Fine cut not cutting / kerf filling in?

[rosonowski]

So we banged out a bunch of signs, and switched to a fresh new set of consumables (electrode and nozzle).

Go to cut some more steel, and the kerf is either filling in behind itself or not cutting, I don't know. My boss wants me to note that the dross on the last couple of cuts has been worse. We've got a water table and dessicant air dryer, for what that's worth.
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We also have a digital torch height control, although I'm not honestly sure if it's being used correctly. My boss has been 'eye balling' the initial height above the work piece. The torch comes down and touches off the plate for each cut, so I figured it probably wasn't a big deal (since it finds z with each cut, and has been working OK that way for awhile...)

We're using the settings that jimcolt recommended, so I'm not sure what to do here. The 'fine cut fast' seems to be better than 'fine cut slow', if that helps. It's a bit of a showstopper, hoping you guys would have some input. Sorry if it's a noob question, but this is all new to us!

[cefab]

Are you using candcnc system? Either way your volts look way to low and your thc won't perform right.

[rosonowski]

Yeah, it's a CandCNC system, an ArcPro 4800.

Is the voltage just a little too low, or do you think it's WAY too low? I know it has to be lower for the finecut consumables, we tried the normal voltage and it burned super bright and warped the plate.

We had been cutting without major issue with those settings before, so it's something of a mystery to us. Tried a few more cuts, ran into 0-21 on our Hypertherm unit (gas flow stopped while cutting) which Jim Colt said was actually more of a voltage issue as well. We swapped out the swirl ring for a new one, and that seemed to help, as we were able to do another two pieces involving 50 or so cuts, but then the same error started cropping up again.

[cefab]

You know i am really not 100% positive. I did not know fine cut used a lower voltage. I would wait for Jim to chime in or call them. I use a miller and have never used a hypertherm

[jimcolt]

The height (torch to work distance) is much more critical whith the fine cut parts that with any other consumables. A little too high...and the arc will not fully penetrate the material being cut. In the pics I would guess that you are cutting too high.

The arc voltag on your height control is just a reference voltage.....you should adjust it while cutting so that the cut height matches the height suggested in your Hypertherm operators manual for the consumables and the plate thickness being cut. I am on the road....and don't have a manual handy....but I believe the torch cut height should be .06".


Jim Colt

[rosonowski]

We reduced the cutting speed by ten percent, and this seems to have solved the issue for us.

[Team Tracker]

I have seen many times operators using the 65 amp shield (part # 220817) with Finecut nozzles which will increase your nozzle to workpiece distance and have you cutting too high off the plate. If you are using THC system that has you set the torch to workpiece distance visually rather than setting the height by specifying an arc voltage than it is easy to cut using this incorrect shield and this can cause the problem you are seeing. Be sure to have the proper shield in place. I know this is basic stuff but it's worth putting out there in the event that it may help yourself or another member on the site.

[jimcolt]

I believe the height is incorrect. You can somewhat compensate from being to high by reducing the cut speed. The Fine Cut parts are more critical to speed and height than any other set of consumables. If it is not set close to book specs (from a physical height perspective) then they will not cut through the plate.


Jim Colt Hypertherm

[Marty]

Just to follow up on this subjectand how it resolved for me ( fingers crossed )

I have a Shop Sabre 4x8 water table, Hypertherm M65, WIN CNC Controller with THC
I pretty much only use Fine Cut consumables at 45 amps. I mostly cut metal art using 10-14 gauge mild cold rolled steel. The two main reasons I went with Hypertherm were mainly because of the Fine Cut consumables and then also the Hypertherm reputation.

In December I was battling a severe problem of "fine cut not cutting all the way through" making for many recuts and wasted material, late shipments, and temporary loss of my ability to smile and laugh. I measured amperage returned through the ground cable to the sheet with a DC Current clamp meter, (amperage output from the Hypertherm meaured just as set at the control panel) , changed out Fine Cut consumables including swirl ring, tried different cut heights, (lower cut heigth = torch dive, good thing it has a magnetic break away or the resultant train wrecks would have been much worse) tried just about everything except vary from the Hypertherm Manual's cut charts, I was resolved not to because I read alot that "you should not vary much if at all from the Hypertherm manual's cut charts"......

To make a long story short, the solution was to decrease cut speed by 20% below the Hypertherm Manual's charts for Fine Cut Consumables. I think 20% is a huge variance from the cut charts but it works for me. It is a coincidence, but for the other consumable's cut charts, IE 45 amp and 65 amp, there are 2 cut speeds to pick from. One is "Best Quality and the other speed is "Production" There is also 20% difference between those choices also. Maybe the Fine Cut chart should be revised??

This 20% speed decrease solved the "not cutting through" problem which in turn created a warping problem, even on 10 gauge. Slower speed = higher temp.

Then I noticed my water level was about 1 inch below the material being cut, so I raised the level higher than ever, so that the water level meets and is in contact with the material being cut. Made a lot more test cuts and then some cuts of art designs, and no problems finally ( so far)

I had experimented with 64,45, and Fine Cut consumables, changing cut heights, amperages etc. The Fine Cut consumables consistently were the challenge to get the cuts nice and clean, regardless of water level

I want to give kudos to Shop Sabre, (Jim Bombardo, Jason and Ben) for their assistance in the past and with this most recent problem. It is a great company to work with

By the way, yes my shop air is adequate capacity, pressure and dryness..........I have no less than 4 prefilters, an oversized dessicant dryer with new beads, and 2 post filters. I use the same filtered air tp spray paint and airbrush with and never have a moisture problem. The compressor always maintains 90-135 psi at the back of the Hypertherm, the manual says it needs 6.7 cfm at 85 psi, my compressor outputs 11 cfm at 90 psi, so it is not undersized

If anyone has any suggestion on how to use Fine Cut consumables at the factory recommended cut speeds, it would be intereresting to see and maybe try. I am open to suggestions, but for now, the table is cutting nicely with Fine Cut Consumables

Marty

[jimcolt]

The cut charts in the Hypertherm manual are correct.....they were developed by cutting tons of steel, stainless and aluminum in our labs....but I would have to say that they are correct under laboratory conditions....meaning every single process parameter is checked and verified in order to develop good data. I always use the cut chart specs for my Powermax 45 and my Powermax85. I use the 85 quite often with FineCut consumables. I must say though that the specs in the book were all developed cutting on a downdraft table...water splash can have an effect. If it is not the water....then I would expect one of your other parameters could be off just enough to cause the slower speeds.....could be an air leak or restriction in the plasma or the torch, could be the height is not always staying right at .060" off the plate, could be your cut speed is not exactly what you set it at. Something is not spot on! This is not the first case.....we occasionally hear that users get better performnce at different speed...however the majority of the time users stick pretty close to the suggestions in the chart.

I occasionally will find a sheet of steel that cuts better at either a slower...and sometimes faster speed then listed in the manual as well. Changes in silicon content (which wanders a lot on steel) and carbon content as well as manganese and a few other trace elements found in steel will affect dross and speed.

If you want to....send me a couple of 8.5" x 11.5" pieces of the material you are cutting (you can send them usps flat rate in an envelope for $4.95, the envelopes are free in any post office)....I'd be interested to try it on my Powermax85 with the FineCut parts...then cut the same things on some in house steel that I have of the same thickness.

I only use the Fine Cuts on 12 gauge and thinner....anything between 12 ga. and 5/16" I use the 45 amp shielded parts....I do that because the shielded parts last about twice as long, cut at faster speeds and with less dross on the thicker materials. The Fine Cut parts do best on thinner....and definitely better on stainless steel.


Jim Colt Hypertherm

[Marty]

Hey Jim Thanks for the response

And thanks for your offer to cut some of the actual sheet I had problems with...and the reminder that the cut charts are under lab conditions with the variables held to minimum.....with a down draft table...........This time I learned not only how to solve the immediate problem, but also that there will be variables present in each shop that can make troubleshooting a cut problem an art (intuition and experience) and not a science (checklist) .......I am the kind that tends to not want to leave not much in the "un explained" area so that repeat ability is constant ............... but having said that, my goal is to get finished product out the door on time and to my quality standards. So I am back to on time delivery, and joy is present in the shop, even though I do not know why the slower speed works. It could be a site specific issue . I mean as you said, the metal makeup itself can be off as to silicon ,manganese and carbon levels can vary effecting cut quality, even speed. I changed suppliers once last year because their metal was grainy and porous on the interior. The present supplier seems to supply cleaner metal and their service is great, not to say the mineral levels could still vary. The Edison grid I am on could be acting strangely, maybe even EMF solar flares hitting the Southwest US, maybe there are microwave signals going through my shop, maybe my Ipad is throwing EMF, and and on, could be a lot of different causes, maybe I need to wear a tin foil hat!

So even if you cut my metal in your shop, it may not prove anything, except that there may be variables here, that are not in your shop, or were not present at the factory when the cut charts were developed

So the bottom line for me is that now each and every time I load a sheet , even from the same shipment, I run several straight line tests, and a couple of more challenging files that have lots of curves and straightaways, understanding that the new sheet might cut differently.....this way I hope not to have a crash in the middle of a detailed 15 minute 3x6 foot cut:)

The other lesson here is when a cut problem arises, then methodically experiment with the basics, speed, height, verify ample clean air, inspect consumables , even log consumable changout, it sneaks up on you! Every time I am experimenting I document the results and I keep a Table Log Book with details on what solved which problem.

I will never buy any brand of Plasma Cutter other than Hypertherm, (or anything but a Shop Sabre Table) I appreciate the engineering basis of the companies, and the support from Hypertherm either to Shop Sabre or directly to me. And I am glad you responded and keep an eye out. I was a manufacturer rep for many years in a different field and know you have a "wording challenge" every time one of these "un explained" less obvious cause, type of problems are tossed out .......good job Jim!