Cimco, a manufacturer of thermoplastic components and subassemblies, said net income for the third quarter of fiscal 1988 rose 84% to a new high of $555,340, up from $302,144 a year earlier. Net sales for the three-month period increased 29% to set a third-quarter record of $9.4 million, compared to $7.3 million for the same period last year. For the first nine months of fiscal 1988, net income rose 15% to $1.6 million, compared to $1.4 million a year ago. Net sales increased 9% to $27.1 million from $24.8 million for the first nine months of last fiscal year. The third-quarter performance was attributed to strong incoming orders from nearly every segment of CIMCO's customer base, higher plant utilization and further improvements in productivity.