Arc Delay on 2nd cut

[Kim_CF]

Hi all, having an issue with my plasma table. We had to replace our plasma and went with the Hypertherm powermax 85sync.
When I do a cut, the first cut is perfect. Then when it goes to the second cut the torch moves about an inch before the arc is activated. I tried the same cut with a .1 second pierce delay and a 1 second pierce delay and I get the same cut. No change. Please see the pictures that I attached.
I’m using : Inkscape, sheet cam and uccnc software programs.

I had someone on another forum say the following: I ran into the same issue! It all has to do with the “arc ok” signal and the way the Hypertherm is designed. I never was able to get it sorted out and eventually went to a different plasma cutter. I believe if you can get the post processer to only allow the torch to move after the arc starts (which is how it is supposed to work) you will not have that issue anymore.

Any suggestions would be greatly appreciated. Thank you - Kim

[weldguy]

Sounds like your system does not use the OK to Move signal and relies on timing to pierce the material before the torch moves.

Looking at the settings that are available to you with your system you have 2 options:

1-Increase the pierce delay (currently .1) so the torch remains still long enough to pierce the material on the cuts after the first cut while the post flow air is till flowing from the torch. The disadvantage is the initial pierce will be a bit too long and will burn a bigger hole and be a little harder on consumables.

2-Use the pause at end of cut timing (currently set to 0s) so that at the end of every cut it remains paused long enough for the post flow air to stop flowing and keep your pierce delay where it is. The disadvantage to that is it will take a little longer to complete your program.

Let us know what you choose and how it works out.

[tcaudle]

The reason the first cut works and the others do not is because the purge air (post flow) is not flowing so the timing is different and it delays some before it statists moving.. I lot depends on the controls. Pierce delay causes ALL motion to stop until its over after the torch fires, As stated delay comes with other problems like big divots and even loss of arc from lack of cut current..

The whole purpose of Arc OK from the plasma is to take out the variables and start moving at the same place every time and if you can control your THC via M codes , be able to turn it on at exactly the same place in the motion every time

Doing it with pierce delay requires a different setting for every material and amp setting. You have that in the tool set in SheetCAM .

The Arc ok signal on a Hypertherm aka START(every one that has ever been built with a CPC connector) does the same thing. It measures the Amps at the torch and it turns one when the cut current reaches a preset level (usually around 10Amps or more). That line goes LOW and a THC with a simple input detects that and HOLDS motion until it gets the signal. Signal; says: "Hey, I'm actually cutting metal now, you can start moving"

Of course if your THC has no provision for ARC OK and can't Hold motion based on a signal then you just have to do it with timing and its going to take some trial and error to get optimum dealys on each type material and setting.

[acourtjester]

Question do you have a THC being used on the table, what are you using to detect the metal surface for each cut. Like an Ohmic sensor or floating head switch. Have you checked that touch off to see if it is accurate, your SheetCam tool setting are not as Hypertherm shows in the manual you have a pierce height of 0.150" and cut height of 0.125" the book calls for 0.060" cut height. Attached is the Hypertherm cut chart and a screen shot of UCCNC setting "I/O setting" page these signal are needed for correct operations. The pierce delay is only to blow a hole in the metal not for pierce or cut height. If it worked with the other plasma unit you may not have the Arc On/OK signal wired correctly.

[adbuch]

Question do you have a THC being used on the table, what are you using to detect the metal surface for each cut. Like an Ohmic sensor or floating head switch. Have you checked that touch off to see if it is accurate, your SheetCam tool setting are not as Hypertherm shows in the manual you have a pierce height of 0.150" and cut height of 0.125" the book calls for 0.060" cut height. Attached is the Hypertherm cut chart and a screen shot of UCCNC setting "I/O setting" page these signal are needed for correct operations. The pierce delay is only to blow a hole in the metal not for pierce or cut height. If it worked with the other plasma unit you may not have the Arc On/OK signal wired correctly.

Tom - the Sync uses higher cut height than the non-Sync Hypertherm cutters.

David

https://stvcnc.com/stv-parameters-hyper ... -105-sync/

[acourtjester]

Thanks I'm still old school (: (:

[adbuch]

Thanks I'm still old school (: (:

Same here. My Hypertherm cutters are both non-sync versions.

David

[Kim_CF]

Hi everyone - thank you so much for the information. attached are the images of the UCCNC I/O Setup - unfortunately all of this is foreign to me. Hoping that maybe the issue is somewhere in the settings here. Thank you so much for helping me with this.

[weldguy]

The easiest fix for now is what i posted in my previous post above. Super simple until you become more familiar with your system.

[Kim_CF]

@ weldguy - I did exactly as you said - I did 1 second pierce delay and 5 seconds for pause at end of cut. Got the exact same results

[weldguy]

@ weldguy - I did exactly as you said - I did 1 second pierce delay and 5 seconds for pause at end of cut. Got the exact same results

Well that is odd. Was the 5 second delay at the end of the cut long enough for the post flow air to shut off?

[acourtjester]

have you tried to add lead outs to your plan in SheetCam, or using a cut rule(also called path rules) to extend the cutting at the end on the travel. If you want to this you will need to find which code is use with UCCNC in the cut rule. I am using LinuxCNC so it may be different for your use. I was having a dive at the end of the cut and this cut rule turned off the THC as it reached the end of my cut plan. I know this is not your problem but a cut rule fixed mine.

[acourtjester]

To help you understand the different parts of CNC operations. The UCCNC setup software for the electronics portion and for the wiring and control paths communications from the PC to the table. SheetCam or other CAM software is to generate the G-code that the controller uses for direction of the table operations. So the G-code is correct for your electronics you select the Post processor in SheetCam for UCCNC as there are different codes that belong only to UCCNC. This is a simple overview for you to have a Big Picture of the parts of the puzzle. I am no expert just I have used different electronics and software on different tables. Member here will help you get to where you need to be due to the knowledge base and willingness to help.