How do I make my animation work no matter the rotation?

So I have this animation that basically looks like smaller parts growing out of a big part. I want it to be some kind hand/blade weapon thingy. Using this script I made:

local source = script.Parent -- the part where parts will grow out of


function growAniamtion(source, speed, multiplier, multiplier2) -- the animation function
    local part1 =  Instance.new("Part", workspace) -- the first part to grow
    part1.CFrame = source.CFrame
    part1.Size = source.Size
    part1.Name = "part1"
    part1.Anchored = true

    while part1.Size.x <= source.Size.x and part1.Size.z <= source.Size.z and part1.Size.y <= source.Size.y*multiplier do --animating, while the part is smaller than the source part and while it is not taller than the source height * multiplier
        wait(speed)
        part1.Size = part1.Size - Vector3.new(0.2,0,0.2) -- lower the size
        part1.Size = part1.Size + Vector3.new(0,0.2,0) -- increase the height
        print(part1.Size)
    end

    local part2 =  Instance.new("Part", workspace) --the second part to grow
    part2.CFrame = source.CFrame
    part2.Size = part1.Size
    part2.Name = "part1"
    part2.Anchored = true

    while part2.Size.x <= part1.Size.x and part2.Size.z <= part1.Size.z and part2.Size.y <= part1.Size.y*multiplier2 do
        wait(speed)
        part2.Size = part2.Size - Vector3.new(0.2,0,0.2) -- lower size
        part2.Size = part2.Size + Vector3.new(0,0.2,0) -- increase height
        print(part2.Size)
    end
end

growAniamtion(source, 0.8, 1.5, 1.2) --executing the function

This works fine and gives me this:

http://imgur.com/zTzGAzi

However If I rotate the source part then the animation gets messed up:

http://imgur.com/kPeeWYT

What can I do to remedy this?