cutting 3/4" steel

[GoingCustom]

Going to be cutting some spindles out of 3/4" hot rolled steel using my Miller Spectrum 625. I have a few questions though: A) suggested cut speed? (using first gen plasmacam) B) suggested amps/air pressure? For those who aren't familiar with spindles, it's the part your wheels attach to on the front suspenion of a vehicle. They are going on a truck a buddy of mine is building for a customer.

I know pierce points are a cause for consumables going bad, but normally I cut stuff 1/4" or less. The spindles are in the design process right now and will take up less than 1'x1' of material. I have the material costs already, and doin the design time for free being that he brings me business on occasion. Mostly concerned about getting my consumable costs covered and what not.

I haven't cut anything this thick before, so mostly looking for someone who has some experience/suggestions/things to watch out for?

Thank you

P.S. the spectrum is rated at a quality cut at 5/8" and sever up to an 1"

[WSS]

Practice some small parts first before you try the actual spindle. Expect a lot of taper at first. It takes some time to learn the tricks with your system. cut out circles and squares if you can to check top and bottom tolerance. The trick with thick plate is to get way back after the arc initiates during the pierce and hold still until the arc pops through then start to move (anti-spatter helps too). For internal small holes use Jim Colt's guide for movement and leads. I know the PlasmaCam has good motion, so you should do OK. What is the top amp of your 625? Does it have a max mechanical pierce rating?

WSS

Link to Jim's PDF:

http://plasmaspider.com/viewtopic.php?f=45&t=3306

[Batcat]

I don't think you will be happy with the cut. Your plasma is rated at 5/8 inch at 10 ipm. (50% duty cycle at 40 amps) that means you can cut for 5 min and let it cool for 5 min. You will have to do edge starts even if you were able to pierce 3/4 torch life will be very short. Sorry for the bad news .

[WSS]

Ahh, I have a Hypertherm 1650 and it tops out at 3/4" mech. pierce (80 or 100 amp). I can squeeze 1" once in awhile, but as you said torch parts suffer greatly.

WSS

[GoingCustom]

Thanks for the advice so far!

Max amps is 40. I bought the cutter new several years ago, but looking up the specs online, it shows a max cut/severed cut 7/8 and a "quality" cut at 5/8.

Thank you WSS for the link!

[WSS]

Your welcome for the link, I have a copy of it at my command center all the time.

Check the specs for a machine torch even if you have the hand torch mounted on your PlasmaCam that will tell what it can do w/ CNC. I think the early miller gear was made by Hypertherm, just a thought.

WSS

[jimcolt]

First...if you must pierce....drill the holes where the pierce points are....trying to pierce 3/4" with the 40 Amp Miller will take out a nozzle, a shield, and possibly the retaing cap on the torch. If you drill holes, then start on the edge...use the following cut specs:

40 amps

Shielded 40 amp consumables

Cut height: .06" (1/16")

time to pierce (use this even on an edge start as it allows the plasma jet to stabilize) 1 second

Cut speed: 8 inches per minute


Good luck....the torch is made by Hypertherm..it is similar to the torch that was used on the Hypertherm Powermax600 system. I'm not sure if you will have an issue with exceeding the duty cycle of the Miller or not! Use new consumables...the cut will have a lot of bottom dross...but edge quality will be nice.

Jim Colt Hypertherm

[GoingCustom]

Thank you very much for the info! I will be sure to double check everything and be patient! And of course post pictures of the spindles should they turn out half way decent lol.