Sketchup crashes when import,purge_unused,export dae files

[YoungOSG]

Sketchup crashes when import,purge_unused,export hundreds of *.dae files.
I use api to do this.It works fine while handling few *.dae files.
anyone konws why?

Here is my code

require 'sketchup.rb'
require 'fileutils'

UI.menu("Plugins").add_item("purge_multi_daeE") {

@import_folder = selectImportDaefolder()
break if @import_folder==nil
@export_folder = selectExportDaefolder()
break if @export_folder==nil


@daeFiles = getDaeFiles(@import_folder,".dae")


purgeDaeFile(@daeFiles,@import_folder,@export_folder)



Sketchup.send_action("selectSelectionTool:")

}

def purgeDaeFile(daeFiles, import_folder,export_folder)
model = Sketchup.active_model

subName = getDirName(import_folder)
Dir.chdir(export_folder)
FileUtils.rm_r subName if Dir.exist?(subName)	


i = 0
Dir.mkdir(subName)
daeFiles.each{|singleDaeFile|
	Sketchup::set_status_text("purge " + File.basename(singleDaeFile))

    status = Sketchup.active_model.definitions.purge_unused
 
	f.puts(singleDaeFile)

	importDaeFile(singleDaeFile)


	purgeModel()


	resultFileName = File.join(export_folder,subName,File.basename(singleDaeFile))
	Sketchup.active_model.export(resultFileName, false)


	deleteLastModel()
	
}

end#def

purge dae model

def purgeModel()
# 1. purge styles
styles = Sketchup.active_model.styles
status = styles.purge_unused

# 2. purge materials 
materials = Sketchup.active_model.materials
materials.purge_unused

# 3. purge definitions
 definitions = Sketchup.active_model.definitions
 status = definitions.purge_unused

# 4. purge layers
layers = Sketchup.active_model.layers
status = layers.purge_unused

end#def

导入dae file

def importDaeFile(singleDaeFile)
model = Sketchup.active_model
model.import(singleDaeFile,false)
entities = model.entities
definitions = model.definitions
definitions.each {|definition|
transformation = Geom::Transformation.new([0,0,0])
componentinstance = entities.add_instance(definition, transformation)
}

Sketchup.send_action("selectSelectionTool:")

end#def

def deleteLastModel()
model = Sketchup.active_model
entities = model.active_entities
entities.erase_entities entities.to_a

end#def