Phan tich hien tuong cong vet cong cua PA6 gia cuong
Cong vet cong cua san pham PA6 gia cuong (PA6 + soi thuy tinh) sau khi ep phun la mot trong nhung thach thuc pho bien nhat ma cac ky su va ky thuat vien ep phun phai doi mat. Cong vet cong khong chi anh huong den do chinh xac lap rap ma trong truong hop nang co the dan den loi san pham hoan toan. Van de cong vet cong cua PA6 gia cuong phuc tap hon PA6 tinh vi viec them soi thuy tinh tao them bien so co gian cua do hut that anisotropi. Bai viet nay phan tich he thong cac nguyen nhan goc cua cong vet cong PA6 gia cuong tu ba chieu — dac tinh vat lieu, thiet ke khuon, qua trinh ep phun — va cung cap cac giai phap co the thuc hien duoc.
Co che cong vet cong: Dac diem cua PA6 gia cuong
Cong vet cong cua PA6 gia cuong chu yeu xuat phat tu su chong lan cua hai loai yeu to: co gian tinh the va co gian do dinh huong soi thuy tinh. PA6 la polymer ban tinh the voi do tinh the co the dat 30%-45%, va su hinh thanh cac vung tinh the trong qua trinh lam nguoi tao ra su co gian the tich dang ke (3%-5%). Sau khi them soi thuy tinh, su sap xep dinh huong cua soi theo huong dong lam cho su chenh lech do hut that giua huong dong va huong vuong goc co the dat 2-5 lan — su bat dong cu this nghiem trong la nguyen nhan goc cua cong vet cong PA6 gia cuong.
Khi ti le co gian theo huong dong (vi du: 0.3%-0.5%) va ti le co gian theo huong vuong goc (vi du: 1.0%-1.5%) khac nhau lon, noi luc se hinh thanh ben trong ban pham, va su giai phong noi luc trong qua trinh lam nguoi gay ra cong vet cong. Ngoai ra, nhiet do that khong deu cua thanh khuon, thiet ke duong dan lam nguoi khong doi xung cung co the lam trong trong hieu ung nay.
Nguyen nhan 1: Dinh huong soi thuy tinh va co gian bat dong cu
Trong qua trinh dap day ep phun, soi thuy tinh sap xep theo huong dong cua chat no chay. Sau khi dap day xong, trong giai doan giu ap va lam nguoi, su co gian theo huong dinh huong soi duoc kiem soat boi khung xuong soi, vi vay ti le co gian nho hon; trong khi su co gian vuong goc voi huong dinh huong soi hieu nhu khong bi han che va lon hon dang ke. Su khac biet nay dac biet ro ret trong cac cau truc phang mong.
Giai phap: Toi uu hoa thiet ke vi tri cong nap de dam bao mat truoc dong chat no chay tien trien deu deu va duong di dong mot chieu ngan nhat co the. Su dung he thong cong nap nhieu diem co the rut ngan duong di dong va giam thieu bat dong cu do dinh huong dai. Khi co the, su dung cong nap quat hoac cong nap mang de cai thien phan bo soi theo chieu rong.
Nguyen nhan 2: Nhiet do khuon khong deu
Pham vi nhiet do khuon duoc khuen cho PA6 gia cuong la 80-120°C. Neu su chenh lech nhiet do giua cac vung khac nhau cua hop kinh khuon vuot qua 15-20°C, vung nhiet do cao lam nguoi cham, tinh the hoa day du hon, co gian lon hon; vung nhiet do thap thi nguoc lai. Su khac biet nay bien hien thanh cong vet cong ve phia vung nhiet do cao cua san pham.
Giai phap: Su dung may dieu nhiet khuon de dam bao nhiet do khuon duoc kiem soat chinh xac trong pham vi ±5°C so voi gia tri cai dat; toi uu hoa bo tri duong dan lam nguoi de dat duong dan lam nguoi can bang — khuon lon nen su dung nhieu mach lam nguoi doc lap; khi can thiet, them cac kenh lam nguoi bo sung tai cac vi tri de xuat cong vet cong.
Nguyen nhan 3: Thoi gian giu ap va lam nguoi khong du
Thoi gian giu ap khong du lam cho chat no chay khong the bu du vung co gian truoc khi dong cua, tao ra noi luc ben trong. Thoi gian lam nguoi khong du lam cho san pham van con nhiet do cao khi lay ra khoi khuon, gay ra co gian sau va bien dang khi lam nguoi trong khong khi.
Giai phap: Thoi gian giu ap thuong nen keo dai cho den khi cong nap dong cung hoan toan; doi voi PA6 gia cuong, khuen su dung thoi gian giu ap it nhat 4-6 giay (tuy thuoc do day tuong); thoi gian lam nguoi nen dua tren nhiet do tam dien cua phan day nhat cua san pham ha xuong duoi nhiet do bien dang nhiet cua vat lieu; su dung phan mem phan tich dong khuon CAE de toi uu hoa cac thong so quy trinh.
Danh sach giai phap tong hop
Tu goc do thuc hanh, xu ly van de cong vet cong PA6 gia cuong nen tuan theo thu tu uu tien: thiet ke khuon truoc, dieu chinh quy trinh chinh, lua chon vat lieu bo tro. Truoc tien, su dung phan mem phan tich dong khuon trong giai doan thiet ke khuon de mo phong dap day va lam nguoi, du doan xu huong cong vet cong va toi uu hoa he thong cong nap va lam nguoi. Trong giai doan hieu chinh quy trinh, tuan theo thu tu dieu chinh sau: giam su chenh lech nhiet do khuon, tang ap luc va thoi gian giu ap, dieu chinh toc do va toc do ep phun, toi uu hoa nhiet do chat no chay.
Viec kiem soat cong vet cong PA6 gia cuong khong phai la cong viec co the lam mot lan roi xong — su khac nhau giua cac khuon, cac lo vat lieu, cac may ep phun deu yeu cau nhan vien ky thuat co kha nang phan tich he thong va dieu chinh nhanh chong.
