Not Connected lines

[ColoradoWayne]

I've seen a lot of photos that show unbelievable work on this site. I would like to be able to minimize the pierce holes on the ends of unconnected lines like many of you have. I am using a PowerMax 65 on a LDR Motion Systems table. The photo is 14GA steel of a hot rod that someone from this site generously shared. As you can see the start points are significant, and the end points are pretty obvious too. Thanks to everyone's knowledge sharing I've improved tremendously over the past several months - but boy is there a LOT more to learn about this business. Thanks!

[CNCCAJUN]

I've seen a lot of photos that show unbelievable work on this site. I would like to be able to minimize the pierce holes on the ends of unconnected lines like many of you have. I am using a PowerMax 65 on a LDR Motion Systems table. The photo is 14GA steel of a hot rod that someone from this site generously shared. As you can see the start points are significant, and the end points are pretty obvious too. Thanks to everyone's knowledge sharing I've improved tremendously over the past several months - but boy is there a LOT more to learn about this business. Thanks!

Thanks for the post, I am having the same problem . . . .

Mine are not quite as pronounced . .

I have thought maybe my pierce delays were too long . . .

Steve

[ColoradoWayne]

Based on comments here I changed my pierce delay to zero (0), and didn't see any change. I think sheetcam is pretty incredible, it sure tries to tell be where I am messing up - but nothing can catch all my errors.

[tnbndr]

I assume you also tried to turn off "lead out", "lead in" with pierce delay to zero.
Are you using regular consumables or fine cut? Fine cut may do better for you.

[jimcolt]

The large holes are obviously caused by the plasma sitting still......which causes a larger burn hole at the beginning of the cut, and the motion and the plasma shut off are not well co-ordinated at the end of the cut. On closed paths this is generally not critical as you can start and stop (lead-in, lead-out) in scrap areas, however when you have open paths with the start and stop on the finished part...it is critical.

Beginning or pierce point:
-First, ensure that you are using the lowest amperage set of consumables that will cut the material you are cutting. With the Hypertherm Powermax65 that will be the Finecut consumables. Following the book specs will get you a nice cut, however, experimenting with faster speeds and lower amperage (run them down to 20 amps if you want) will get a narrower cut kerf.

-Ensure that pierce height and cut height are correct. Too high and the kerf gets wider. On materials thinner than 10 gauge it is ok to pierce and cut at the recommended cut height of .060", and may help with the pierce blowhole. Piercing closer on thin materials may have a slight effect on consumable life, but may produce better quality cuts...it may be a worthwhile tradeoff.

- Reducing the pierce delay time will reduce the blowhole size. If zero doesn't work.....I suspect there is some sort of delay created by the software/electronics on your machine that does not start the motion and the plasma simultaneously.....actually, the plasma start takes about 80 miliseconds or so....so a machine that will move instantly will take off before the pierce is all the way through.

- With some software you may be able to start the x-y motion before the plasma start command is issued. With some software....you can actually enter a negative number for pierce delay, which will start the motion before the plasma.


End of cut blowhole:

- The characteristics of an air plasma arc are that it electrically shuts down when the stop signal is issued, however, the exothermic reaction between the steel and the oxygen (20% of air) continues for a few miliseconds. If the motion stops at exactly the same time as the plasma off signal is issued, then expect an end of cut blowhole......more so if you are cutting at higher power levels. Maybe lower powered consumables running at lower amperage will solve the end of cut issue.

-Some softwares have an advanced off (plasma) at end of cut that can be set.

Keep in mind that when you change parameters for open path cutting.....you may be changing the parameters for closed paths as well, and some of them may be adversely affected.

Jim Colt Hypertherm

[acourtjester]

You may look are the F number after the command to move from pierce to cut height that is the speed of the movement. If there is not F# at that point look at what the f# is for the commands above Mach only changes speed when told to by a command (F#). This is the plunge rate number in the tool setting of SheetCam. You could edit the G-code in a cut routine (try different speeds) to see what effect it has . If the number is low it is the same as long pierce delay.
.02 given

Have fun
tom

[ColoradoWayne]

Very cool - thank you for the advice. I will begin experimenting today

[BrianMick]

First of all thanks for the compliments
The "open paths" that I created in that drawing are intended for a fine cut process so that you can cut the whole car at a smaller size. To avoid the bad starts and stops you would have to offset those lines and link the two lines together forming a "closed path" the drawback to this is you must cut the part much larger(Which that may be what you want to do anyway)
With the closed path you would have a much more pronounced line on a bigger part.
Hope this makes sense
On most of my new drawing I have learned to make a open path copy and a closed path copy for flexibility in either case

Brian

edit:
As I was sitting here pondering the bigger questions in life I realized that this was not in fact my drawing.... (at least I don't think so) I apologize for the mistake, as I have drawn many vehicles for the spider community.....Also this is done in the same style of drawing that I do use.....but all of the other above statements are true

[CNCCAJUN]

You got me . . . it does not make sense to me

But really want to learn how to correct this . . .

Steve

First of all thanks for the compliments
The "open paths" that I created in that drawing are intended for a fine cut process so that you can cut the whole car at a smaller size. To avoid the bad starts and stops you would have to offset those lines and link the two lines together forming a "closed path" the drawback to this is you must cut the part much larger(Which that may be what you want to do anyway)
With the closed path you would have a much more pronounced line on a bigger part.
Hope this makes sense
On most of my new drawing I have learned to make a open path copy and a closed path copy for flexibility in either case

Brian

edit:
As I was sitting here pondering the bigger questions in life I realized that this was not in fact my drawing.... (at least I don't think so) I apologize for the mistake, as I have drawn many vehicles for the spider community.....Also this is done in the same style of drawing that I do use.....but all of the other above statements are true

[plain ol Bill]

Brian I believe the original file was one of Jasons.

[Gamelord]

Not sure what program you are using, if you mentioned above then sorry, don't have time to re-read the entire thread. For creating closed paths from single cut lines there is an easy way to do this in Corel with the contour tool.

Just click the line that you want to make a closed path, then select the contour tool. Set the size of the outlined closed path you want to make and make sure that you select "outside", then click the "apply" button. This will create a contoured object all the way around your single line.

Then what you need to do is to right click on the newly created contour and select "Break Contour Apart". This will break the contoured line apart from the single drawn line. Once broken apart, click on the single line and delete. What will be left is a closed path that is nearly identical to the single closed line in shape but slightly larger in size.

You may find something similar in the drawing program you are using to the Contour tool.

Hope this helps.

The above picture is an example of the contour tool. In the first single line, the torch will pierce, cut the single line and then shut down. This will leave pierce and exit divots with a single cut. The middle is the single line with the contour applied. The last is the contour that is left after the single line has been deleted. Cutting the last one, you can set a lead-in and lead-out so that your torch will cut the inside of the object and will not leave pierce and exit divots. Obviously, the inside of the object must be large enough to be able to pierce and then cut. If it is too small, you could minimize the pierce divot, but it may still show a little.

[CNCCAJUN]

Thank you . . .

Neat trick . . .

Steve

[ColoradoWayne]

You guys are great! Thanks for sharing all the ideas and advice.

[dhelfter]

Coloradowayne,

I would set pierce delay to 0, raise plunge rate for that tool in sheetcam to something like 100. And also maybe try lower amp consumables. Using the pathrules in sheetcam you can actually create a rule to turn the plasma of x distance before end, like Jim colt suggested.
Thanks
Dan
LDR Motion Systems.