Mr Ed was kind enough to send me the gear pattern he had printed. This was the first printed pattern that I had seen first hand. I was very interested to see its surface finish as I intend to cast it with either green sand or silicate bound sand. Ed said he was fine with a review of the pattern. What I write here will somewhat superficial as I have limited time to spend at the keyboard given the work that needs to get done in the foundry. Here is an image made with strong directional side light to try to represent the finish of the gear. The best way I could characterize the surface that is generated by the layers laid down by the printer would be to say it has the smoothness similar to a LP Record (sorry for those to young to know what I am talking about). It is not slick smooth by any means but has visible and palpable striations reminiscent of sedimentary rock only much finer, of course. Here it is chucked up on a mandrel (for concentricity) with a tailstock center stabilizing it. Here it is having been sanded some on the hub OD and the OD of the teeth and with the shrp corner knocked off on the hub side. And here the other half the gear pattern is in place and some sanding and chamfering completed. Final sanding was 350 grit. It sands pretty easily and nicely. Those OD surfaces were the easy ones. All those teeth require some sort of handwork. I used files and sand paper. Just getting a good start on this. I did spray a little lacquer on sanded and filed areas and it looks like a usable surface will result. More later as work progress. Here is a video of the gear spinning. Note there is a little hop in its motion indicating the Hub ID is not perfectly concentric with the OD of the hub and teeth. I did some wuick OD measurements of the hub and it varied by about 10 thousandths. Denis
I'll be watching with great interest! It's looking really good. I notice there are a few depressed areas on the surface. Are you going to fill those or sand them out? I was hoping to have cast my second by now but my paint does not seem to want to dry so I'm having to wait 24 hours between coats. Almost there.
I am filling , filing, and sanding. I am using lacquer paint which is dry enough to sand in 30 mins or so. You can see the surface is much smoother but would still grab sand. Maybe one or two more sand/spray cycles and it will be there. Isolated divots I’ll fill with Bondo. I like the way the white lacquer really makes defects stand out so I can see and correct them. Denis
This is like a "gears gone wild" thread. I have never seen so much creativity with a gear casting. Going for more popcorn. This is getting good. .
Yes, I actually think this somewhat unusual circumstance is a really great chance to see the same problem approached by different folks with each person able to demonstrate the “style” they have developed. It’s a super chance to learn from each other. Denis
Now the pattern is getting close to molding condition. Still a half dozen bumps on each half to smooth out. But close. Denis
You do good work. Why are we making more than one pattern? My paint was dry so I sanded. I like different colors for different layers. Purple was on top and when I have dulled all the purple I know I have leveled that area. Light blue was the previous color, and the 3D printer plastic is red. A little more sanding to do on the short part of the gear. Edit: Removed non-pattern preparation related text.
I think my pattern is ready for sand. I will be using a 3-part flask too. Probably pack tomorrow and hope to pour Monday. I am sure I’ll still find a few boogies to knock off when I look again tomorrow. In some ways I was using contrasting colors as well since the plastic is dark grey. That did help highlight defects and a very strong spotlight grazing the surface helped a lot as well. Denis
Not sure about gating. Probably will discuss that part in the other long thread “Casting a windmill gear in grey iron” Denis
See the casting windmill gear in grey iron thread. I did test mold the pattern in less-than-optimal green sand and it pulled OK. Pictures on the other thread. http://forums.thehomefoundry.org/in...mill-gear-in-grey-iron.533/page-15#post-17448 Denis
Holy moly, I just found this thread. Hmmm … it that center hub was out of round, I must have something up with my printer. Mine is quite different operation than Andy and Pat's … it relies on belts to run the XY directions. Sounds like I need to print more test patterns and adjust.
We were hiding it from you. I think the hub is concentric with the bore but maybe how the teeth were generated created the error.
