That’s correct - both hand and machine torch behave exactly the same. I checked freedom of movement of the electrode and lubricated both torch mechanisms with silicon grease. Both seemed very smooth. So logically its something external and common to both torches… Looks like air.
Totally agree - I don’t think its the pumping capacity or reservoir volume. I am thinking after all of your considered comments its a limitation on the air system to provide transient bursts to retract the electrode and initiate the arc.
I think George has worded the summary very well but my input is that I don’t think the compressor output (14 CFM & reservoir volume 24 gal) are limiting factors. But I do think air is the problem due to the distance from the compressor and the narrow 1/2" bore pipe. I think the remedy to try in ease are
-
A new regulator just before the Cut 60. Input as high as possible at 115 psi and output regulated to 95 psi which is the highest recommended by Primeweld. (Cost = $0 as I have a better regulator)
-
Item 1 above plus a new reservoir positioned close to the Cut 60 (Cost = $750 for 25 gal reservoir in the UK
Realistically, if 1) doesn’t work I will add the 5s delay between cuts. Cycle time to me really doesn’t matter so an extra 50s on a 10 cut job really doesn’t matter to me.
I’m not a commercial operation so time isn’t money for me; I just don’t like unexplained things!
Can you bring the plasma closer to the compressor? If not then repeat that #2 test while recording slow mo video of the pressure gauge. Maybe it’ll show something
I’m sure you can find a broken oilless compressor super cheap and use that tank. I’ve seen them free over here
Two different machine torch mounting strategies using the Langmuir mount and staying away from the torch head. Taken from other members of these forums, and I forget now which was posted by whom, but either one should work. After reading through, it sounds like this isn’t your issue, but according to @mechanic416, you might create a new one if you continue to hold the Tecmo by the torch head. 
Good luck!
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Ok I read the thread again and did not see where it said his cut off was 150 are you sure on that?
he also says he has a 24 gallon tank not 30 and 24 gallons is pretty small.
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I will relocate the compressor within a few feet of the Cut 60 tomorrow. I tried changing the regulator to a better quality triple filter unit but it made absolutely no difference.
Yes, my attachment was incorrect at the start of this puzzle but both Primeweld and George pointed out the correct method. So mine is attached to a fixed (no Z motion) mount like the top photo.
It’s actually a 100 Litre tank that I converted to gallons. Hopefully correctly at 24 usg. But I don’t think it’s the tank being too small - it’s just a reservoir and provided the compressor input to reservoir (14cfm) is greater than demand (5.5cfm) then it should remain at full pressure - which it does.
The only thing air-wise left is to eliminate the 100 ft of 1/2” hose between reservoir and the Cut 60. Tomorrow’s job.
This may be true on all accounts. Some things you may want to take in
to account.
Is the compressor new or is it used and showing its age?
Is it a brand name that would not have over inflated specs?
There are a lot of air compressors that are being sold these days, that are of very poor quality.
I think your on the right track just remember anything that you don’t confirm with testing may come back to bite you. Make sure you post what you finally find so other can learn from it.
You have done a good job of listing everything you have done to solve the problem, this will be a good thread to help others
Thank you
Thanks Knick. The compressor is a few years old but not many hours use in that time. I bought this one as it’s the largest compressor at 14.5cfm that can be connected to a single phase 13A UK socket.
It’s here listed on the UK supplier.
https://www.machinemart.co.uk/p/airmaster-tiger-161050-3hp-100-litre-air-compr/
I’m sure it’s made elsewhere probably in China so maybe appears in US hardware stores under a different brand?
I most certainly will let the forum know when I locate the issue. I am so grateful for the effort the forum people have put into reading my posts and offering their experience and advice
Hmm, with a steady flow rate of 6 CFM, the calculated pressure drop assuming:
100 psi
100 ft pipe run between reservoir and Cut 60
0.5” pipe
Is only 0.5 psi
I will still try relocating the compressor closer but my expectation of benefit has just got lower …
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I am not familiar with that brand but I do know that style.
couple of things to look at:
1- Max pressure is 116 PSI so that 150 PSI that was being used to calculate output is out.
2 - CMF is listed as displacement. This is not the CFM that compressor will put out under operating pressures.
If you look at compressor specs on a name brand compressor it will list the CFM along with the pressure and you will notice CFM drops as pressure goes up.
here is a link that explains it better then I did
Not saying your compressor may not do the job, but I dont think its the power house you think it is.
I will be curious as to what you find.
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@Thanet58, do you have a meter to test the voltage on the power supply? another user on FB posted something similar to your problems and found out the voltage coming out of the power supply was set too high. once he adjusted a pot on it to correct voltage, he was off and running again. Wouldn’t hurt to check to rule that out.
when you test between a pair of the black(+) and white(-) contacts on the power supply, you should be getting around 36v. the Guy on FB was reading around 45v. he turn the pot down until he was close to 36v and ran a file that was gibing him trouble before and it cut without issues.
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Thanks, I didn’t get to try this as I had other results before I felt ready to open the case. Appreciate the pointer though.
Well I dragged the compressor 100 yds uphill through gravel to place close to the Cut 60. The racket when it is going reminded me why I placed it 100 ft away in its own vibration and noise isolating min-shed… Anyway, absolutely no change whatsoever when the hose length was now closer to 10’ All the regulators seemed to be doing their thing correctly as did the compressor auto-start.
So, I decided that I would accept defeat and just use the 5s pause between cuts. No biggie really as this reliable workaround would add 2 minutes at the most to any job I had planned.
I did one last test to check that long single cuts are fine and they were. This was a single cut twice around the perimeter of a 20" x 20" piece of 1/4" mild steel so it was close to an 18’ continuous cut. The two cuts in the corner are pass 1 and pass 2 are raw without any clean up whatsoever - i’m quite pleased with those and used the parameters straight out of the Primeweld owner guide. 45A, 60psi and 47 IPM. The air didn’t falter once and the compressor only coming on after about 12’ of cut.
I decided then to accept the anomaly and use the 5 pause workaround but did one last thing…
Solved - A classic case of confirmation bias
Well I have to come clean as embarrassing as it is. The last thing I did before I actually started to cut a project piece was to change the consumables. I changed everything including the shield.and then did one last test on my “slots” The slots cut without interruption!
Going back a few weeks, after the hand torch showed the intermittent cutting, I bought the machine torch thinking the hand torch had some sort of issue. But the new machine torch had exactly the same issue of failing to arc on the second slot. Exactly the same.
So there lies the issue; the confirmation that both torches behaved the same biased my view that it was something other than the torch. Seems like I was wrong.
So, I went back and used brand new consumables on the hand torch and the problem remains! This wasn’t the first time I had changed consumables on the hand torch. In the early days of fault-finding I changed them several times using Primeweld parts and lubricated the electrode with silicon grease.
All, I can assume is that I had two torches each with its own problem. The machine torch problem fixed with new consumables, the hand torch not fixed by consumables and remains unreliable.
So, I thank you all for taking the time to read and respond.
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I congratulate you for getting through this…
You have learned a huge amount from all this trouble shooting…
you will have problems from time to time…it is all taking small steps to solve it…
nothing should ever be this hard again…well done!!!
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Thank you for the encouraging words Glen - its the Z-axis motion and THC next…
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