Torch on timing question for Jim Colt.

[beefy]

Hi Jim,

got another weird technical question that I'm guessing you don't get asked every day. I'll consider myself lucky if you know the answer to this one.

Does Hypertherm have any timing specs that show how long the "delay" is from when the plasma cutter receives the TORCH ON signal from a dry relay contact, to when the plasma arc is established.

Likewise, is there any timing spec that tells how long the "delay" is from when the TORCH ON signal is removed to when the plasma arc current is cut off.

This is all to do with my little THC/controller project I've been working on forever. I've got the timing down to about 1 millisecond from when the motion controller gives a logic 1 output to when the relay contacts have closed, and likewise for opening. However, that's not so whoopy doo if the plasma cutter takes much longer than that with its reaction times.

This is all to do with having precision control and switching the torch on and off during motion, as well as doing hole marking with a very short arc on time.

My particular plasma cutter is a Powermax 1250.

Keith.

[jimcolt]

Keith,

Here is the timing diagram from the Powermax1250 service manual (which you can download from http://www.hypertherm.com )

Keep in mind that there is no set delay from when the plasma on signal is received and when the cutting arc is established. The pilot arc is established first, and if there is no current sensed on the work cable it will extinguish in 5 seconds (you can see that on the timing chart). At any time during that 5 seconds...if the arc is close enough to the material then current flow occurs through the work lead, that is when the plasma cutting arc starts (stepped current ramp up begins, this is for consumable life). So the time between the start input and the cutting arc is dependent on distance from the material.

Jim Colt Hypertherm

Hi Jim,

got another weird technical question that I'm guessing you don't get asked every day. I'll consider myself lucky if you know the answer to this one.

Does Hypertherm have any timing specs that show how long the "delay" is from when the plasma cutter receives the TORCH ON signal from a dry relay contact, to when the plasma arc is established.

Likewise, is there any timing spec that tells how long the "delay" is from when the TORCH ON signal is removed to when the plasma arc current is cut off.

This is all to do with my little THC/controller project I've been working on forever. I've got the timing down to about 1 millisecond from when the motion controller gives a logic 1 output to when the relay contacts have closed, and likewise for opening. However, that's not so whoopy doo if the plasma cutter takes much longer than that with its reaction times.

This is all to do with having precision control and switching the torch on and off during motion, as well as doing hole marking with a very short arc on time.

My particular plasma cutter is a Powermax 1250.

Keith.

[beefy]

Thanks very much Jim.

The timing diagram is great, I bet the cheap Chinese cutters don't have that.

I put the word "delay" in inverted commas because I couldn't think of a more appropriate phrase when I asked the question, not that I thought there was a delay where the plasma unit did nothing.

I like the ramp up idea for consumable life and I'm even wondering if that can help with avoiding start divots with a moving start. Will have to experiment.

If I've read the diagram correctly, at 45 amps the total time to reach the set current is going to be roughly 212 milliseconds, but for me the most important bit is the current turn off time and according to the timing diagram it seems quite instant which is great.

Keith

[jimcolt]

We design torches and consumables...then build the power supply around the process to provide the best performance in terms of cut quality and consumable life. It is a lot easier today with microprocessor based inverters as we have control over everything.

The low cost imports build low cost power supplies....then they buy whatever cheap copy of a torch that is low priced....bolt them together and start cutting. Consumable life on similar thicknesses and materials is often 1/10th that of Hypertherm units. You get a good price buying the system, but you pay much more over time as you use it. You also do more grinding!

Glad you could use the timing chart. You should download the service manual, there is a lot of good info there that could help. Jim