Welding Tips and Tricks

Hey guys I was wondering if you guys have some of your parts sent out to a CNC plasma and if so what do you expect from the parts. Accuracy and how do the small holes look like 1/41/4" holes any any contemplates you have about stuff that comes in. If you are looking for parts what is your main concern?

All input is valued!

Thanks,
Jason

Hey mate.

In my experience, plasma cutting is nice and accurate.....but, has a bit of a slanted kerf that can affect the tolerance of the parts, depending on what you need them to do. Brackets and plates and broad shapes, good as gold. Small highly detailed bits, Small holes, not as much.

Keep in mind that my experience is a plasma cutter that was probably 30 years old. I believe there are "high accuracy" cutters out there now.

If you really after fit up quality, go for laser cut parts. Less than 1mm kerf that can cut with almost no kerf angle. Ive seen 4mm holes cut in 8mm plate, no probs, any shape you can imagine.

Mick

weldin mike 27 wrote:Hey mate.

In my experience, plasma cutting is nice and accurate.....but, has a bit of a slanted kerf that can affect the tolerance of the parts, depending on what you need them to do. Brackets and plates and broad shapes, good as gold. Small highly detailed bits, Small holes, not as much.

Keep in mind that my experience is a plasma cutter that was probably 30 years old. I believe there are "high accuracy" cutters out there now.

If you really after fit up quality, go for laser cut parts. Less than 1mm kerf that can cut with almost no kerf angle. Ive seen 4mm holes cut in 8mm plate, no probs, any shape you can imagine.

Mick

Have you ever got parts in from a high definition shop? I want to make sure that I am putting out the best parts possible for plasma and see if anyone has a complaint with this cut edge on 1/2" plate. We are just starting up so I was wanting to hear some complaints of plasma parts so I can do my absolute best to avoid any problems.

That is seriously aproaching the cleanliness and accuracy of water-jet, and I'm sure faster by a factor of five or more on 1/2" material.

How about a transverse image... Straightedge along the length of the kerf, to show "ripples" in the cut? I'm guessing they're minimal. I'll have to dig up and photograph some wedges given me by a (top-notch) vessel shop, cut on a CNC plasma. All carbon steel, but stunningly precise for 3/4" thick. I turned three into pipefitter wedges with a couple minutes with a flap-disk, a dial-caliper, and a scribe.

Steve S

Let me run out and grab a picture, the ripples are almost non-existent at 1/2", any other pictures?

I get A LOT of parts plasma cut. Some of the complaints I would have are, one of our main suppliers we use cant do a hole in plate less than 1/2". When it is attempted it is never round or even 1/2" for that matter. I would guess they are set up for thicker material and this is not their forte. I do like the fact they can do our bevels on plate for us. This saves us a lot of time and money! Most everything we order in, we get processed so all I have to do is put said pieces together. As far as the kerf in the picture I don't see any complaint with that. I have seen worse, that is for sure. I have a friend that has a table and he says as long as he keeps a good tip in his cut stays good, but when it gets wore out the accuracy goes down the tubes. I had some ( actually 300' +/-) 6" T1 waterjet into a gear rack and over the 6" we got a average of .060 out. I think my biggest complaint with plasma is the slag left on the sides. My friend has made it a point with his shop to always sand the sides and get any slag that is left off. I ordered parts from him a while ago and I will say it is nice not having to drag out the sander before starting to weld.

If there are any other pictures you want to see let me know. The run speed is at 65 ipm. This was done on a HD plasma, We do always clear the slag off parts, if there is any. I would guess if they can not cut holes 1/2" it is in there gear box or track.... I always want to put out the best product possible and take the extra steps.

That IS slick, and on par with the wedges I described earlier (made with top-notch plasma equipment).

Steve S

Thanks,

I appreciate your input we are just starting up, and I am all about putting out the best parts. I am glad to hear it looks good.

Repeat that last pic, with the blade of the straightedge lit from behind (to show off the precision), and you'll have the cover shot for your sales flyer...

Steve S

I think it looks great! Looks like most everything we get in. I will take some pictures on Monday ( if I don't forget ) of some of our plasma cut parts for your comparison.

Thanks guys, just wanted to make sure I was on track for quality, and wanted to know what you expect from your cutters.

Jason,
I was right in front of some good samples today and did not take any pictures. I promise I will get them to you tomorrow night!

HAHA sounds good, Thanks

As promised here are some pictures of 2" plate. For us this is very acceptable. Enjoy.

This is a very very thick cut for hy-definition plasma at 2" about how much taper do you guys have on that (3/16")?

Very interesting on the ripple pattern as well. At 2" I would of thought it would of been cleaner to cut it with oxy-fuel to get a straighter line, although I am new to this, and I have a lot to learn.

Thank you for the pictures. Our plasma will max out at 3/4" production cut and after that we cut oxy-fuel a little slower but the cut angle is amazing for being old technology like it is.

Thanks for these good pics!

You know now that you say that this might be oxy-fuel. The plate bottom stops around the 7-1/4" mark on scale. I would say it is around .060 out. I actually was going over to get my feeler gauges and was side tracked. I will look for more samples for you. I did think of one thing that really messed with a part we received earlier. I ordered 3" pl that was supposed to be burned with a pdf. When we got it, it measured correctly and we started to assemble. I couldn't figure out at first why one side met all measurements while the other was off by 3/16". We got looking and apparently either something happened to the torch or they stopped for the night in the middle of the cut. From that point on it tapered down causing us to almost mess up on a part. I have seen this with a waterjet as well. I was running some thick plate and I stopped the machine for the night and continued the next morning. Come to find out either the piece was bumped or the head did not return to the location it was supposed to causing the part to be slightly off. The point is run your part until it is done whenever possible.

oops sorry was looking at wrong side of scale, I mean 6-3/4".

I think oxy-fuel would be even straighter than that and the top edge would be just slightly rounded. dosnt mater what it looks like, it looks good.

Here is a photo of 8.75mm "bisalloy 80" which is a quenched and tempered low alloy steel. It is a cutout on an exisiting part. You can clearly see the laser cut edge and an edge cut with high end, hand held plasma with comp air. Though the plasma edge was ground, that was mostly to do with the quality of the operator rather than the machine. Its a Lincoln invertec 50 i believe and is a 3 phase machine with drag tip.

Mick.

Mick,
I think both edges look great! The hand held on the right is very consistent. I assume that you had a guide to help make the cut straight. Looks like you had a consistent travel speed.

Hey,

It wasnt me, was a "know all" apprentice, (never learned a thing in the 5 years he was with us) so imagine what a good tradesman who gives a damn could do. Haha. I it was free hand. It is a killer machine.

Mick

Mick,
Freehand....that's even better!

Yep, i think the biggest problem people have is the machine, because i have used that one on steel and al and its faultless.

Mick.

that is an amazing cut for free hand!