Garagejunkie wrote:
botbasher,
Iv'e built plasma cutter that works ok , but would like to improve the cut and increase max cut depth.
Dose it make a difference on how the caps are connected, Ive connected them only across the DC side of the recifier and not like the plasnator guy plans that show the caps connected via the AC side and connected the DC side ?
Also will changing the tip size will this allow thicker metals to cut. (I have the same PT31 gun) ?
Have increased resistance which has inproved cutting thicker steel but this increases current and would prefer to keep the current down.
Cheers
DS
Hey GJunkie!
Sorry for the delay in answering.. Life called and I had to answer!! I got to meet my daughter for the 1st time just a few days before her 1st birthday and have been making regular 1000 mile trips to deal with all that entails!
OK.. back to car stuff!!!
Caps: You have to connect the caps to the DC side otherwise it won't work (or will work, but not nearly as well!). Caps store energy and if you put them on the AC side, the alternating cycle charges and discharges them instantly (ok, 60x a sec..), but if you put them on the DC side, they accept the increased voltage, store it and then discharge it all at once into the work, creating the plasma arc you need to cut.
Cut Depth: While trying to keep the amperage down yet cut deep, is the holy grail of the DIY PC units. Since we typically have rudimentary controls, our only real variable is air pressure. Increasing the air pressure (to a point) will help cut thicker materials. Unfortunately this has limits, because if you increase the pressure too much you blow the arc out the tip and either damage the tip or make horrible stuttering cuts.
I found a secret to this effort, allowing me to cut 3/8" easily as I would 1/8"! That secret... Drill a hole! If your cutting a 3/8 plate, drill a hole within about 1/8" of your starting point in the same line as the cut. The hole only needs to be a bit bigger than the hole in the tip.. I tend to use 1/8" bits
Why you ask? Think of it like a lens on a laser in that what it does is force ALL the plasma into a single channel and forces it to make the cut where you want it instead of going in any direction the material or tip send it. Once started it's easy to run from there. Then you simply cut the remaining 1/8" section between the parts from the edge. I have used this several times to start cuts in thick pieces or in tubes with great success. It will gouge start, but this assures that I can control not only the molten spray, but have minimal dressing to do.
The "starter hole" method combined with air pressure manipulation (up to a max of about 48psi before the tips paid a price!!) have let me cut pieces that I didn't think I could have. Using a new tip on the thicker cuts also helps, but that would be the same on any unit, even purchased ones.
Hope this helps you to obtain better cuts from your unit. Love to see some pics of what you ended up with!
Cheers!
KS
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