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Holding tolerance

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S G Ryder
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Holding tolerance

Postby S G Ryder » Thu Feb 18, 2016 2:20 pm

Hello from the Gulf Coast,

Have a fairly new TM-3 machine and trying to use TM Cad. the machine will not hold tolerance. I'm not a veteran CAD user but would appreciate some direction as to how to fix this issue. Otherwise we can't risk scraping material or parts. tried to use the LIVE CHat and that proved fruitless.
So I'm hoping somebody here with experience with this machine can ofer a way to fix either my drawing issues or the machine issues. Very frustrated with the lack of concern by Lincoln folks. Thanks,

S G.

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Gamelord
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Re: Holding tolerance

Postby Gamelord » Thu Feb 18, 2016 3:46 pm

What do you mean "not hold tolerance?" Is it the height control, the gantry, etc... Also, what plasma are you using and what are your settings at, what are you cutting, material thickness and type. This will help us understand your issue and give advice.
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S G Ryder
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Re: Holding tolerance

Postby S G Ryder » Fri Feb 19, 2016 4:08 pm

Quite surprised at your question. don't want to play 20 questions just need some advice from a Torchmate 3 operator who understands what NOT HOLDING TOLERance means.

Hypertherm 65 PLasma
1/8" steel plate

I draw a 6 x 6 square plate and the machine wil NOT cut it 6 x 6. Or Hold the dimension programmed. It is a software hiccup I think but again would you or another owner to shed light on what is happening. have parts to cut but have NO confidence that we can make the part. I'm used to working with lathes and Mills. When working from drawings or prints you MUST HOLD TOLERANCE.

Does this clear it up for you ?

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Re: Holding tolerance

Postby muzza » Fri Feb 19, 2016 5:16 pm

S G Ryder wrote:Quite surprised at your question. don't want to play 20 questions just need some advice from a Torchmate 3 operator who understands what NOT HOLDING TOLERance means.

Hypertherm 65 PLasma
1/8" steel plate

I draw a 6 x 6 square plate and the machine wil NOT cut it 6 x 6. Or Hold the dimension programmed. It is a software hiccup I think but again would you or another owner to shed light on what is happening. have parts to cut but have NO confidence that we can make the part. I'm used to working with lathes and Mills. When working from drawings or prints you MUST HOLD TOLERANCE.

Does this clear it up for you ?



Great attitude for someone who asks for help and a fellow Torchmate user offers it :? :roll:

You have had a reply with an offer of help from one of the more experience and most helpful users on this forum and you shitcan him for trying to help you by asking some questions, maybe that tells us a bit about why you can't get the answers that you chase from Lincoln.

I'm a Torchmate owner and user too (along with 3 other setups) but I'd rather spend my time helping those who appreciate it and aren't so arrogant. :evil:

Good luck
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islander261
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Re: Holding tolerance

Postby islander261 » Fri Feb 19, 2016 5:28 pm

Ok, to repeat what Gamelord asked again, what is the out of tolerance problem you are having? Parts not square? Finished dimensions off, bigger or smaller than planned? What material and thickness are you trying to cut? What are the cut parameters you are using? What consumables are you using? Are they new or used? What is the kerf width your CAM is using? Is it the same as the kerf width from the Hypertherm manual for your cut parameters? What is the measured kerf width from your speed/voltage test lines? Please post photos of both sides of cut test pieces, there are many here that will help you. The TM tech was not trying to jerk you around all these things affect the cutting performance of a plasma cutting table.

I have a much modified Torchmate 2 table running TM3 controls that now resembles the drive on a Torchmate 3 table. These are among the lowest powered drive, least ridged machines in their class. Because these machines cannot independently home each side of the long side drive they will develop gantry racking over use and require adjustment. The low drive power means that they don't cut well at high speeds and accelerations (thin materials) without being perfectly adjusted. If your machine is not in good adjustment running with the correct plasma settings I consider (my opinion as a machine owner/operator) that 1/8" steel is the the thinnest a stock TM machine will do a good job of cutting without a lot of operator intervention (testing and adjustment). I routinely test with a " torture path" at my max cut speed to to test for lost steps. I can always get the machine to return to 0,0 +/- .003" or better measured with a dial indicator if everything is working well. Do you have the Torchmate manual? It is very complete on explaining the correct setup procedures. It is available on line if you don't have one.

You don't need to waste material if you think the problem is with the table mechanics or software settings. Use a Sharpy pen in the torch holder and draw on paper taped to a piece of steel. That way you can change settings without burning up a lot of steel. If you can't get the pen to draw the correct picture you have no chance of the machine working well on steel.

John

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Re: Holding tolerance

Postby Gamelord » Fri Feb 19, 2016 7:49 pm

Been running a Torchmate table for many years now and love it and would recommend it to anyone. it works perfectly for me, cuts perfectly on steel/stainless/aluminum ranging from 22 guage all the way up to 3/4" plate (max size for my plasma) and if I draw a 6x6 square, it cuts a perfect 6x6 square. It always returns back to home positon withing .05" or closer even after cutting a full size 4' x 12' plate. If your table is not holding tolerance, then you have a problem with either the gantry slipping and losing steps or your table is not square or your TMCad program is not setup correctly.

Notice that I didn't ask you any questions this time. Glad I was able to help you solve your problem.
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S G Ryder
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Re: Holding tolerance

Postby S G Ryder » Sat Feb 20, 2016 2:30 pm

First to GameLord:

I'm sorry if I offended you. this is one reason I do not like typed messages because it does not convey the heart. I'm trying to help a young friend of mine that spent his very hard earned money on this Torchmate 3 machine which is new. He has owned it about 2 months. We are now on our 3 Accumove box from Lincoln and one of their computers. My young friend had simply given up on ever being able to use it. So I tell him I will begin the process of learning all I can about the machine. I was not here for the set up of the machine so I haven't any experience with that but I'm not afraid to learn and take advice. So, GameLord, I'm way too old to make enemies, I am 70 and want to finish out my life making friends. You and John are the folks I want to learn from.

John, thank you for your response to my query, my friend got a thumb drive with the machine and I don't know if that has a complete manual on it but I will look at it and see. We went through the set up of the table and Gantry again and as best as I can determine there isn't any slack in the gears and racks but I'm willing to redo anything to get the machine and me on the same page.

I made a drawing in the torchcad of a part we are hoping to be able to produce. It was from a print and I plugged all the correct dimensions into TorchCad completed the drawing saved it and also created a GM file which we took to the machine thinking we should be correct. The machine cut the internal holes and slots correctly but the overall piece was undersize by 1/32" on both the X and Y cut.

The consumables are correct according to the Hypertherm manual for the 1/8" steel plate. I can get the numbers off those pieces also if you need them.

Thank you for the suggestion of paper and magic marker. The Kerf setting you spoke of... Is that in the TorchCad program or the VMD program. If those are settings which were made on set up then I need to go through them and check to see what they are. I honestly feel like it is somekind of software setting because the machine hasn't been used enough to have worn parts. The square of the table we can check.

We have been using 70.000"/m cutting speed

Thank you for your help and suggestions.

S G

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Re: Holding tolerance

Postby Gamelord » Sat Feb 20, 2016 9:03 pm

One thing to check is are you cutting stright from the drawing or are you using a tool path? If you are cutting straight from the drawing then the kerf of the torch cut will make your part undersized. In the TorchmateCad program, there is an area to create a tool path, this will allow you to set up your cut directions as well as set the sequence in which your parts are cut. Normally you would cut the inside parts first, then the outside cuts. To create your tool paths (cut paths) load your drawing into TMCad and then from the menu drop down you will find "Create tool path" You can select female or male for your tool path. Female will cut on the inside of your object (holes or slots in the piece) and male will cut on the outside of your object (outside cut).

Once you create your tool paths, you will want to delete your orginal drawings, leaving just the tool paths to be exported to the cutting program. In the settings of your tool paths, you should be able to set your material settings and kerf (offset) settings. When exporting your tool path, make sure to use a different name from the original drawing so it doesn't overwrite your origial drawing. I.E. If your file is called 6insquare.dxf - I would export the file calling it 6insquare-toolpath. That way you can always go back to your original should you need to change something.

This should fix the issue if your cutting straight from the original drawing. If not, then you may have an issue with your gear ratio settings in the torchmate cutting program. Not sure how big your table is, but if it has an 8 ft. bed, draw a single line drawing that is 8 ft long and set up your table to cut it (but dont actually cut it, just run the torch through the cut motion), start at the very bottom edge of your plate and then run the program without cutting so the torch thinks it cuts from the starting point to the very end of the 8 ft. cut line. Stop the torch at that point and measure to see if it is at 8 ft. (if you only have a 4' bed, then use 4' instead of 8ft. ). This large distance will show you if there is any problems with the gear ratio's. If it runs out at 8 ft then you are fine. If it runs out and is a couple inches short then you most likely have a gear ratio problem. In your torchmate cutting program, you will have a setup page that lists the gear ratio's for your x and y axis motors. In there you can adjust the ratios as needed. Your manual should have the exact number but you can tweak it as needed until you get it exact. Run the test a bunch of times just to make sure that you aren't actually getting some kind of slippage in your gear motors or gantry. If it runs exactly the same every single time in different areas and at multiple speeds (mostly high speeds) then you are probably fine and the issue is probably your gear ratio settings.

Because you are off 1/32, I would most likely assume that you are not cutting from an ofset cut path and instead, cutting directly on top of the original piece line. Your torch will have a kerf of 1/16" to 1/8" depending on what amperage and tip you are using. The tool path will offset this to compensate for the thickness of the torch kerf.

Hope that helps get your issue fixed. If you need more explanition on the above then let me know.
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Re: Holding tolerance

Postby gamble » Sat Feb 20, 2016 10:52 pm

Gamelord wrote:Been running a Torchmate table for many years now and love it and would recommend it to anyone. it works perfectly for me, cuts perfectly on steel/stainless/aluminum ranging from 22 guage all the way up to 3/4" plate (max size for my plasma) and if I draw a 6x6 square, it cuts a perfect 6x6 square. It always returns back to home positon withing .05" or closer even after cutting a full size 4' x 12' plate. If your table is not holding tolerance, then you have a problem with either the gantry slipping and losing steps or your table is not square or your TMCad program is not setup correctly.

Notice that I didn't ask you any questions this time. Glad I was able to help you solve your problem.

Is that with a male toolpath? Or online path?
I had someone want something cut that was .500 wide and he designed it and it cut around .480 and customer just kept crying about it
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Re: Holding tolerance

Postby Gamelord » Sun Feb 21, 2016 4:59 pm

Gamble,

Your tool path needs to have the correct offset to compensate for the kerf of your torch. The kerf will vary depending on what your tip size is, amperage and model of your plasma. If your part is not cutting correctly to exact dimensions, something is not set up right. Keep in mind that plasma cutting is not waterjet or laser so tolerances will vary a bit more but most projects can be cut to pretty darn close tolerances and be acceptable to the cutsomer. If they need to go down to the .001 tolerance, plasma is probably not the right path to take.
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Re: Holding tolerance

Postby gamble » Sun Feb 21, 2016 5:16 pm

How do you adjust the offset on torchmate?
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Re: Holding tolerance

Postby S G Ryder » Mon Feb 22, 2016 4:28 pm

GameLord,
I totally redrew the part today and then Created Tool Path I Zoomed into the drawing and there was only one red line which I assume is my drawing. Then behind it was the black cut line which was centered on the red line. From that point I was told to simply go to Machine, then select Output, then select the G-code generator which is what I have been doing. Save the file then bring it up in VMD and cut the part.

Oh and we are using TorchCAD version 9 which I think is the latest version of the program.

So my statement to you is this: I have NOT Been exporting the file because my young friend had never mentioned this. So your suggestion of "EXPORTING" the file and changing the name. I have not been doing that so based on reading your message that could be the very reason that the part is undersized. I would just like to confirm that with you in case you might be using an older version of the Tcad/cam program where I know that was required.

BTW- the Test you suggested we ran and the machine is coming back to "0" within +/- .005" so I think that part we are confident about now.

Our table is 5' x 10' just so you have that info.

I'm feeling more like its a software issue now. I haven't run my latest cut file to see if I've made any difference in our final size.

I would very much like to PM you with the file so you could have a look at it and see if there is anything wrong with my drawing.

Thank you for the very nice explanation you sent in your last post for me.

Kind regards,
S G

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Re: Holding tolerance

Postby Gamelord » Mon Feb 22, 2016 6:52 pm

Your toolpath should be offset the thickness of your kerf. If it is right on top of your original part then there is no offset and the torch will cut right on top of the line. This is why your part is coming in undersized. The torch is cutting exactly on top of the line so half the kerf is cutting away your part, the other half is on the waste. If your part is coming in 1/32" short, your kerf is proably 1/16". This should be the setting for your offset for your toolpath. The toolpath must be oversized from the original part (on outside cuts) and undersized for inside cuts. i will have to check the version of my software but am away from my table for a few days.

The setting for your toolpath should be in the flyout menu that appears when you go to create the toolpath, along with the lead-in/lead-out and other settings.
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Re: Holding tolerance

Postby motoguy » Mon Feb 22, 2016 8:51 pm

Not sure if this will help or not, but this is what Gamelord is talking about:

Image

The grey line is the area that is cut by the plasma beam. The black line is the original drawing. If you need to cut an outside perimeter, you set up for an outside offset, as in the first photo. If you need to cut a "hole", or inside perimeter, then you set up for an inside offset (second photo). If you are not setting -any- offset, then the plasma beam is cutting right on your line...half in your scrap area, half into your part. This may be the cause of it being consistently undersize.
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Re: Holding tolerance

Postby S G Ryder » Fri Feb 26, 2016 1:18 pm

Just when I think its safe to go back in the water....Up jumps "JAWS"

Gamelord, I so wish I had your years of experience but I Know that all comes with time and effort. I'm willing to put out the effort if you can help me determine what is happening.

Again we are using TorchCAD Version 9 which does not require us to 'export' files into dxf format. We simply make a drawing in the small windows at the top of the program we can input our dimensions. Make path, then create a path, then go to "Machine" select "Output" to create our G-code then save it to our Thumb drive then take that to our machine computer and cut the part.

Yesterday, we needed a simple 7" circle cut out for a bracket we were building. I did the drawing to set the dimensions at 7", selected "Male" Path, saved the Toolpath took it to our machine, cut the part and the "OD" cut was 6.875". In the TorchCAD program the kerf is set .059" which is roughly 1/16" which computes in my mind to the fact that my part ended up being 1/8' undersized. The frustrating part for me is I don't know why its not cutting the correct dimension.

One other thing that the program does, when I plug in 7" OD and then create the path the dimension changed to 7.118" which I found out this morning and that is 2 x .059" which is the Kerf. Yesterday when I saved the file I changed that back to 7.000". My question: IS this why it cut it undersized?

Now, just for added information we were cutting 5/16" steel so we slowed the speed to 40"/m and it literally made a beautiful cut, it was simply undersized.

It is just so bothersome to me with my machining background to have a part not come out closer than 1/8".

Another question I have: Can this have anything to do with cutting tip,Ohmic cup, air pressure?

On a positive note we have cut some decorative pieces which I drew up and they are gorgeous, but we weren't concerned about "holding tolerance". It really gave us a boost to at least have some pieces which we can sell.

Thank you for your patience with an "Old Dog" learning a new "trick"! <smiling>

SG

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Re: Holding tolerance

Postby exapprentice » Fri Feb 26, 2016 1:51 pm

Hi S G Ryder

using your "machining background" Just think of the kerf as a cutter diameter on a mill when using digital read outs
If you want to machine a square 5"x 5" you must allow for the diameter of the cutter, other wise you will cut the 5" x 5" square under size by the size of the cutter you are using.

you say "One other thing that the program does, when I plug in 7" OD and then create the path the dimension changed to 7.118" which I found out this morning and that is 2 x .059" which is the Kerf. Yesterday when I saved the file I changed that back to 7.000". My question: IS this why it cut it undersized?"

Because you changed the setting back to 7" so it cut 7" minus the kerf around your circle (2 x Kerf = undersize)
If you had left it at 7.118" and your kerf is 0.059" then it would cut a 7" circle I think :?:

But then again I am probably wrong and some one will tell me why, only trying to help ;)
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Re: Holding tolerance

Postby Gamelord » Fri Feb 26, 2016 8:35 pm

One question, when you cut the 7" circle, does the cutter cut it one time or does it run around it twice?

If it seems to be cutting twice, then your problem is that you are not deleting the original drawing when you send your g-code to the plasma. Your version is newer than mine so you obviously don't have to export. No problem as long as you are getting your g-code to your cutter ok.

When I create a drawing, I load it into TorchCAD, from there I create all my tool paths (male & female as needed). Then when I have the tool paths created and my lead-in's & out's done and my order of cut set, I then go and delete all parts of the original drawing, leaving ONLY the tool paths. Then I export the tool paths out so the plasma to cut. (You obviously don't need to export). If I don't delete the original drawing, it exports both the tool paths AND the original drawing to the plasma to cut.

You may actually be cutting both the tool paths (giving you the correct offset) AND the original drawing which is why your parts are coming out undersized.

If it is only cutting once then what I would do is to play with the offset setting (kerf) in TorchCAD. If every piece is coming out undersized the exact same, I would just increase the offset so that it compensates for the difference. So if the piece is undersized 1/8", I would increase the offset in my tool path an additonal .125" so your total offset in TorchCAD is .184" It is possible that your kerf setting in TorchCAD is expecting the ENTIRE kerf width and then adjusting it appropriately, if that's the case then .059 may be much to small. My machine has a kerf of .095 when cutting 30A. It has a kerf of around .187 when cutting at 80A.

Give those a try and see what happens.

Also keep in mind that different nozzles and amperage will change the kerf size and you may need to edit from time to time. My TorchCAD has a setting for materials where I can set up different paramaters for different sized and/or types of materials including offset settings. Cutting 3/4" is much different than cutting 22ga. :)
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S G Ryder
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Re: Holding tolerance

Postby S G Ryder » Wed Mar 09, 2016 5:05 pm

GameLord,

Thanks to your excellent advice I'm satisfied that we are cutting as accurately as is possible with Plasma. So thank you for your patience and help.

Now, I have another question about the machine not finishing a job. We've had two different signs which I drew up and everything seems fine with my drawing and G-code however the machine did a nose dive into one of the projects breaking the torch off the magnetic holder and we essentially lost a very nice piece of material. Today on the second sign (we've cut a lot of stuff without incident) however today we were about 3/4 through with a sign and suddenly the machine just quit after completing a letter of Text. Very frustrating to say the least. I'm hoping you can shed some light on this subject

So as my Mentor is it possible to edit the G-code up to that point where it stopped cutting and then get the machine started again to finish the project?


Also, does my saved file have a way of letting me know where "Program Zero" is? Or is that necessary if I want to edit the G-code?

I'm hoping this is possible so I can complete this and any future projects where the machine simply quits of NO apparent reason.

Thank you,
S G

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Re: Holding tolerance

Postby S G Ryder » Wed Mar 09, 2016 5:10 pm

Oh and to Exapprentice, please accept my sincere thanks for your excellent analogy. Great way to begin my new "Learning Curve" on Kerf versus tool diameter.

Thanks for your input...

S G


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