Edge Issue on 3/8" Plate

[pdjcutandfab]

I am trying to cut some 3/8" plate for a customer and I am not having very good luck (I've attached some pictures that show what I'm talking about). Whats hapening is the machine is cutting thru the material but when you look at the finished part the edge has a pretty decent taper to it. I have a Torchmate 3 w/ a Cutmaster A120 Plasma Cutter. I am using the following settings:

85PSI
80Amps on Plasma Cutter
110 Volts set on AVHC
Cut speed is 35IPM
Cut Height .2"
Pierce Height .22"
Sensing Delay .5 seconds
Piece Delay .4 Seconds

Any help would be great.

Thanks

Pat Weier

PDJ Cutting & Fabricating

[muzza]

I'm not really familiar with Thermal Dynamics as I use Hypertherm but what I have found usually causes that (assuming torch is correctly aligned) is the hole on the nozzle being out of round. If you cant see visual out of roundness try loosening the retainer and rotated the nozzle 90 degrees and see if the taper follows it.
Murray

[jimcolt]

We cut 3/8" plate with a Hypertherm Powermax85. Normally we use the 65 amp shielded consumables at book specs and edges are pretty close to square and uniform all the way around the part. Cutting with the 85 amps consumables will certainly cut faster, but with more edge taper. For best quality and best squareness w cut 3/8" with the 45 amp shielded process, again at book specs for speed, pierce height, cut height.

Book specs for the 65 amp process on a Hypertherm for 3/8" steel are:
Pierce height: .18"
Pierce delay: .7 seconds
Cut height .06"
Cut speed: 45 inches per minute
Arc Voltage: 130 volts (start at this voltage then adjust to achieve cut height)

Your pics are showing a parallogram type edge. Normally it is caused by a damaged nozzle orifice. The nozzle orifice (viwed through a 10x magnifier) must be perfectly round, no cratering and no nicks or notches. Nozzle orifices are usually damaged by piercing too close, or by attempting to pierce without adequate pierce delay.

So, pierce at the correct height, correct pierce delay as suggested in your Plasma operators manual. For best edge angularity use a lower power set of consumables.

Parallel angularity can also be caused by:

- Torch not square to the plate
- Using poorly manufactured consumables (from an aftermarket supplier)
- Defective swirl ring (in a TD torch, start cartridge)
- Defective retaining cap
- worn out shield (in a shielded consumable setup)

Jim Colt

Here is edge angularity with a Hypertherm on 3/8" at 45 amps:

Powermax45 edge angle 003.jpg (28.45 KiB) Viewed 1990 times

Powermax45 edge angle 003.jpg (28.45 KiB) Viewed 1990 times

Powermax45 edge angle 002.jpg (31.68 KiB) Viewed 1990 times

Powermax45 edge angle 002.jpg (31.68 KiB) Viewed 1990 times

[mapequipment]

I also have the A120 I usually move to 100 amps for anything over 1/4". 3/8" is my nemesis, I can cut 1/2" with a better edge then 3/8". Anyways here is the setting I run for both that I usally get good results from

80 AMP
85 PSI
134 Volt
35-40 IPM
.225 Pierce
About 1/2 second delay

100 AMP
75 PSI
116 Volt
70 IPM
.225 Pierce
1/4 second delay

These are what's in the book and work pretty well for me.
Hope this helps.

[mlinehan]

Like Jim said, first check the condition of your consumable parts, especially the tip orifice. Also make sure your plate is squared up to the torch. That was what I first thought of when I looked at the photos. You are looking a more than just a normal bevel issue. Something is out of square.

You will have best results in that application if you use the shielded consumables parts instead of the exposed tip. Cut parameters for that set would be:

80A
Pierce .20
Cut 134V, .19
Pierce delay .5 sec
40 ipm

[natewelding]

looks to me like your torch head is not square. I have an A120 also, and when my cuts have looked like that it means the head isn't square. All your other parameters looks pretty good tho.

[beefy]

looks to me like your torch head is not square. I have an A120 also, and when my cuts have looked like that it means the head isn't square. All your other parameters looks pretty good tho.

I've had this problem too as have others. The head not being square is one of the first things that get mentioned but as in mine and several other cases the heads were checked and found to be square. Not saying the head is square, just it's not the only thing that causes this problem.

Keith.