Feed speed not constant while finishing

[calexpavel]

I tried with and without smoothing. Increased tolerance, it still stops at certain points.

Looked in the toolpath, there s nothing special where it stops.

Attached the file.

Any idea?

Thanks

[ChristopherMarion]

@calexpavel 

What is your tolerance set to?  If it is set to the default of 0.0004", try loosening it to 0.001"

[calexpavel]

It's set to 0.05mm which is 0.002 inch

It was 0.01 before and it still stopped.

Would it stop decreasing it more?

[calexpavel]

I'm using 2 finishing tools. A 20mm one and a smaller 8mm diameter. The small one leaves some marks on the material.

The tools are measured.

It isn't setup to leave cusps.

Attached the file and some pictures.

Any help is appreciated. 

[ChristopherMarion]

@calexpavel 

How are you getting your code to the machine?  Are you drip feeding it or are you uploading it to the control and executing it there?

Also, does it happen with all strategy types or just certain types?

Lastly, does the toolpath always stutter in that same location?

[engineguy · Accepted solution]

@calexpavel 

Looking at the code as generated I see there is no change in feedrate from your F3720 so I don`t think it is from Fusion.

What is the control you are using ??

This may be completely "off the wall" but hey, it makes sense to me anyway 🙂 🙂 🙂

Does the "glitch" appear to move further along that side of the part with each pass, if so then it is possible that as the setting for max feedrate on the Z axis on most machine controls which would normally be less than the X and Y axis feedrates is below the F3720 in the code and the points of the "glitch" would likely be the Z transition move down to the next level where it is suddenly slowing down at the start of Z transition and speeding up again at the end of the transition, look closely at the toolpath and you will see where the Green transition areas are.

This is the code for those areas of transition, it is moving in a series of very small steps which if the machine control has a reduced Z axis maximum feedrate will produce what could be termed the "stutter" 🙂 🙂 🙂

G1 X-142.225 Y30.235 Z-0.514
X-142.367 Y30.888 Z-0.55
X-142.52 Y31.534 Z-0.602
X-142.694 Y32.224 Z-0.664
X-142.837 Y32.889 Z-0.723
X-142.954 Y33.576 Z-0.784
X-143.065 Y34.268 Z-0.846
X-143.156 Y34.961 Z-0.907
X-143.205 Y35.66 Z-0.959
X-143.21 Y36.354 Z-0.992
X-143.172 Y36.881 Z-1.
G2 X-138.734 Y56.568 I122.877 J-17.357
G1 X-137.191 Y61.77

Well, that`s the "off the wall" idea, daft I know but possible and as I said above makes sense to me 🙂 🙂 🙂

Have a close look at the Feedrate indicator on your control panel and check if it changes at the bad areas 🙂 🙂 🙂

Regards

Rob

[calexpavel]

Thanks Marion,

I'm uploading the program to the controller using a usb drive.

Tried adaptive clearing and tracing strategies and didn't have this problem. Only seems to happen on this contour finishing strategy.

The stutter seems to happen in different places when the tool goes lower in Z axis.

[calexpavel]

@engineguy 

Thanks Bob. Very interesting. It may be what you're saying. I'll check tommorow when i get there.
So this transition, how can i change the speed at which it happens? It's not a plunge move, i guess.

Does it stop by default when it makes the transition to a different Z value?

[calexpavel]

And sorry for that "marks on the material" reply. I wanted to make a new post and i think i replied here by mistake. Weird...

[calexpavel]

@engineguy 

The transitions seem to happen every 30mm or so, but in the gcode the z value changes about every mm. 

[engineguy]

@calexpavel 

The moves are in all three axis, it is moving in the X and Y because it is moving outwards to a different size of the part due to the slope and at the same time it is stepping down to get to the next level of cut, what my theory rests on is as I said earlier that if the Z axis maximum feedrate is limited to say 3,500mm/m and the X and Y axis have say a 4,500mm/m maximum then if the X and Y are able to run at the programmed F3720 but the Z axis can only do 3,500mm/m then unless the control can automatically reduce the X and Y axis feedrates then there is a problem.

In answer to your last Post what you see in the code that I uoloaded is a single  transition, on the next level the transition does move further along, have a look at the image below, you can see that the Green transition lines start further along each pass and each Green line will be another set of the very small X,Y and Z moves that I posted earlier!

So the length of the Green transition will depend on the angle you set, each new level seems to start the transition from the end of the previous one, this is really fun 🙂 🙂 🙂

It may well not be the answer but it does look logical to me 🙂 🙂 🙂

Regardsing the marking, a large Ball nose tool will always give a better finish due to the larger radius unless you use very small stepovers/stepdowns with a much smaller tool !!

[calexpavel]

Ooh I see what you mean. Although, it stops a few times in a single pass. Here's a video with it:

But i will check tommorow to see where exactly it stops and if it moves. Also i will reduce the feedspeed to see what happens

[ChristopherMarion]

@calexpavel 

So the stuttering issue I saw in the video has been definitely called out by @engineguy.  The transition between Z levels is causing what I thought was stuttering, which is what I thought you were complaining about.

About the marks on the surface, have you tried turning off smoothing?  It may be worth testing.

[calexpavel]

Thanks a lot! You guys rock! You are some kind of machines doctors 😀

How can i solve this? By reducing the feedspeed or by increasing the controller Z axis maximum feedrate?