Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Davek0974 on January 16, 2016, 10:30:48 AM
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Can someone have a look at the video clip I have linked below?
It shows my Mach3 plasma screen before a file load, during file load and then when pressing my "Set Origin" button.
As you will see, the Z is happily parked at 14.991mm which is where it really was after the end of the previous run. When i press set-origin it jumps to 0.437mm then to -0.9mm then to 0.437mm where it stays. The actual axis does not move - just the DRO freaks out and leaves a meaningless reading on it which puts it in a bad position for a dry run on a new file.
The 14.991mm is wrong as well because my final Z move is always to 15mm dead, the difference between 15mm and 14.991mm is the reading of the "THC Adjustments" DRO when the last cut finishes, if i run with THC off it always ends on 15mm dead.
Here is a link to a video showing what I believe to be odd behaviour of my Z-axis DRO.
https://youtu.be/WCmHRbIpm1o (https://youtu.be/WCmHRbIpm1o)
Is there any logical reason for this, or a cure maybe???
The set-origin button does this...
DoOEMButton(1008)
Sleep(500)
DoOEMButton(1009)
Sleep(500)
DoOEMButton(242) 'Copy X Y Z to G54
Sleep(500)
DoOEMButton(160) 'Regen Path
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Just so I do not have to do a search to figure it out is this a LPT ver or an ESS version ??
(;-) TP
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Comment out the last 4 lines of the button code They are not needed.
IF yo insist on using it then add in another line at teh end
DoOemButton(1010)
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I should have mentioned, this is a parallel port system with a CandCNC Mp3000-DTHC2 on it.
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Comment out the last 4 lines of the button code They are not needed.
IF yo insist on using it then add in another line at teh end
DoOemButton(1010)
Hmm, will try that out tomorrow but I have found odd things happen if the tool path is not reflecting the actual setup - this needs the regen line adding back in.
No idea why this line is there anyway DoOEMButton(242) 'Copy X Y Z to G54 ??
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By simply resetting 0,0 you will NOT change any thing in the toolpath other than where 0,0 actually is. It will NOT effect teh cutting nor even change teh toolpath unelss you are 9 miles off teh tool table in relation to teh toolpath.
Test it you will see (;-) You do not need to regen to make it all work correctly. When you regen you are recycling ALL of teh G28.1 in the file THAT is what effects teh Z values. Same if you try to do a Run from here. The Z will end up WAY OFF position.
Now if you MUST have it then you need to program around teh problem. At the beginning of the script record teh actual Z value and save it to a variable then after teh Regen routine runs reapply teh Saved Z vale BACK to the Z DRO value. I do the same trick for teh Run From Here routine so I do not have to worry about remembering to reset teh Z value back to position before it runs. BUT that is another chapeter in teh CNC plasma cutting book Making teh Run from here work properly so that you can restart Plasma cutting. AND YES teh RFH in Ver .067 is different than other versions (;-) It looks like Art tried to fix it for Plasma cutting but did not quiet get it right.
(;-) TP
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Hi again ;)
My set-origin button was created by someone on this forum I think, many moons ago, i just asked for what i wanted and that was offered up :) It gets used a lot but was told it needed the regen in there, so there it stayed, it is a total PITA though as it can take some time to regen a big file.
I will play with this tomorrow and see how it plays without that feature and if needs be then storing the Z and replacing it is the way to go.
Sounds like you really could write a book there, ever thought of it :)
In theory, my Z DRO should never be off of 15.00mm between cuts, let's see if I can attain that goal.
This still does not explain the small offset related to the THC adjustments DRO but thats always a small amount - still very annoying though as the last line in the code is Z15.00 and it never gets there :( Unless the tHC is off.
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IF you want a quicky test Load your cut file then where 0,0 would normally be set hit zero axis X zero axis Y the do a regen to set teh toolpath exactly .
NOW simply move over to a new Origin Hit ZeroX then ZeroY then look at teh toolpath it is basically the same with just teh cross hairs moved over to the new 0,0 . It will be that way UNLESS you make a move that is WAY off teh table size then it will show the far off offset.
I spent YEARS working with Mach3 plasma making all kinds of time saving gizmos for the shop here. They cut 5 dys a week 8 hrs a day most of teh time. This like autorestart of a torch cutout. auto indexing right , auto indexing up , Preveiw cutting, G68 rotation to fit teh part to the material,etc,etc. I was using teh Sword and T word long before it was popular to do so (;-). When CandCNC came along here I heaviely redid a lot of the functions like I used his Cut table and Mach3 tool# to autosetup cut files based on the tool#.
But like I said that is another story. I tried to get the Website to setup a specific plasma cutting section but that never happened so a lot of things over the years just all got blended into the mainstream Mach3 stuff. ANd A lot never made it here. I have stacks of notebooks somewhere on teh plasma CNC process and Mach3.
(;-) TP
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If we ever meet, i'd buy you a pint, but bring your notebooks ;) ;)
I will be trying this out tomorrow, I was just always led to believe that the toolpath display actually had more relevance, it seems not.
Don't go anywhere, I may have several hundred more questions :)
And yes a plasma section would have been cool, it's not really the same as mills and lathes, needs a different touch.
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YEP there is an ART to plasma cutting that most millers or routers do not understand. The real trick is to maintain Constant velocity for cutting. Slowing down for a corner does not make any sense for plasma cutting (;-)
THAT is another chapter in teh book(;-)
(;-) TP
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Yep, IMHO, the hard part is building a machine capable of doing CV at all speeds, if it even exists?
My latest build gets close (ish), I think to improve I should have gone with servo motors and closed loop motion control, would likely have to mortgage the house to pay for it all though :)
In reality, CV is impossible though surely? The machine MUST come to a stop to do a sharp 90deg corner??
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In reality, CV is impossible though surely? The machine MUST come to a stop to do a sharp 90deg corner??
Not really as you can, I would imagine, do as you would with a mill or router. Roll round the sharp bend at the radius of the cutter, or kerf width in the case of plasma. That means you do not have to stop as you would in Exact Stop mode.
Of course it will never be exact but if the acceleration is decent on the machine it will be more or less undetectable.
Hood
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Good point, I don't run a mill or router but have seen the diagrams of rolling around a corner producing a point, I guess it would be the same, thanks.
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Back to the topic, the new, reduced set-origin button works perfectly, setting "G28.1 No Initial Move" to OFF has made the Z rapid down to the Z value in the G28.1 command - brilliant.
A short video of the final setup making a couple of cuts...
https://youtu.be/FV6WpuQjFE0 (https://youtu.be/FV6WpuQjFE0)
That just leaves the fact that if the THC does not finish at zero as it started (which it never does) the difference between my 15.00mm safe height and the final THC adjustment is what shows in the Z DRO even though the machine was told to go to Z15.00 at the end.
Now, I have a theory -
The THC adjustments DRO is updating the Z DRO AFTER the machine has finished - the cut completes, the machine goes to Z15 as commanded but then the THC system adjusts the Z DRO to a wrong value.
I see no reason why the THC should deb adjusting the Z DRO though, I will post this again on the CandCNC forum, probably won't get anywhere again though.
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Interesting method for deployment of the switch, might be worth considering something similar when I build mine :)
Hood
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Looks good from here(;-) Good Job. One thing I do notice is it may be a problem with a heavily nested cut and using an offset probe as teh probe could easily end up in a hole from a previous cut. Maybe consider a compromise of your earlier design where teh Air cylinder was on a slight angle to help slide teh probe tip under teh Torch tip ???
Also keep teh sliding Z as a backup to the touch probe. Even though I have RARELY ever seen teh G28.1 fail to cycle. But a backup would be nice to have set up as a safety. IF you do not have a breakaway torch mount each time you crash the head and break the torch insulator sleeve it is a $100 bill.
BUT then you get to learn how to get GOOD at repairing those sleeves (;-).
(;-) TP
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Thanks
I did think of the switch falling into a hole but the arc it travels is very small and lands exactly where the torch would, I have been messing today and tried tight spacings, near-edge etc and all worked fine, if it would work with the torch, I think it will work with this. A true edge-start might be tricky, don't know yet, never done one.
The sliding Z is staying and i will be moving the limit switch wiring to the e-stop circuit as the limits do nothing when g28.1 is running, luckily I wired every switch with its own cable back to the control cabinet.
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IF you have ever watched a real comercial plasma cutter OR laser cutting thin sheet goods they are WICKEDLY fast on Accelleration. Most use an Scurve planner that makes it not only wickedly fast but very smooth . Almost ALL runs servos. There are also designed with very low inertia Drives and gantries and are very rigid as well.
Now that said A well planned Mach3 CNC plasma is a GREAT machine for the money and the normal useage for the average users.
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IF you have ever watched a real comercial plasma cutter OR laser cutting thin sheet goods they are WICKEDLY fast on Accelleration. Most use an Scurve planner that makes it not only wickedly fast but very smooth . Almost ALL runs servos. There are also designed with very low inertia Drives and gantries and are very rigid as well.
Now that said A well planned Mach3 CNC plasma is a GREAT machine for the money and the normal useage for the average users.
Low inertia, high rigidity is the holy grail I think, very hard to do.
Personally I am very pleased with my table, for what it cost i think it's amazing, even more so when, after a couple of days messing around I have improved it ten-fold :)