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Cutting a 45 degree bevel on 3/8" plate

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WyoGreen
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Cutting a 45 degree bevel on 3/8" plate

Postby WyoGreen » Mon Nov 06, 2017 8:51 pm

I'm working on a project that requires a 32" long, 40 to 45 degree bevel on a piece of 3/8" plate. I've rebuilt my magnetic torch mount to enable me to set the torch to any angle I wish. That turned out really nice, if I do say so myself. ;)
I've got ohmic sensing, so touch off should be no problem. The thing I'm asking for help on is the pierce distance and cut distance. Since I'm sensing the metal top with the corner of the torch head rather than the flat of the torch head it makes sense to me that those distances will have to be adjusted to account for this offset.
So, has anyone done any bevel cutting like this, and did you have to adjust any settings to do it?

Thanks, Steve
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Re: Cutting a 45 degree bevel on 3/8" plate

Postby djreiswig » Mon Nov 06, 2017 9:20 pm

I have not done any beveling, but I assume you would still need to maintain the correct torch to work distance. You might have to reduce your cut height setting to account for the inaccurate referencing.
I'm interested in seeing a picture of your torch mount.

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby Bobkovacs » Mon Nov 06, 2017 9:36 pm

You'll probably have to use settings that are based on the length of the bevel, not on the thickness of the plate. A 3/8" plate being beveled at a 45 will have a little over 1/2" of actual length on the bevel

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby _Ogre » Tue Nov 07, 2017 11:26 am

i cut a lot of holes in tube clamped to the table, the bigger the hole the greater the angle as you drop down the side of the tube
my setup was thru experimentation and manual g-code manipulations, at one point the cut height is almost .25''; ugly but it works :mrgreen:

i'd do a little experimentation before cutting the finished piece, i doubt you will be able to use any tables to set up the cut
probably not going to get anywhere near .06 cut height, use the shield that will hold the tip as close to the metal as possible
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Re: Cutting a 45 degree bevel on 3/8" plate

Postby WyoGreen » Tue Nov 07, 2017 12:37 pm

All good suggestions. A little math (remember that stuff we learned in school?), tells me that the pierce height probably should be about .11 and the cut height will be around .04 because of touching off on the corner of the shield. It looks like the diagonal length will be about .5303, so 1/2" cut parameters should be close.

Ogre, while researching this, I came across a utube video of a robotic arm cutting bevels. It was amazing to watch it change the angle of torch as it moved around the shape. All you need to do is put a motor on your torch mount and figure out how to program it to change the torch angle as it moves down the tube. ;)

Another factor to consider (again from my research) is the bevel the torch cuts naturally, which from what I've read on here seems to be 1 or 2 degrees. I'll attach a picture of what I'm talking about. And after I've got this all working, I'll attach a picture of my torch mount and the finished product. One thing I might also mention is the Angle Grinder mount I've made for my table that I've used to square up the cut edge of the rectangular pieces I've made for this project. It works pretty slick and produces a pretty nice edge (after a few passes moving the y axis slightly each pass).

Anyway, off to play, Steve

Torch Bevel.jpg

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby mdwalker » Tue Nov 07, 2017 2:05 pm

If I were you I would try cutting a small hole, square, or whatever shape you want near the pierce point. Then I would use that to do an edge start for your cut. As stated above I would do some experimenting before you cut the final project.

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby WyoGreen » Tue Nov 07, 2017 8:04 pm

I got some practice cuts in today and learned a few things. I ended up with pierce and cut heights lower than my math indicated. The 1/2 inch plate settings were close, although I did end up slowing the feed-rate down some. Figuring out where the cut will actually be is also a fun thing. I set the torch at 45 degrees, and ended up with a bevel of 40 degrees. I suspect as I fine tune the settings that the bevel will change

Other things learned, it cuts better if you remember to reattach the plasma return cable after removing it to adjust something. It also cuts better with new consumables after changing settings a dozen times in an effort to get the torch to cut. :oops:

A picture of the torch mount.
DSC_0177.JPG


Also a picture of one of my practice cuts.
DSC_0180.JPG

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby djreiswig » Tue Nov 07, 2017 11:16 pm

Cool. Do you have to remove the torch to set the angle?

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby WyoGreen » Wed Nov 08, 2017 1:20 pm

Yes I remove the torch to change the angle, there is a socket head screw in the center of the torch mount hidden behind the torch. I figure that I'm not going to be cutting that many bevels, so it's not too big of a deal. I hold a digital angle gauge on the side of the torch mount to set oddball angles. I've scribed the common angles on the mounting surface so it's easy to set to 30, 45, and 60 degrees. The arc shape compensation talked about earlier also plays into the angle setting. Test cuts on the left side of the arc yielded a greater angle difference than test cuts on the right side of the arc. Right now that right side difference is about 5 degrees. The left side was almost 20 degrees. I think the arc shape compensation will change once I get the torch dialed in. One of the problems you run into is the distance from the center of the torch to the material changes with the angle, so you have to come up with different pierce and cut heights for each angle. On really shallow angles, it's impossible to get the cut height to the desired .060 because the edge of the shield hits the plate.

This is my 2nd generation torch mount, and I've already got in mind generation 3, which would involve a worm gear so you could just turn a screw on the side to change the bevel angle. (That way I get to practice making gears on my lathe!) 8-)

Later, Steve
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Re: Cutting a 45 degree bevel on 3/8" plate

Postby _Ogre » Wed Nov 08, 2017 1:44 pm

looks like a pretty good cut :mrgreen:

i've seen those 7 axis robotic pipe cutters on you tube when i was researching tube cutting
pretty sweet, also pretty expensive :shock:

we have a rotary head for our bulltear table that works nice on straight tube
it's bent tube that needs the holes cut flat on the table
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Re: Cutting a 45 degree bevel on 3/8" plate

Postby WyoGreen » Thu Nov 09, 2017 10:39 pm

Got my part cut. Here's a picture of the part being ground smooth to the required angle with my first generation grinder mount. Note the high tech. grinder alignment pieces. (translation: I'm holding the grinder in alignment with chunks of scrap wood) ;)

Steve

image3344.png

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby SeanP » Fri Nov 10, 2017 4:36 pm

Interesting read!
Fair play to you for a bit of experimentation.
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Re: Cutting a 45 degree bevel on 3/8" plate

Postby jimcolt » Mon Nov 13, 2017 11:43 am

You simply need one of these industrial grade CNC plasma bevelers....this one from AKS out of Cleveland. Other companies that make them are Machitech, Hornet Plasma, Koike Aronson, Messer Cutting and more.

http://www.amirapress.com/tag/plasma-bevel-head

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby _Ogre » Mon Nov 13, 2017 12:35 pm

jimcolt wrote:You simply need one of these ....

one of these $75,000 attachments for your $12,000 plasma table :mrgreen: :mrgreen: :mrgreen:
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Re: Cutting a 45 degree bevel on 3/8" plate

Postby jimcolt » Mon Nov 13, 2017 1:08 pm

Last time I had to cut 45 degree bevels on a log splitter wedge I used wire ties and duct tape to hold the torch on its carriage at the right angle.....it worked great! Jim Colt Hypertherm

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Re: Cutting a 45 degree bevel on 3/8" plate

Postby WyoGreen » Tue Nov 14, 2017 11:06 pm

Wire ties and duct tape is much closer to my price range! :mrgreen:
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