Disable THC head lock?

[aaronbee]

Is there a way around the "Tip Saver" 10% limit? I want 30%.

I'm cutting 22 gauge galvanized and it warps real easy under any amount of heat. The trouble is, on a long cut along the edge of the material, it can start to warp as much as a 1/2 inch off the table. The THC follows it up the warp fine enough, but all the sudden, the warp can "pop" back the other direction. Now the torch is hanging out .5" off the table, the actual volts are in the 130 rang and it's locked there because 130 is well over 10% of 98 volts.

I mean, I understand the idea behind the anti-dive function, but I'm not cutting over a void. I don't plan on cutting over a void. Sometimes I actually want it to dive. Is there some way to prevent it from using the head lock? It's the MP3000 THC.

[Torchhead]

There is a button on the MACH screen to turn it off. The Tip Saver is pretty useful in normal cutting. It's not just about cutting over a void or off of the edge. The tendency of a THC to dive as the cut comes around close to the lead-in is an aggravating problem that the the TIP saver resolves. Even the natural tendency of the motion to slow down on tight turns can cause a normal THC to dive into the work. I have always cut thinner material (even 14ga will pop when you cut close to the edge from stress relief) with the edges clamped to the grid. i just use some of the cheap metal spring clamps. I always cut with a 1" "gripper" space.

I can see about writing a macro to turn the Tip saver ON/Off in g-code and you can insert it in SheetCAM as a code snip. I would suggest leaving the setting at no more than 5% and enable or disable the Tip Saver in areas (like the edges) if you don't want to use clamps.

Maybe we need to add a TIP SAVER DELAY function in the Cut Profiles that will cause the Head lock to be delayed (and give the DTHC time to lower the torch. Only problem is that on a normal cut where the gap is a lot smaller ANY delay would probably result in the tip banging down on the metal at the end of a cut. We already have a "Fault Delay" that lets the DTHC ignore the big voltage spikes during and right after a pierce event.

You know how to get in touch with me (:-)

TOM caudle
www.CandCNC.com

[Dustin407]

Originally Posted by aaronbee Is there a way around the "Tip Saver" 10% limit? I want 30%. I'm cutting 22 gauge galvanized and it warps real easy under any amount of heat. The trouble is, on a long cut along the edge of the material, it can start to warp as much as a 1/2 inch off the table. The THC follows it up the warp fine enough, but all the sudden, the warp can "pop" back the other direction. Now the torch is hanging out .5" off the table, the actual volts are in the 130 rang and it's locked there because 130 is well over 10% of 98 volts.

I have ecountered this problem before, I had a sheet of alum. that was really bent up so I just put some heavy weights on it to hold it down (outside the box). If your getting 1/2" plus warp on thin ga. you should put weights on the ends not in the path of the g code obviously. This will make life alot easier because you cant always rely on the DTHC when things are out of control by as much as 1/2" plus... Here is a video link of what I am talking about.. You'll notice the thick steel plate on the alum. Let me know if you cant view the video...


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[aaronbee]

Originally Posted by Torchhead There is a button on the MACH screen to turn it off. The Tip Saver is pretty useful in normal cutting. It's not just about cutting over a void or off of the edge. The tendency of a THC to dive as the cut comes around close to the lead-in is an aggravating problem that the the TIP saver resolves. Even the natural tendency of the motion to slow down on tight turns can cause a normal THC to dive into the work. I have always cut thinner material (even 14ga will pop when you cut close to the edge from stress relief) with the edges clamped to the grid. i just use some of the cheap metal spring clamps. I always cut with a 1" "gripper" space. I can see about writing a macro to turn the Tip saver ON/Off in g-code and you can insert it in SheetCAM as a code snip. I would suggest leaving the setting at no more than 5% and enable or disable the Tip Saver in areas (like the edges) if you don't want to use clamps. Maybe we need to add a TIP SAVER DELAY function in the Cut Profiles that will cause the Head lock to be delayed (and give the DTHC time to lower the torch. Only problem is that on a normal cut where the gap is a lot smaller ANY delay would probably result in the tip banging down on the metal at the end of a cut. We already have a "Fault Delay" that lets the DTHC ignore the big voltage spikes during and right after a pierce event. You know how to get in touch with me (:-) TOM caudle www.CandCNC.com

I've noticed while cutting the voltage can spike around corners to as much as 108v with the target being 95v. If I'm understanding it right, with a target of 95v, anything over 104.5v would be over 10%.

I don't know if it would work, but if I knew how to do it I might try throwing the current voltage in a variable and then lower the head some increment, create a second variable with the new current voltage in it from the lower increment and compare the two variables. If variable two (after lowering some increment) is less than variable 1, then keep diving, otherwise, lock the head. In other words, if lowering the torch isn't lowering the voltage, then lock the head.

You, of course, know the programing side a whole lot better than I would. That's just my guess.

Anyway, I've been using strategically placed neo magnets to hold things down and that's helped a lot. I keep them far enough away from the torch, but close enough to keep things flat and it's kept things from warping really bad.

[aaronbee]

Originally Posted by Dustin407 I have ecountered this problem before, I had a sheet of alum. that was really bent up so I just put some heavy weights on it to hold it down (outside the box). If your getting 1/2" plus warp on thin ga. you should put weights on the ends not in the path of the g code obviously. This will make life alot easier because you cant always rely on the DTHC when things are out of control by as much as 1/2" plus... Here is a video link of what I am talking about.. You'll notice the thick steel plate on the alum. Let me know if you cant view the video... Welcome to Facebook - Log In, Sign Up or Learn More

I cut a lot of the same parts over and over. Like 200 of this or 400 of that, so I've considered creating a custom-fitted set of slats that would allow the torch to cut without hitting the underlying grid and heat warping that, and also including a set of magnetic attachment points to hold things down. You couldn't do it for one-off stuff, but I might try it sometime. I've used weights and clamps before but I don't like having to make sure I navigate around them without crashing into them. I have an old vacuum pump and I've considered doing something with that. I'd just have to make sure I didn't burn the suction cups off. :-)

[Torchhead]

The problem with the code part of it is that a simple macro in MACH is not going to be fast enough to do a bunch of comparisons and moves so it would need to be put into the DTHC microcode. The problem is also amplified by the fact that each volt of change represents from 015 to ,020 of gap change so 9.5 volts would in theory drop the torch .135 inches. Another factor is the speed of your Z. of course, if it pulls the metal out from under the torch by a big amount so it has nothing to follow, the lower and test the voltage thing is not going to work very well either. How many times does it try before it locks? What if it is .063 above thin material and it runs off the edge. how far should it lower before it is too low? What should it do if it loses arc ok? It could get sticky with exceptions. By leaving a 1" gripper space around all of the edges in your artwork you cna clamp with impunity. I have onely cut a FEW of the clamps off over the years (:-)