pierce holes

[ssbn.981]

hey everyone. i am making some lines that can't have any lead ins. the pierce hole is quite small
but larger then the line that is being cut. as you know it looks like a small dot on top of the line.
is there a way to blend that in or........?
thanks

[vmax549]

It depends on what control software you are using.

IF you can turn off the arc good signal then you can strike the arc on the fly and it does not leave the dimple but it does leave a very small gouge on the start of the line as the arc is established. It looks like a small taper cut inline with the line.

wITH mACH3 I sometimes do it with fancy art where the DIMPLE(START HOLE) IS UGLY.

Just a thought, (;-) TP

[jmsrbrt]

With the Torchmate software you could decrease your dwell time (the time from when the torch senses the material to when it strikes an arc) which would get the torch moving before an arc is established. Never actually tried to do this, but it would seem too, that a really good "pierce" wouldn't be at the start of the line, but you could program the cut to maybe retrace itself?

[beefy]

Terry,

I wish you would write a book on everything you know, I'd be one of the first ones to buy it

would you be able to go into a bit more detail about how you'd do that. Sheetcam only has "pierce height", "plunge rate", and "cut height".

With the method you are talking about do you just turn the torch on as it's moving at normal cut height. I know Sheetcam has a ramp feature but when I played with that the gcode seemd to produce only a 45 degree ramp from pierce height to cut height.

It would be good to minimise that pierce HOLE you get, not only for intricate cuts but also on open lines.

I'm a bit lost too about why disabling the "arc OK" feedback is necessay in this case. I know it can be done by turning off THC in Mach.

Keith.

[ssbn.981]

hey,

thanks for the help. i am using torchmate programs. i will
try those ideas and see what happens. new at this and appreicate
all the help.

doug

[vmax549]

HIYA Keith When you are waiting on the ARC ok signal the torch is lit and burning a hole. IF you by pass the arc ok signal and start motion directly after the M3 then motion starts immediatly and does not wait on the signal. That creates the start on the fly function. The arc strikes and continues to penetrate as the axis is moving.

With thicker metal one can use the delay as it takes a little to get it pierce anyway BUT with thin gauge metal you have to get MAch3 to react as fast as possible to avoid the Dimple.

ANother problem in MACH3 is a longer delay to start motion on the FIRST pierce point. THere after it is quicker. SO I add a first start OFF the main cutting area to let it settle in and be quicker to start on all the rest of the pierces.

Doing fine art having a LOT of no offset lines the DImple Hole (starthole) on every start is most times UGLY.

There IS a method one can use with MACH3 that has a faster reaction time than the M3/M4 (;-) M10/M11 and another trick that I will have to look back up. BUT it requires a non standard gcode approach and a POST mod to make it work. The laser guys use it beacuse it has NO delays that the M3/4 has.

(;-) TP

[Oldsarge]

On thin gauge stuff I also reduce the pierce height to the cut height and that gets things moving faster as soon as the torch fires you're off, no waiting for the torch to come down to cutting height....

Oldsarge

[beefy]

Terry, thanks again.

I remember Tom once posting and some of his words were, "Mach will not release motion until it receives a valid arc OK signal". However, it never occurred to me it could be used to advantage like this. I've often been frustrated at the gaping hole size from the pierce.

With the new cutting rules in Sheetcam I can turn the THC on at any point in the cut or any point in the lead in BUT with my present Mach/Candcnc setup I get a pause in motion when THC is turned on, which causes a divot.

So I think my options are either to get Toms later DTHC II card so I can take advantage of the no pause feature, OR see if I can make a little electronic cct which gives an arc OK signal immediately upon recieving a torch on command. This "bypass" arc OK signal would just have a short duration (about 1 sec) and operate in parallel with the "real" arc OK signal. Or have I missed another way LOL.

Regarding what you said about the first pierce having a longer duration. So that is a "quirck" specific to Mach ?? I never knew about that one. Aha, no wait, I have came across this when playing with marking hole centres and the first torch on time was longer, but I didn't know why.

Wow Terry you have taught me some seriously usefull stuff.

Oldsarge,

When I've been playing with marking hole centres on thin material, I've seen just how quickly a hole is blown through (can be hard to get it not to blow through LOL) so yes I'll have no hesitation piercing at cut height when I don't want that gaping hole.

Cheers,

Keith.

[beefy]

Terry,

do you have any idea if Mach would get confused if I created a method of giving it an arc OK signal just BEFORE it gave the torch on output.

Keith.

[vmax549]

HIYA Keith, It should not have any problems that I know of it is just a input that mach3 moniters I have used a push bottom switch to do it(;-).

[vmax549]

Another thought would be to use a Brain to tun ON the arcgood signal and hold it for say 1 sec then release. BY that time the arc good signal should be present from the THC. You could control the function from a Button OR Gcode via a Mcode. That way on line cuts that needed it(no offset single cuts) the post could apply the Mcode and there should.

AND there are OTHER ways, I will do a bit of research.

(;-) TP

[vmax549]

OK I just tested a Brain and it works very well and you can control the DWELL on the arcgood signal.

You can use the i/o relay board to jump over to the arcgood input on the board from a relay on the board.

Use a UserLEd to turn on the function. From the M3 macro insert code as the first line

SetUserLed(2001,1)

When the Brain sees the LED go active it sets and holds the relay for the defined time(2sec) then releases control. By that time the arcGood signal from the THC has gained control and there should be less lag as MACH3 is free to move as soon as it fires the M3.

Thats one way(;-)

Just a thought, (;-) TP

[Largemouthlou]

If you're using mach 3 then simply try turning off the THC button on your screen and have your peirce set to 0 in SC.. The time I tried it, it took out the short delay and started cutting right away. If it gouges any then add a very short pierce delay.. you can turn the THC button back on at any time.