Problem Varying cutting speed on straight lines and curves

# Thread: Varying cutting speed on straight lines and curves

1. ## Varying cutting speed on straight lines and curves

Hello world,

I'm new to this community and this is my first post. I've tried searching for the answers to my questions, but to no avail so if you could please help it would be much appreciated!

I'm running LaserCut5.3 on a 150W GWeike LC 1290 and have two questions regarding its speed settings and minimum power setting.

I'm trying to cut a model airplane out of thin balsa wood such that the user can pop out the shapes and assemble the plane and im running into two problems.

1- when cutting along a curved line, the laser head moves much slower than when cutting along a straight line. even when the speed settings are the same (100speed 20 power) the result is that the material burns up where it goes too slow, and barely cuts through where it goes too fast. Is there a way to make these speeds equal? I have checked the machine settings for circle speed, and the machine has a limit of 150 for a 3cm radius which is faster than im trying to cut anyway. How do i make the machine speed up around the curves? its going so slow that its burning material even at minimum power settings.

2- I find if i set the power lower than 10 the laser does not even fire... is that normal? I'm trying to reduce the power of the laser and speed up the head to avoid burning, but the head slows down for the curves so much that i have to reduce the power. I'm finding no mater how fast i turn the speed up, the head slows down so much that i have to reduce the power to combat burning. The problem, is i cant go much lower on the power without it turning off entirely, and im still burning my material.

I'm sorry if this was tough to understand, but i hope i've done a decent job explaining my predicament.
tl;dr: despite speed setting, laser head slows down on curves so much so that it burns material even at lowest power setting. how do i get the head to go the same speed on the curves as it does on straights?

-Henry

2. ## Re: Varying cutting speed on straight lines and curves

Hi Henry, sorry I can't help you just yet as I am having the same issue which I am still working through. Just to get some thoughts down and bump this thread along a bit and which may get some help from the many people out there.

I do all my drawing using Vectric Aspire and although I can output in more than one format I only save in a DXF format as lasercut will only import a DXF file. I can't get it to open up AI files so for me DXF works.
Depending on how I make and save that DXF can influence how many node points that the vector line contains, anywhere up to about a gazillion! Although I have had some success in node reduction I still have issues.

When I run certain parts the straight lines run smooth and at programmed speed but as the same as your problem, when coming to the curves my machine slows right down and makes jerky movements. These jerky movements are extremely rapid and make the X and Y axes motors make a not real nice squealing sound. The axis motors are stopping and starting at each point along the curve, albeit rapidly but enough to make the motors just sound crap.

Really messes with the time taken to make parts as I have a LC1390 size laser (For those wondering 1300mm x 900mm or 51" x 35") especially when I have a full sheet of components.
Also really buggers up the cut quality on those curves. On one project I was doing in thin MDF all I wanted to do was to mark out some numbers using low power and very fast speed and all it would do was to slow down on the curves and in places burn through, so damn frustrating.

Even though I have got my files to what I believe acceptably low node points the cutting is still not right, it seems that the software needs the look ahead function setting played with. ( if possible) so it just zooms through those curves.

I have had a go at changing the curve disperse and the corner acceleration, but has not helped my case. I suppose what I need is the settings from someones machine that is working for them and a curvy ECP and MOL file from and run on my machine to see how it goes. I suppose apples have to be compared with apples but I have a G Weike machine which are rebranded as Boss lasers, Rabbit lasers and probably others so there are many out there, and presumably many people to aid.

One other very annoying issue that I have just remembered is on job I did was differing speeds on some straight line sections just to muddle up what I mentioned earlier. This flat part has a sawtooth pattern along 2 edges, one side big teeth and one side medium teeth. The teeth are about 15mm (1/2") and 20mm (3/4")

The cutting speed of those teeth was sporadic. The parts were laid out horizontally and cut path was obviously just simple sawtooth movements but some teeth would cut smooth and normal but some would be jerky as described above as per the curves. Seemed very random as well. Fast, fast, slow, slow, fast, slow................ you get the message. Looking at the drawing and ECP file there were only a node point for each tooth, so I was just stumped.

10% sounds about right for the tube minimum turndown.

Cheers M

3. ## Re: Varying cutting speed on straight lines and curves

I can cut many vectors in the same file, and a diagonal one will cut slow. All are set to same speed. Re-running the file causes the same vector to cut slow so I believe it is in lasercut.
2 parallel diagonal vectors, and 1 will cut fine and the other slow.

4. ## Re: Varying cutting speed on straight lines and curves

For God's sake, someone, anyone PLEASE solve this problem!!! I'm not even loading or importing files from any CAD/CAM program. If I just draw straight lines using the LC 5.3 editor, any line that is not parallel to the X or Y axis cuts slowly and axis-parallel lines speed up to about 2x speed. All lines are "united" under the Tools drop-down tab and there is only one color, one speed and one power setting. Still the speeds vary. WTF?? also, the servos "groan" when they are translating at the higher speeds if that helps with diagnosing the issue.

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