CNC Plasma Table - TPI

[Degrom]

Hi.

What TPI will suit a CNC Plasma table the best.
I want to cut steel between 1/8" (1.6mm) and 1/2" (12mm)
I can get the following TPI lead screw: 10 , 14.5 , 17 , 25.4 .

Any advice on the topic would be very welcome.
Thanks.

[jcc3inc]

Sir,

I would consider rack and pinion. You can get 6 foot lengths of rack from Standard Steel Specialties, www.stdsteel.com/gear.htm for about $23/each in quantities of (2). Pinions can be had from Boston Gear, Martin Gear and Sprocket. Be sure to use 20 degree pressure angle gears. SSS has 20 dp rack as stock items.

With rack and pinion, there is no critical rotating speed, a limitation of leadscrews, especially when they are long.

Regards,
Jack C.

[Degrom]

Originally Posted by jcc3inc Sir, I would consider rack and pinion. You can get 6 foot lengths of rack from Standard Steel Specialties, www.stdsteel.com/gear.htm for about $23/each in quantities of (2). Pinions can be had from Boston Gear, Martin Gear and Sprocket. Be sure to use 20 degree pressure angle gears. SSS has 20 dp rack as stock items. With rack and pinion, there is no critical rotating speed, a limitation of leadscrews, especially when they are long. Regards, Jack C.

Thanks Jack,

Unfortunately I am not from the US. Getting parts local is problem so I trying the stuff I can get my hands on...

The plasma table is not a very big one. (36" x 36")

[Torchhead]

Leadscrews and plasma dust/smoke don't play well together. Because plasma smoke is vaporized metal it is both conductive and abrasive. Even with dust extraction it gets everywhere. You will need to keep your leadscrews cleans and lubricated on a daily basis if you cut a lot.

The choice of pitch is a function of the type motors you are looking to use. You need to design the table to hit at least 200 IPM (300 would be better) for cutting thin material. Figure how fast you would have to spin the lead screw to achieve those speeds then see if lead whip (better know what that term means) will be an issue. You can only spin a leadscrew so fast before it will vibrate itself cause damage.

The next limitation is the drive motor. Steppers will max out at 800 rpm but have little torque at the speed so the practical limit may be closer to 600 RPM. Servo's will spin up to 3500 RPM and maintain torque all the way up the curve.

A 36 X 36 plasma cutter will still need leadscrews at least 42" long.

[Degrom]

Originally Posted by Torchhead Leadscrews and plasma dust/smoke don't play well together. Because plasma smoke is vaporized metal it is both conductive and abrasive. Even with dust extraction it gets everywhere. You will need to keep your leadscrews cleans and lubricated on a daily basis if you cut a lot. The choice of pitch is a function of the type motors you are looking to use. You need to design the table to hit at least 200 IPM (300 would be better) for cutting thin material. Figure how fast you would have to spin the lead screw to achieve those speeds then see if lead whip (better know what that term means) will be an issue. You can only spin a leadscrew so fast before it will vibrate itself cause damage. The next limitation is the drive motor. Steppers will max out at 800 rpm but have little torque at the speed so the practical limit may be closer to 600 RPM. Servo's will spin up to 3500 RPM and maintain torque all the way up the curve. A 36 X 36 plasma cutter will still need leadscrews at least 42" long.

Thanks Torchhead,

When you talk about thin metal, are you revering to 1/16 thin or even thicker?

I would love to work with 1/8 at least.(Do you have a recommended speed for 1/8 thickness?)

Thanks for the info...

[Greolt]

Originally Posted by Degrom Thanks Jack, Unfortunately I am not from the US. Getting parts local is problem so I trying the stuff I can get my hands on... The plasma table is not a very big one. (36" x 36")

As others have said R&P is ideal for plasma.

Rack is not hard to source in Aus. TEA in Qld have it at good prices.

Freight would have to be cheaper from Australia. Wouldn't it ???

Greg

[Degrom]

Originally Posted by Greolt As others have said R&P is ideal for plasma. Rack is not hard to source in Aus. TEA in Qld have it at good prices. Freight would have to be cheaper from Australia. Wouldn't it ??? Greg

Thanks for that Greg,

I will give them a call.
(You are referring to http://www.tea.net.au/ , right?)

[Greolt]

Yes that's where I got mine.

Greg