Simple Mechanized Oxy-Fuel Cutting

[finleysh1]

First and foremost I am very new to mechanized oxy cutting so I apologize for what might be considered elementary questions. I am trying to use a single solenoid valve set-up for doing oxy-propane cutting with a 3 hose torch. The set-up is very basic (schematic attached), using a manual valve (and flow valves on the torch) to turn on the propane and low pre-heat. The cutting oxygen is activated by a solenoid which I am setting to the tip chart oxygen cutting pressure minus the low pre-heat value such that the combined pressure of the low pre-heat and cutting oxygen total the recommended cutting oxygen level. I am getting fairly good pierce times and cut edge quality by using only a low preheat (no high pre-heat) on material ranging from .5"-1" (i.e. 30 seconds).

Question #1- I seem to be getting excessive blow back during pierces. I am piercing at .5" off of the material and find that I am getting the best cut quality at that height as well. From what I have read this could be a result of excess pre-heat, but based on the fact that I am only using a low preheat I find this hard to believe. Any input on reducing blowback? Is this pierce and cutting height the culprit or is the pre-heat time window between piercing with minimal and excessive blow back very narrow?

Question #2- I am getting quite a bit of slag on the top side of the material during the cut while cutting at the recommended feed rate. I have been able to diminish this condition quite a bit by increasing my cutting speed from the recommended 15 ipm to 22ipm. Are their other considerations for topside slag that I should be trying.

Question #3- When cutting holes in the 1:1 material thickness range I am finding that the cutout material really becomes just a ball of molten metal that is incredibly difficult to remove from the part. Is the avenue to improve this condition to have "small" holes in the range of 1:1 cut at a faster feed rate. i.e. if I am getting good cut quality on profiles at 22 ipm, cut small holes at say (just throwing a number out here) 125% [27.5 ipm] to reduce the heat on this concentrated area?

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[millman52]

.5" Preheats on my machine in apx 22 seconds, however I have High preheat setting That I control through a homemade box using solenoid valves & flow tubes to regulate post preheat flame to a manageable level. Also, I am using Propane/Oxygen. 1" steel preheat is 27 seconds with the high preheat. Without it more like 1 1/2 min.

Small holes, Yes, I run a much higher feed rate Probably double.