THCAD-10 + hypertherm 45 (nonXP)

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03 Oct 2017 19:37 #99838 by robertspark
Looking at the test piece cut again (on a bigger screen than a phone...)

It appears you may have a slight bevel (inwards at the top), which may indicate that the torch is a little too high

image.thefabricator.com/a/articles/photos/1445/fig7.jpg

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03 Oct 2017 20:04 #99842 by skunkworks
I am certainly going to try to get torch height control working... :) (it is all there now)

sam

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03 Oct 2017 20:10 #99843 by rodw

I am certainly going to try to get torch height control working... :) (it is all there now)

sam


Sam, are you using the external offset branch?

Rod

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03 Oct 2017 20:14 #99844 by robertspark
The autoleveler was not to avoid THC, but provide a means to calibrate the THC if required given the Z axis will then track between points A-B and level according to the advanced probing routine (it won't work for long cuts and it won't work for thin metal or near the end of the cut where the metal may twist and bend upwards with expansion).

Plasma beds & slats always have slag on them and the plate is never level hence this is just one thing I thought may allow someone to set the z to track from A-B whilst monitoring the voltage so you know a constant 0.08" cut height IS XXX voltage.

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03 Oct 2017 20:37 #99845 by skunkworks
No - not currently. going to get it working in 2.7.mumble first

I am certainly going to try to get torch height control working... :) (it is all there now)

sam


Sam, are you using the external offset branch?

Rod

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04 Oct 2017 03:53 #99890 by kb8wmc
Just one more question for now. On the thcad-10 pinout on the pdf it shows connection 3 and 4 as shield, I thought I read that this is not the shield from the pin 13 on the hypertherm cable but frame/earth ground on the machine. Can some one clear this up for me?
And I want to thank all who have helped me through this. thanks

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04 Oct 2017 04:21 #99891 by rodw
I've connected one of these to the electrical cabinet and the other one to the cable shield. The cable shield should not be connected at the plasma end.
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04 Oct 2017 04:32 #99892 by kb8wmc
What do you mean when you say cable shield? There is 3 bare wires in the cable I bought from hypertherm. One stranded wire with each pair that comes in the cable. But is I use any of those I would be using pin 13 in the hypertherm cable which is ground.

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04 Oct 2017 05:18 #99894 by rodw

What do you mean when you say cable shield? There is 3 bare wires in the cable I bought from hypertherm. One stranded wire with each pair that comes in the cable. But is I use any of those I would be using pin 13 in the hypertherm cable which is ground.


I can't really help as I don't have a Hypertherm and made my own cable. Usually a cable is shielded with foil or braided wire. It is normal practice to connect this shield to ground at one end (eg control box end). The other end (plasma end) should not be connected. This is what I did. I also followed the same wiring for all my stepper motor wires.
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04 Oct 2017 10:20 #99910 by robertspark
Rod is correct

If your cable has a shielding or screening, then connect this to the shield pins (either pin, they are both soldered together on the PCB)

At the other end of the cable, the safe and normal practice will be to NOT connect it to the ground pin of the CPC (pin #13).

The shield terminal on the THCAD-10's purpose to to aide in removing electrical noise from the shielding of the cable.... only beneficial if you have an shield or a spare core in the cable to use as an electrical noise receiving core and you can use this via the filter circuit of resistors and capacitors to attempt to remove potential electrical induced noise.

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However like everything in life.... There is a catch.... And it all depends on your own viewpoint and wiring arrangement.

First are foremost you want to prevent any and all ground loops. These are where you may have multiple ground connections running in parallel and terminated at both ends. This is because you can get an eddy current forming around this parallel connection that may affect the signal.... It all depends how much electrical noise you have in the system. A good example of this is Variable Frequency Drives and the shielding arrangements required to prevent electrical noise and the shielding acting as an antenna and broadcasting the electrical noise signals of the high frequency VFD.


Like I said above..... It depends on your wiring arrangement.... I chose NOT to ground my table. My choice each to their own. The reason for this was because the table is connected to the clamp of the plasma cutter (I also connect the clamp to the workpiece, given if you connect only the table to the plasma clamp you are relying on the conductivity of the slats to the work to provide the plasma clamp to workpiece connectivity). Note I use the word "clamp" and not ground, because the plasma clamp is not ground polarity.

In plasma cutting, the clamp is (DC+) positive, and the torch (electrode) is (DC-) negative (the reason for this is electrons flow from negative to positive). The plasma cutter also has a ground or earth connection point as part of its power supply cable which is connected to the casing of the plasma cutter, this is also connected to the CPC ground pin (pin #13)

Given the plasma cutter has an isolation power supply within it, and also the way power supplies work here in the uk, (230v), the neutral conductor and the earth conductor are (more often than not) can be joined together at the point of supply (domestic supplies), called TN-C-S. I decided I did not want to bridge a perfectly good isolation power supply arrangement and effectively join the plasma clamp (DC+) to ground or earth.

earthing / supplies in the uk is discussed here at length:
electrical.theiet.org/wiring-matters/16/earthing-questions.cfm?type=pdf

Hence in my case, the plasma cutter is earthed / grounded at the point of electrical supply. My pc is grounded / earthed at the point of electrical supply, and my control case is grounded / earthed rather at the point of electrical supply.

All screened cables brackets to my control cabinet are grounded at one end ( the case end ).

The thcad-10 is electrically isolated between input (plasma connection) and output (7i76e), so I will connect pin 13 of the CPC to the cable shield and the other end of the shield to the thcad-10 shield connection. But this is only because it will provide better electrical noise cancellation because my plasma table is NOT connected to the ground / earth of my plasma cutter.

The official grounding arrangement from hyperthem is listed here should you wish to follow it.
www.hypertherm.com/Download?fileId=HYP103900&zip=False

However you probably want to consider how earth / ground is derived in your locality of the world. Here in the UK, we use the star point of the secondary side of the high voltage transformers to provide both neutral AND earth / ground and our power supplies are provided as live feeds with respect to ground at 240v, 415v (to domestic + light industrial / commercial)

In the US, you have "hot wires".... All are live (have potential difference between them and ground / earth) and a separate neutral connection.... Essentially US 220v appears to be derived from a multi tap delta transformer, hence each phase is tapped (connected in the center) which provides your neutral point. And I don't believe that the neutral are at the same potential as earth / ground. The center tapping of the 220V provides the option for 2 hot wires (with 220V potential difference) and either hot wire to neutral at 110V potential difference).

Hence in the US, the ground / earth point really is separate from the neutral or any of the "hot wires" (live feeds).... so grounding or earthing everything via a star topology is a good thing and will have less inpact in my opinion of grounding / earthing the table than in a scenario where the power supply neutral and earth are combined.

If you are running the plasma off 3-phase (400v {380 or 415V or whatever your locality flavour}) or odd ball 2-phase supply then earth / ground ground your table same as the US, just not on a single phase supply in my opinion.

Earthing and grounding can be very emotive discussions and they really are locality based and scenario based, each to their own + make your own mind up about your wiring after carefully thinking it through

A terminal may say zero volt, (0V) .... or ground (gnd) but is it REALLY zero volt or ground and with respect to what? Earth or the other wire?

Rob

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