[Torchhead]

ok a little update to my question.. i investigated my machine and found a few mechanical things that might have been contributing to vibration in the machine.

for one, the pinon gear on my gantry was rubbing the structure (leaving imprints from the teeth)



the big factor though effecting the cut is the DTHC. it seems to have a very fast / erratic motion when trying to maintain torch height. the quick motion causes the torch to vibrate.

I need to add some bracing on my Z axis (k2 assembly), but i'm wondering what controls the speed that it corrects at?

would this simply be in my acceleration / motor tuning? or is there another setting specific to the torch control?

There are several settings that effect the DTHC response curve. See the section in the DTHC manual on each of the settings. Find the section on THC RATE (a MACH setting on the SETTINGS TAB. The Z while in THC mode does not use an acceleration/deacceleration curve. To prevent stalling the motor you have to lower the VELOCITY. The THC Rate defines the percentage of the Z velocity (set in the motor tuning) that it uses WHILE unrer THC control.

One of the steps we advise is to get the system setup and running good with conventional tips (40A or 60A) at the conventional gaps (.063). If you get good results there THEN advance to doing Fine Cuts. Be aware that Fine Cut charts call for different parameters (arc gap, voltage presets, feedrates, etc.

Another setting that determines the response curve is the SPAN setting in the Cut Profile. You will find that different nozzle sizes on different material may need some fine tuning of the SPAN and maybe even the Fault trip points and/or the TIP Saver %. The concept of having the CUT PROFILE and being able to have stored settings is to be able to make some specific changes and have the DTHC use them for a given type of material.

The THC Rate setting in MACH is of course Global for all cutting with THC. The final mechanics have a lot to do with what those settings need to be. Cutting with Fine Cut consummables is the most challenging and you have to adhere to the suggested arc gap, current and feedrates for the given material. If the DTHC is moving a lot it means the voltage feedback is changing rapidly. The unit will respond and correct very rapidly and the SPAN setting determines how tightly it tries to hold the voltage to the preset. Example: the default 4/4 setting = 1Volt so the torch will adjust to try and hold the voltage to + or - one volt. If you are cutting too slow the voltage may be moving around a lot.

What I am trying to convey is that if you don't have the other factors set right (feedrate, clean-dry air, arc gap, cut current, air pressure, good workclamp connection, etc) then you can see voltage fluctuations that can cause problems holding a constant height/ Changing the THC rate down can dampen the movement but that also impacts the response time and may result in bad cuts.

Do not make wholesale changes to the settings and never more than one at a time.

First do some test cuts with THC off in MACH and observe what kind of feedback you are getting. The TORCH VOLTS on the screen will give you a real time read out of what it is seeing.

One of the reasons we introduced the new DCP-01 Digital Current Probe is with it you can actually see another of the important factors of a good cut: The actual cutting current at the torch. That value is supposed to remain constant and be close to the dial setting you have on the Plasma BUT if it's not you have no way to know. If it varies during a cut then the voltage will vary and the DTHC will see that as a varying arc gap distance and try to adjust.



TOM caudle
www.CandCNC.com

[Dustin407]

i'm using a hypertherm 1000, with 60A tip and machine shield.

i've been cutting both 1/4" and 1/2" CRS, at 86 & 27 IPM respectively

for controls i'm using the bladerunner setup, with DTHC

questions

1. how much bevel should i expect on 1/4"? Is it possible to get none? 1/2" i'm getting about .025" bevel from top to bottom. But i'm also getting that with the 1/4"

Multiplex,

I think you are traveling a little fast with your IPM. I cut an entire sheet of 1/4" CRS the other day and I was running at 45 IPM volts was about 110 60 amp tip. I had almost zero bevel to 1 degree. I noticed the slower you go the less bevel but the more dross. I had alot of dross on the bottom but I dont care because the edge quality was perfect and almost no bevel. I was watching your video, you have alot of top sparks flying around. Which means too fast!!

[jimcolt]

You will not get "zero" bevel with either a plasma cutting system or a water jet or a laser, all produce a certain amount of bevel.

With a Hypertherm Powermax1000, which is an air plasma system (relatively low cost as compared to a high definition plasma, a water jet, or a laser cutter) you should expect bevel typically in the 2 to 4 degree range on 1/4" materials. The bevel (if measured in degrees angularity from square) will be less on thicker materials and more on thinner materials if the system is operated at the correct speeds, the correct height, and piercing technique is used to minimize damage to the torch nozzle.

To minimize bevel, match the power to the material thickness, as a rule of thumb the lowest power level that will cut a particular thickness will produce the least bevel. If I wanted the best edge angularity on 1/4" with a Powermax1000.....I would choose the 40 Amp shielded consumables and I would follow the Hypertherm mechanized cut charts using the optimal cut speeds listed.

Amps, 40
Cut speed, 48 ipm
Cut height, .062"
Peirce height, .12"
Pierce delay, 1 second

By using similar specs with a Powermax45, I was able to get an average of about a 2.5 degree bevel on a 1/4" steel cut sample with a Powermax system. Measurement was done with a precision protractor, see attached pictures. Many would look at this part (without using a measuring device) and say it had "zero bevel"! It will stand up on all four sides. The key to getting repetitive cuts like this? A good plasma system and a good height control. The plasma cannot do this alone.

Jim Colt Hypertherm

[Dustin407]

Jim,

Those are beautiful cuts on the 1/4". If you have an average bevel of 2.5 on that part, my cuts prob slighly more 3-4 range. I was guessing at the bevel on the parts I cut out of 1/4" I never actually measured them... I would love to see more pictures of parts with cut information next to them (IPM, volt, CH, Tip, etc...) Thanks...