lead ins, holes

[99guy]

Cutting 16gauge, 30 amps .04 kerf, holes from 1" to 1.4", inside offset. I have my lead in set to arc and tried lengths of .06 to .15. Think I could improve a little ..... what would you change in my settings.


TIA

[trucutcnc]

A larger radius lead-in will give you smoother transition into the part. The lead-out can stay at .15. Since you're cutting air during the lead-out phase, you want a shorter lead-out. I would also use 40A consumables. The TD 30A consumables are not specifically designed for mechanized cutting with a standoff. They are made for drag cutting with a hand torch. 40A consumables will give you a better cut on a CNC machine.

[jimcolt]

I suggest different lead ins depending on the acceleration and mechanical rigidity of the machine. Machines that have excellent acceleration and have close to zero mechanical backlash will provide best hole quality with a straight lead in, and no lead out, rather....do an over burn staying on the radius of the hole about .100 past the lead in kerf.

If the machine has rather sluggish acceleration....a radius lead in works best. The problem with a radius lead in is that the plasma arc has a hard time transitioning into the radius when it is reentering it near the end of a hole.

Lead outs that enter back into the center slug of a hole are extremely tough on nozzle and electrode life. Overburns work best......and are even better if you can shut the plasma off at about 360 degrees while the motion continues past that point. An air plasma arc does not extinguish immediately as there is an exothermic reaction occuring with the oxygen content of the air and the steel plate.

Even more important on holes is ensuring that the pierce height transitions to the cut height while the torch is still on the lead in kerf. Once at cut height.....the height control should freeze at this height for all holes that are under about 1.25"....as a rulle of thumb. This means that the arc voltage feedback control should not be active.

Jim Colt Hypertherm

[trucutcnc]

do an over burn staying on the radius of the hole about .100 past the lead in kerf.

SheetCAM won't do an overburn. A short arc lead out serves roughly the same purpose. We do use perpendicular leads with no lead-out from time to time. I like them on heavier material where the speeds are under 100IPM or so.

Even more important on holes is ensuring that the pierce height transitions to the cut height while the torch is still on the lead in kerf. Once at cut height.....the height control should freeze at this height for all holes that are under about 1.25"....as a rulle of thumb. This means that the arc voltage feedback control should not be active.

Our THC can make Z corrections at max velocity if required. Going from pierce to cut height and maintaining torch height in the hole isn't a problem. There is no need to deactivate the THC. We cut rivet holes as small as 3/16 all day long.

[99guy]

a120 pdf page 110.jpg (58.75 KiB) Viewed 5667 times

a120 pdf page 110.jpg (58.75 KiB) Viewed 5667 times

I would also use 40A consumables. The TD 30A consumables are not specifically designed for mechanized cutting with a standoff. They are made for drag cutting with a hand torch. 40A consumables will give you a better cut on a CNC machine.

Ross, I saw that you have mentioned this before in another thread. Page 6-6 from the A120 manual lists 20, 30, 40 amp tips and beyond for the SL100 machine torch, that page does not mention these are drag tips. It they are then TD should correct the book.

However ... in the cut speed charts of the same book the 40 amp tip is the smallest tip mentioned. IE 40 amp on 16 gauge mild listed at 140 ipm. I've been cutting some art stuff with a lot of short segments , that's why I tried lowering the amps and going to the 30 amp tip (9-8206) shown in the manual.

If you do a little looking you can find that the 9-8208 40amp tip, shown on the same page, listed by some on line retailers as stand off and others as drag ...... hmmmmmmm .........

So ...... what's the real scoop?

[trucutcnc]

The hand and machine torches take the same consumables, so you can go all the way down to 20A and the consumables will fit just fine. Our dealer price sheet shows 20 and 30A as drag tips. We've tried them and get better results with 40A consumables running at 30A.

I'll match the numbers from the manual to the price sheets tomorrow. They do show 20 and 30A stand off consumables. You can tell if it's a drag tip by looking at the hole in the tip. If it's a straight hole it's a stand off tip. If it's a drag tip, it will have a small counterbore at the tip. I think once you get to 60A, there is no drag tip. Drag cutting is done by using a drag shield.

[trucutcnc]

Attached is a PDF of the Victor price sheet for consumables. As per TD tech support, the 9-8205(20A), 9-8206(30A) and 9-8207(40A) were designed for drag cutting in the hand torch. The orifice in all 3 is the same size, but the orifice length differs which changes the arc characteristics. The 9-8208(40A) is designed for machine stand off cutting. The orifice characteristics are different than the drag tips in that the stand off tips are designed to operate at a higher stand off while the drag tips are designed to run while in contact with the material. Tech confirmed what we've seen from experience in that a 9-8208 running at 30A will produce a better cut than 9-8206 because the 9-8206 is not designed to run with a stand off.

As a side note, the 20, 30 and 40A drag tips for that fit the SL60 and SL100 torches do not have a counterbore at the tip like the rendering above shows. I believe that's a design change as I have some older 30A drag tips that have a counterbore. I pulled a new one and it has no counterbore. The drag tips for the CutMaster42 do have a counterbore

MASTER-TDC Plasma Price Sheet.pdf

(45.43 KiB) Downloaded 108 times

MASTER-TDC Plasma Price Sheet.pdf

(45.43 KiB) Downloaded 108 times

[99guy]

Interesting ........... thanks for providing the information Ross. I too had not seen improvement in the 8206 30 amp tip at 30 amps over the 8208 40 amp tip at 30 amps. That said, I'm still a newbie and wanted to test the idea.

If TD reads this thread I would suggest you consider clarifying the manual that ships with the A120 to reflect that the 8205 and 8206 tips are considered drag tips for hand torch. Confusing to me , to say the least, as it's published now.

[trucutcnc]

They don't get involved with the forums. I think the reason the manual is written that way is that the drag tips will work in the machine torch. Although maybe not as well, they will work.

[BTA Plasma]

Your best holes are made by no radial lead but a strait lead in and no lead out. The reason no lead out is preffered is due to the plasma beam hogging the material at the end of the cut. This leaves a deep dimple in the hole where the material has been cut away yet the torch must still travel and it will cut away the wall of the hole. Hypertherm says it best and that is to lower the amperage at the last edge of travel in any circlular hole so you get a round hole not a round hole with a dimple. This rule also applies to entry lead in. Where you have a radius lead in you have less material left over a longer distance on the circle your cutting versus a strait lead in. This leaves you with larger dimples as you reach the endpoint of the circle your cutting. This is something you will find after alot of experience cutting circles.

[BTA Plasma]

do an over burn staying on the radius of the hole about .100 past the lead in kerf.

SheetCAM won't do an overburn. A short arc lead out serves roughly the same purpose. We do use perpendicular leads with no lead-out from time to time. I like them on heavier material where the speeds are under 100IPM or so.

Even more important on holes is ensuring that the pierce height transitions to the cut height while the torch is still on the lead in kerf. Once at cut height.....the height control should freeze at this height for all holes that are under about 1.25"....as a rulle of thumb. This means that the arc voltage feedback control should not be active.

Our THC can make Z corrections at max velocity if required. Going from pierce to cut height and maintaining torch height in the hole isn't a problem. There is no need to deactivate the THC. We cut rivet holes as small as 3/16 all day long.

What Jim is saying is the Z axis should not move when cutting a hole. The reason for this is that the hole speed is less than a strait line due to the radius and the tip voltage should change due to the added amount of material being cut when cutting a hole versus a strait line move. The constant surface footage requires a THC to lock or to automatically change tip volts for the holes based on a lowered feedrate per amperage. For instance cutting 1/4 steel at 65 amps lets say you cutting at 130ipm then your holes can be 40-70% of that feed rate but the amperage doesnt change. So if you feed rate is lower then your tip volts should also be lower otherwise the Z axis will lower and the hole geometry will be affected.

[vmax549]

I cut tons of 16 ga. Use a small arc leadin .150 and NO leadout for inside cuts. You have already cut that part with the leadin cut. No point in crossing empty space trying to recut it.

I use HT fine cut 40 amp tips UNSHIELDED cover. .060 cut height, no dwell and 130 IPM. Little to NO dross.

Works great on fine detailed artsy work with LONG consumables life.

That setup ALSO works great for alum up to 1/4 " ,Dwell .5 at 30 IPM for detailed work. Clean cutting and long life.

Just a thought, (;-) TP

[TAP]

vmax549, are you using HT/PM 45 ? if so, could you give me the part #'s that I would need to purchase, I spend more time looking at #'s than working and get really confused, I looked at the HT charts and got even more confused...afraid if I start drinking I wont stop.

Using PM 45 Shielded.

Tim

[vmax549]

Hi Tim, Here are the parts I use with a PM1000 and T60 machine torch.

Deflector 120979
Electrode 120926
Swirl Ring 120925
Nozzle 220329

(;-) TP

[Largemouthlou]

Terry, I use the 40 amp FC nozzles a lot with .125 down to .050 alum, also works good for me on .125 diamond plate .. never tried it on the .25 alum.. Are your IPM and tip volts the same or do you have separate settings for the .25?

Also Terry, What do you set your plunge rate at in SC?? Seems to be a lot of discussion about that lately.. I remember one time Tom had said something about a certain percent of your velocity or accel but CRS has set in on that one.. I see others from 100 to 150 set in SC Heck I've been using 36

Thanks
Louis

[TAP]

Thanks vmax549,

Tim

[vmax549]

Hi Louis, On plunge rate you are worring about nothing(;-) It is ONLY from pierce height to cut height and in that length of movement you are NEVER going to see 100/150 IPM. There is NOT enough room to get up to speed ,IT is only a .050" move. Mine is set to 35 and have never had to change it. Would not really matter anyway I would never get up to that speed in that short of a move(;-)

I would have to look at the arc voltage charts at the shop but reguardless, IF you cut at the correct height and look at the cut voltage ,that would be YOUR setting which could be different from mine.

(;-) TP

[Largemouthlou]

Thanks Terry!!