Angularity Issues 2.0

[Ironken]

I have a JD2 MAD 4x4 with a Powermax 45xp. I am getting a lot of bevel on 11g, 1/4 and 5/16. This is only occurring on Y axis moves and the bevel is in opposing directions (kinda like looking at the profile of a pyramid). The X axis moves are fine. I am using Finecut on the 11g and standard shielded consumables on the 1/4 and 5/16.

Anybody have any suggestions?

On the 1/4, I am getting consistent angularity around holes when cutting 27/64 holes. I have to cut 27/64 to get a 3/8 bolt to pass through the hole. I know that for the material thickness, I am a bit smaller than ideal on hole diameter for quality holes.

In an unrelated-ish topic....I would like to slow the feed rate in my MAD v3 cnc program to see if that produces less angularity on thicker material. Anybody have suggestions on how to slow the feed correctly without making the ATHC go crazy? The MAD cnc sets the feed rates in the cnc program, not following what was entered in Sheetcam.

Thanks for any help!

[plasmanewbie]

If your angularity issues are opposing as you mention then I suspect your cut height is too high. Try pausing your machine mid-cut and measure the distance between the tip and the material with feeler gauges. It should be around .060". See diagram below to see how cut height affects cut edge angle.

cutangle.jpg (97.11 KiB) Viewed 1105 times

cutangle.jpg (97.11 KiB) Viewed 1105 times

[Ironken]

Thank you, Plasmanewbie. That is great info......the only strange part to me is that the excessive bevel example above is only occurring in Y axis moves.

On adjusting torch height and speeds.....when I have changed torch height before by changing the voltage, the dimensions of the cut get outta whack. In this scenario, I am cutting profiles in rec. tube along with bolt holes. When measured, the torch height is about .067"

Also, with ATHC, is it acceptable to simply reduce the feed rate or do I need to adjust THC accordingly?

Again, thanks for posting those diagrams!

[jimcolt]

-If excessive bevel is only on the y axis, rotate your torch 90 degrees in the holder and see if the bevel shifts to only the x axis. This will help you determine if it is a torch issue or a cnc machine issue.
- If the bevel moves with the torch rotation, here are things that can cause an uneven bevel: 1. Damaged or worn nozzle. 2. Damaged or worn shield. 3. Damaged or worn swirl ring, 4. Damaged or worn retaining cap, 5.Incorrect cut pressure setting , 6. incorrect inlet pressure , 7. Bad oring on the torch, 8. Flow restriction in torch leads or torch body.
- If you slow down the feed rate expect the THC to lower the torch. Slower speeds will require an increase in arc voltage in order to maintain the physical cut height. The voltage setting is only there to achieve the physical cut height. The voltage settings in the operators manual cut charts are correct assuming everything else is set at the cut chart settings (cut speed, cut pressure (leave in auto for best results), amperage) and that you have new consumables in the torch. As the consumables wear you must increase arc voltage as well to maintain proper height. If the electrode has a .010" deep wear pit....expect the torch to run .010" closer to the material....increase the arc voltage by roughly 2.5 volts per .010" pit depth on the electrode, change the electrode when the pit depth reaches .060" per the section in your manual called "inspecting consumables". Jim Colt Hypertherm

[Ironken]

Thank you, Jim for the detailed help. I'm still working on the issue. Rotating the torch had no affect. I replaced all front end torch parts including o-ring with genuine Hypertherm new in box parts....no change. Checked torch to make sure it is perpendicular. Used a Starrett machinist level on both Y rails and the gantry to verify the machine is level......it is very level.

After I did all of this, I started running test cuts at book specs across the board and now I am getting bevel on adjacent axis of a square cut out of 1/4 HR. That is if you were looking down at a square, the bevel is on the RH side of the square and the top line of the square. The other two sides are perfect. I think I am chasing a moving target here. I almost think I have a THC issue. I did stop the machine after probing and the torch height was .062. I stopped during a cut with the THC active and got about .063.

Kinda outta ideas.

[acourtjester]

I don't think you have a THC problem, the THC controls the torch height as it cuts. And therefore would show as the display Jim posted with angles caused by to high or too low but not in one direction of the kerf. You state the cut height and actual cutting height is about 0.060" as it should be this again shows the THC is working as it should. You checked the torch for square in a static state, could you have a cable drape issue where it could pull the torch when moving about. On the tables I built the torch is held at 2 locations to insure it does not wobble.

[Ironken]

Thank you Jester. You are correct on the THC. I disabled it and cut with the same results. The torch cable rides in what I call Cat Track or cable track and has sufficient slack. I will fix a dial indicator to the Z and look for deflection in cut when I get a chance. The torch holder does have a sheet metal clamp to a piece of aluminum billet with a nicely machined v groove for the torch body and is pretty darn solid.

As far as cable routing/work lead routing goes...I have no data cables touching the work leads (this machine has a bus bar that the work lead from the plasma power source connects to with a lug and the work lead with clamp connects to the same bar with a lug this leaves a lot of excess work lead between the table and power source). Is it acceptable to lay the excess work lead parallel to itself in a long kinda zig-zag? Would it be acceptable to zip tie several passes of work lead together for tidiness?

I still like this machine, just gotta sort some pepper from fly shit and get things back where I want them to be.