A few questions : jerk, offsets, hotkeys .

Good afternoon, Tom everybody.
I'm from Ukraine. I’ve been working with your control board (Kflop) and KmotionCNC more than a year. During this time, I’ve made and launched two CNC machines. You can watch the video, which shows their work, here . In general I’m satisfied with the work of control board and software, but there are several issues/details I’d like to improve/fix for more reliable and productive work of CNC machine.

1 .Offsets saving. I know that this feature is implemented in version 4.30, but I don’t understand how it works and how can I save and then call out any of the offsets. Could you show me the process on several examples?

2. For more comfortable work of CNC-operator, I need to assign hotkeys for the user buttons, for example Init, Home, Probe, Execute, etc. Could you tell how can I do this?

3. Recently I’ve reconfigured all axes with Jerk parameter and I liked those step responses (graphs) that I’ve got using this option.
http://uploads.ru/jREpS.png

But at the same time I was very surprised that this option doesn’t work with G1, G2, G3 commands. As a result during the processing of linear trajectories with the usage of G1, a very strong vibration appeared.
So, tell me, please, how I can use Jerk parameter with G1, G2, G3 commands.

4. While using the Feedrate Override option a maximum speed limitation doesn’t work. I mean that I can set the speed that will be faster than the one set in Tool Setup. For example, the operating speed is 3500 mm / min. With the Feedrate Override parameter 2, the speed will be - 7000 mm / min. and won’t be limited by that one, which is set in Tool Setup (5000 mm / min.)

Thank you

Hi Abarmot,

Thanks for the feedback and good suggestions.

Regarding:

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1 .Offsets saving. I know that this feature is implemented in version 4.30, but I don’t understand how it works and how can I save and then call out any of the offsets. Could you show me the process on several examples?

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We don't really have a feature to view/save Tool Offsets. When KMotionCNC starts the offsets are loaded from the <install>\GCode Programs\emc.var file.

You can also place offsets in a GCode file with:

G10L2P1X0Y0Z0

Could you suggest exactly how you would like it to work?

Quote:

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2. For more comfortable work of CNC-operator, I need to assign hotkeys for the user buttons, for example Init, Home, Probe, Execute, etc. Could you tell how can I do this?

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We don't have Hot Keys for User Buttons. Which Keys were you thinking to assign?

You can add external buttons and trigger them from a C program with:

DoPCInt(PC_COMM_USER_BUTTON,xx);

Quote:

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3. Recently I’ve reconfigured all axes with Jerk parameter and I liked those step responses (graphs) that I’ve got using this option.


But at the same time I was very surprised that this option doesn’t work with G1, G2, G3 commands. As a result during the processing of linear trajectories with the usage of G1, a very strong vibration appeared.
So, tell me, please, how I can use Jerk parameter with G1, G2, G3 commands.

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Sorry we don't have that. I don't know of anyone who does (and does it well). Trajectory Planning is extremely complex. I think KFLOP/KMotionCNC has one of the best Trajectory Planners but it is still unlimited Jerk. Do you speak Russian? Here is a review of a few Trajectory Planners. KMotionCNC has the highest speed while still honoring all acceleration, velocity, and path constraints.

We do have a Coordinated Low Pass Filter option that can smooth Jerk Spikes. Have you tried this?

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4. While using the Feedrate Override option a maximum speed limitation doesn’t work. I mean that I can set the speed that will be faster than the one set in Tool Setup. For example, the operating speed is 3500 mm / min. With the Feedrate Override parameter 2, the speed will be - 7000 mm / min. and won’t be limited by that one, which is set in Tool Setup (5000 mm / min.)

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We do honor all max axis velocity settings specified in the Tool Setup with Feedrate Override. However if for example your axes are both capable of going 5000mm/min then it is possible to move both axes at 5000mm/min in which case the total diagonal motion can be sqrt(2) x 5000mm/min or 7000mm/min. We think this is the correct behavior. Is this what you are observing?

Regards

Hello Tom. Thank you very much for your response and I’m very sorry for the delay with mine.

1. You wrote that all the offsets are saved in the emc.var file. Could you tell me, please, how I can save there my own data, so that when the KmotionCNC is loaded and the first offset is selected (fixture offset 1) the equivalent to G-code G10L2P1X ... Y ... Z ... program launches (X ... Y ... Z ... listed in the file emc.var). I know about the possibility of setting the offset by using G10L2P1X0Y0Z0, but it is rather uncomfortable to set 3 or 4 working offsets each time I launch the program.

It’s how I see the perfect work of offsets: for example, we move the CNC-machine to the coordinate x-10, y-20, z-30, and then press the button or select from the menu to save the current point as the first offset. With this the setup process is completed, so that these coordinates are saved in the program and we can set the appropriate offset simply by selecting it from the list at any time. This algorithm is implemented in the NC-studio, it is very simple and reliable and makes CNC operator’s work much easier.

2. Ideally I would like to have a combination of hotkeys for each button in Tool Setup. But right now I need such hotkeys only for those buttons, indicated in the figure below. You have already hotkeys for such buttons as Keyboard Jog, Feed Hold, Stop, and Start, so, maybe it’s reasonable to create hotkeys for all buttons so that it will be much easier to use this program.

http://www.cnczone.com/forums/attach...1&d=1361436163

3.To tell the truth I don’t even know what to do now ... Probably I will have to decelerate speed and acceleration in Tool Setup until vibration disappears. Perhaps because of the large mass of the portal( Y-axis 270 kg), it’s impossible to work with such speeds and accelerations, that are indicated in the figure below.

http://www.cnczone.com/forums/attach...1&d=1361436163

Y-axis ( portal)

http://www.cnczone.com/forums/attach...1&d=1361436298

I read the review from the reference you’d sent. I even know the author of the article and runed his test on my CNCmachine, the results were 2:59 as it was pointed there. But my problem is that the vibration appears even when the spindle moves from X0 coordinate to X30 coordinate (it’s just an example) with using G1. At the same time when G0 is used there’s no vibration.Do you plan to finish Trajectory Planer so that the Jerk parameter will be taken into account while using G1 (in the process the acceleration is growing).

4. I understand everything concerning this point. Excessive speeds were set in Tool setup. I will check everything again, but I still think that the problem was in the settings.

Hi Abarmot,

Yes I can see the mass is large and high so it probably has a low resonant frequency. Regarding the Jerk limited Trajectory Planner: we realize that is very important but we will not have that anytime soon.

What are your KFLOP axis Velocity, Acceleration, and Jerk settings? Those are used for G0, Independent, Jerk limited moves. They are in units of encoder counts rather than inches. For a relatively small move like 30mm it may be that your Jerk limit is keeping the Acceleration and Velocity low so it is not really a fair comparison.

A fairer comparison would be to complete the move in the same amount of time with limited Jerk and with unlimited Jerk. In general limiting Jerk will require more time to make a move. But with increased acceleration and velocity it should be possible to complete the motion in the same or less time with still lower disturbance to the system.

You can simulate unlimited Jerk moves in the KMotion Step Response Screen by setting the Jerk to a huge value (ie 100X the Acceleration).

Regards
TK

Delete a duplicate)

Everything is quite clear with parameter Jerk and the principle of its operation. You were right as to its operation at very small movements, it really does not allow the machine to get the set speed, which is good illustrated by Step response. If you are interested, here are my settings of speed, acceleration and Jerk:

Code:

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ch0->Vel=320000;
ch0->Accel=1500000;
ch0->Jerk=6e+006;

ch1->Vel=340000;
ch1->Accel=1600000;
ch1->Jerk=6e+006;

ch2->Vel=230000;
ch2->Accel=1300000;
ch2->Jerk=1e+007;

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You can also view a video which demonstrates the maximum speeds of motion using G0.
http://www.youtube.com/watch?v=u9EbqIAQ8mE

And what about the first two paragraphs of my theme, namely offset storage and hot keys. Could you tell me when we can wait for their realization, it's very important for me ?

I have also another, probably a little bit stupid, question: How can I make the machine raise the spindle when G-code pauses or stops? I know that there is C-code External Buttons, but I actually can’t understand how it works. Could you show me its work by example of any button, please?

Hi Abarmot,

We hope to have a version for you to try soon. Sorry it is taking longer than I thought it would.

Regarding raising the spindle. It isn't clear how we would know it is appropriate to raise the spindle. Could you be more specific on how you expect it to work? You could do something with a special button that would do something like: Feedhold. Wait for Feedhold to stop. Halt the Interpreter, Then move Z up. Turn off Spindle. Another button might Turn on spindle, move Z back to where it was. Cycle Start.

Regards

Please try out KMotion/KFLOP Test Release 4.31a

KMotionCNC new features:

New Work/Fixture Offset Edit/Save Dialog

Custom Buttons now can have Hot Keys Assigned

A B C Axes can be driven in Degrees instead of Inches/mm

See post on our Yahoo group here