Proma SD Voltages

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FeralCutter
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Proma SD Voltages

Post by FeralCutter »

Hey guys I've been lurking for a few months and I could use your input on some issues.

I've got a home brew Mach3 table setup that we started building in February and have had it cutting for a while. I'm using a 45XP with the machine torch and regular consumables. I'm also using a Proma SD THC with the 45XP 50:1 voltage divider setup. And we are using the ohmic cap and have the touch-off's prior to each pierce working great. We also have a magnetic breakaway setup.

The THC seems to be working on 10ga and thinner material. The THC seems to be making adjustments as cuts are made and the cut quality is OK. We have done some tests with the material at an angle and the THC adjusts the height as needed but the voltages we are running are quite a bit different than the 45XP spec. When we jump to 1/2" using the Hypertherm book specs we are running into all types of issues. I think it's THC related and I'm wondering what voltage we should be using on the Proma. We've tried all sorts of voltages but end up diving into the plate and damaging the consumables or going too high and not cutting. We can't seem to find the secret sauce to make it work. Piercing the center of a .75" circle seems to be one issue because the dross build up is so high it knocks the torch off sometimes. We've tried changing plunge rate and pierce delay. We are not sending the arc OK or arc transferred signal coming from the 45XP to Mach3 so that could be affecting the pierce delay. I think what we could really use is real world numbers from someone using a Proma SD with a 45XP on 1/2" plate.

Is anyone out there that is running the Proma SD that can share your setup details or anyone with advise on how to troubleshoot further?
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Re: Proma SD Voltages

Post by acourtjester »

What I have seen with my own use and another person's is the Proma sometimes works better using the raw plasma voltage not the 50:1. Both were with a Hypertherm PM65. I know others have use the 50:1 successfully,
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FeralCutter
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Re: Proma SD Voltages

Post by FeralCutter »

I can give that a shot if I can find a raw voltage kit for the 45XP or hack one up myself. The manual is online and seems to be just a cable more or less.

Do you run book specs using raw voltage?
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Re: Proma SD Voltages

Post by acourtjester »

yes sir very close
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Re: Proma SD Voltages

Post by Jtucker7000 »

I hesitate to offer any advice because I'm very new to cnc (<1yr) so take what I say with a grain of salt. I use a proma SD with a powermax 45. I use it with Mach 4 as a standalone solution because Mach 4 doesn't have thc control available with my setup. My settings are 94 while cutting, speed 100, d-t .7, h-t 200. These settings work all the way up to 1/4" for me but my stuff is far from perfect. I've never attempted to cut 1/2" with a pm45 Maybe it's more practical with the 45xp. I picked these settings through trial and error and it seems to work for me, I gave up trying to make my table perform to the book specs. If movement is too slow or the pierce delay too long it will try to drive the torch into the table. Are you using the proma SD to control the z axis directly or are you connecting the outputs to a breakout board and controling the z with mach3? The reason I ask is most people use the proma 150 with Mach 3 the SD I thought only worked as a standalone. If I was using mach3 I would use the proma 150 so I would have the benefit to turn off THC until after the pierce was complete, when slowing down, cutting small circles, etc....
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Re: Proma SD Voltages

Post by jimcolt »

A couple of comments.

-I hear from a lot of Proma (and other low cost THC solutions) that the voltages required for good cuts are quite different as compared to the voltages listed in the operators manual. Keep in mind that what you end if with for arc voltage settings does not matter....what matters is that the physical distance between the shield and the top surface of the material being cut stays as close (within .005" is recommended) to the suggested physical cut height (usually .060") as possible. Often, the lower cost electronics read a different voltage (than some of the better developed systems) because of the electrical noise and "hash" that is present on the analog DC voltage (it is there on the divided voltage output as well as on Raw Arc voltage)....remember that this is a reading of the actual cutting arc voltage between the electrode and the workpiece, it is not pure DC voltage. So....determine what voltage you need to set to achieve and maintain the physical cut height on each material and use that for your machines correct voltage setting. I find that in most cases you simply find that an offset (as an example....add 14 volts to the listings in the manual for each thickness) will compensate for the discrepancy.
- Keep in mind also...that the plasma arc is a resistor that varies in its resistance value. If air pressure varies the arc voltage across the arc will change, if there is moisture in your air the voltage will change.
- Keep in mind that changing the cut speed will require a voltage change in order to maintain suggested cut height. If you cut slower than the book says, you will need a higher voltage, faster will need a lower voltage.
- As the torch electrode wears...you need to add voltage to maintain height. a .06 pit in the electrode will make the torch move .06" closer to the material...and will cause the torch to drag. Better height controls have the ability to auto-compensate for electrode wear and even speed changes.

You will need to use the arc transferred signal from your Powermax. Mach 3 has inherent delays that affect motion, and if your pierce delay varies you can get short nozzle life, you can get slag piles that cause collisions, etc. By monitoring the actual arc (this signal sends a contact closure when current is sensed on the work cable...indicating the arc is cutting) and then starting a pierce timer....piercing will be more accurate and controllable.

Since every cnc machine will have a slowdown during fine features and corners...there should always be a height freeze that occurs whenever cut speed drops below about 90% of the programmed cut speed. This height freeze holds the height at .06" until the x and y speeds have accelerated....without this function expect the torch to dive when slowdowns occur.

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Re: Proma SD Voltages

Post by FeralCutter »

Jtucker7000 wrote:I hesitate to offer any advice because I'm very new to cnc (<1yr) so take what I say with a grain of salt. I use a proma SD with a powermax 45. I use it with Mach 4 as a standalone solution because Mach 4 doesn't have thc control available with my setup. My settings are 94 while cutting, speed 100, d-t .7, h-t 200. These settings work all the way up to 1/4" for me but my stuff is far from perfect. I've never attempted to cut 1/2" with a pm45 Maybe it's more practical with the 45xp. I picked these settings through trial and error and it seems to work for me, I gave up trying to make my table perform to the book specs. If movement is too slow or the pierce delay too long it will try to drive the torch into the table. Are you using the proma SD to control the z axis directly or are you connecting the outputs to a breakout board and controling the z with mach3? The reason I ask is most people use the proma 150 with Mach 3 the SD I thought only worked as a standalone. If I was using mach3 I would use the proma 150 so I would have the benefit to turn off THC until after the pierce was complete, when slowing down, cutting small circles, etc....
Thanks for the numbers, your about 8 months ahead of me so I'll take any input I can get.

The Proma SD does control the Z directly and seems to do a reasonable job of it but like you we are brand new at the plasma stuff. We built a CNC router several years ago but we've learned there are all kinds of new things to consider and learn. We use the ohmic cap on the 45Xp to sense the surface before each pierce and that mod helped quite a bit. I did not know enough to consider the 150 before I purchased the SD but I can see how it might help. The direct interface seemed more advanced.
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Re: Proma SD Voltages

Post by FeralCutter »

jimcolt wrote:A couple of comments.
-I hear from a lot of Proma (and other low cost THC solutions) that the voltages required for good cuts are quite different as compared to the voltages listed in the operators manual. Keep in mind that what you end if with for arc voltage settings does not matter....what matters is that the physical distance between the shield and the top surface of the material being cut stays as close (within .005" is recommended) to the suggested physical cut height (usually .060") as possible. Often, the lower cost electronics read a different voltage (than some of the better developed systems) because of the electrical noise and "hash" that is present on the analog DC voltage (it is there on the divided voltage output as well as on Raw Arc voltage)....remember that this is a reading of the actual cutting arc voltage between the electrode and the workpiece, it is not pure DC voltage. So....determine what voltage you need to set to achieve and maintain the physical cut height on each material and use that for your machines correct voltage setting. I find that in most cases you simply find that an offset (as an example....add 14 volts to the listings in the manual for each thickness) will compensate for the discrepancy.
So would you recommend any particular test to determine the correct voltage and offset. Maybe cutting straight lines and watching the voltage on the Proma? Would you recommend raw voltage over 50:1 for the Proma or will either work in theory?
- Keep in mind also...that the plasma arc is a resistor that varies in its resistance value. If air pressure varies the arc voltage across the arc will change, if there is moisture in your air the voltage will change.
How much difference will that make in voltage? Are we talking less than 5v or?
- Keep in mind that changing the cut speed will require a voltage change in order to maintain suggested cut height. If you cut slower than the book says, you will need a higher voltage, faster will need a lower voltage.

- As the torch electrode wears...you need to add voltage to maintain height. a .06 pit in the electrode will make the torch move .06" closer to the material...and will cause the torch to drag. Better height controls have the ability to auto-compensate for electrode wear and even speed changes.
Good to know!
You will need to use the arc transferred signal from your Powermax. Mach 3 has inherent delays that affect motion, and if your pierce delay varies you can get short nozzle life, you can get slag piles that cause collisions, etc. By monitoring the actual arc (this signal sends a contact closure when current is sensed on the work cable...indicating the arc is cutting) and then starting a pierce timer....piercing will be more accurate and controllable.
I've done some cursory searching but I'm not clear on how arc transferred works in Mach3 and that is why I'm not using it. I would
assume that the process happens something like this:

1 Mach3 reads gcode that causes the touch to do a touch off using the ohmic sensor
2. Mach3 sends Z to pierce height
3. Mach3 sends ArcStart signal to 45xp based on gcode
4. 45xp toggles arc transferred signal to Mach3 when arc is good and the torch is cutting and can start motion
5. Does mach 3 starts timing pierce delay from the time the arc transferred is received or when ArcOn is sent?
6. torch moves to cut height and starts moving/cutting
7. What happens if Arc transferred signal drops? Does mach3 stop?

Step 4 is where my understanding breaks down. In step 4 is there a gcode that makes Mach3 wait until the arc transferred signal is there?
Since every cnc machine will have a slowdown during fine features and corners...there should always be a height freeze that occurs whenever cut speed drops below about 90% of the programmed cut speed. This height freeze holds the height at .06" until the x and y speeds have accelerated....without this function expect the torch to dive when slowdowns occur.
I assumed (incorrectly) the SD would handle this but now I realize that it would have no way of knowing since all it has is the z axis signals. Sounds like the 150 would be a better choice. Not sure that the SD could ever handle slowdowns at corners etc without crashing. Does Mach3 somehow compensate or is the SD a flawed design?
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Re: Proma SD Voltages

Post by tcaudle »

The ARC OK (THC ON) signal in MACH is an INPUT. Its only on MACH3. While the Touch off , torch fire and plunge to cut height are all g-code controlled and have nothing to do with THC control, Arc ok signal is something used by MACH to perform a motion hold IF the (internal) THC logic is active. When you go to an external THC that does not use the internal THC logic then ARC OK won't stop motion because the internal THC is not used.

Unless the SP THC has a HOLD input that you could use to disable the THC FROM the control program then there is no way the external THC knows if the cut has slowed down or not. Even if you could rig an output to trigger the THC on/off its unlikely it will work with MACH3 and an external Pulse card because the timing would be all off. For velocity sensing it has to be real time (no delay between the software velocity and the real motion.
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Re: Proma SD Voltages

Post by FeralCutter »

The ARC OK (THC ON) signal in MACH is an INPUT. Its only on MACH3. While the Touch off , torch fire and plunge to cut height are all g-code controlled and have nothing to do with THC control, Arc ok signal is something used by MACH to perform a motion hold IF the (internal) THC logic is active. When you go to an external THC that does not use the internal THC logic then ARC OK won't stop motion because the internal THC is not used.
That makes sense, thanks for the input.

Sounds like I need a different THC if the Arc OK(or ark transfer) signal is important to the pierce and getting the cut started right. And add in the issue with slowdowns it seems the Proma SD is not really suitable at all. Or am I misunderstanding something?
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Re: Proma SD Voltages

Post by tm america »

I run the proma sd on my machines..Kind of odd seeing someone running one on a mach machine .Being that the sd uses step and dir to control the stepper driver.Not a torch up and torch down signal like you would use with mach...Usually one would use a proma 150 with mach as it has torch up and torch down signals..But that being said anything the senses voltage pulls from that voltage.. The proma thc draws from the arc voltage a fair amount so you will never see actual arc voltage on the screen but more of a modified voltage.. This is even more compound when you use divided arc voltage .. Especially since hypertherm doesn't list divided arc voltages in their manuals...
What i can tell you is that there is an easy way to set it and predict what your voltage will be for other thickness metals...So here it goes. This will only apply to machines using material sensing technoligy ..you will need to use all the settings right out of the hypertherm book other than the torch volts ..I like to do this with say 12ga steel..I start off with torch volts set at say 95 if i am running divided arc voltage with a hypertherm powermax 45 or 45xp ..Now with all the book setting for that material do a test cut. Once the torch finds the metal the torch will go to the pierce height and trigger the torch ..After it has reached its programmed pierce delay it will drop down to the cut height and start moving..AT this point it is at the correct cut height.It will start moving the x and y axis.. If the torch drops at this point you need to raise torch volts.If it raises you need to lower torch voltage..Once you have the voltage set where the torch doesn't raise or lower at the point you have your proper torch voltage for that material thickness.and you can look at your hypertherm book and see how many volts it differs from what is in the book..That is the number you will need to subtract from whatever the book says for a given material..Hope this helps ..i can help further explain it if you need
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Re: Proma SD Voltages

Post by FeralCutter »

Thanks for the reply, I'm just now getting back to this.

I'll give your voltage monitoring technique a try the next time we do some testing. Sounds like a great method.

We discovered a couple of things that were causing us problems.

The first is we had the 45XP set to gouge mode somehow. Not sure how that happened or how long it's been
set that way but things started working a whole lot better when that was discovered by my son. We must have
punched the button accidentally at some point. It's amazing we were somewhat cutting 1/2" steel in gouge mode.

I also discovered the post processor we had set to do a touch off before each pierce had reverted back
and was only doing it on the first pierce. With the Proma SD I think a touch off each pierce is probably a good thing.
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