Machine Torch to work distance.

[alanmccabe]

Hi all I wonder can anyone help

I am just finishing my 4x4 build and had a few questions, wondered if anyone can help.

I have a Trafimet AUTOCUT S 65P machine torch and cant find anywhere that states the optimum torch to work distance.

Any thoughts would be useful. Thanks Alan

[acourtjester]

That depends on the thickness of the metal being cut but most of the time it will be about .060" for cutting and 0.150" for pierce. Google and download a Hypertherm manual and there cutting charts in there that will get you very close, (speeds, pierce height, amps and cutting height. This video shows me setting up a Price THC (same for most of them). It does show how to check the mechanical setup for doing test cuts to check the operations without plasma on too.

https://www.google.com/search?q=Hyperth ... e&ie=UTF-8

[adbuch]

I agree with Tom. Cut height = 0.060", Pierce height = 0.150". Here is the Hypertherm cut chart for 45 Amp Shielded Mild Steel.
David

45 A Shielded Mild Steel.jpg

[alanmccabe]

Thanks guys

[weldguy]

Check out this topic https://plasmaspider.com/viewtopic.php?f=202&t=30283 and it explains how to read your cut edge and determine if the cut height is correct. Do your testing with a simple square cut in a CW direction so you have 4 sides to read from. Pick up the square, all 4 sides should look the same and you can read the taper and determine if you are too high or too low. I would use some scrap .125" or thicker so you have a decent edge to read from. If all 4 sides are not the same taper than you need to resolve that issue first, could be consumable condition, torch not square to the material, incorrect air pressure, etc. Remember if your consumable condition is poor you will not get an accurate read, use new consumables and make sure speed is pretty close to where is should be.

[Rodw]

Forget the Hypertherm cutting charts. They are not even close for a Traffimet torch. Eg your cut speed for 2mm steel will be about 2000-2200 mm/min and they say 6600mm/min.

The Thermal Dynamics charts would be closer but you will have to experiment

[adbuch]

a little slower.jpg

[Rodw]

a little slower.jpg

Still too fast. the Thermal Dynamics book speed for 2mm mild steel is 2219 mm/min @ 40 amps. It cuts perfect for me at that speed
Hypertherm cut charts are for hypertherm machines and are useless for others.
The speeds I arrived at for my Everlast machine with a trafimet torch were similar to the thermal dynamics.
You can't get away from trial and error. You pay a lot for premium brands but having cut charts is a big part of that.

[alanmccabe]

I can now see the value in maybe saving for a hypertherm .
I ran a few tests today and at 40 amps at 2500mm p/m I have a clean cut with zero dross. When I slow for the corners I do get dross but I expect this is normal. I have to say plasma cutting makes CO2 laser cutting seem like a toy. So many variables and things to consider lol.

[Rodw]

Yes, when you negotiate the corner, the laws of physics says you have to slow down so you are not at your cut speed and cut quality can suffer.

The only way to improve that is by increasing machine acceleration but that can get expensive too!
my table achieves 5 m/sec/sec (0.5G) after nearly AUD $3k upgrade on motors and drivers.
Corner quality improved immensely because it can slow down and get back to speed so much quicker.

[adbuch]

One of the nice things about Plasmacam Design Edge is that it allow for setting corner acceleration as well as slower on circles under a specified size, both independently of speed. I also agree that an upgrade to the Hypertherm 45xp could be a big plus for you. Then no more guessing about cut speeds, etc.

David

cutting motion.jpg

[Rodw]

The acceleration for arcs is interesting. But in a system without that setting. you should achieve the same objective by using a cut rule something like "reduce cut speed by 60% on holes < 32mm diameter".

This is becasue the centripetal acceleration formula (a = v^2/r) has a direct relationship between velocity and acceleration for a given arc radius. I e the faster the acceleration, the tighter a a radius can be at a given velocity.

So by limiting acceleration on holes, Plasmacam is reducing the velocity a hole can be negotiated at.

[adbuch]

So by limiting acceleration on holes, Plasmacam is reducing the velocity a hole can be negotiated at.

The "slow on circles/curves under (diameter, inch) limits the velocity/acceleration for holes and/or curves below the specified diameter (or radius for curve). The corner acceleration (G) setting also applies to corners with no curvature - i.e. right angles. So this allows for faster straight line cutting speed with "look-ahead" to decelerate before reaching a tight corner such that the corner is negotiated at the specified acceleration limit. This makes for better cuts on fine details without the "jerky" motion that would/could be associated with higher corner acceleration rates.

The reason that Hypertherm provides both FineCut Mild Steel and Low Speed FineCut Mild Steel mechanized cut charts is because not all cutting table systems have the ability to control corner acceleration as well as some of the more sophisticated systems do. For example - 18 ga. mild steel regular speed cut speed is specified at 325 ipm vs. 150 ipm for mild steel slow speed. Quite a difference.

David