Cutting 1 inch thick bar

I work for a company that has 25 welding robots. We have converted 3 of the robots to plasma cutting. We are currently using Hypertherm air plasma on all the robots with excellent results. We currently own 2 Powermax 1250's and one of the new 65's We use them to cut scrap frames from press drawn parts. This has proven to be a very cost effective way to trim the parts. We do a lot of forming for Kubota. Plasma cutting has replaced many of their pinch trim dies which are costly to build and maintain. We cut hoods, floorpans, fenders, and mower decks this way. We normally cut steel gauges 18 thru 7 ga. Now we are going to cut a project on the other end of the scale. We are going to cut some 1 inch thick hot rolled bar with a 6 axis robot We will be buying a Powermax 1650 with a small mechanical torch for this job. My question has to do with starting and ending the cut. Since the bar has rounded edges from the rolling process would it be better for consumable life to start the cut angling away from the edge and roll into the bar or start square to the material? The reason I am concerned is that we made sample cuts with a 1250 using 80 amp consumables and saw erosion of the cutting nozzle after just a handful of cuts. The edge quality of the cuts was good with some dross that easily removed with a solid tap on the part. These samples were produced using the torch sq to the material at the start of the cut. I am concerned that with the rounded edges of the bar stock the pilot arc will be stretching a long way before it actually contacts the material edge. I am also wondering if the air quality becomes more critical as the cutting amperage goes up? Is anyone doing anything like this that can point me the right direction?

From reading the description, it sounds like you will be edge starting? If so the 1650 should work. Piercing 1" is tough on the machine. Edge starting tends to allow the parts to shift , giving less tolerance to the parts. Air works good of course dry. I think you can use nitrogen with a air plasma torch, but not sure if it will gain much.

WSS

Your pilot arc concern is right on the money. It is important that you are edge starting...as the 1650 will not pierce the 1" material (at least not with acceptable nozzle and shield life!)....and since you are using a robot...simply teach it to start at an angle to get the torch to work distance as close as possible. Since you are edge starting...there is no real need for pierce height...so roll the torch over and try to achieve the cut height (which I think at 100 amps is 1/8"), delay slightly to let the arc establish (maybe .3 seconds or so) then rotate the torch up to vertical and get on with the cut off. At the end of the cut you may want to do something similar...or at least a velocity slowdown to drop the cut.

When you see nozzle wear on the outside of a nozzle that is kid of like a crater effect around the nozzle orifice...that indicates wear from too long (duration) of the pilot arc.

I'd be happy to help you out with these applications. We are actually reviewing some new torch technologies specific for robotic applications...if you are interested contact me directly...our engineering group may want to pick your brain!


Jim Colt Hypertherm [email protected]

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Originally Posted by JOHNBOY

I work for a company that has 25 welding robots. We have converted 3 of the robots to plasma cutting. We are currently using Hypertherm air plasma on all the robots with excellent results. We currently own 2 Powermax 1250's and one of the new 65's We use them to cut scrap frames from press drawn parts. This has proven to be a very cost effective way to trim the parts. We do a lot of forming for Kubota. Plasma cutting has replaced many of their pinch trim dies which are costly to build and maintain. We cut hoods, floorpans, fenders, and mower decks this way. We normally cut steel gauges 18 thru 7 ga. Now we are going to cut a project on the other end of the scale. We are going to cut some 1 inch thick hot rolled bar with a 6 axis robot We will be buying a Powermax 1650 with a small mechanical torch for this job. My question has to do with starting and ending the cut. Since the bar has rounded edges from the rolling process would it be better for consumable life to start the cut angling away from the edge and roll into the bar or start square to the material? The reason I am concerned is that we made sample cuts with a 1250 using 80 amp consumables and saw erosion of the cutting nozzle after just a handful of cuts. The edge quality of the cuts was good with some dross that easily removed with a solid tap on the part. These samples were produced using the torch sq to the material at the start of the cut. I am concerned that with the rounded edges of the bar stock the pilot arc will be stretching a long way before it actually contacts the material edge. I am also wondering if the air quality becomes more critical as the cutting amperage goes up? Is anyone doing anything like this that can point me the right direction?

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Johnboy-

Sounds like a good project. I would think if you pierce a little off of 90 degrees so that the slag does not blow back into the tip.

What brand robots are you using. I am trying to get a motoman and do this also.

Steve

The cut will be started and end from an edge. From my previous experience with air plasma I know how critical clean dry air is. I am located in Mo and our spring rainy season is ahead of us. This always puts more moisture in our compressed air system. So far all our plasma cutting has been at or below 40 amps so I realy don't what to expect cutting something this thick.

Here is an 85 amp cut that I just did a couple of days ago...it is 3/4" carbon steel. Piercing was done with the torch perpendicular at a .25" pierc height, 1.2 seconds pierce time, after the 1.2 seconds the height control indexed down to .06" cut height and cut at 33 inches per minute. This was cut with the Hypertherm Powermax85 air plasma.

Jim Colt Hypertherm

I'm going to try to reply to a couple of posts. First off I didn't mention what kind of robots we are using. All are Panasonic, as I understand the North American division of their robot division has been purchased by Miller Electric. Both companies are in process of ironing out the details. Jim thanks for your pictures of the 3/4 parts. The part that we are going to cut has a large radius on opposite ends. We are going to progressively feed the bar stock to the robot as we need to. I haven't checked out the work envelope yet but we may get by with indexing the bar to the robot just 3 times. Since I have have 6 axis to play with the usual draft angle caused by the cut will be adjusted out so I get a 90 degree cut face. We have some tooling to build and equipment to buy before we kick off the project. I won't have final results for 5- 6 weeks. I have been a regular reader of the cnc plasma section and have gotten lots of great info from it. If anyone out else is using a robot or considering one, I might be able to help out. Thanks for you input

Sounds like you are doing a lot of robotic plasma cutting. Rather than converting your own robots, you might wanna take a look at one of these:
robotic plasma cutting machine
Maybe their builder can incorporate yor existing robot into one of their systems.