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Blue Screen AVHC Hack

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islander261
Posts: 110
Joined: Sun Jan 12, 2014 2:30 pm

Blue Screen AVHC Hack

Postby islander261 » Tue May 05, 2015 4:29 pm

Hello

I have come to the conclusion that most of my cut quality problems are related to to poor torch height control. This is compounded by the fact that I only cut thin (14ga) sheet that is always floppy on the table, so if you only cut thicker plate most of what I have to say here may not interest you. I have a Torchmate blue screen stand alone AVHC that does work most of the time. This story is about my hack of this device to give it the ability to to use ohmic sensing to detect the plate and set pierce and initial cut height. The old blue screen AVHC senses the plate by driving the torch tip into it until the drive stalls and then lifts the torch the set distance for pierce height. This works pretty good for thicker plate (>.25" or 6mm) but doesn't work so well for thin floppy plate that just bends out of way and then springs back when the torch lifts.

First I want to thank Jim Colt for his patients in replying to all my previous questions about torch height control. It wasn't until later that I found several rather extensive threads over on CNCZONE where he explained the operation of torch height controls from the Hypertherm perspective in depth without sinking into the back biting and bickering of other posters.

Now as I progress through this keep in mind that this information is for educational purposes only. Some of the things I will describe can cause your equipment to fail or operate incorrectly resulting in all manor of mayhem, broken torches and possible personal injury not to mention lost production. Don't even think about trying this if you aren't absolutely sure you know what you are doing. I will not be able to help you reload the original firmware in your equipment if it doesn't work, I am sure that TM is unable to do this and will only offer to sell you replacement parts. You have been warned!

The AVHC is a pretty typical stand alone torch height control from what I can tell. There are two main parts, a controller that connects to the other parts of the plasma cutting system, and a torch mount/lifter that forms the Z axis of the table. So throwing caution to the wind I opened up the black box after first disconnecting all cables and the power cord. Inside I found a 24VDC power supply and circuit board that had most everything on it accept the keypad and LCD display. The arc voltage sensing circuit is about as simple as you can get and still have optical isolation. There is a single pole RC filter to limit bandwidth set at about 1khz between the optical isolation and the micro controller. The micro controller is a Cubloc CU280 plug in module. The details of this can be found on the Comfile Technology web site, http://www.comfiletech.com . I was disappointed when I read through the CU280 documentation to find that the program cannot be uploaded and reverse engineered by any method supported by Cubloc. So off to the web to find a hack, well no such luck I couldn't find any information on reverse engineering the software from one of these little things. Time for a new approach. Of course if any of you know how to do this I am all ears, please PM me.

The torch mount lifter looks like a pretty conventional setup with a small motor that looks like a stepper but isn't providing the motion. The motor connects to the control box with a multi conductor cable that has standard DB9 connector on the controller end and special DB connector on the motor end. The motor on my unit is a SM2315D made by Animatics, http://www.animatics.com/products/smartmotor.html . This thing is much more than just a simple motor! I realized that the motor is commanded by the controller over a standard serial link. But first I needed to learn as much about the little motor as possible. I will just be giving links to documents here because I am not sure about Plasmaspider's policy about posting others copyrighted documents. So I down loaded these for a little light reading:
http://www.animatics.com/download/legac ... uideV5.pdf
http://www.animatics.com/download/legac ... 100908.pdf
http://www.animatics.com/download/legac ... 23165D.pdf
http://www.animatics.com/index.php?opti ... _4_3_7.msi
Opps, I also included the link to the software needed to program the motor as well. I then made my self a crude breakout cable so I could snoop on the communication between the controller and a the motor, see photo. This is getting pretty long so it is time for a break.

John

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islander261
Posts: 110
Joined: Sun Jan 12, 2014 2:30 pm

Re: Blue Screen AVHC Hack

Postby islander261 » Fri May 08, 2015 6:04 pm

Hello

To continue on, I used my trusty sniffer cable while running hyperterminal in another window on my control computer. The default settings for the smart motor are 9600baud, 8 bits, no parity, 1stop bit and no flow control. With the plasma power supply OFF I went to the AUX control tab in the Torchmate 3 program and switched on the AVHC. Success, I got data displayed in the hyperterminal window! Next I commanded the torch on in the TM3 window and got more data displayed on the ht window. A quick switch of the connections to the monitor the data flow from the sm to the AVHC box. Repeating the previous and again data on the ht window. Ok now for a real test. I loaded a simple cut file (see photo) and set up system for cutting. I set up ht to capture the data from the AVHC to the sm in a file. I then turned on the AVHC and paused until it was ready to cut. I then started the cut file running. Sparks flying and data scrolling the crab was being cut out. When the cut was finished I save the capture file and shut the plasma power supply and AVHC off so I could change connections. See the edited (removed repetitive stuff to keep file small) file below. Once I had the sniffer cable connected so I could capture the data flow from the smart motor to the AVHC I turned everything on again and cut out another crab. Again I saved the capture file which is attached below. Wow, this is pretty cool. The AVHC only passes 4 different commands to the smart motor along with a few variables. The data from the the smart motor to the AVHC is even simpler, just a text OK to signal the completion of the command.

There appeared to be just 4 special or sub program commands sent to the smart motor, the rest where found in the smart motor language guide. The first was GOSUB0 which happened when the AVHC was turned on. This cause the Z axis to raise up against the top mechanical stop and then back off a short distance. The second was GOSUB1 which caused the Z axis to lower the torch and touch the plate and then raise to pierce height, fire the torch and lower to the initial cut height and then move. The next command is GOSUB2 which caused the Z axis to raise the torch at the end of the cut to the rapid height. The last command is GOSUB3 which is used along with sending height correction data when the AVHC is in the automatic mode.

Well that's all for now folks, I don't want to put anyone to sleep. The next installment will look at what I found for software in the smart motor.

John

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jimcolt
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Re: Blue Screen AVHC Hack

Postby jimcolt » Sat May 09, 2015 8:40 am

The biggest issues you with find with the Torchmate THC is that it is not intimately linked to the machine cut speed. Whenever the machine has to decelerate (corners, intricate details, etc.) the plasma burns a wider kerf (slower speeds, same power level) so the voltage increases, the height control reacts by moving the torch closer to the material to correct the voltage...often a collision occurs. Almost all other brands of cnc machines and height controls auto freeze the z axis when cut speeds drop below 85% to 90% of the programmed cut speeds, eliminating dive during slowdown.

Jim Colt Hypertherm

islander261
Posts: 110
Joined: Sun Jan 12, 2014 2:30 pm

Re: Blue Screen AVHC Hack

Postby islander261 » Sat May 09, 2015 1:56 pm

Hi Jim

The TM AVHC I have does have an input for corner hold. It causes the torch height to not be updated with the GOSUB3 command when active (torch holds at height when command received). Now it is controlled with an extra relay attached to the 501A signal generator. The TM3 software isn't smart enough to detect corners on it's own, at least I can't figure out how to make it happen. So I use two auxiliary G codes (M60 and M61)to control the relay. I then use the cutting rules in Sheetcam with a custom post to insert the required code just before each corner or small hole or arc. This is very similar to the way CandCNC does it, I studied several Sheetcam posts and cutting rules sets to figure out how this works. This works very well when cutting engineering pieces but is of little help with the artsy stuff I usually cut. What I have found for my artsy stuff is a long delay before voltage tracking keeps the torch at the starting height for short segments and I just have to live with what happens on long curves. This is actually the reason I finally bought Sheetcam, prior to this I was using the Gcodetools extension for Inkscape (free) for my cam. The real problem is with the TM mechanics which only allow reliable operation up to about 150ipm, I usually run a little less, and an acceleration of 12ips^2. I will modify the smart motor software to help prevent torch diving in the future but first I want to finish this thread on the basic hack. I am sure that the more sophisticated Sheetcam users can improve on my cutting rules and post to get better performance than I have.

John

islander261
Posts: 110
Joined: Sun Jan 12, 2014 2:30 pm

Re: Blue Screen AVHC Hack

Postby islander261 » Mon May 25, 2015 10:09 pm

Hello

Well life gets in the way of the best plans some times.

I took the magic break out cable and reconnected it so that the both data lines to the smart motor are connected to my computer and not to the AVHC. This allows me to run the Animatics Smart Motor Interface program. After several false starts I managed to get everyone talking. I uploaded the the program out of the Smart Motor, see stock program attached below. Well it is a pretty simple program and it is easy to see how it works with the captured data flow from the AVHC box to control the torch height. After saving the program in a secure place it is time to think about how I am going to control the AVHC system for better initial height sensing. I am thinking I want to add ohmic plate sensing to stop the TM smash and stall that is cause of much of my cut quality problems not to mention short consumable life. The Smart Motor has a number of external interface pins that can be configured to operate in a veriety of ways. One of the stock ways is as a travel limit input. I figure that an interface circuit that closes a relay or opto coupler should isolate the Smart Motor from the torch tip and the plate keeping all the nasty stuff (noise, high voltage) away from my control electronics. I wired up two wires to CN2 pin 3 (Positive Limit Input) and Pin 13 (Signal Ground) to act as my limit switch and ran them back to my CNC control station. I wanted to work out at least part of the software before getting near any torch tip voltages! I didn't save copies as I worked but I have attached below the listing of the final software I have on my Smart Motor.

It was a real chore to use the Animatics Smart Motor Interface software to download new programs to the motor, at least when it was working correctly I could drive the smart motor from it and didn't have to use the AVHC box for anything other than a power supply. So after finally getting everything turned on and the software down loaded I sent a GOSUB0 command from the terminal and the torch raised to the top of the Z travel setting the zero position when it backed one half turn off of the mechanical stop. Then I sent a GOSUB1 command from the terminal and the torch lowered till it hit the plate and raised back up to pierce height. this was looking good so I sent a GOSUB2 command from the terminal and the torch raised back up to Z zero position. Things where looking good. Now my control strategy was keep the code for the torch stall on hitting the plate intact because my mechanics don't have a floating torch holder and switch to act as a Z limit to protect the torch. This is why I dared to try this, actually I had a couple of sheets of cardboard on the steel plate to protect the torch tip. Now I had tested the limit switch wires by connecting them together and seeing the monitoring indicator on the Smart Motor Interface program change state so I knew that the Smart Motor was reading the signal. I sent the GOSUB1 command command from the terminal and while the torch was lowering I connected the wire end together. The torch stopped and raised to the pierce height and waited for the next command. Well I almost broke my arm patting my self on the back as I cycled the torch up and down some times stopping it with the limit wires and sometimes letting it hit the plate (cardboard) from the terminal program. Now it is one thing to use the terminal program but may well be another with the AVHC control box in charge.

The AVHC control box was reconnected to the Smart Motor. The TM3 control program was started. The AVHC control box was turned on and the torch raised up to the top of the Z travel and backed off 1/2 turn and stopped as always. With my plasma power supply turned OFF I selected the AUX controls menu and instructed the torch to fire from screen via the mouse (AUX 1 ON Button). The torch lowered and touched the plate and raised to the pierce height just as it should have. Selecting the AUX 1 OFF button caused the torch to raise back up to the rapid travel position (Z zero). Again I played with this several times to make sure it was repeatable and not some dumb luck. Now for the real test, I selected the AUX 1 ON button and before the torch hit the plate I connected the limit switch wires together and the torch stopped and raised to the pierce height. Disconnecting the limit switch wires and selecting the AUX 1 OFF button caused the torch to return to the rapid (Z zero) position. Yes this is going to work! Again many cycles up and down to try and find a problem. Now a bigger test was did the system still work without the limit signal being used, Again a small crab cut out later and things looked good for now.

Now all I had at this point was two wires connected to logic level inputs, quite a ways from a functioning ohmic sensor. I played around with a few circuit ideas and methods in my head and on paper but in the end I decided that why reinvent the wheel when I could buy one from C and C NC for about the same cost I could go out and buy all the parts for and still have to make and prove the circuit. So to the web and C and C NC's web site to order a Feather Cut ohmic sensor module.

http://www.candcnc.net/index.php/spare- ... 169-detail

The wait was on for the white truck (no UPS here only their delivery contractor).

John

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modelaratrod
Posts: 83
Joined: Tue Jul 23, 2013 12:41 pm
Location: Colorado

Re: Blue Screen AVHC Hack

Postby modelaratrod » Mon Aug 24, 2015 5:29 pm

Hey John have you made any more progress on this hack?
5x10 Torchmate 2 w/AVHC
Hypertherm PM85 w/ machine & hand torch.

islander261
Posts: 110
Joined: Sun Jan 12, 2014 2:30 pm

Re: Blue Screen AVHC Hack

Postby islander261 » Tue Aug 25, 2015 1:34 pm

modelaratrod

Yes, I have been remiss in not updating this thread. I have the Feather touch ohmic sensor working with my TM AVHC now. Now I get accurate touch off height with the flexy and not flat 14ga HR I usually use. The down side is the increased time it takes sense the plate surface.

John

User avatar
modelaratrod
Posts: 83
Joined: Tue Jul 23, 2013 12:41 pm
Location: Colorado

Re: Blue Screen AVHC Hack

Postby modelaratrod » Sun Aug 30, 2015 1:02 pm

Awesome!!! Great job.
5x10 Torchmate 2 w/AVHC
Hypertherm PM85 w/ machine & hand torch.

User avatar
modelaratrod
Posts: 83
Joined: Tue Jul 23, 2013 12:41 pm
Location: Colorado

Re: Blue Screen AVHC Hack

Postby modelaratrod » Sun Mar 05, 2017 10:00 pm

Islander hows the ohmic avhc working out?
5x10 Torchmate 2 w/AVHC
Hypertherm PM85 w/ machine & hand torch.


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