I have the following function
ALTER FUNCTION [dbo].[ActualWeightDIMS] ( -- Add the parameters for the function here @ActualWeight int, @Actual_D
Try casting the ints to varchar, before adding them to a string:
SET @ActualWeightDIMS = cast(@Actual_Dims_Lenght as varchar(8)) + 'x' + cast(@Actual_Dims_Width as varchar(8)) + 'x' + cast(@Actual_Dims_Height as varhcar(8))