Plasma Cutter

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Re: Plasma Cutter

Postby Cre8ivdsgn » Thu Sep 27, 2012 2:50 pm

The only downside is that now his box surrounds the X axis (or Y depending on what you call it) and precludes mounting non-traveling stuff to it (cable carriers, encoders, or anything to stiffen the axis for less deflection on longer travels).

The other possible issue is that now there is definately an order of operations to assembly.

Now that I have listed the downside, let me say that cutting parts down to one piece is more than worth all the sacrifices! And plenty of rigidity would be retained even if the hole for the X axis (or Y) were changed to a slot.

My 2 cents and folks here are kind enough to put up with this sort of thing! (Thanks again, Bart for maintaining the site!)
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Re: Plasma Cutter

Postby bdring » Thu Sep 27, 2012 3:44 pm

The idea can be sized to what you need. I use an overhead cable carrier. Keeping the window as small as possible helps the strength.

If you want larger rails there is a 6" x 3" x 3/16" rectangular tube at some suppliers.
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Re: Plasma Cutter

Postby Cre8ivdsgn » Thu Sep 27, 2012 4:15 pm

Bart,

My intention was only to point out that because the axis is now surrounded, it forces you to build the carriage to the X before mounting things to the Y. It was also to point out that cable carriers which would be mounted along the X would no longer work and you would have to go to a tether loop that now would move in X and Y (and maybe Z).

Its also amazing when you consider how strong 1/8" aluminum tube stock is, especially when you preserve corners when notching. I make a cover out of 1/8" aluminum that is 24" x 5", and sometimes the material has a bow to it (when cut from a larger sheet now that Kaiser Aluminum no longer supplies 6061 "flattened" or "stretched" sheet stock - or at least I can't get it). I cannot get the bow out or even change the shape when I stand on it! (Ok, its been a while since I tried that last bit and I might have been lighter then!) I'd try this now, but the covers I have are all painted and only bad things could happen if I stood on them now.

Certainly making the hole small gives maximum strength. I am only trying to point out that turning it into a slot and yet preserving the corners would give a minor reduction in strength but now return the functionality that would allow a cable carrier along the axis or encoder or whatever.

Well, and I think I got caught in the trap of thinking out loud in a blog post. Can outright senility be far away?
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Re: Plasma Cutter

Postby lasersafe1 » Fri Sep 28, 2012 5:14 pm

Perhaps I missed it in your log. Did you end up with the Hypertherm? I routinely cut .035" aluminum plates. I normally stack them 5 at a time and use my mill with a 1/8" bit. This thread has got me thinking about Plasma. I would be curious if anyone has experienced any success with units costing about $1000 less than the Hypertherm since my thickness requirement is so low. I looked up "thin aluminum plasma" on CNCZone and most everyone is mentioning Hypertherm.
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What torch?

Postby bdring » Fri Sep 28, 2012 5:43 pm

I did buy the Hypertherm 45. I have heard it is the best for fine detail. When you dial in the power and feed rate it is quite amazing. I am only having a little dross where I can't get the feed rate I want yet like a fine saw tooth profile. I think I just need to play with acceleration and add in a little CV.

I saw this torch comparison at a CNC plasma supplier. It puts Hypertherm at the top and the cheap Chinese ones at the bottom.

http://www.gotorch.com/plasma-cutter-comparison/
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Re: Plasma Cutter

Postby macona » Fri Sep 28, 2012 11:20 pm

Plasma cutting of aluminum is usually not very pretty. You need a lot of power to get a clean cut and even then there is a lot of cleanup. When cutting Steel or Stainless you get a reaction with the air that burns the metal away.With aluminum it melts it and the air just blows it away. There are gas mixes for aluminum but standard air plasma systems cant use them.

If you need a whole lot of a part try a local water jet place. I have found it to be very reasonable.
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Re: Plasma Cutter

Postby lasersafe1 » Sun Sep 30, 2012 1:45 pm

macona wrote:Plasma cutting of aluminum is usually not very pretty.


According to many posts over at CNCzone, this was true until about 5 years ago. Apparently the new inverter controls of the best systems can produce results on aluminum that are very clean with no slag using only air. Accuracies down to .003", which approaches that of laser and water cutting.

The model that Bart has purchased is among these newer types. Perhaps we will soon start to see videos of his cuts. It took me a few months to get my laser "dialed in" to be satisfactory on every type of material. I'm sure Bart is going through the same thing now as he jumps between his many projects.
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Re: Plasma Cutter

Postby orcinus » Sun Sep 30, 2012 3:27 pm

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Re: Plasma Cutter

Postby Cre8ivdsgn » Sun Sep 30, 2012 8:14 pm

Bart,

Did you end up going with Moore Gear and the 20 pitch rack? My calibrated eyeball is off and the rack shown mounted up against the makerslide seems smaller than 1/2" square. I was wondering if you ended up sticking with the 14.5pa, 20 pitch, 24 tooth pinion that I think you were originally planning on using. I have some helical rack and pinion stuff in my sample box, but the pinion is a 2" pd and is overkill for what I am working on.

Shamelessly picking your brain!

Thanks!
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Re: Plasma Cutter

Postby bdring » Mon Oct 01, 2012 12:29 pm

I went with the 14.5deg 24 pitch rack and 15 tooth gear. I had a lot of trouble finding a low profile rack and gear with a reasonable shaft size for a good price. I sort of ended up with this configuration rather than scientifically chose it.

It works fine. I probably would have preferred a few more teeth on the gear, but the shaft size quickly grows. Larger gears mesh a little smoother with the rack.
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