14ga Lettering

[slvr98svt]

Trying to do a small sign for a customer. I am using maxine script font, lower case and I can't get the thing to produce decent cuts. I have a 5x10 tracker cnc pro table, with a hypertherm powermax 1250. Using 40amp finecut consumables. I do mostly larger thicker stuff not this decorative stuff and its really getting to me! 1st problem is the cut quality, using like font size 36-48 its just not thick enough. Do you guys not do stuff that small or what is the trick? and 2ndly, the plasma air supply after it finishes with 1 letter is still "purging" and wont relight the torch until after it is done, so I have the ramp speed turn down to 14 or so and still have to pause the cut to wait for the air to purge to relight the torch?

I am getting frustrated and need some input from the professional "decorative" guys that do this daily!

Thanks,
-Matt

[jimcolt]

First, The 1250 goes into a post flow after every cut cycle.....however it will refire if given a start signal...although there is a 1/2 second or so delay. As soon as the start signal enegizes, the air stops for about 1/2 second, then refires. All Hypertherm Powermax systems have an automatic postflow, and all of them are designed to refire at any time during that postflow. This feature helps improve consumable life....and it can not be shut off....nor would you want to.

That font size is relatively small for an air plasma ....mostly because plasma works best at a fixed speed, and your cutting machine cannot maintain that speed on small intricate contours. Here is what you need to do to cut intricate details....and I'll assume this is steel.....you only said 14 ga.

1. Ensure that your acceleration rate for your machine is at its maximum.
2. For 14 ga steel.....lets try to slow things down so your machine can keep up with the plasma....
a. Use Fine cut consumables....for best results use the 220404 deflector/shield
b. Set current to 35 amps, cut speed to 100 ipm, torch pierce height to .08", and make sure torch cut height is .08" as well.....with you machine you may have to adjust arc voltage during the cut until the torch is exactly at .08".

You can experiment with speed.....slower will give better detail but will produce a bit more dross. Try spraying mig welding antispatter spray on the bottom of the steel before cutting....if you don't have any, try cooking spray (PAM)...this will minimize or eliminate dross. The most important thing....trying to get you machine to maintain speed.....truning up the acceleration may help....although accleration too high will make the machine overshoot on corners. Also of highest importance.....cut height.

Let me know if this helps.

Jim Colt Hypertherm

Trying to do a small sign for a customer. I am using maxine script font, lower case and I can't get the thing to produce decent cuts. I have a 5x10 tracker cnc pro table, with a hypertherm powermax 1250. Using 40amp finecut consumables. I do mostly larger thicker stuff not this decorative stuff and its really getting to me! 1st problem is the cut quality, using like font size 36-48 its just not thick enough. Do you guys not do stuff that small or what is the trick? and 2ndly, the plasma air supply after it finishes with 1 letter is still "purging" and wont relight the torch until after it is done, so I have the ramp speed turn down to 14 or so and still have to pause the cut to wait for the air to purge to relight the torch?

I am getting frustrated and need some input from the professional "decorative" guys that do this daily!

Thanks,
-Matt

[griffin]

Not meaning to hyjack the thread, but Jim you said make sure your cut height is .08. I have a THC unit that I set the volts on. How do I know what the exact height is? Sorry for the newbie questions, still trying to figure out cutting this thinner stuff.

Thanks,
Scott

[jimcolt]

Use the recomended voltage listed in the Hypertherm manual on the "machine cutting charts" as a starting voltage for your THC setting. Once the cut starts, adjust the voltage on your THC up to go higher and down to go lower....often the actual cut voltage varies quite a bit from the recommended voltage, but physical height is what is important for best cut quality. There are many factors that affect the voltage/height relationship....and every machine installed in the field is calibrated somewhat differently....so just make sure physical height is right.

I am not familiar with your thc system....on some, you can do a test cut and stop the plasma and the torch will stop at the height it was cutting at....then measure it. If it is higher than .08", reducing the voltage by 5 volts will lower the torch by roughly .020" (varies a little with each process power level). A nickel is approximately .080" for easy reference!

Jim

Not meaning to hyjack the thread, but Jim you said make sure your cut height is .08. I have a THC unit that I set the volts on. How do I know what the exact height is? Sorry for the newbie questions, still trying to figure out cutting this thinner stuff.

Thanks,
Scott

[griffin]

Thanks Jim

I never even thought about stopping it and measuring it then.

I'll do that today.

[mdwalker]

Best way to accurately measure the distance is to go to your local auto parts store & buy a set of feeler gauges. Well worth the money, they are only a few bucks. They are just thin metal strips with the thickness of each one stamped on it.

Danny

[slvr98svt]

Jim, I know it's only 2 weeks later, but thanks for the tips. I am just not getting the time to mess around with this. All these are great things I never thought of.

Yes it is 14ga steel. As well I am using a 220404 cup like you mentioned. However, I can't remember if I mentioned I have a Tracker CNC, now I guess I am lost on the voltage part. How do you adjust the voltage? The THC is in direct relation to the arc voltage? In the "cut charts" in the Hypertherm manual there is an arc voltage column and I always wondered what or how you adjust it?

With the Tracker I can stop it and measure. I guess I will start there!

Thanks,
-Matt

[Loyd]

Matt,
These are cut with a Hypertherm 1250. The letters are probably 72. I have cut some smaller but everything has to be perfect! I have done my share of blowing them away! These are all 16 ga.
If I had a lot of small stuff to cut I would put my 380 back on my PlasmaCam it does a great job! Experiment and good luck.
Loyd

[bobwelding]

Hi! We've been reading your posts and have learned a lot. But I have one question. We have a Torchmate 2 4x4 with a Hypertherm powermax 45 machine torch. We're using 18 g cold rolled steel and we're not happy with the cuts on some of our finished projects. Is there a certain thickness of metal that works better than others? We'd love some feedback from all of you. Thanks.

[jimcolt]

The Powermax45 is capable of excellent cut quality from 26 gauge up though 1/2" and beyond. The key to getting good cut quality is with:

1. Good motion control (smooth motion).
2. Cutting at the right speed....the speed and thickness specs that are correct are listed in the Hypertherm operators manual.
3. Cutting and piercing at the correct heights....listed in the manual.
4. Using the correct set of cunsumables and power settings.

I'd be happy to help you get the system dialed in if you provide details of what you would like to cut...as well as details of your machine.....does it have the AVHC height control?


Jim Colt

Hi! We've been reading your posts and have learned a lot. But I have one question. We have a Torchmate 2 4x4 with a Hypertherm powermax 45 machine torch. We're using 18 g cold rolled steel and we're not happy with the cuts on some of our finished projects. Is there a certain thickness of metal that works better than others? We'd love some feedback from all of you. Thanks.

[just_wanna_drive]

So what does it take to build a machine that can keep up with the power and high cut speeds that the Hypertherm units demand? High output servos and linear rails? An upgrade from the typical rack and spur gear setup? Lightweight, but very strong gantry design?

Maybe I should start another thread about this, sry for the thread jack!

I know my torchmate tm1 would violently self destruct at 400ipm.

[jimcolt]

While I certainly am not knocking any machine designs.....there certainly are machines available for plasma cutting that have higher acceleration rates, higher (maintainable) cutting speeds, and higher positioning and contouring accuracy. They also have higher prices.

On the highest capability machines you will find precision helical rack and pinion drives (on smaller machines with less travel....sometimes there will be ballscrew drives) that are coupled through planetary...low or no backlash gearboxes to AC Brushless servo drives. The drives are inertia matched, and tuned for the least amount of folowing error....while maintaining the highest levels of accleration...even at speeds of 300 to 500 inches per minute. The CNC control would often be linked to the drive electronics through a fiber optic network (such as Sercos), and the plasma power supply, gas flow control and height control would all be interfaced with an ethernet style interface. Construction of the machine frame would usually be welded structural steel that was stress relieved...then way sufaces would be simultaneously milled for accuracy...the gantry and carriage often are lightweight yet rigid, and designed to tune out harmonic vibrations. As a final touch...the x and y motion are often mapped using a laser interferometer system....which compensates in the cnc control for any dimensional discrepancies. A typical 5 x 10 precision table with the above features would typically sell in the $150,000 range (with plasma, CAD/CAM software, fume control, installation included).

Compare that to a 5 x 10 entry level machine with an air plasma that may sell in the $15 to $20k range....and you will see differences in cut quality, reliability and productivity. You can put an air plasma on the expensive machine as well...and experience improvements in cut part accuracy as compared to entry level machines....and further, the construction of the high priced industrial type machine is conducive to a decade or two of 3 shift per day industrial use.

In a high percentage of cutting application...the low cost machines will produce adequate cut quality...however expect to have a more savvy machine operator operator...one that needs to understand how to fine tune (cut speeds, cut heights, pierce heights, how to read the consumable wear, how to modify part programs to improve quality, etc.) cut quality as well as doing more secondary (grinding, drilling) operations to ensure the cut parts fit the need.

What's important to plasma?:

- Pierce height must be repeatable and accurate. One pierce too close can cause minot consumable damage that will affect cut quality until the consumables are changed.
-Pierce delay times....same as above.
- Consumable parts choice (amperage level for the materiual being cut...on high end systems this is somewhat automated)
- Machine motion fluidity....any vibration, overshoot, dwells, speed changes will affect the cut edge. On the best machines....plasma cut edges are very smooth with virtually no lag lines.
- Speed consistency. Plasma likes consistency....many machines have to slow down dramatically when cornering, making small holes or on small features.....this is often because the drive motors are not adequately matched to the inertial load and the payload of the particular machine.
-A good quality industrial cnc control will also have multiple accel settings embedded for that particular machines payload and speed ranges. Acceleration capability at 100 ipm likely cannot be identical to acceleration at 400 ipm.....and most cnc controls can only have one setting for this!
- Coordination of height control, plasma on/off timing with the beginning of the cut, the end of the cut, and cornering/holes/small features. Very critical for cut quality.....higher end machines actually use the CAM (also known as nesting) software to coordinate all of the timing...as well as to develop and insert the best type and location of lead ins, lead outs and speeds for optimizing hole quality, fine feature quality, process gasses, kerf width...all automated and transparent to the operator.

I could go on for hours about the differences between the new breed of low cost plasma cnc's and the industrial high end machines! I own two low cost machines (PlasmaCam and Torchmate) in my home shop.....they are both perfectly adequate for my current needs.....but if I was a high production shop with high accuracy needs...I'd be looking at the industrial machines as my best choice.

I just recently presented a webinar that talks a bit about the differences you can expect between all the different plasma cnc offerings. The webinar can be viewed at www.hypertherm.com , click on the education tab, then go to webinars. There is a lot of good educational info as well as online courses regarding plasma cutting on the site as well.


Jim Colt Hypertherm

So what does it take to build a machine that can keep up with the power and high cut speeds that the Hypertherm units demand? High output servos and linear rails? An upgrade from the typical rack and spur gear setup? Lightweight, but very strong gantry design?

Maybe I should start another thread about this, sry for the thread jack!

I know my torchmate tm1 would violently self destruct at 400ipm.

[just_wanna_drive]

Sweet, thanks again for another classic info-packed Jim Colt answer!

I'm glad to hear (read) about the videos, I'm pretty slow at work today after rushing for the last couple of days to finish a big project, so hopefully I can download them on my droid.

I'm currently designing and building a better table, so maybe the videos will help me make some big decisions that I've been pondering. Btw, any tips on upgrading my drive system ? I have a build/design thread on pirate with details of my new table... [:/threadjack]
Thanks again Jim!

[SomethingMetal]

Jim the wealth of knowledge and help that you provide to us for free is greatly appreciated. I know if I see a post where you have given your advice, it is nothing but the truth. Thanks

[Groth]

Jim, I also want to thank you for all of the information you have provided. I am very new to this and am doing research to try and get started in the decretive/art area of cnc. I have been looking at PlasmaCam and Torchmate tables, I know they are both great tools, but like all machinery I'm sure there are pro's and con's with both machines. Being a novice in this area I was wondering if you could give me some information on the two set-ups?
Greg