Cutting rules

[BensPlasmaAu]

I have finally had a play with creating rules for cutting. For example i have a rule for cutting inside holes. It is slow 60%, DTHC off 5mm before corner DTHC on 5mm after corner. Or something similar to that. What are some of your rules you have created to help with your cuts? I ask so i can see if i'm doing it the correct way. Kinda winging it at the moment, and not so sure they are really effective. I did find that on one cut which was a really intricate sign, I left the cut rule on and it came close to ruining the piece.

I find lots of layers is the way to go so i can apply the different rules i am pulling out of my hat. I just hope i'm not over complicating everything.

[Capstone]

I've gone back and forth now three times with using and not using rules. It seems that SheetCAM and MACH 3 on my PC with DragonCUT CandCNC electronics simply can NOT process the cut rules fast enough anymore; that or some recent update to SheetCAM has fuxored yet again settings that used to work.

Now I'm back to just slowing everything down to no more than 85ipm on anything that normally recommends higher book speeds on my PM45; mainly because my VeloxCNC/PrecisionPlasma gantry just can't manage to NOT shudder the hell out of my machine torch coming out of turns at any speeds above 85. Add to that the fact that there are now huge pauses when processing the cutting rules like "turn off DTHC .5 in before Corners 90' and slow to 60% speed" causes visible divots at the .5in marks, I've stopped using cut rules and even the DTHC dues to g-code hang-ups I just can't sort out..

If they are working for you, don't mess with them too much. The biggest areas where most people use them are with holes and small cut-outs, turning off the DTHC. I'm no longer convinced that rules which are there to have the torch run fast on straightaways, only to slow at corners works very well anymore with SheetCAM and MACH3. There's something getting gummed in the works.

[motoguy]

I too find the pauses (and associated divots) at rule implementation to be an annoyance. I've only used 2 versions of Sheetcam (current, and the previous revision), so I've not known a time without these pauses/divots. I can't imagine going down to 85imp on all my cuts, though. I shudder to think how ragged/enlarged the kerf would be on 14, 16, 18ga materials.

[SeanP]

It can be fun and games sometimes with rules Ben, but I use these for holes, it seems to cover most holes well.
As far as I can make out the rule which fits the hole the lower feed rate wins.
The last one in blue probably isn't needed, it was just used on bigger than 50mm holes.

Adding to many different rules can have weird effects sometimes.

I also get a slight divot just into the cut using off at corners rule and I can't quite find the reason, yet sometimes it runs through fine and smooth, it's no problem on thicker than 5mm or so and once it's past the first corner it's fine,,dunno

[East German]

Hallo

I am a big fan of cutting rules.

It works very well. I turn it on and off with a relay.

Here are my settings.


Greetings Peter

[tcaudle]

I too find the pauses (and associated divots) at rule implementation to be an annoyance. I've only used 2 versions of Sheetcam (current, and the previous revision), so I've not known a time without these pauses/divots. I can't imagine going down to 85imp on all my cuts, though. I shudder to think how ragged/enlarged the kerf would be on 14, 16, 18ga materials.

What works for us and a lot of others:

Use the custom setting in the operations for "Min Cut Length for DTHC". Set it to the total cut length of the biggest object whether is a hole (circle) or a small shape or even an open online cut. That keeps the DTHC form ever turning on in the first place. The DTHC turns off at the end of each cut and then back on at the beginning of the next, provided it does not violate the cut length setting. If you need to cut slower then group and move the cuts the be made slower onto another layer and simply lower the feedrate for that whole operation operation. Getting too many cut rules in a job creates havoc. Turning the DTHC on or off should not cause a motion change BUT the process may take up to 100 msec. You have to take that into consideration using MACH and turn it off sooner and then you have dueling on/off calls. The normal ON and off us the S codes and happen when the torch reaches cut height. It the cut rule is applied at the pierce it can be overwritten by the auto ON/off. The fewer cut rules you use the better. The Before end is the most useful and prevents torch dive.