innovations CASTING
metalcasting facilities pour. It con- tains carbides in its microstructure to increase toughness and wear resistance after austempering. Abrasion resistance and hardness increase as carbidic con- tent increases. In fi eld trials, the CADI knife prototype exhibited increased impact resistance compared to the 27% high-chrome iron prototype and superior abrasion and wear resistance
over ADI grade 5. Yetter and Lethbridge selected CADI as the production material. Yetter wanted the new knife design
to off er better protection for the as- sembly’s anhydrous ammonia delivery tubes and beavertail components, which were prone to wear on the origi- nal fabrication. Consolidating various parts into a single casting also would
eliminate the need for additional part numbers. Other non-critical components could be off ered as optional add-ons. Lethbridge produced the fi nal de-
sign in green sand with two cores and supplied it to Yetter as-cast, without any machining required. Shell coring was chosen for the mounting ears and holes, which kept the ears parallel to each other and provided dimensional stability for fi nal assembly. A second core was used to produce the cavity for the fertilizer delivery tube and incorpo- rate a mounting hole for the beavertail, which had been a separate part welded onto the knife. A square carriage bolt hole for the tube assembly was incor- porated into the mold to eliminate ma- chining requirements. At Lethbridge’s suggestion, the knife features a carbide insert on the leading edge for superior wear over an as-cast edge. Lethbridge grinds the parting lines robotically with a diamond-coated wheel for superior dimensional control. With the fi nal cast design, Yet-
The fertilizer knife, shown in blue, is attached to the Coulter disc to keep the blade free of residue and protect the fertilizer tubes from wear.
Cores
ter achieved a 60% cost savings and reduced its part numbers to two for right and left hand versions of the one-piece casting. One casting may be used for several end-products, such as a single tube, double tube or vapor tube. T e cast knife provides greater protec- tion of the delivery tubes from the soil, leading to signifi cantly longer wear life. Yetter’s order accuracy also increased due to the decrease in part numbers and ability of the same knife to be used with various tube kits. “We needed to clean the part up [by
casting it],” Lucas said. “We cleaned it up in every aspect, including inven- tory. We were able to cut down on the number of parts, which helps maintain our tolerance.”
@
Lethbridge Iron Works used shell cores for the mounting ears and holes at the top of the casting. A second core was used to produce the cavity for the fertilizer delivery tube.
50 | METAL CASTING DESIGN & PURCHASING | Jul/Aug 2012
ONLINE RESOURCE
To see an interac- tive 3-D view of the CADI fertilizer knife, go to
www.metalcast-
ingdesign.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60