[needonemoretool]

Hello,

I need some help with my new build plasma machine. I probably have been making this more complicated than needed but it seemed logical at the time. I am mostly complete and trying to finalize the floating head. Here is the concept of the operation of my floating head.

(1) Torch moves to first location to start cutting.
(2) Z starts moving down.
(3) Torch touches material and continues down until mechincal switch trips.
(4) Z switch sends "home" reference to Mach and to mechanical brake.
(5) Z floating head brake locks floating head.
(6) Z then travels up using the home locked head position as 0.000.


I tried to post some pictures but not sure how because it asked for web location of the picture and they are on my computer.

Any help would be great.

Thanks

Needonemoretool

[plain ol Bill]

IF you are using Sheetcam there is a torch offset factor that needs to be put in. That will allow your torch to touch the material and keep going down until the switch is tripped - that sets the Z dro to 0.0000 then the torch will rise to the preset offset in sheetcam and reset to 0.0000. Then the torch raises to pierce height, pierces, and goes to cut height. Hope this helps.

[Torchhead]

Hello,

I need some help with my new build plasma machine. I probably have been making this more complicated than needed but it seemed logical at the time. I am mostly complete and trying to finalize the floating head. Here is the concept of the operation of my floating head.

(1) Torch moves to first location to start cutting.
(2) Z starts moving down.
(3) Torch touches material and continues down until mechincal switch trips.
(4) Z switch sends "home" reference to Mach and to mechanical brake.
(5) Z floating head brake locks floating head.
(6) Z then travels up using the home locked head position as 0.000.


I tried to post some pictures but not sure how because it asked for web location of the picture and they are on my computer.

Any help would be great.

Thanks

Needonemoretool

You are making it a lot more complicated than it has to be. You don't need a "brake". Here is the sequence (in g-code with comments)

G00 X6.000Y6.000 (rapid to first pierce point)
G28.1 Z.5 (move Z down towards material and Z home switch is tripped)
G92 Z0.000 (reset Z DRO to zero)
G00 Z .085 (raise Z to Swtichoffset value so tip is setting on top of material)
G92 Z0.000 (reset Z to zero as top of material)
G00 Z .125 (raise Z to pierce height
M03 (fire torch)
G01 Z0.063 F60 (plunge Z from pierce height to initial cut height)

There is no need to lock the floating torch holder. It is at the bottom of its stroke (held by gravity). The SwitchOffset is a fixed value and is the overtravel of YOUR Z from the time the tip hits to top of the material until it stops from the swtich). If you use SheetCAm or a CAM program you can modify the POST, you can put in the SwitchOffset value (once). The value in the example is .085 but your number will be different.

Within SheetCAm you can set parameters in the tool table for the Plasma Tool(s) for the Pierce Height, Initial Cut Height, Plunge Rate and other parameters and it will generate the above sequence automatically for you. It also has another variable in the POST that is named RefDistance. It is a measurement in MM of how far the X&Y move BEFORE you get the next aoutomatic touch -off. This keeps you from wasting time touching off before every pierce on cuts where the pierces are close together. It can be changed (default is 500 mm about 20in). That is TOTAL X + Y so is not a long distance. You copy the POST, rename and make changes. I use a different post for thin material (16ga and less) where I touch off every pierce and the deafult one for other material.


In plain text, you move to the pierce point,
move the Z down until the home switch "makes",
zero the Z and raise it up the switch overtravel (swtichoffset) value,
zero it again.
At this point the end of the torch tip should be on or just slightly above the top of the material.
Then you zero the Z again and raise it to the pierce height.
The plunge to cut height becomes part of the pierce delay and the plunge rate effects that time. Piercing higher keeps blowback (molten metal) for clogging yet tiny nozzle opening and ruining the consumables.

All you need to do the above is the floating torch holder and the Z home switch hooked up to an input and mounted so the upward move of the torch when it touches the top of the material trips the switch.

It's not as elegant as an Ohmic touch off but it's more reliable and a LOT cheaper. The shock absorber action of the floating head can help protect the torch as well.

TOM caudle
www.CandCNC.com


here is an ebay seller that offers a complete Z with the floating head and rails and the torch bracket. Just add the motor and you have a full Z.

http://cgi.ebay.com/ws/eBayISAPI.dll...4#ht_683wt_958

[needonemoretool]

I will move forward with your comments. I am using BobCad and I am sure that I can get the post to include the offset.

After looking around on the CNCZone site you have been a savior for many just like me.

Needonemoretool

[Torchhead]

When you get frustrated enough with BCAD and writing a good POST and trying to figure out how to program in lead-ins, kerf offset and the piercing moves, you might want to try the SheetCAM eval. It has all that stuff for plasma cutting built in and costs about 160 USD. You can still draw with BCAD if you want but do your CAM work with SheetCAM.

TOM caudle
www.CandCNC.com