DownloadFTPFile.ps1

function DownloadFTPFile ($Source, $Target, $UserName, $Password) {  
    $ftprequest = [System.Net.FtpWebRequest]::create($Source)  
    $ftprequest.Credentials = New-Object System.Net.NetworkCredential($username, $password)  
    $ftprequest.Method = [System.Net.WebRequestMethods+Ftp]::DownloadFile  
    $ftprequest.UseBinary = $true  
    $ftprequest.KeepAlive = $false  
  
    # send the ftp request to the server  
    $ftpresponse = $ftprequest.GetResponse()  
  
    # get a download stream from the server response  
    $responsestream = $ftpresponse.GetResponseStream()  
  
    # create the target file on the local system and the download buffer  
    $targetfile = New-Object IO.FileStream ($Target, [IO.FileMode]::Create)  
    [byte[]]$readbuffer = New-Object byte[] 1024  
  
    # loop through the download stream and send the data to the target file  
    do {  
        $readlength = $responsestream.Read($readbuffer, 0, 1024)  
        $targetfile.Write($readbuffer, 0, $readlength)  
    }  
    while ($readlength -ne 0)  
  
    $targetfile.close()  
}