do that.
Ofcourse they will not accelerate up in zero time as that would be ofcourse impossible, but they can accelerate up so fast in that low frequency range that they can follow an immediate (zero time) change in the frequency without loosing steps, so it is close to infinite acceleration.

Again: S-curve profiling means that you can still use trapezoidal profile, you just setting the S parameter to zero and then there will be no S curve but the curve will be trapezoidal.
In addition we will have a frequency start/stop parameter under which the axis will accelerate with infinite acceleration and will deccelerate with infinite decceleration from that point down to zero velocity.
When accelerating to above that point then it will use the normal setup acceleration and the same when deccelerating and when reaching that frequency point.
So, in summary you can do trapezoidal profiling with the S-curve profiler and you can even do a 1(t) step frequency jump (or bang bang or whatever you calling it) below a setable frequency point.
But I think we already discussed the same months ago though...

[Vmax549]

Hi Robert yes it has been tried. In theory it works but in reality it does not. IF you set teh Z values for THC control then any other Z move in UCCNC is bascially messed up . Hence the request to change THC Z motion in UCCNC.

I am all for experimenting with Scurve but I also know what other controllers have tried without success. That is why I said that Scurve is NOT teh holy grail of CNC.

In teh meantime UCCNC needs a better THC Z axis control until Scurve can be proven to work better.

Just a thought, (;-) TP

[Robertspark]

Hi Robert yes it has been tried. In theory it works but in reality it does not. IF you set teh Z values for THC control then any other Z move in UCCNC is bascially messed up . Hence the request to change THC Z motion in UCCNC.

I have not tried it, but have you tried changing the acceleration relative to the operation?

I mean change the acceleration for Z axis touchoff.

I am not sure if it could be changed on the fly, but the only Z axis operations are:
- move to safe Z
- touchoff + retract to pierce height
- drop to cut height

all other Z operations are automatic THC {are they not}?

So the only operation that may be a problem to change the acceleration on the fly as part of a macro would be the drop to cut height?

[Vmax549]

Hi Robert

Retract to Z home (UP) Clearance for loading table
Lower to clear Z
Retract to clear Z
touch off routine (TOM) Sometimes every pierce
Set pierce height
lower to cut height

Trying to adjust everything on the fly is out of the question.

(;-) TP

[Robertspark]

Oh well, just keep using Mach3 then if it does what you want it to do.

You could try Linuxcnc too as there seems to be a hive of development going on with Plasmac
https://forum.linuxcnc.org/plasmac/3723 ... umentation

surprised you've not got involved with plasmac

[Vmax549]

HI Robert, Yes to Plasmac and yes to PathPilot and yes to LinuxCNC and yes to Mach3 and yes to Mach4 and yes to UCCNC and several others. I have controllers running them.

UCCNC is close to being a very good Simple Plasma controller. BUT close only counts with handgrenades and thermo nuculear warfare

(;-) TP

[beefy]

Hi Robert yes it has been tried. In theory it works but in reality it does not. IF you set teh Z values for THC control then any other Z move in UCCNC is bascially messed up . Hence the request to change THC Z motion in UCCNC.

I am all for experimenting with Scurve but I also know what other controllers have tried without success. That is why I said that Scurve is NOT teh holy grail of CNC.

In teh meantime UCCNC needs a better THC Z axis control until Scurve can be proven to work better.

Terry,

what do you mean when you say in theory it works but in reality it does not. Do you just mean that it makes the Z rapid speed worthless ?

I think Rob knows that the very low rapid speed makes the cure as worse as the disease, but he's only talking about testing UCCNC basic bang bang THC control by having infinite (or as high as can be programmed in UCCNC) acceleration applied, to see if it works just like Mach3.

Keith

[Robertspark]

I've given up asking for things, uccnc is just one tool in my toolbox of Mach3, Mach4, Uccnc and Linuxcnc with uc300eth, uc400eth, Mesa 7i76e and Pokeys 75E + Pobob available and all interchangeable to run plasma +4th axis tube cutter, router, 3 axis mill + 4th axis rotary table, and 2 axis lathe with step+dir servo spindle.

S-Curve won't fix everything, it will just bring new & different issues to consider + more options (I presume it will be able to be selected as to whether you want to use it for an axis or not)?

As far as I can see only Terry, Keith and Stirling have asked for any change (or consideration of a change) out of how many users.... I know Keith has a Neuron as I do, but I still have a miniTHC setup too to a UC400eth

I know Andrew (shad) has hundreds, if not a thousand (maybe more ??) uc motion controllers running on plasma tables.... but they don't use the THC as they use his THC system within his own BoB.

Think you are flogging a dead horse as UCCNC will never be Fanuc etc, its 55Euro software that runs on an 80-150 Euro motion controller board. Its cost effective at doing linear and some rotary motion, and has too many users for a couple of users to wish / ask for something else. If it gets developed further, great, if not, ok not a problem.

Like I said, suggest you take up using Linuxcnc as you can programme it to do whatever you want (given sufficient time and learning). No I don't find it plug and play and always find linux a laborious operating system if you want anything non-standard or optimised to your hardware compiling kernels and modules etc. I keep having on and off goes at it.

eg: I don't use G42/G43 within uccnc as sheetcam + estlcam + grblgru does what I want and I understand it and can visualise what its doing for me for 2.5D + lathe / turning
https://www.grblgru.com/

Choose the appropriate tool from the toolbox for the task.

[Vmax549]

HI Keith did you not test that as well ?? I believe you said it was still to slow. Ian also tested it with his Razordance THC system. You can make the thc usable with extreme Accell setting but it messes up the normal Z motion.

I will try it again on the actual table when I get the chance. But the results will still be the same. That part is not going to change from teh first time I tried it here.

The problem is teh owner of the table is NOT going wait a long time just for a workable solution. He will simply go to another controller that THC works properly.

Robert Robert, The world does not think as you do. Pouring more money and time into an application by buying things until you find a solution or not is not how the world operates. No one is asking UCCNC to be Fanuc. BUT if you are going to play in teh CNC world you have to have SOME compliance as to how things are suppose to work. (;-) OTHERWISE you are just trying to reinvent teh wheel. There are several new things in UCCNC that work in an unusal way but if that is how they want it to work they need to explain in detail in the MANUAL as to how it is to be used. USING other learning options will not help because it does not work in teh normal CNC way that was refined over decades of use.

I already work in teh Linux , LinuxCNC ,PathPilot, Command Pilot world. And it is NOT a simple or easy place to be CNC wise. BUT if you are willing to spend teh time and money and HAVE the ability to learn various programming lanuages (8) it can be made to do just about anything. But that makes it very DIY unfriendly( by todays definition of DIY) for most that try it. Today teh users CNC Hobby is NOT continuously working on teh machine to get it to work But the HOBBY is actually using teh machine to make other things(slinging chips, not soldering chips).

Certainly Balazs and company will do as they see fit for their market share in teh DIY CNC market. The ones actually using it for a hobby AND using it to make a living, testing and giving solutions are just giving UCCNC options to consider and advice on functions they use on a daily basis. Most have run multiple platforms and KNOW how it SHOULD work. But in teh end it is just advice for consideration to make UCCNC a better product.

IF you guys DON'T want to hear discussions then there is not much need to have a forum is there. The DIY world evolved to what it is today from discussions like this. I have the collection of EVERY discussion on teh Yahoo Master5/Mach1/2/3 forum. From teh beginning with Master5 to teh current Mach3. Up until Yahoo changed teh forum platform. Art had already retired at that time. The discussions would fill MANY volumes of books if printed out. And some of them are extremly interesting discussions.

Just a set of thoughts , Something to consider

(;-) TP

[cncdrive]

If infinate acceleration is still too slow then I think we can't help, I mean we cannot overrule the physics. If you set the acceleration to double.maxvalue means infinate acceleration for the controller when it instantly changing the step frequency from 0 to the programmed value. There is no need to have a plasma table to test this, you only need a storage scope or a logic analyser to measure the step frequency.

I cannot tell you guys other thing what I already told, that there is no need to have 2 different acceleration parameters as the new motion profiler will solve this without having 2 accelerations. This was already planned months ago and we will start implementing it soon.