Fine tune circles??

[desertfabmotorsports]

Where do I start in fine tuning circle cuts?? Everything else I cut is really nice but the circle cuts are not round. The smaller the worst it is.

[TorchmateSupport]

Are your circles misshaped or round but with excessive bevel?

If they are not round on the top or bottom of the cut are they showing flat spots?

In general most minor mechanical problems will present themselves in small circles. Check your gear to gear rack spacing and belt tightness. When the motor drive box is on the stepper motors you have will lock, if you try to move the gantry or the cassette it should not move. If you are getting any wiggle then something is loose.

If the shape is correct but the bevel is excessive causing the bottom of the cut to be misshapen the height or speed may need to be adjusted. Slowing down circles allows for less bevel and a overall small circle cut. Go do Configuration --> Machine --> Feedrate/Ramping in here the max arc feed rate and continuous contouring feed rate should be lowered to allow for slower circle cutting.

If you could post pictures or a better description of what is cutting this would help diagnose the problem.

-Jack

[ademster]

Here is a small circle he cut out for some brackets for a mount I am making, Granted the holes are smaller then what I need.. but here it is

[carslut]

wow, toughs were cut exactly w/ the same file/ machine and such but came out that different?

[BESRK]

Are you using a THC? I know sometimes if I have it set on "auto" and I cut a small hole, the material will burn away causing the torch to dive into the material and cause a similar looking hole. It usually only happens on small holes. Of course, if you're cutting with manual height adjusment.. disregard my rambling..

I also get a "rounder" hole if I use an "arc" lead-in versus a straight lead-in.

How thick is that material?

[HardcorewannabeXJ]

Seems like those are two different files, with the same small bolt hole.

First things to check are mechanical, any amount of backlash or loose set screws will present itself here. Beyond that, it's all Plasma. The general rule of thumb is 1.5 times thicker than the material is the smallest hole you can cut. If you aren't using the proper amperage/feedrate/height, then this will also cause the hole to cut out worse. Slowing down the circle cuts will also make them cut out better.

[MikeRenz]

yea i'm hitting the same thing. I'll try slowing down my circles...i'd sped them up a while ago since i didn't like how slow it'd go around turns. hehe.

[abnaasefmb]

same here


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[jimcolt]

Its not "all plasma" that makes bad holes! There are some bad plasma's that do not cut nice holes, but a high quality (read major brand) moder day plasma with good engineering and technology...can produce very nice holes.....if the motion control and height control as well as the part program are all coordinated properly. Here is something I have posted many times on many forums:

In a nutshell….here are the things necessary to get the best quality holes, but the mix and condition of your equipment (plasma, torch height control and machine motion capability) certainly has an impact as well:

1. Make your lead ins as long as possible…preferably near the center of holes under 1-1/4” diameter.
2. Ensure your torch height control is operating correctly….pierce height is critical, and the ability to index from pierce height to cut height while still on the lead in is critical as well.
3. Your machine part program (machine code) should have a federate override that cuts all holes under 1-1/4” diameter at a slower speed (a rule of thumb is 60%) than the rest of the part contours.
4. The arc voltage height control should be frozen at cut height on all holes under 1-1/4” diameter. Absolutely critical. This should e done in machine code, and with some types of nesting software this and other functions related to good holes can be automatically set (MTC software can do this)
5.There should be no lead out, rather an overburn (staying on the radius of the hole) should go past the lead in kerf by approx. .200”.
6.If your software and controller (I don’t know what equipment you have!) is capable, the plasma (depending on model, as they all have different arc ramp-down characteristics) should receive an off signal so that the arc starts extinguishing slightly before crossing the lead in kerf. Plasma arcs do not instantly shut off….as there is an exothermic reaction occurring, as well as gas and current ramp down’s that are used to extend consumable life. If all of these shut down delays are allowed to occur after the machine motion has stopped….a rather large ding/divot will be present in the cut.

All of the above will take some experimentation to get the best results….every power level, every thickness and every hole diameter will require slightly different parameters to be perfect, but you should be able to make some pretty good improvements…again, assuming that your machine motion is good (no slop or backlash, good acceleration and de-acceleration), your height control works well, and you have a good plasma system.

Attached are some pictures of holes cut with a Hypertherm Powermax 45 on an entry level (low cost) cnc machine with a full function THC, using the techniques listed above. I can cut holes that are very round, but there always will be a small amount of taper with any air plasma. I just oversize the holes a few thousandths (usually about .010") and bolts will go through perfectly.

First two pics are of 3/8" steel with 3/8", 1/2" and 3/4" diameter holes, front and back, untouched (no dross removed). Third and fourth pics are of 1/4" steel with holes starting at 3/16" up to about 1-1/4".

You can make holes like this with any tight (minimal backlash) machine with a full function torch height control. If you are cutting without a THC.....decent holes can be done if you keep your hand on the height adjust screw, can accurately pierce at pierce height (so the nozzle does not get damaged on the first pierce from piercing at cut height), then quickly index the torch down to cut height while still on the lead in kerf. This all has to happen rather quickly.....to me the height control is every bit as important as the x and y motion, and is worth every penny you pay for them in terms of cut quality, consumable life, and ease of use!

Jim Colt Hypertherm

[Torchmate]

Jim,

What's the word on the test units and your trip out here to show us what they can do? And why you gotta go posting up pic's of that blue and yellow machine in my forum?

Let me know what the plan is moving forward. If there is one that is.

Bill

[jimcolt]

Bill,

It is still in my plans to ship a couple of units to Reno, they are budgeted for. The problem is on my side....my travel has been pretty much non-stop, business is doing far better than we expected this year. I promise it will be fit in before summer is over....and I will work on the scheduling this week.

Sorry on the picture of that machine....it is the only machine I have....and honestly I did not pay attention to the particular forum that I saw the posting in regards to hole quality. If you read my post.....I am not being particular about any machine model or brand, rather I am focusing on what is necessary to get the best possible holes. You can put the best industrial high definoition class plasma on any cutting machine, but it will not cut good holes unless all of the systems work together, and a proper part program and cut parameters are set up. I have seen many holes cut with Torchmate machines that are as nice or nicer than the pics I posted!

Best regards, Jim

[Torchmate]

Thanks Jim! I read the post. Just giving you a hard time. Let me know when you know more.

[wendleburger]

It would be really nice if the arc feedrate parameter in the TM software ignored radii over 3/4" or thereabouts.

As it is, it's a bit of a tradeoff. If you slow it down you can get really nice internal circles and filleted corners, but then you are cutting at speeds well below ideal on larger external curves that could really be treated as straight lines.

[MQYJ]

I have never adjusted any arc speeds on my machine. What I generally do is group all the small holes together to be cut first and simply adjust the speed in the g-code. All the smaller holes get cut at about 50-60% of the feed rate of the rest of the file. I also figured out through the assistance of the TM support that I was piercing a little too close to the material. Once I made some small adjustments to pierce height I was able to get much better looking small holes. Like Jim said above, if your pierce height isn't set properly then you will burn up the tips on the first pierce and then it won't matter what your height setting are because it won't put out a straight arc anyway.

[BESRK]

Originally Posted by jimcolt

The arc voltage height control should be frozen at cut height on all holes under 1-1/4” diameter. Absolutely critical. This should e done in machine code, and with some types of nesting software this and other functions related to good holes can be automatically set (MTC software can do this)

How do we do this in the driver program? I've gotten pretty comfortable with basic functions that just require "clicking on buttons" but I haven't messed with writing/editing G-code.

Sometimes I find myself standing at the THC box and manually switching from "manual" to "auto" when doing a small diameter hole. I'd rather be able to program it in and forget about it.

[cvc9216]

Originally Posted by jimcolt

Its not "all plasma" that makes bad holes! ..............
Jim Colt Hypertherm

In the short time I've been playing around with the 2x2, I can get "decent" holes, but nowhere near that nice. I was making a mounting plate out of 1/4" steel with four 7/16 (.44) holes. I had the holes at .46 in the program. Every time one or two of the holes would need to be cleaned up just for the bolt to fit through. I was running the torch a bit higher than recommended pierce height as I was having problems ruining the nozzles after a few pierces on 1/4. Is there anything I can do to get better holes without the height control? Anyone have examples of nice holes cut without the THC? If that's what I need to get perfect holes, I might have to buy one as most of what I cut is small brackets and parts where some precision is necessary in the bolt hole dimensions.

I have the Powermax 45 with the machine torch. I was thinking the other day, would there be any benefit to using the hand torch shield since I don't have THC?

[jimcolt]

Yes.....the hand torch shield is designed to drag on the plate......holding the nozzle at the correct height off the plate. You still need to pierce at a higher height to keep the blowback slag from damaging the nozzle orifice.....then index down when the pierce is complete and lightly drag.

A torch height control (in my opinion) is just as important as good x and y drives.....worth every penny you pay for it......at least after you have used it for a while and realize how much better your cut quality is (less grinding and rework) and how much longer your plasma torch consumables last (usually this savings alone will pay for the THC after a period of time).

Jim Colt

[BESRK]

Here's a few holes I cut in 1/4" this morning.. some tube flanges for a buddy. These are .40" dia holes. Cut @48ipm with 33ipm for the arc feedrate.. HT1250 cutting at 40amps with 40amp shielded nozzle. Pierced at .22" height and cut height at .080.

[jimcolt]

Nice job.....its a great plasma, the Powermax 1250, but its the height control, the plasma, good programming that makes it produce the best quality holes. There are so many plasma users....even with high end industrial systems...that don't get holes as good as the ones you and I have pictured. They can.....just have to pay attention to all of the parameters, and must have a good torch height control!

There is some new technology from Hypertherm on expensive high definition class oxygen plasmas that automatically sets all the parameters as well as automatically adjust lead in styles, plasma on/off time, feedrates, etc for every different hole diameter and material thickness.....it also uses a new gas flow technoogy that eliminates the taper in holes. Hypertherm calls it True Hole technology. You won't see it available on entry level machines as it is costly, but on high end industrial machines it has revolutionized hole cutting.

Jim

[BESRK]

I think I learn the most with a shade 5 lens in my hand, bent over the table watching the torch from about a foot away. My wife says I look like a mad scientist in a lab. The other thing that helps me out is meticulous notes. I've been working on a spreadsheet with all the adjustable parameters layed out so I can "zero in" on good setups.

[jimcolt]

Well, unlike many other brands, Hypertherm has 85 "mad scientists" that have already done the work for you. We have 85 engineers, 15 with pHD's that speend thousands of man hours in our R&D and Engineering labs each year developing cutting parameters that work. If you have a Hypertherm system and open the manual up to the machine cut parameter charts, set everything up exactly as suggested....you will get nice cuts.

Jim

[YuNiT]

Originally Posted by jimcolt

If you have a Hypertherm system and open the manual up to the machine cut parameter charts, set everything up exactly as suggested....you will get nice cuts.

Jim

That may be true for other cnc tables, but definitely not a Torchmate.

[carslut]

yikes, this making me wonder if i should rebox my Thermal Dynamics unit and get an hypertherm system ... or just sink deeper into my setup and try an automated torch height control in hopes to get consistent results. .....

[HardcorewannabeXJ]

Originally Posted by jimcolt

Well, unlike many other brands, Hypertherm has 85 "mad scientists" that have already done the work for you. We have 85 engineers, 15 with pHD's that speend thousands of man hours in our R&D and Engineering labs each year developing cutting parameters that work. If you have a Hypertherm system and open the manual up to the machine cut parameter charts, set everything up exactly as suggested....you will get nice cuts.

Jim

Originally Posted by YuNiT

That may be true for other cnc tables, but definitely not a Torchmate.

I wish the manual just had parameters that cut out perfect, it would make my Job a lot easier. Not saying that the thousands of man hours and 15 phd's are worthless, but I could run out in the shop and within an hour and a few sample cuts give you some settings that might be somewhere around the book values. You'll never know how good or bad the machine can cut without pushing the limits.

I guess we'll wait on our HT units to arrive and do some book value testing!

[jimcolt]

When I come to Reno with a couple of Hypertherm systems we will test at book specs. When I cut in my home shop with a Powermax45....I use the specs from the manual. Occasionally I will play with speed if I have an odd alloy, or different surface conditions....but the cut height, pierce height and amperage settings in the manual are right over 90% of the time.

The nice thing about that is.....if I cannot get a decent cut at the book specs....then I know something is wrong. First thing to do is look for operator error (perhaps I set the height incorrectly), then I inspect the consumables (instructions on how to inspect the consumables and what to look for are in the Hypertherm manual as well), and if that does not work I will look for things outside of the plasma that will affect cut quality such as: 1. excess moisture in the air, 2. roughness or backlash in the x or y axis, 3. oscillation in the z axis, etc.

If the Torchmate machine and the height control are dialed in correctly...I will stand behind the book settings! I disagree with YuNiT's post that states "That may be true for other cnc tables, but definitely not a Torchmate".....no reason why a Torchmate machine (with height control) can not cut at the book settings.

Jim Colt