One of Those Nights

My casting hobby is directly linked to my boating 'thing'.
I have been, for lack of a better word, obsessing over a vintage style caulking mallet and caulking iron.
This was the tool used to pound the cotton material between the planking of a wooden boat or ship to help unitize the structure and to help keep it from leaking.
I called and filled out the online form for a iron maker, no response.
I decided to model 1 or 2 that I like in CAD to 3D print and see if I like the feel in aluminum before committing to buying in steel.
First model seemed a little 'delicate'. Second one seems to have a nice solid look and feel.
Nice fall day, first day back at work after a few days off and I wanted to get something done 'in the shop'.
It's been months since I have cast anything. I start rummaging through the garage to find flasks, tools, Petrobond. Most of it is in the corner where it is stored. Safety gear- jacket-gloves-face shield at the ready.
I start the furnace and load the crucible with 1/2 and 1/2 new and old gating aluminum.
-Could not find tongs #1. Had to use tongs #2 that started life as 3 jaw fireplace tongs, think Jeff turned us on to those. Lit furnace, loaded crucible, barely got tongs #2 to come out (need bigger furnace...) Went back to corner and tongs #1 are staring me in the face...
-Flasks, the small ones are too small, the big ones too big. Found an odd-shaped one for casting a diamond logo but gating will have to enter a non-ideal spot...
-Sand is handling and ramming is going nicely until I go to fiddle with the sprue hitting the gate and I loose a big chuck out of the cope. Used some 'sailor talk' to express my disappointment. Check furnace, aluminum is about ready. Drag is still good so I dump cope and ram it up again...
-Quick carry the mold out to the 'foundry', leaving the moldboard behind on the bench...
-Go to skim dross. Cannot find either dross stick, not with tongs, forced to use an old stainless ladle that lives in the dross bucket. Dross seems to be in somewhat of a sheet form. Did not think hard about it...
-Found weights, weighted mold, poured. That went fine and yielded a small ingot with the overage. About ten minutes later I see there is no moldboard. Slide the firebricks together and nothing caught so assuming all is OK...
-Went to de-flask. Part turned out better than expected for a direct 3D print to mold-making scenario. The filaments look like a driftwood sort of wood grain with the subtle curves in the piece. The gate was pretty brittle and a little porous so I may have gotten some dross in there.

Why write all this? Encouragement not to give up when things are not going 100% rainbows and butterflies in the foundry and as thanks to those who have coached me. I should have wrote a checklist of sorts to remember what not to forget.

Anyways, pics of the part and the part cleaned up with the mallet.

Anyone want to make a couple-3-4-5 in cast iron? I could clean up the pattern a bit

 

I suppose you know these caulking irons are available for 19 dollars from Defender Industries as an example. Fun project. But, if getting one just as a "user" is your goal, it is likely cheaper and a whole lot faster to let your Visa do the walking.....

https://www.defender.com/product.js...A03dBaW1kH-0R4ENq_sz06jSt-lBeYTATsuSgjELe4Lgg

Denis

 

Hi Denis-yes, aware . Also aware of people still making them by hand and vintage ones on Ebay. Until such a time I am really caulking on a wooden boat I really do not need one other than a prop to go with the mallet.

 

Tops, one of the things I learned early on is to have the mould ready to go before lighting the furnace.
Aluminium melts so fast you need to monitor it as the last ingot melts so it doesn't overheat.

 

Thanks. I have been a slow learner on this practice. I will add this to my list.

 

The same thing happens with cast iron, ramming a mold and trying to keep an eye on the furnace at the same time is like juggling most people cannot do it.

 

Thanks for all of the likes/comments/tips.

The day after I did the casting I realized that I was doing something in CAD that was not being faithful to the typical form of the tool.
Since many were forged, the blade portion would have been thinned and splayed between flat planes like a hammer and anvil .
My first couple attempts I did the transition from round shaft to the end of the blade in CAD as a loft, sort of a mathematical way to get from A to B to C with smooth transitions . So the shape had 'flow' but not the 'feature' of two flats tapering toward each other. The next couple designs I did as a revolve and sliced it off with a construction plane to better get that look.

As printed, the flat tapered plane have more of a stair-step pattern so I filled one in with glazing putty.

The print with the putty had some issues too. I had to use hot melt glue on the fly to repair one of the holes for the alignment pins. The small features that are the start of one pin hole and once extraction screw hole came off the bed due to a goober on the nozzle about 12 minutes into the print. So rather than restart the print I smeared in/over the missing features and got it as flat as I could with the side of the glue gun nozzle. After about 3 more layers the PLA+ print settled down and acted like nothing happened.

I decided to cut down #2 largest flask to have a shallower drag and less width. And since it was getting 'chopped and dropped' I thought it needed some flames. I really butchered masking them, normally I would laser cut a template and airbrush model paint but this was cheap masking tape cut with a dull razor right on top of the rough wood. Cold and gray and misting rain and 45 degrees F (8 C) outside so I painted it quick with rattle cans and brought it inside to dry. The clear can was bad, and when I wiped off the blotchy clear coat, I took off some of the color as well. And since flames are not done unless they are pinstriped...this is such a flashback to grade school Hot Wheel cars and doodles in notebooks... I got out a brush and paint out and came to grips with how unsteady/unpracticed I am at doing stuff like that. It was definitely a 'happening', execution of process over quality of product.

Some pics to go with the words. CAD software is Fusion360, slicer is Cura, 3D printer is a Creality Ender 3-something, filament PLA+, putty is Dynatron 650. The iron pattern with putty is the fourth drawing on the paper without its matching print.

 

Try printing them vertically to get the print lines to coincide with the sand pulling away from the pattern. It will draw much cleaner and you will not have as much warpage as you will on flat printed parts. I print all of my gating parts vertically. It seems to me that you can print much smaller layer heights and almost eliminate print lines at a much faster rate vs horizontally.

 

For smoothing printed patterns, I just learned of a purpose-made epoxy with a 2-hr cure time, variable viscosity, and heat accelerated made by Smooth-On.

https://www.smooth-on.com/product-line/xtc-3d/

I have some on order and will report on it in a couple weeks. It sounds perfect for this application. It is, evidently, a high-quality product used in aerospace and military applications as well.

Denis

 

Well this could certainly up the game! Thanks Denis!

 

Billy, I will try the vertical printing. I am about 500 programs deep on my CNC where the flat side is always down so that is a hard-to-break habit.



Denis, also curious to hear how that Smooth-On product works. The instructions seem in line with most 2:1 epoxies. I would use xylene or denatured alcohol in much smaller quantities to thin rather than acetone. I have a canned 'spiel' that I can go into about epoxy, let me know if you want any safety or clean-up tips.
The spot putty is 1-part and dries pretty fast. I did not like it as much when trying to thin and spray it through the airbrush. When used as intended I like it pretty good.

 

The vertical print turned out nice. A couple layers with 'jitter' but no more so than normal. The support material came off pretty easy too.

 

I also piled on to order the XTX Smooth-On product in question. It says it works on foam as well.

Nice vertical print!

 

Nice! Turned out pretty good. I will sometimes add a rib to the backside of very tall, thin models to give it some support on the flat side. It helps with the wiggle you get at the top and also helps keep them on the building plate. Usually just a half inch rib will hold parts still and adds adhesion to the plate. I also build all of my fillets into the model so they do not require any tuffill or bondo around the parts that are being mounted to the pattern plate....especially gating. I do add bolt holes for mounting the parts if they are going to be subjected to tens of thousands of molds but if they are just trial or low volume we will just glue them on and run them. Little extra work on the modeling but can save you lots of time on the mounting and scrap castings!

 

Thanks Everyone!

I have put epoxy on PLA+ before just to try it but never painted a printed part with epoxy to make it smoother. I have a collection of tail ends from gallon jugs of resin and hardener that I have decanted into smaller containers. Those make it easy to dispense by weight into a cup tared out on a small scale.

I mixed 14.5g (2:1 system but 10 g resin and 4.5g hardener by weight), no solvents, and added a little green tint and doped the parts that I had hot-glued to a piece of foam board for easier handling. As cool as the garage was I still did not get it all on the parts before it started getting a little stiff in the cup. There was still about 4g in the cup and whatever I lost to the brush and trying to knock off chunks along the way.
The place I was working was not 'clean' and I ended up picking out sawdust, a small bug, and various other debris as I coated them.
There are also some 'fish eyes' or surface tension issues, some from dust and some for no other apparent reason. I might have been better off sanding them with 100 or 150 grit instead of finer like I did or just mixing 5g and rubbing it into the parts (sometime called a cheater coat) and letting that tack up followed by a more normal second coat.

I also ordered an iron from Defender (Denis' link, thanks) and a ball of cotton. The mallet has two inner rings towards the handle and is ready for finish and a final decision about handle attach (fixed or removable).

 

Cleaned off the goobers on the backs and added pins to the lightning bolt pattern.
I like it when the epoxy cures and you can pull it all out out of the mixing cup hooked to the brush or stir stick.
I think I'd want to sand them and touch them up a bit before molding. The parting lines are a bit rough from the various drips and skips.
Curious to see how everyone makes out with the Smooth-On coating, open to tips and tricks to coating 3D printed parts.

 

Sanded the parts last night. The epoxy was well-cured so sanding was easy. I still have some holidays in the coating. Some of the spots seem to be initiated by particles, some by contamination or just plain being too thick of a coating. Adding the epoxy to the PLA+ parts does give them a little extra weight and a nice feel.

 

I decided to make a match plate for the sake of never having done one before.
Drew the inside of the flask into the 3D program and positioned the irons. Captured the center of the plate and hole locations of the patterns. Drilled plate to flask hole by hand. Scaled CAD data to match the pattern scale of the 3D parts (1.015) and CNC drilled the 1/8"(3.2mm) holes to align parts and clearances for the 3/16"(4.5mm) pins in the parts. Glued patterns down with 5 minute epoxy, gating with hot melt glue. Tried some of the spot putty to help seal the parting line after gluing. Maybe would have been better off using slow cure epoxy and weight, open to suggestions here. One coat of paint, waited about 8 hours, dusted with graphite.

I rammed the flask before lighting furnace. No issues pulling out the plate. Melt and de-dross go fine. I could see some air along the sprue during the pour, guessing it was too large at 3/8" (9mm) for my basin and speed...Happy with the parting lines and drag results, saw some defects in the larger two patterns, cope side. Had I a bigger flask I might have ran them all in the same direction, fed the striking ends with a longer runner, and tipped the blade ends up. I did not poke any vents this time.

It was below freezing outside so I did not bring the flask outside until right before the pour and kept the basin covered until the pour. I also messed up the gating, drew it bass-ackwards and then 3D printed it so it did not fit on my pokey-yoked pins in the match plate. I just used one pin on the runner/gate and cut the runner/bridge thing into 2 pieces so they each could have a pin.

 

May just need to feed that on cope side to get that out.... move the sprue close enough and it will act as a riser.

 

Thanks Billy. Would a riser on each of the cross arm runners be useful too, left and right of the center cavity?