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MINIMUM AMP SETTING ON POWERMAX 45

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enzed
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MINIMUM AMP SETTING ON POWERMAX 45

Postby enzed » Tue Aug 15, 2017 8:16 am

According to the Powermax 45’s manual, the lowest amp setting is 30A for cutting mild steel between a thickness of 0.018” (26 Ga) to 0.060” (16 Ga). Yet the amp adjusting knob can be turned down lower than this, to 20A.

Considering that 0.018” is pretty thin, then under what circumstances would the amps be set lower - to between under 30 and 20A? This is confusing and an explanation and guidance etc. from the Hypertherm guys would be useful.
enzed

robertspark
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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby robertspark » Thu Aug 17, 2017 8:43 am

Don't know what your definition of a hypertherm guy is (employer or owner)

I am an owner, and setting the ampage lower allows for lower cutting feedrate. I was told by a rep from hypertherm that the book feedrates could be adjusted proportionally, although this was just a rough guide....

Ie freedrate at 30 amps is approximately 2/3rds at 20 amps for the same material.... You would need to tune this for feedrate and voltage though in practice

Rob

enzed
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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby enzed » Fri Aug 18, 2017 1:16 am

Hello robertspark,

By "Hypertherm guys" I am referring to an employee of Hypertherm, simply because being the manufacturers of the cutter, they are most likely to provide a detailed answer to my question. But obviously, if anyone else (such as yourself) can also provide an answer or guidance, it would also be much appreciated.

For me as a beginner in plasma cutting, what happens or what can be done at a setting of under 30 amps is unclear, nor does the manual for the 45 provide any guidance on this either. So what I was expecting from the Hypertherm manufacturers is something like a basic formula or rule which relates material thickness to amps, volts and cutting speed, for a particular type of metal, to give optimum performance and results.

Anyway, thank you for your advice, it points me in the right direction.

enzed

robertspark
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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby robertspark » Fri Aug 18, 2017 4:50 am

The book listed values are the optimum for best cut and production cutting.

The 30a and 45a are chosen as they match the design parameters of the nozzle (ie arc density of airflow and ampage)

By reducing the setting you go away from these optimum values.

These optimum values would have been obtained on a commercial grade machine (high acceleration, good step resolution, highly repeatable accuracy, ridgid and stable, with a constant air supply using moisture control with three stage filtration

There are other things that come into in like torch height control voltage..... Are you sure your THC is reading the voltage right... Is it calibrated... Does it suffer from drift... Component age or fatigue? Is it calibrated?

If you are new you have more things to worry about than ampage adjustment and optimization as even the weather can affect cut quality some times (hence there are things like moisture control on your compressed air)

I would focus on your table and trying to get the best acceleration you can from your setup, with a good rapid z axis for thc. And finding a good THC.

Ampage you can adjust easily and test and experiment with test cuts.

I unfortunately bought a 45 April 2016. About 6 months before the 45xp came out .... Pity as I really wanted an rs485 interface and will at some point have a go at hacking my 45 for arc control via digital pot (or DAC) as I'd like to be able to adjust ampage during the cut for inside corners to allow for a slowdown in feedrate

But the 45xp with rs485 interface to me seems a really great machine for full CNC integration (with the right CNC motion control software and motion controller that is)

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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby robertspark » Fri Aug 18, 2017 4:57 am

For the official response from when I asked hypertherm here you go


Problem statement:
Hello, I am in need of some general guidance on the Powermax 350, I've seen the operator manual, and page 4-7 provides the recommended feed rates at 25Amp for various material thicknesses. The question I have is do you have a calculation or table or publication that can show how the feed rates may be changed if the current is reduced from 25Amps (35% duty cycle) to 20Amps (60% duty cycle) or 17Amps (100% duty cycle). Any guidance would be greatly appreciated. Kind regards


On 15 Oct 2014, at 07:30, Technical Service EMEA <[email protected]> wrote:

Hi Rob,

There is no real rule for this; it would be more trial and error for these older systems. I would use the percentage of current drop relative to the speed decrease.

Regards,

Technical Service Engineer
Hypertherm Europe B.V.
Last edited by robertspark on Mon Aug 28, 2017 11:11 am, edited 2 times in total.

enzed
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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby enzed » Fri Aug 18, 2017 8:53 am

Thank you very much robertspark, much appreciated. Moisture content is taken care of, but I don't know the answers to your questions and comments about THC.

But what surprises me in all this is that there seems to be quite a bit of trial and error, and apparently with no set scientifically-based rules or guidance on the relations between amps, volts, material thickness, and cutting speed. So as you say, I will have to experiment and 'feel' my way forward.

Regarding the 45XP, I too bought my 45 six months before the 45XP was released, not knowing that an updated model was on its way.

Best wishes,

enzed

jimcolt
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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby jimcolt » Fri Aug 18, 2017 9:09 am

The cut charts listed in the Hypertherm operators manual are developed by cutting a lot of materials and thicknesses. The goal of these specifications is to provide good, repeatable cut quality in terms of edge angularity and minimal bottom dross.

With any plasma system you could cut 16 gauge steel at the minimum amperage setting or the maximum amperage setting. If we provided cut details for every possible combination of amperage for 16 gauge steel, we would likely have 20 different specifications (different speed, cut height, arc voltage, etc.), which would prove very confusing.....especially if you multiplied these 20 specs x all of the different thicknesses of steel, stainless, aluminum and other metals.

Every set of consumables has a designed in energy density (calculated as amps per square inch), and our process engineers choose the amperage setting with the known best density to develop the cut chart specs, because our experience shows the best results at this level. That is why you see a 45 amp nozzle most often used at 45 amps.

When you use a 45 amp nozzle at 30 amps...it produces a softer arc, which will provide a narrower "dross free" cut speed rang (the speed range between low speed dross and high speed dross).....which generally will make the cut quality worse.

So.....nothing wrong with experimenting. The amperage knob is there for that! My suggestions are: 1. Stick with the recommended pierce height, pierce delay and cut heights (physical torch to work distance). Expeiment with amperage, cut speed, cut air pressure, etc. I strongly recommend that you do not exceed the amperage rating of a particular nozzle (a 45 amp nozzle will not last long at more than 45 amps).

What do I do after 40 years of plasma cutting? I use the exact specs listed in the operators manual 99.9% of the time. If I experiment to fine tune the cut it generally involves changing cut speed (faster for less dross, slower for better edge angularity (often with easy to remove dross).

Jim Colt Hypertherm

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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby robertspark » Fri Aug 18, 2017 10:17 am

Thanks Jim for the insight

enzed
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Re: MINIMUM AMP SETTING ON POWERMAX 45

Postby enzed » Mon Aug 21, 2017 2:48 pm

Hello Jim,

Thank you very much for your valuable guidance, it is much appreciated. Because the 45's manual does not deal with amp settings below 30A, I was just not sure of what can be done with these lower settings and how. But your advice has certainly clarified matters a great deal and I will experiment as you suggest.

Best wishes,
enzed


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