Needing help

[Cbert10]

I have recently undated an older tracker plasma table with ESS and the TMC 3in1. I am a complete newbie to cnc so this has been a large learning curve.
I am having troubles when cutting a image. Some of the lines cut perfectly and some lines are jagged or blown out. If you look at the starS it looks like 2 of the stars are perfect and the rest have some form of deformities.
I have made sure that my gantry is tight and moving smoothly. I am thinking that there is something that I am doing wrong when setting up Mach 4 or sheet cam.

5D887F05-5EF9-4C40-BC4B-3BFAF232DD6F.jpeg (83.36 KiB) Viewed 817 times

5D887F05-5EF9-4C40-BC4B-3BFAF232DD6F.jpeg (83.36 KiB) Viewed 817 times

[adbuch]

Is this the image your are attempting to cut? It doesn't look like and actual cut part. More information please.
David

[Cbert10]

This is the part that I have cut, it is kinda hard to see but some of the stars are normal and some of the star legs are much wider than others

[Cbert10]

[robertspark]

Acceleration too low?

What is the acceleration for X and Y?

What was the intended feedrate you were trying to cut at?

Servos or stepper motors?

[Cbert10]

I was set to cut at 250 ipm and I believe the acceleration was set to 15

[robertspark]

That acceleration is very low...... 15 in/s/s means that the smallest arc you can cut at 250 in/ min is 1.15 inch radius (2.3 inch diameter) WITHOUT the torch having to slow down (physics)

It is sort of accepted that the torch can slow down to 60% of its linear feedrate without too much dross forming and the kerf becoming too wide and deformed.

250 X 60% means that at 150 in/min the smallest arc you can cut is 0.42 inch radius (0.84 inch diameter)..... To cut smaller details than this the torch HAS to slow down further....

Unless you increase your acceleration.....

The target is 0.3g (115.9 inches / s/sec)..... That would cover tables up to 600 inch/min feedrate able to cut arcs of radius of 0.3 inch (0.6 inch diameter) at 60% drop in feedrate....

Or for 400 inch per min (top end of book specs for hypertherm cutting tables in the air range) 0.14 inches radius (0.28" dia) with a 60% drop in linear feedrate for arcs

If you are using mach3 then you will struggle a bit as there is no tolerance adjustment between linear motion where one axis slows down and the other begins to accelerate.... Also mach3 apparently can do some odd things with acceleration and not stick to the set acceleration parameter....


So.... Simple answer.... Increase your acceleration to improve your cut quality!.... It's too low for detailed work at 250inch per min

[Cbert10]

Awesome! Thank you for the reply I will try that when I get off work

[Rodw]

Stars are probably the most difficult shape for a plasma cutter to cut because there is no getting around the fact that the sudden direction reversal means the torch has to come to a complete stop before reversing direction.

I would strongly recommend undertaking some tests so you can come up with the highest acceleration you can get away with without loosing steps but in the real world come back to about 80% of what you come up with as the max. I have been there, done that and substantially reduced my carefully researched settings!

Without knowing your table, 0.3 G (115 in/s^2 or 2950 mm/s^2) might be a bit of a stretch on a basic table but hopefully you can get to at least half that (say 1500 m/s^2 or 60 in/s^2) But the top of the range plasma tables are pulling 0.7 g (say 7,000 mm/s^2 or 275 mm/s^2) but they run 3 hp (5 kW) servo motors!
0.3-0.5 G should be achievable on a well engineered stepper system