[jpcuttergrinder]

I have a small machine shop and I have a job that requires me to cut 3/8" off of the flanges of 3" channel iron. I am milling them now and it is taking longer than I would like.

I was thinking about making a conveyor type machine that would run continuosly and pass the channels past two plasma cutters so that it would cut both flanges at the same time.

I am just wondering how fast it would cut and how much maintence it would require to keep it running continuously like this? I have to cut 1,200 pieces per month and they are 3' long.

Any help on this would be apprecciated.

[massajamesb]

You could also design the machine to rotate the channel 180 degrees, as to save money on an extra plasma.
Will the plasma's 5 degree bevel be an issue on the flanges?
Depending on the amperage and duty cycle of your plasma, that will determine your efficiency, I would think. You would have to spend a lot of money to buy two machines with the duty cycle and sufficient power to cut 3/8 all day long.
I am guessing you're looking at 120 feet of material a day. A larger machine (minimum 50-60 amps) should cut anywhere from 35"/min to 50"/min (possibly more +- 10%) so 1440 inches a day / 36" min = 40 minutes of cutting time per day. This is if you are running 2 plasma machines simultaneously. With one plasma, double that time.
In other words, theoretically, you are looking at cutting one 3' piece per minute if you are using dual plasmas. Total cutting time will be in the 1 hour range per day, if you run 7 days a week with dual plasma.
Figure in downtime for consumable replacement, stock loading and unloading, cleanup, etc. Don't know if you load these channels in full sticks, 3' pieces, use a forklift, etc. That is another matter.
Consumable efficiency varies with each machine, but the best IMO is Hypertherm. Electrodes last longer but cost a little more than the competition.
I might be completely wrong about all this, if I am I apologize. I know larger production or industrial plasma's can cut faster (such as High Def plasma) but you will break the bank on one that big.
It all boils down to what my racer buddies all tell me. " Speed costs money. How fast do you want to go?"

[jpcuttergrinder]

Thank You very much for the reply.

The channel flange is only 1/4" thick after I mill them.

Would it be possible to mount the plasma torch at a 5 degree angle to compensate for the bevel?

Now, I am milling these and I am getting 10 pieces per hour. The cutters are lasting for about 100 pieces before they need replacing. The pieces are already cut to length when I get them. I realize that consumables life will very but do you have a ball park figure? I was just wondering if might be 10 pieces or 100 pieces? I have no idea.

[massajamesb]

You bring up an excellent point about changing the torch angle. That might be very well possible, as most people don't do it because they are going to be cutting in different directions, whereas you will only be cutting in one direction. I would definately give it some thought.
As far as consumable life, it again depends on your machine, how clean your air is, how clean the steel is, and the cutting distance.
Now, are you milling them to be 1/4" thick, or ?? I don't quite understand.
1/4 thick steel will not have a real noticeable bevel. Anything thicker will.
I would bet if you had a dessicant air dryer inline with the plasma, cutting at a constant 40 amps, using a Hypertherm 1250, you could probably get (at a guess) 15-20 pieces, both sides, possibly. I have never cut 3/8 constantly, in a straight line, like you are asking.

[jpcuttergrinder]

Just to clear this up, the channel flange is tapered but it is 1/4 thick at the place where the plasma would make the cut.

[massajamesb]

Ahhh. Gotcha. Bevel should not be a real problem, then.
Do you have a plasma you are keeping in mind?
Are you open for suggestions, I should say?
Are you for sure you are going to run two plasmas at once?

[jpcuttergrinder]

I am very open to suggestions. I will definitely use just one plasma at first to see how things go.

I was looking at a Miller 625 but I was just looking.

[massajamesb]

That is a great plasma, no doubt, but it will not have the duty cycle you need nor will the consumables last very long while cutting 3/8. I suggest you look into Hypertherm, minimum 1000 model. Thermal dynamics has a PAK85 unit that aint bad and is a tad cheaper. For Miller, I would look at the 2050.

A 30 amp machine will cut 3/8 just fine, but it will not have the duty cycle to run continuously. Beyond that the consumables will not last long enough as some that are designed for a larger machine.
A 50 amp machine should be the minimum you are looking for, IMO.

[jcc3inc]

Sir,

Now this might sound kinda silly, but couldn't you saw them off?? Maybe there
is some other aspect that eliminates sawing?

Jack C.

[jpcuttergrinder]

Jack,

Yes you could saw them off but what kind of saw would cut at 35" per minute on 1/4" steel?

[ViperTX]

jpcuttergrinder....if it's only taking you 6 minutes to do each piece....then you may have the most optimum method, short of using a shear press...

[Redline]

This may sound stupid but you could make a single axis CNC plasma cutter to do that job.It would be cheap and easy.

[massajamesb]

Ummm... I think that is what he was going to do....He just wanted to know how fast it would cut, and how long consumables would last.
Really, he wouldn't have to build a cnc, just a simple dc motor driven slide to mount the plasma to, with limit switches at either end, and a motor speed control.

[jpcuttergrinder]

Vipertx,

I actually thought of using a shear but I don't know how it would work. I would think that the tapered flange of the channel would make it kick out when you tried to shear it.

The milling is really not going that bad but it is very noisy. I will probably just continue to mill them until I see for sure if I am going to keep getting them. I was just trying to find a little faster way of doing them since I have a regular job and just do these in the evenings and weekends. I also have to drill three holes in each one but my son is doing these on my cnc mill. He drills and deburs about 40 channels an hour and he is only ten years old.

This job gets to you after a while but it does pay $6.00 each so thats $7,200 per month. It gives my son and I a little extra spending money.

[jcc3inc]

Sir,

Well, here's another approach; use either an abrasive cutoff saw or a metal cuttiing chop saw. I've used both and like the chop saw better. It is fast and leaves a cleaner cut than abrasive cutting. I'm assuming the cut is square???

Regards,
Jack C.

[jpcuttergrinder]

The pieces I am cutting are 3" channel iron that comes to me already cut to 3' length. The flanges of the channel iron are 1 7/16" tall. I have to mill these down to 1 1/16" the full length of the channels. I am sure you could probably cut these on a table saw or something similar using an abrasive blade but I think it would be slow compared to milling them or using a plasma cutter.

[massajamesb]

Plasma will probably be your fastest and overall most efficient method.
Even going oxyfuel would be faster, I think.