Vertical and Horizontal Welding Practice Project

Before I started tacking the base of the table together, I decided I should organize a pile of scrap on the floor by using some of it to build a rack. In the process I’d have a chance to practice some out of position welding. All of the parts I’d made up to that point could be clamped flat onto the workbench. Once I got it tacked together, I’d have to start doing welds however they happened to be oriented.

Welding in the vertical and horizontal (not to be confused with flat…) positions is challenging because gravity is always trying to take the puddle of molten metal in directions you don’t want it to go. In the photo below, you can see how gravity caused the bead to sag to the bottom of the joint. That bead was done with a wire feed rate of 290 inches per minute. Once I slowed the feed down to 200 ipm, it got a lot easier to control the puddle. I still got some sagging on my last try. I think I was moving too slowly and therefore depositing too much metal.

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I’m still too young to sag like this.

 

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Got the Miller 250MP dialed down a bit to 200 ipm.

 

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The smaller upper beads were at 200 inches/minute. Not pretty, but much easier to manage the puddle.

 

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Ready to take another crack at the horizontal.

 

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Started on the right. Thought I had it dialed in. Did the left and decided maybe not…

For the vertical up, I was practicing the technique described at welding tips and tricks which is basically an upside down V pattern. It took me a while to get the pace right on this one too.

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Vertical up came together after a few tries. Think I got the gas off it too soon at the end causing the porosity.

 

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Regular ol’ flat fillet.

 

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Goal posts for our new hangar football league.

 

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My first “completed” welding project.

 

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Scrap holding scrap.

All in all, it was an afternoon well spent. I didn’t want my first experiments with out of position welding to be on my cnc table. I’m sure I’ll still have some beads on the table that I wish looked better, but now I know I should at least be in the ball park. Plus the workshop is a bit tidier now!

Reconsidering the Electronics…

After consulting with folks on WeldingWeb and cnczone, I’ve redone my trusty electronics comparison chart.  A new entry that I was previously unaware of uses Mesa Electronics’ breakout cards and torch height control with Keling stepper motor drivers. It also uses the open source Linux CNC instead of Mach 3. The consensus among those polled who had used both Mach 3 and LCNC was that LCNC provided better performance in terms of speed, flexibility, and reliability… AFTER you conquer the somewhat steep learning curve.

Ad Hoc Mesa/LCNC Ad Hoc Proma/Mach Partial Kit/Mach Turn Key Kit/Mach
Motors $220 $220 incl. incl.
Controllers / BOB $280(KL5056)+ $199 (7I76+5I25PNG) $260 incl. incl.
Power Supply $120 $120 incl. incl.
Enclosure $100 $100 $100 incl.
Torch Height Control $70 $268 $268 incl.
Misc. Cables, Switches, Cooling $250? $250? $200? $100 (recently learned limit switches not included)
Time 60 hrs? 30 hrs? 20 hrs? incl.
Kit $0 $0 $668 $1575
Support Community None None Included + 2 yr Warranty
Software $175 – SheetCam $350 $350 $320
Total $1414 + time $1568 + time $1606 + time $1995

I’ve seen LOTS of folks using Mach 3 and the CandCNC kit who are doing great. I’m sure I’d be up and running quicker if I went that route. However, I’m going to take the $600 bet on LCNC and Mesa and hopefully have a more robust machine in the end. I’ll undoubtedly learn a lot in the process.

Surgery

After I welded the first wheel bracket onto the one of the legs, I realized I had totally messed it up. I used one of my new Harbor Freight pipe clamps to hold it in place and somehow I missed the fact that it wasn’t remotely square.

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Fail.

After some deliberation as to how big a deal this was (it would be attached to a wheel, after all), I decided it’d be better just to cut it off and try again. Problem was that I couldn’t get a grinding wheel into the welded joint due to the vertical walls of the U channel. I thought about using a cutting wheel on the walls to give access to the joint, but in the end I decided it’d be easier to use the chop saw on the leg and start over.

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The amputation. Used the blue legged table to hold the frame up and let the saw cut through the square tubing at an angle.

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Someone should play “Taps.”

Made another wheel mounting bracket.

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Cutting some more U channel to make another wheel bracket. Cut the walls….

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…Then the back.

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Using one of the wheels to line up holes for the bolts.

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The wire cup brush does a nice job cleaning up the bracket.

Once I had cut, drilled, and cleaned up the bracket, I grabbed a piece of scrap tubing and ground angles in it and the leg. I used some heavy bar magnets to line the two pieces up and then tacked it together.

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Used some heavy bar magnets to line up the prosthesis.

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Tacking up the leg extension.

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Welding the leg extension.

On the last bead of the weld, I decided it’d be a good chance to practice some vertical welding. This did not go well. I’m not sure how I managed it but I blew a big hole in one edge and the wire just started feeding into the hole. It was pretty ugly. Should have gotten a pic but I was too focused fixing it.  I did some grinding, laid the piece flat and put down a big fat bead to fill in the hole. I’m going to have to grab some scraps and practice welding in the vertical and overhead positions before I weld the frame together. Good news is the leg seems to have ended up pretty much straight.

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Another ugly attempt at out of position welding.

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Cutting the leg back down to size.

Once I cut the leg back to size and welded the new bracket on, I was finally able to test fit the four sides and start to get a sense of the scale of the monster I’m creating. Can’t wait to clamp it together and start tacking it up!

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Finally able to test fit the four sides of the base.

 

Frame Assembly, Wheel Mounts, and Carriages!

Hello! Lots of progress lately. Here goes:

I welded up one side of the base of the table.

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Laying out a side of the table base to be welded.

 

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Spacers clamped into place to counteract warping. When I do the other side, I’ll do this BEFORE I weld.

After I welded this, I noticed both ends were bowed inward. I put the vertical members for the other side in the ends as spacers during cooling. I think I’m going to have to jam them in when it’s time to tack together the sides and ends to ensure squareness.

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Would like to know why my fillets get gouged out like this from time to time.

Also made some wheel mounts out of some salvaged heavy duty U channel. No pics of this, but when I cut this U channel with the chop saw, I did it in two cuts. The first was through the two uprights. Then I turned it 90 degrees and cut through the bottom. The saw cuts much easier this way.

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Cool old Bridgeport mill in the hangar serves as drill press for my wheel mount plates.

Drilled through the wheels’ mounting holes and attached one bolt at a time to ensure proper hole alignment to my mounting plates. The plan is to clean these up with the angle grinder and a wire cup brush and weld them to the bottom of the table’s legs.

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Salvaged some heavy duty U channel for my wheel mounting plates.

Got a few shipments of hardware for the ShopDroids mounting brackets. I was really pleased by McMaster-Carr’s service as well as that of VXB Bearings and Modern Linear. All of the items from McMaster-Carr came in numbered bags that corresponded with the packing list, making it really easy to match up with the bill of materials supplied by Shopdroids.

Assembly of the brackets was fairly intuitive after consulting photos on Shopdroids’ Facebook page. One discrepancy I noticed was the omission on the supplied bill of materials of a washer that seems to go between the red tensioning spring and the motor mount.

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Misc. Hardware has arrived!

 

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Assembly order of bearing hardware.

 

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The eccentric bushing installed in the V-bearing.

 

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The Z axis gets mounted to this carriage. There should be a washer between the left spring and the motor mount. Also, I don’t have the anti-backlash spring installed yet on the left side.

 

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X Axis carriage and motor mount.

 

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Note the eccentric bushing on the bottom has flat edges so you can turn it with a wrench to tighten the carriage onto the V-rail.

 

Electronics Rundown

So Adam, you’re building a robotic cutting machine… How do you plan on getting the cutting tool to draw the pretty pictures on your workpiece? Hopefully this post will answer that question at least from the hardware perspective.

30,000 ft View of Components

The machine has a gantry that moves across the x axis of the workspace. The cutting tool is mounted to a carriage that traverses the gantry in the y direction. I’m using x and y fairly arbitrarily as I’ve seen different machines oriented differently. This carriage also raises and lowers the tool in the z axis.

This motion is actuated by stepper motors through rack and pinion gears. More on steppers later, but for now just know that they’re a type of electric motor able to rotate a specified number of degrees and stop.  Some folks use servo motors here, but they’re beyond my requirements and budget, so I’m not going to get into that discussion at this point.

Stepper motors are connected to controllers that tell the motors when and how far to turn. Each controller is connected to the power supply and the break out board. The break out board interfaces with a PC via parallel port. The break out board may also have inputs for limit switches, emergency stops and torch height control. Torch height control measures the voltage of a plasma cutter’s arc to determine its distance from the workpiece. (Similar concept to why I kept blowing the breaker when I was stick welding and let the electrode get too far from the weld…) This is handy when you’re cutting material that isn’t perfectly flat.

Street View

There are several options when it comes to acquiring and assembling the electronics portion of a CNC table. One can purchase components separately, as part of a package deal that include various combinations of parts, or as a turn key kit including motors, controllers, power supply, torch height control, enclosure and wiring.

Ad Hoc Partial Kit Turn Key Kit
Motors  $296  incl.  incl.
Controllers / BOB  $260   incl.   incl.
Power Supply  $120   incl.   incl.
Enclosure  $100  $100   incl.
Torch Height Control  $268  $268   incl.
Misc. Cables, Switches, Cooling  $250?  $200?   incl.
Time  30 hrs?  20 hrs?   incl.
Kit  $0 $668  $1575
Support None None Included + 2 yr Warranty
Total  $1294 + time  $1256 + time  $1575

I put together the above table to try to compare the options for putting together the electronics for my table. The “Ad Hoc” column is basically sourcing different components off ebay. The “Partial Kit” column is using the supplier recommended in the Bill of Materials that came with my gantry kit.  This kit uses slightly less powerful motors than those quoted in the other two columns.  The “Turn Key Kit” column is the Dragon Cut 620-4 kit from candcnc.   The THC quoted in the first two columns is a really basic unit. I’ve seen it demoed on youtube, and it seems to work all right. The candcnc THC seems more robust though. It also has custom integration with Mach 3 software and is made and supported in the USA.

I think the table pretty much speaks for itself. There’s no way the time and (most likely) frustration of putting together one of the DIY options is worth the $300 difference.  This is especially true if you take into account the warranty and support going forward.

On that note, I wrote Tom at candcnc an email asking for clarification on which of his systems would be best suited for my project. His site advises using the 620 oz. in. motor kit for gantry weights over 50 lbs.  I figure that’s almost exactly what my gantry will weigh. I wasn’t sure if that advice was assuming one or two motors to drive the gantry. He responded within an hour with a very informative email.  He informed me that they assumed two motors driving the gantry, so the 620’s are the way to go.