Water Table Design and Checking Squareness

Hello! I got a message this morning that the rest of the steel I need for the frame is waiting for me to pick it up next time I’m in Seattle.  I’m trying to think of things I can work ahead on. Finally got around to adding the water table and gantry (with my own digital versions of the shopdroid brackets) to my design in Blender. I was happy to see the gantry (shown in white) fit up nicely.

Latest Blender Render

Latest Blender Render. Purple in honor of my Kansas State Wildcats!

I really haven’t decided if I’m going to do the water table right away or not. I did this mostly to make sure it could be retrofitted if I decided not to put it in initially.  As I understand it, the argument for is that the water traps the vaporized metal and greatly reduces dust in the shop and in your lungs.  Since I’m in borrowed shop space, I’m leaning toward installing water from the start so I don’t coat my benefactor’s airplanes with metal dust. In either case, it’ll work. I’ll just have to alter the design of the slats (a grid of vertical strips of metal that supports the work piece during cutting) a little based on which way I decide to go.

If I go with the water table, it’d be 50″ x 98″ and could sit on top of the frame, unattached. On my list of things to do is looking into sheet metal sizes to figure out if I could make this out of one piece.  I actually haven’t even determined what material and thickness would be best for this.  I’ve heard of some folks using spray on truck bed liner for their water tables. Any thoughts?

Hip to be Square

I went to the hangar this morning to check the squareness of the one end of the frame I’ve fabricated. Pythagorean Theorem said it should be 59.1 inches diagonally across this section. Both diagonals were just over 59 inches. That should  mean it’s  pretty square. I’m planning on using this section as a jig for the other side and keeping them clamped together till the new one cools. Thanks to John (aka zappafan1 on cnczone.com) for the tips!

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Stay tuned!

MIG Welding the First Table End

Had an interesting day welding up the first end of my CNC table with the Millermatic 250 MIG welder the other day. I had this section all tacked together, so I just had to run beads along the seams in such a way as not to warp the heck out of everything. I got to the shop and clamped my work down flat on the table. I checked the settings on the welding machine and got to it. I ran about an inch of bead before I realized I’d forgotten to listen for the gas… AGAIN. This time instead of turning on the wrong bottle, I’d forgotten to turn the gas on at all. Shame. I need a checklist for this apparently.

I did my penance of grinding out the porous weld, turned on the gas and sat down to try again. This time I didn’t make it an inch.  As soon as I struck an arc, I flashed myself in the eyes. Another item on the checklist needs to be to switch the auto-darkening welding mask setting from “grind” back to “weld.”

After rubbing my eyes and blinking for a minute, I finally ran my first bead of the day. I think it turned out more or less decently. The only issue was I had my mask set too dark this time and I couldn’t see where the end of the joint was. As a result I kept going till the arc went out because there was no material underneath it. This left an arc mark as I finally pulled it away.

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I welded this originally in the flat position. Note the arc mark to the right resulting from my inability to see I was at the end of the joint. I turned down the darkness setting on my mask to improve visibility.

After the early hiccups, I finally settled down into a bit of a groove. I had the work piece clamped down flat at first, welding flat and moving around to different areas of the piece to keep too much heat from building up in one area and to give plenty of time for cooling. This should help prevent warping. Then I flipped it and did the other sides before turning it on its various ends for the fillet welds.

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Got a little skinny in the middle of this one and forgot to leave the gas on the end of the weld for a moment at the end. Think that’s the cause of the dimple.

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Not sure how I ended up with this porosity. Had to grind that out. remembered to switch back to the “weld” mask setting this time…

At one point I was feeling cocky and tried to do a vertical weld. I should have waited and reviewed the technique on that as I ended up with a pretty ugly weld with a big droop at the bottom.

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Less than stellar results of my first attempt at vertical welding. After this I reoriented my work so I could weld flat until I do some more research and practice with the vertical position. Also note nice cut quality from the Rage II cold chop saw.

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I’m not sure what the brown precipitate is on some of these welds. I think I probably need to clean the joints better before welding. I’ll try that next time. Seems to come off easily enough but it leaves indentations in the weld.

So to recap, today I learned:

1. (Again) Double check the gas bottle is turned on before welding.

2. Double check welding mask reset from “grind” to “weld” after grinding.

3. Don’t forget to hover over the end of the bead with the gas for a moment to keep the puddle shielded as it cools.

4. Don’t set the mask so dark that you can’t see where the end of the weld should be.

5. Going to try cleaning the joints with a wire cup brush on the angle grinder next time to see if that gets rid of the brown precipitate.

6. I wasn’t satisfied with how the corners blended together. Next time I’m going to try to weld around the corners and mate the beads up on the flat sides.

While there are lots of ways I hope to improve, I’m pretty happy with how this is turning out so far. It’s cool to be learning and practicing welding on something that’s useful but not critical for life and limb. I’m going to pop in for a minute tomorrow after it’s all cooled off and measure the piece on both diagonals to see how I did at keeping it square. I’ll try to post some pics of that.  I’ve got a call in to my steel supplier in Seattle and hopefully next week I’ll get the rest of the tubing I need.

Thanks for reading and don’t forget you can subscribe and get email updates as they happen.

 

Let the Build Begin!

I finally got my Chop Saw! So far I’m reasonably happy with it. There were a few chips in the paint when I pulled it out of the box. I was annoyed by this, but not enough to delay my project a month by sending it back. At about $280 plus shipping, it was a little more than half the cost of the comparable DeWalt I could buy locally. If it lasts through this project, it will have paid for itself. As far as cutting goes, it’s like butter so far. I’m glad I went with a cold cut saw versus the slow, hot, abrasive wheels.

Bar stock cut with the Rage saw.

Bar stock cut with the Rage saw.

So having the welding more or less figured out and the ability to cut steel, the only thing left was to get some steel.  In Juneau, steel is about 75% more expensive than in Seattle because it has to be shipped up on a barge.  I have access to discounted shipping so it makes sense to source my steel from Seattle. However, since I’m new at this and I didn’t want to order 140 feet of steel from a supplier in Seattle only to discover that the fabrication was over my head, I went ahead and bought a 20′ length of 2″x2″x3/16″ steel from the local supplier. This, I figured, would be enough to build one end of the table frame. If I could keep that square and level, I’d go ahead and get the rest from Seattle.

Measure 3 times, Cut Once

First cut on 2X2 tubing. Clamped per the instruction manual.

First cut on 2X2 tubing. Clamped per the instruction manual.

I made two marks that the blade should go between. Then I remeasured and marked again. Sometimes even one or two more times, just to be sure. Steel is expensive.

I made two marks that the blade should go between. Then I remeasured and marked again. Sometimes even one or two more times, just to be sure. Steel is expensive.

After being super diligent about measuring and marking, I was thrilled at the accuracy of the cuts. Parts lined up perfectly.

After being super diligent about measuring and marking, I was thrilled at the accuracy of the cuts. Parts lined up perfectly.

Then I beveled the edges as required with my angle grinder.

Then I beveled the edges as required with my angle grinder. I only had to do 2 edges per joint since the tubing is rounded and provides a gap for the weld to penetrate into.

Tacking It Up

More measuring and marking. The magnets were pretty helpful in squaring things up and holding them in place before using the C clamps.

More measuring and marking. The magnets were pretty helpful in squaring things up and holding them in place before using the C clamps.

This is what your tack welds will look like if you turn the gas on to the wrong welding machine. I could have sworn that was the right tank! Now I listen for the hiss of gas when I pull the trigger.

This is what your tack welds will look like if you turn the gas on to the wrong welding machine. I could have sworn that was the right tank! Ground those out with the angle grinder and re-tacked. Now I listen for the hiss of gas when I pull the trigger.

The right angle magnets are good for getting things set up, but Bill wisely suggested that I clamp stuff down to keep it secure.

The right angle magnets are good for getting things set up, but Bill wisely suggested that I clamp stuff down to keep it secure and prevent warping.

It stands! After tacking everything looked square and true.

It stands! After tacking everything looked square and true.

In the next post, I’ll see if my MIG welding skills are up to the task of finishing up this end of the table. Stay tuned!

Welding Practice

Greetings,

I’ve spent the last couple of weeks trying to teach myself how to weld. I purchased an EVERLAST PowerARC 140 a while back because I thought I’d use stick or TIG welding to build my table. I did some practice stick welding with this unit and discovered that on a regular household 120 V circuit, I was pretty limited on which rods I could use effectively without tripping the breaker. Starting out with 1/8″ 6011, I found I needed at least 85 amps to keep a good arc going.  At that setting, if I pulled the arc long at all I’d trip the breaker. Longer arc means higher voltage. The voltage coming out of the wall is constant, so if you ask for more watts it tries to draw more current. I wish I had found this chart sooner.

electrode_current_chart

This is how I decided to try 3/32″ 6013, since it should work well at lower amperage settings. It did work a lot better. I turned out some beads that looked respectable to my untrained eyes, including a butt joint with 1/8″ bar stock. The fillet welds were not turning out though.

One of my first arc strikes with 1/8" 6011. Note scratch marks and divots from over-zealous slag hammering.

One of my first arc strikes with 1/8″ 6011. Note scratch marks and divots from over-zealous slag hammering. Shame.

First bead with 1/8" 6011. This was running up against the duty cycle limit of the machine.

First bead with 1/8″ 6011. This 2 inch bead was running up against the duty cycle limit of the machine.

3/32" 6013 @ 67 amps. Sorta looks like a weld at least...

3/32″ 6013 @ 67 amps. Sorta looks like a weld at least…

Butt Joint with 3/32" 6013.

Butt Joint with 3/32″ 6013.

Junk.

Fillet of Junk.

Bill is another tenant of the hangar I’m using.  A few days ago, he was working on repairing his airplane which had been hit by a snow plow last winter. He saw me scratching my head over my junky fillet welds and came over. It turns out that in addition to being an Airframe and Power Plant Mechanic, he’s a pretty experienced welder. He offered to let me watch him run a few beads.  Right away he said, “this isn’t how you want to build your table! Why aren’t you using that MIG Machine?” I told him it wasn’t mine and I didn’t know how to use it.

He turned it on and found a preset that looked right for what we were welding on and ran a couple beads for me. He made it look easy, but I was pretty blown away by how easy it actually was when I tried it. I had a couple tries where the wire seemed to come out way too fast, but I figured out I wasn’t keeping the tip down close enough to the weld. Once I got a feel for it I even ran a couple of fillet welds that turned out way better than what I’d been doing with the stick welder.

More like it.

More like it, I think.

The shop I’m being allowed to squat in has 120, 220 and 250 volt service. It doesn’t have 240 though, which is the other option with the EVERLAST PowerARC 140. I think this would be a fine stick welder if you had 240 volt service or if you have light duty welding to do using smaller electrodes. I’m not sure why my fillet welds weren’t turning out. Pretty sure it was my technique. I still want to try it with some 7018  just to see how it does, but after about an hour practicing with the Millermatic I felt confident that I could start building my table.