Golf Trophy

I'm a golfer. Occassionally my Club Pro asks me to make something and I succumb.

Tee Box Marker Match Plate – Model Hand Pump | The Home Foundry
Well Pump Trophy | The Home Foundry

This time it was a trophy for an interclub competition. Since he had artwork that I could import, and it was only one piece, in a weak moment I said yes. -Never a bad thing to have the pro feeling indebted to you.

He sent me the artwork and I knocked the CAM program out for this while watching night time coverage of the US Open played at LA Country Club......seemed fitting. This morning it took about an hour on the CNC router to make the pattern. I hollowed the backside to approximate .25" wall. It's 13.5"D x .875"h.



I'll update the post when I gate, cast, and finish it. It's as close to artwork as I get.

Best,
Kelly

 

Gated



Best,
Kelly

 

Since this is an ornament, I was planning to polish the raised surfaces of the casting. To minimize labor, I wanted a good as-cast finish.

I usually just spritz down the foam pattern with soapy water to serve as a surfactant which works fairly well, but inevitably you get a few BBs here and there from air bubbles and it can still be difficult to get slurry to fully penetrate all the little nooks and crannies. So in a break from normal procedure, I thought I’d just brush the whole front side with a thin coat of refractory to try to eliminate any bubbles caused by surface tension and then used a small brush to fill the engraving, lettering, and finer grooves.



This may have been a mistake, or at least letting it dry before I dipped it was. When I dipped it, the front side with dried refractory had air bubbles coming through the topcoat all over the place. I guess I could have wetted the initial coat before I dipped it but didn’t think it was needed. -Wrong!

I ended up having to remove most of the wet refractory by brushing the entire front side while it was hanging by the sprue and then redipping it. This seemed to work as far as getting rid of the bubbles but the first coat of dried refractory apparently absorbed water from the topcoat making it more viscous and it didn’t drain, thin, and level from the hanging pattern as well, thus producing quite a bit thicker coating than usual.



I wasn’t sure how this was going to affect the casting. Common sense said thicker refractory meant less permeability and slower venting of the evaporated foam pattern. I was way past the point of no return so I just pressed on and everything turned out ok. Here it is degated.



I spent 15 minutes or so with a couple of fine grit abrasive discs just to see how it would look. Still have plenty of polishing to do.



Best,
Kelly

 

Thanks Mark. I'm glad it was a one and done.

Dipping is very fast and works pretty darn well, but since I mostly make machine parts, I keep the viscosity a little higher so I get the one-dip coverage desired. For fine detail, it should be lower viscosity, but one 30 gallon drum is already a little over the top for hobbyist. I had a similar YouTube viewer comment on spraying. The slurry is water based so could easily be thinned to work in guns like used to spray textured plaster. I could see how it could be useful for a large fragile patterns since they are very buoyant for dipping and get very heavy while wet coated. The one downside may be spraying is more line of site process, so cores and intricate gating may be difficult. There are alcohol based refractories. They dry much faster but I opted for water based for safety and ease of use.

LoL. I did manage to get that gating off the casting in one piece and it was a crazy looking thing, but after taking that photo, I chopped it up into smaller pieces and threw it into my remelt bucket.

As a side note, I'm glad I used my largest pouring basin. That gating took metal and distributed it to the casting in a gulp and without the large buffer volume of metal in the cup, probably would have sucked a smaller cup dry before I could top it off, so I was a bit over gated.

Best,
Kelly

 

Maybe. It would have to be very low melt point wax, and the carrier if any would need to be compatible with/not attack the foam. I've seen folks dip 3D printed PLA patterns in parafin as a smoothing method but the PLA can withstand considerably higher temps than foam.

Applying paste wax in multiple coats and lightly buffing might accomplish something similar. Easy to do on simple surfaces but not so on fine details. I have done this to serve as a release agent foam molds I've used for casting one off refractory shapes. I was sort of surprised because I believe the solvent used to reduce carnuba and parafins in such waxes is typically mineral sprits, which will attack polystyrene, but apparently is in low enough concentration that it's not really noticable.

I haven't actually tried this as a method for improving pattern/casting finish. The other issue is wax is even more hydrophobic than polystyrene, so getting the refractory coating to wet the surface may be more of a challenge. As I mentioned above, I use water based refractory coating and it should really be less viscous to produce fine detail and have less tendancy to retain small air bubbles on the pattern surface, but diluting the refractory coating with water can create more problems with getting the coating to self level and cover the wax and polystyrene. I precoat the pattern with soapy (Dawn dishwashing soap) water because the active ingredient in Dawn is propylene glycol, which acts as a surfactant, but increased water in the coating will dilute the surfactant, so all of this can be a bit of a balancing act.

All of the above are really fine tuning. I just don't do as much art and ornamental work and the typical finishes with present processes are as good or better than most sand castings and machine parts.

For jewlery and artwork, as far a finish and detail go, investment or shell with evaporative pattern material that can achieve better finishes than foam would be a better method. But if the parts become large, mold costs, size and weight increase, requiring a large burn out oven, and chipping away the mold make it quite laborious compared to lost foam.......thus my use of LF.

Best,
Kelly

 

With pupose built foam cutting bits 18krpm should do just fine, feedrate dependent of course. I use dual flute spirals at 24krpm but they are mostly .25" diameter so the extra speed helps the smaller bit. Woodworking bits generally cut just fine too because the wide gullets clear chips well and the cutting angles and reliefs are suited for soft materials. They are also very economical and even the junk import variety perform well on foam. Although you can use metal working bits, I've found their geometry is not as favorable. A light climb/finish cut will sometimes produce better finishes but this can be subtle and regardless, I lightly sand most patterns where cosmetics are of interest because it is so quickly and easily done on foam. XPS foam machines and finishes much better than EPS.

Best,
Kelly