A number of innovative developments (has, have) been made in the multi-component injection molding process in recent years.

A number of innovative developments (has, have) been made in the multi-component injection molding process in recent years.

The number of takes singular verb while A number of takes a plural verb.

A gas channel design 【 that (guides, guide) the gas flow to the desired locations 】 (is, are) one of the key factors that determine a successful application.

The delay time along with gas injection points (is, are) important in producing injection-molded parts of quality.

Expressions such as as well as, in addition to, along with, accompanied by and with should not confuse the reader into thinking that the sentence has a compound subject and, therefore, should have a plural verb.

The verb in this sentence should be singular since the subject, The delay time, is singular in form.

Neither the processing parameters nor the amount of polymer melt injection solely (determine, determines) a successful gas channel design.

The verb in the sentence is singular in form since the amount of polymer injection, not the processing parameters, is the closest to the verb.

【 To select the number and locations of gas injection points 】 and 【 to determine the amount of polymer melt injection 】 (is, are) essential to a successful application.

A compound subject, To select the number and locations of gas injection points and to determine the amount of polymer melt injection, takes a plural verb.

Ergonomics (aim, aims) to integrate worker comfort and productivity.

(Original) Each of the factors contributes to a successful design.

(Revised) Each factor contributes to a successful design.

(Revised) The simulation 【 in which the polymer melt flow occurs in thin cavities 】 provides accurate predictions.

Writers should be careful not to choose the wrong verb form by becoming distracted by words or phrases between the subject and the verb.

【 Establishing a general model or empirical formula in addition to describing the thickness variation of the skin melt that exists between the gas/melt interference and the cavity wall 】 appears to be necessary for further development.

The number of gas injection points is important in producing quality injection-modeled parts.

The majority of factors heavily influence product performance.

The verb should be plural in this sentence since the noun refers to individual factors.

【 Accurately determining the interface shape of a bubble nose 】 and 【 properly selecting the film thickness 】 are of primary concern.