Hy Def & shop built gantries

[PlasmaGuy]

Jim,

What experience do you have with small operators having built their own tables and gantries and using Hypertherms hi-definition plasma sources?

It's my understanding that you're wasting your time if the gantry is not capable of holding very tight tolerances.

There has been discussion on several forums of late about moving up to either Hypertherms HPR or HPRXD technology.

I've sure there have been systems paired with this technology and shop built tables but I'm guessing this is rare?

I would like to be able the step up from my current G3 1650 machine to some form of HPR machine. The issue is whether I buy a complete system v. built a new more high-tolerence gantry and table using servos, etc.

Thank you Jim for your guideance.

Tom

[jimcolt]

The Hypertherm high definition class plasma systems can in theory be installed on any cutting machine that can handle a high frequency start torch. The thing to remember is that these systems cannot fix issues with rough motion, inadequate cut speed in small holes and features, and torch height control innacuracies.

High definition plasma is a plasma arc (usually oxygen based plasma with an air shield) that has more constriction on the arc, increasing its energy density. A typical air plasma system provides an arc with approximately 15,000 amps per square in energy density, while a high definition plasma arc can produce as much as 60,000 amps per square inch. The stiffer arc provides squarer edges, especially on thinner steel, a narrower kerf width, and the oxygen provides for a softer cut edge.

In order to take advantage of the higher density arc, and to achieve consumable life (with Hypertherm HPR systems) that can reach 3000 or more starts per set, the following have to occur:
1. Torch pierce height must be accurately set to within .005" of the suggested pierce height. One pierce too close can damage a nozzle. In order to succesfullay achieve this...ohmic contact sensing must be used on thin materials that may deflect with contact sense initial sensors.
2. A pierce complete signal (contact closure) must be issued to the plasma system from the cnc controller after the pierce delay timer times out. These systems use a different pierce flow, and must quickly switch to cut gas flow once this event ocurrs. Industrial plasma cnc controls (Hypertherm and Burny) have this functionality....I'm not sure if any of the entry level machines do.
3. Cut height and arc voltage controlled height must be controlled to plus or minus .004" (1 arc volt) in order to meet Hypertherms cut edge angularity (traceable to ISO9013) specs.
4. Acceleration at maximum cut speed must be in the 40 miligee or better range. If acceleration of a machine is sluggish, holes will be out of round and cut quality in general will suffer in terms of angularity and dross.
5. Smooth, fluid motion. If you can feel any roughness in motion (motor or belt cogging) it will show up in the cut face with high definition plasma.

So, typically high definition plasma cnc machines use linear motion bearings, zero backlash gearboxes, inertia match AC servo drives, highly accurate full featured torch height control systems, industrially hardened, PC based cnc controls. These machines are typically built with lightweight, low profile gantrys to help with acceleration and to ensure smooth motion, and are built on a heavy unitized welded frame thatis stress relieved and has milled way surfaces to ensure parallelism and acuracy. A 5 x 10 machine with all of the normal features for high definition accuracy normally retails in the $100k range with a 130 amp plasma. High definition systems are available to 400 Amps.

Can you put a high def plasma on any machine? Yes....results will vary!

Jim

[PlasmaGuy]

Originally Posted by jimcolt The Hypertherm high definition class plasma systems can in theory be installed on any cutting machine that can handle a high frequency start torch. The thing to remember is that these systems cannot fix issues with rough motion, inadequate cut speed in small holes and features, and torch height control innacuracies. High definition plasma is a plasma arc (usually oxygen based plasma with an air shield) that has more constriction on the arc, increasing its energy density. A typical air plasma system provides an arc with approximately 15,000 amps per square in energy density, while a high definition plasma arc can produce as much as 60,000 amps per square inch. The stiffer arc provides squarer edges, especially on thinner steel, a narrower kerf width, and the oxygen provides for a softer cut edge. In order to take advantage of the higher density arc, and to achieve consumable life (with Hypertherm HPR systems) that can reach 3000 or more starts per set, the following have to occur: 1. Torch pierce height must be accurately set to within .005" of the suggested pierce height. One pierce too close can damage a nozzle. In order to succesfullay achieve this...ohmic contact sensing must be used on thin materials that may deflect with contact sense initial sensors. 2. A pierce complete signal (contact closure) must be issued to the plasma system from the cnc controller after the pierce delay timer times out. These systems use a different pierce flow, and must quickly switch to cut gas flow once this event ocurrs. Industrial plasma cnc controls (Hypertherm and Burny) have this functionality....I'm not sure if any of the entry level machines do.3. Cut height and arc voltage controlled height must be controlled to plus or minus .004" (1 arc volt) in order to meet Hypertherms cut edge angularity (traceable to ISO9013) specs. 4. Acceleration at maximum cut speed must be in the 40 miligee or better range. If acceleration of a machine is sluggish, holes will be out of round and cut quality in general will suffer in terms of angularity and dross. 5. Smooth, fluid motion. If you can feel any roughness in motion (motor or belt cogging) it will show up in the cut face with high definition plasma. So, typically high definition plasma cnc machines use linear motion bearings, zero backlash gearboxes, inertia match AC servo drives, highly accurate full featured torch height control systems, industrially hardened, PC based cnc controls. These machines are typically built with lightweight, low profile gantrys to help with acceleration and to ensure smooth motion, and are built on a heavy unitized welded frame thatis stress relieved and has milled way surfaces to ensure parallelism and acuracy. A 5 x 10 machine with all of the normal features for high definition accuracy normally retails in the $100k range with a 130 amp plasma. High definition systems are available to 400 Amps. Can you put a high def plasma on any machine? Yes....results will vary! Jim

Jim, as expected that was a very concise report as to what I was expecting to hear.

I too I'm curious to know if Hypertherm & Burny are the only companies offering the gas flow switching required for high-definition use.
Thanks again!

Tom

[jimcolt]

The Hypertherm plasma system controls the gas flow....only a simple contact closure is needed to activate the switch.