Open line cutting...

[davek0974]

On an open line, I have managed to massively improve the cut by getting rid of the end hole, this was achieved by a sheet cam rule that turned the torch off 3mm before the end of movement. I may need to tweak the position but that seems to work well and gives a nice sharp end.

Is there a way to remove or reduce the start hole?

This is 1.2mm stainless with a PM45 at 30A on 30A consumables. I have no pierce delay set but the system has a loop delay of around 0.3s so I cant get less than that.

[tcaudle]

Have you tried spoofing the ARC OK so there is no delay from that?. ANY pause is going to cause a divot and it;s milliseconds difference between full penetration and a divot. You need to have the pierce height the same as the cut height (maybe .01 higher) so the is NO delay during a plunge . The "plunge time IS part of pierce delay because the torch is fired and is sitting on one spot as the Z moves down. It only starts moving in XY AFTER ti finishes the Z move. The danger of course is that you won't get full penetration ans as you start moving it may not keep a full penetration cut This would be a circumstance where an auto set THC that samples voltage could work against you I would increase my DTHC Delay so you get well past any start area. What you will also find is that is will change based on the material and conditions much like the lead out settings

[davek0974]

Hmm,

what about a ramp lead-in?

I think sheet-cam has a "lead-in on open path" option, fudge the arc-ok and use something like a 5mm ramp lead-in ???

piercing at 0.5mm sounds like short nozzle life maybe, normal pierce is 2.5mm so a ramp might work?

[davek0974]

Setting a ramp gives code like this on a straight line cut...

N0200 M00 (Paused: Check the DTHC Settings - Hit RUN to continue)
N0210 G00 X-5.000 Y-0.000 Z15.000
N0220 M08 (Turn on extract fan)
N0230 M98 (HeightSense.tap)
N0240 G00 Z2.5000
N0250 M03
N0260 G01 X-3.000 Z0.500 F1300.0
N0270 S20 (DTHC is ON)
N0280 G01 X0.000 Y0.000 F4000.0
N0290 X497.000
N0300 M10P1 (Torch Off By Code Snippet) (Before end)
N0310 X500.000
N0320 M05

The only oddity seems to be that it steps back from the start for the ramp - X-3.000 but it then ramps down from 2.5 to 0.5mm over 2mm.
No idea what it will do in a cut but with the arc-ok fudged it may work?

[tcaudle]

Ramped or wiggle lead-ins simply do not work with the Posts for the DTHC and its automation. You will have to use another POST

[exapprentice]

Hi Dave
Search for "overcut support" you might find the answer to reduce the divot at the start of the cut

[davek0974]

Thanks, looking now:)

[vmax549]

Because with Mach3 you do NOT have precise timing control The only way I know of to reduce the start divot is to use a flying start .

(;-) TP

[davek0974]

Yep, seems that way but it can be improved a bit by bypassing the Arc-Ok signal with a link or switch so it's instant-on when doing a line.

Will be trying that i think.

[vmax549]

Yes that IS the flying start (;-).

(;-) TP

[davek0974]

Great

[Drgoogs]

I know this is an old thread, but I hope someone will be able to help me. I am running Mach 4 on an Avid CNC with a Hypertherm 45XP I have the same issue as the OP cutting 14 gauge mild steel. I have set the tool in to "0 delay" Pierce Height to same as cut Height .06 and have set the "Time Delay Anti Dive" to "On" and "Delay after Arc" to 0.0. The divot is better, but I am trying to figure out how to wire an ARC OK bypass. I have search this forum, other forums, Google and youtube, but I am coming up short. any help is appreciated. Thanks in advance!

[exapprentice]

Hi drgoogs
Did you try looking at the "overcut support" topic mentioned above I am pretty sure I explained how to wire in the switch to fake the arc okay signal
I think if you click on my ID you will be able to search my post's and find the info and results I achieved??

[Drgoogs]

Hi Pete, thanks for the reply. I did a search on overcut support and someone mentioned an overcut setting in sheetcam but I didn't see any settings for overcut in sheetcam and a look in the help files didn't prove helpful in finding anything... I am using ver 6.0.30 I will definitely look through your posts.
Thank you and Happy Holidays!
David

[exapprentice]

Hi David
Good luck
Have a great day yourself