Graphtec FC8000-160 wobbly cuts on small files

[Krashwraps]

Hello all,
Purchased used FC8000-160 back in December 2021, gave it some TLC, cleaned the head, new strip, new blades, cleaned rollers and etc.
Love the plotter, been using it a lot, mostly big stickers and never noticed any issues with cutting until couple of days ago when trying to do more intricate designs with thin lines and rounded corners, straight lines are straight no matter the size of the file, but round edges are wobbly and round corners are cut at 90Degrees if file is 1x1in, and if file is 6x6in round corners are exactly how the file is and straight lines are perfect.

Here are the examples:
1. File is cut 1x1 in round corners are not round but square
2. File is cut 2x2 in round corners have almost triangle shape
3. File is cut 6x6 in round corners are round but the curve lines are wobble
4. Is original .ai file

program used Sure Cuts A Lot 5, pressure 15, speed 10.

I have tried bunch of different sizes on exact same size and My understanding FC8000 is not able to do precise round cuts on files smaller than 6 inches unless it’s straight cut, or its an error on my side and I do not know what I am doing

To fix the wobble I am thinking I need new blade holder and see if that fixes the issue, but precise small cuts I have no idea how to fix it.

If anyone has any ideas, or ran into similar issues, your help is greatly appreciate as I am going crazy trying to figure it out

Thank you,
Alex

 

[Joe House]

Check your cutting strip and blade again. It could be time to replace those. Also, the bearings in the blade holder will wear down causing sloppy cutting. Also check that the Y-slider is solid on the rail. There is a spring at the top the will lose its tension and cause your cuts to be less precise.
The FC series is a precise machine. Old machines may be the ones not capable of doing acceptable small work, but I used to cut the Starbucks logo at 1/2" high when I was selling Graphtec plotters - it was a pain to weed, but it cut them beautifully. That was back on a FC5100.

 

[Attila Nagy]

Change step size on the cutter and in SCaL as well.

 

[Krashwraps]

Check your cutting strip and blade again. It could be time to replace those. Also, the bearings in the blade holder will wear down causing sloppy cutting. Also check that the Y-slider is solid on the rail. There is a spring at the top the will lose its tension and cause your cuts to be less precise.
The FC series is a precise machine. Old machines may be the ones not capable of doing acceptable small work, but I used to cut the Starbucks logo at 1/2" high when I was selling Graphtec plotters - it was a pain to weed, but it cut them beautifully. That was back on a FC5100.

Hello Joe, thank you for quick reply.
Cutting strip was replaced 2 weeks ago, brand new CB90UB blade holder was delivered today and nothing has changed. Spring on Y-slider looks in good shape. Did factory reset, same difference.
I did try to do self test that is in the Graphtec menu and it did flawless job on cutting small circles and even numbers that have rounded edges (3, 8, 9 etc) could it be issue with SCAL5 software?

 

[Krashwraps]

Change step size on the cutter and in SCaL as well.

View attachment 161330

Attila, thank you for your reply.
step size is at 254 on Graphtec and SCAL5.
I did a self test on Graphtec and it did perfect cuts, which makes me thing SCAL5 software might have issues with transferring correct info to the plotter that is why cuts are square. With everything replaced and cleaned that is the only thing that makes me think that SCAL5 my be my issue..

 

[Ronny Axelsson]

Attila, thank you for your reply.
step size is at 254 on Graphtec and SCAL5.
I did a self test on Graphtec and it did perfect cuts, which makes me thing SCAL5 software might have issues with transferring correct info to the plotter that is why cuts are square. With everything replaced and cleaned that is the only thing that makes me think that SCAL5 my be my issue..
View attachment 161338 View attachment 161340 View attachment 161339

My first action would definitely be to change the step size.
Long time since I used my old Graphtec cutter but I believe the GPGL default step size is 1016 (same as HPGL plotter language default), and 2032 should cut excellent details, although very slow.
I'm not surprised at all if 254 steps cut square corners instead of round.

 

[Ronny Axelsson]

I did a self test on Graphtec and it did perfect cuts

My guess is that the self test uses default step size (1016?) instead of the cutter driver setting, which may explain why the test cuts look perfect.

 

[Joseph44708]

You might be cutting to slow. Change to 25.
Knife is dragging through instead of gliding.

 

[Krashwraps]

Thank you all, I was able to figure out my issue with your help.
Indeed it was a STEP SIZE, I never played with changing the step size as I wasn’t fully aware what it was for nor what it did as I never got in depth, but now I do and it helps a lot.

 

[Solventinkjet]

If I remember correctly, HPGL has a better resolution than GPGL. You might switch to see if it does any better.

 

[Ronny Axelsson]

The HPGL (Hewlett-Packard Graphics Language) has a fixed step size of 1016 steps/inch (0.025 mm) I think, while GPGL (Graphtec Plotter Graphics Language) has four options, 254 (0.1), 508 (0.05), 1016 (0.025) and 2540 (0.01).
I believe 1016 is the GPGL default and it is fast and good enough for most jobs, but I have kept my twenty year old Graphtec FC4100-130 just to be able to use the extreme 2540 accuracy.
In combination with tangential emulation, this mode gives an unmatched precision and excellent details (it is very slow though) that usually only can be achieved with flatbed cutters and tangential knife.