A step by step guide to my final project

In Sanskrit, as an adverb, Tapan means “burning” or “heating”. As an adjective, it means “bright”, “effulgent” or “hot”.

Download all the source files from here

Idea

• Initially i planned to producing Filament From PET Bottles. But later I changed PET bottles to granules and recycled 3D prints.
  Initial Scribbles :

  1. 

  2. 

Plan

• At the starting of the course, Neil suggested that it would be beneficial if we utitlise our each week and make something for out final prjecr step by step.

• Wanted to do that, but fall behind the schedule many times. Nevertheless I completed the project on time and below is my Prject PLan :

  • The input and Output week contributed the most in my final project, as the board for those week were the same as use din my final prject. I could have

What is it ?

• My final project is an extruder, It Extrude/make filament for 3D printers from pellets fed into it. It’s be a desktop filament maker which would act as an aid to your 3D printer.

• Initially I planned to make filament from PET bottle strips but do to time constrained i’ve now chosen the more conventional path.

• To extrude we need to heat up the barrel/hotend to a certain degree which is closed (more &less)to the melting point of the material to be extruded. The heat from shear is more important than the heat from the heating elements or barrel. The material being pushed forward makes contact with the walls of the barrel-and the shear forces with frictions helps to melt the material.

• The middle section of the barrel should have slightly more temp than the end section near the nozzle. the section near the nozzle should have temp equal to the melting point of the material.

• It should be able to produce filaments form raw Pellets or failed 3d prints which are broken into small granules.

• There are generally three types of filaments used in 3D printing.

• ABS - Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x·​(C4H6)y·​(C3H3N)z) is a common thermoplastic polymer. Its glass transition temperature is approximately 105 °C (221 °F). ABS is amorphous and therefore has no true melting point.
  The most important mechanical properties of ABS are impact resistance and toughness. A variety of modifications can be made to improve impact resistance, toughness, and heat resistance. The impact resistance can be amplified by increasing the proportions of polybutadiene in relation to styrene and also acrylonitrile, although this causes changes in other properties. Impact resistance does not fall off rapidly at lower temperatures. Stability under load is excellent with limited loads. source
• PLA - Poly(lactic acid) or polylactic acid or polylactide (PLA) is a biodegradable and bioactive thermoplastic aliphatic polyester derived from renewable resources, such as corn starch (in the United States and Canada), cassava roots, chips or starch (mostly in Asia), or sugarcane (in the rest of the world). In 2010, PLA had the second highest consumption volume of any bioplastic of the world.
  The name “polylactic acid” does not comply with IUPAC standard nomenclature, and is potentially ambiguous or confusing, because PLA is not a polyacid (polyelectrolyte), but rather a polyester. source
• PETG -Polyethylene terephthalate (sometimes written poly(ethylene terephthalate)), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fibre for engineering resins. source

Bill Of Material

To view the image Kindly open it in a new tab .

Find the BOM here.

CAD

• After going through several projects and past work of fab students, I started with the design . My main aim was to pick the best bits of each product, modify them to my need and finaly incorporate them all into my Final Project.

• The CAD was done on SOLIDWORKS 2016.

• Also I needed to incorporate most of the manufacturing techniques we learned during the fab academy. This clause also affected the thinking and the designof the project, since a part can be manufactured with number of processes and materials but to use a specific one has an affect on the design. For eg. The base/housing of the project could have been made by 2 L brackets of aluminium, but I decided to 3D print it. Which resulted in a lot of design work. Also while designing the base for 3D printing , I had to keep in mind that there are minimum overhangs to minimise the support material. Also to reduce the 3D printing time, I made small windows in the base to eliminate extra material and still keeping the structural integrity strong.

• My final project has the following main/mechanical parts :

  1. Base/housing
  2. Barrel
  3. Nozzle
  4. Motor
  5. Auger Bit
  6. Hopper
  • In addition to these, there is the electronics which is a different chapter altogether and is explained late on.
    

• Assembly

This is how the final product should look like, here the electronic wiring, board and the heat cartridges are not included.

Here is a Black & white sketch of the above model which lets you visualise the product more.

• Exploded View

In the exploded view we can see all the parts taken apart, also there place.

• Barrel

• The design of was pretty easy but deciding the length and the diameter of the hot-end was not. I wanted my final project to be portable and hence decided to keep the length of the barrel short. But i was skeptical about the fact that the heat might reach the 3d printed parts and eventually melt it away.

• This later proved to be a somewhat true. The end of the barrel was pretty hot when the hotend was at the desired temp. I cooled it down with some cloth and hot water.

• Base/Housing

• The base took a lot more time than i decided, since it had to be 3d printed I could just design it like a regular product. It had to be completely optimised so as to use minimum material and time while printing.

• I had to keep the design small,with thin walls and windows, also it had to be strong enough to withstand the forces form the motor and the barrel.

• In the end all worked out well. I printed it in PLA at 30% infill with balanced settings on the makerbot z18.

• Motor

The desing of the motor was very difficult and intricate,I found the same motor which i wanted inline at GrabCad but wiht wronf dimensions and size, which was aquick fix. The original file can be found here.

• Auger Bit

I designed the auger bit just for the sake of CAD, it was off the shelf.

Mechanical Parts

• Mechanical parts manufactured :

  Base / Housing

  • The base/housing for the final project 3D printed on makerbot Z18. Infill was kept at 25% to provide strenth tp the part since the motor and the barrel were to be screwed on to the base itself. -
  • To understand the process of 3D printing better, kindly visit my week- 6 page.
    

  Barrel & Heat block

  • The Barrel and heat block were turned on lathe, I took help of a friend who new how to control the CNC to genreate the parts.

  • Heatblpck/hotend and the barrel were turned seprately. A hole of 16mm was drilled into the barrel since the auger bit was also 16mm.

    • To understand the process of CNC turning and milling, kindly visit my week- 8 page & week- 17 page.
      
      

  Motor Coupling

  • The coupling for the motor and the auer bit was made on a lathe, It was very easy and hence Digital fabrication was overuled for this part.
  • Holes were drilled on both sides of the coupling to accomodate the auger bit and the motor shaft.

  • 

    • To understand the process of CNC turning and milling, kindly visit my week- 8 page & week- 17 page.
      
      

  Hopper - Laser Cut -

  • The hopper for the filament extruder was laser cut acrylic which was press fir together to hold the pallets.
  • One may argue that the hopper should be converging toward the bottom while mines straight, wwll actually it is converging at the bottom where it’s 3d printed. For the simpicity I decided to make the upper part of the hopper straight.

  

  

  • To understand the process of laser cutting better, kindly visit my week-4 page.

  • Mechanical parts Purchased :

    1. Auger Screw –
    • The auger screw was purchased online, I chose the 16mm bit since It seemed the optimum size consedring the volume of filament to be produced. Also I had already found a high torque motor which would easily turn the 16mm bit.
    • You can opt for a 12mm if you have a low torque motor.
    • The purpose of the screw is to feed the material which is fed in the hopper forward. It pushed it thoruhg the entire lenght of the barreland finally out of the nozzle.
    1. Flange & Nozzle –
    • Flange and nozzle were bought from a hardware store, you can make them or buy them off the shelf. nothing important to dicuss here.
    • The nozzle is an END CAP fittng used in plumbing, I dilled a 1.7mm. hole in it.

  

  

  1. Motor –
  • For a extruder machine you nedd a high torque motor in order to push the filament up the barrel eand extrude it through the nozzle.
  • A motor with Stall torque of 5n/m or more should work fine with a 16mm bit.
  • Mine had a Stall torque of 8 N/m and rated speed of 10RPM.

  

Mechanical Working

• Here I’m explaining how the machine works and how the raw material is converted to finished product. Please see the image below for reference.

FIRST You load the plastic pellets/granules, it can be PLA, PET , ABS or nay other pallet as long as it’s melting point can be achieved by the machine. The pellets are loaded into the hopper.

Generally hopper should be converging toward the bottom while mines straight, well actually it is converging at the bottom where it’s 3d printed. For the simpicity I decided to make the upper part of the hopper straight. Since it’s a laser cut part.

The hopper ends end and open at the auger screw which is used to transport the material forward.

SECOND After loading the material it transfers to the auger bit. The bit is shaped in such a way that when it rotates it tranfer the material forward. The auger bit is used in woodwroking to flush out the chips of wood outward.

Generally in a extruder there is a screw to push the material forward, but it is very expensive also the machining is difficult. So instead of the screw i’ve used the auger bit.

Below is a video where you can see how the auger bit performs and push the material forward.

Third The material starts from the back, the rotating auger bit pushes it forward where it reaches the heat block. The heat block is heated with the help of heating catridges. It also has a thermistor to know and maintain the temperature.

Below is an image which explains the various heating zone of the extruder :

FINALLY At the end of the heat block or the barrel there is a nozzle. The hard plastic is liquid by this point and is pushed out of the nozzle. The opening of the nozzle can be different for different applications. Here i wanted to extrude 1.75mm diamter of wire. So I drilled a hole of 1.80. To get 1.75mm we pull the extruded material or provide it a drop. A drop is the height of the machine from the ground, the material fall on the ground and hence is pulled by the gravity.

Electronics

• I decided to make a DIY Arduino and us an ATMEGA328P-AU to control the nozzle temperature. I will use a 100K NTC Thermistor same as in a 3D printer to have accurate temperature measurements. To heat the nozzle I will use 3 Ceramic heater cartridge and for the same I will need 3 mosfet, 1 more MOSFET for the DC geared motor.

How I designed the Board.

• So the first thing was to decide which microcontoller to use.I decided to use an ATMEGA328P-AU instead of using the Attiny44, since I’d be needing a lot more i/o and PWM ports, also more memory.
• The internet is full of DIY arduino, just have to search Hackaduino and you are good to go.
• One such reference i got for the basic schematic was from How-To: Perfboard hackduino. It’s very simple and use very little component to get going.

• Also i looked at Satshakit for baisc schematic and the selection of crystal frequency and capacitors.

• After the basic schematic it went on to add a voltage regulator circuit since input voltage to the board is 12v which is regulated to 5v on board for atmega 328p and 12v raw for the heating cartridges. Here is a basic schematic i found on the internet. . Source - Here

Thermistor

• For Temperature measurements a 100k NTC thermistor will be used. This is the same as used in most of the REP RAP 3D printers.

• Information, theory and basic coded for the thermistor temperature measurement is given on the reprap website.

• Basic Connections

Heating Cartridge

• The heating cartridge I’m using are of 12V and 40W. Mosfet will be used as a switch to turn on and off the heating cartridge since Arduino cannot supply the required power.

• Mosfet used - IRF540N. Datasheet can be find here.

• Basic Connections :

Schematic

Kindly open the image in new tab as to zoom and see the image clearly.

• File’s Name in the source folder - Input/Output.sch

Board

• Image of final board
• Unrouted Nets

• Image showing jumpers which are the unrouted nets.

• File’s Name in the source folder - Input/Output.sch

Traces

• File’s Name in the source folder - traces.png

Milling:

• Milling the board was pretty tricky since 328P-AU has very tiny footprint.

• The Atmega 328 package i was using had very low clearance b/w the footprints. I edited the cad of the model and made the footprint small and have more clearance.

• To mill the board I have used the same process described in week 5. After couple of tries I was able to mill the perfect board.

Final Board

• Here is the milled board stuffed with all the components.

• Front–

• Back–

Here I have marked the programming and the Serial communication pins for better understanding. These pins are used to programme the board and also communicate using a FTDI cable. Bothe of the processes are mentioned in week-9 & week-13.

Temperature Measure and control

• In the code the temperature is used as input and read form a NTC 100k Thermistor, and 12V 40W heating catridges are used a houtput which heat the HotEnd.

• For precison control it’s adviced to use a wheatstone bridge with the NTC thermistor and also have a PID control logic.

• I cannot develop the PID controll code by myself since it’s very advance and the whole programming thing is new to me, but I did try some PID control logic from the net but they did’t work, I tried to debug them but of no use.

• Hence I wrote a simple PWM and On / Off code for the time being. The PID code is a project forthe future.

Optimum Temperature for extrusion

• In the beggining of the documentation i’ve mentioned the temperature if printing for different 3D printing materials. By taking those temperatures as a reference I started playing aroudn with the extrusion temperature.
• I was’t sure if the mentioned temperature could be used for extrusion and hence ran some trials.
• I had a temp difference of 4-5 deg evry iteration. On my third attempt the filament extruded and the temp was ranging from 248 - 252.
• I had PET granules available with me and some shredded PLA 3D prints, the 3D prints were not transporting with the help of screw so i decided to extrude PET.
• The melting point of PET lies in the range of 260 degree celcius depending on the manufacturer additives. I procured it from my uncle’s factory and He also suggested the melting point of aroudn 255 degree celcius.
• I started with 255 but quickly relaise that It’s not gonna work because it started to burn and was too slimy. couple tries later the PET started melting aperfectly at 252 degree celcius.
• Since I was writing a simple on and off code, I wanted a temp range of around 4 degrees so that the On & Off switching does’t fluctuate fast. I tried extruding at 252 aand is also wokred fine, I was a little skeptical about the temp reading but sthe filament extruded fine so i went ahead at fixed the temperture at 248 to 252.

Final Code

• The final code which controls the temperature and the heating is mainly based around PWM which stands fro Pulse Width Modulation. This code is open loop.

• I also wrote a much simpler closed loop program , which digitally turns on and off the heaters.

Temperature Measure and control

• In the code the temperature is used as input and read form a NTC 100k Thermistor, and 12V 40W heating catridges are used a houtput which heat the HotEnd.

• For precison control it’s adviced to use a wheatstone bridge with the NTC thermistor and also have a PID control logic.

• I cannot develop the PID controll code by myself since it’s very advance and the whole programming thing is new to me, but I did try some PID control logic from the net but they did’t work, I tried to debug them but of no use.

• Hence I wrote a simple PWM and On / Off code for the time being. The PID code is a project forthe future.

Optimum Temperature for extrusion

• In the beggining of the documentation i’ve mentioned the temperature if printing for different 3D printing materials. By taking those temperatures as a reference I started playing aroudn with the extrusion temperature.
• I

Understanding PWM

• Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique used to encode a message into a pulsing signal. Below you can see how output signal looks like with the duty cycle.

For better understanding of PWM Signals refer this LINK.

• In my programme the PWM signals control the On/Off of mosfet which i turns the On/Off of the Heat Cartridge. This is done because if a constant power is supplied to the heat Cartridge it may get damaged, hence power is supplied in cycles. Also this helps in heating up the Cartridge to a desired temp and maintaining that temperature.

  • The MOSFET is controlled using an analog signal/voltage. In order to have an analog voltage, you need a DAC (Digital-to-analag converter) but since you don’t have one, you use PWM (analogWrite -terrible name for this function - ref:. By changing the pulse width, you change the average voltage supplied hence controlling the MOSFET’s current output. The PWM signal acts as a tap valve controlling the current (not ON/OFF - this would be a switch) which adjusts the flow of current, which in turn can control the temperature of the heater cartridge. ( explained by my global instrcutor : Rodney )

Open Loop - PWM Code

• With trial and error I got the perfect values of PWM signals, the values are such that the temperature is around 250 degree celcius.
• In the code you can see that the catridges are given 172 PWM to heat them, after that there is a 15 second break and after that a small signal of 20 to maintain the temprature.
• Also the temperature is being taken as input and displayed on the Serial monitor to monitor. If anything goes wrong we switch of the machine.

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int ThermistorPin = A2; //Thermistor attached at analog pin A2
int Vo; 
float R1 = 10000; //voltage divider resistor value
float logR2, R2, T; 
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07; //thermistor co-efficients
#define H1 10
#define H2 9
#define H3 6

void setup() {
Serial.begin(9600);
pinMode(H1, OUTPUT); //setting pin H1 as output, goes to the first mosfet which controls the Heat Cartridge.
pinMode(H2, OUTPUT);//setting pin H2 as output, goes to the second mosfet which controls the Heat Cartridge.
pinMode(H3, OUTPUT);//setting pin H4 as output, goes to the third mosfet which controls the Heat Cartridge.
}

void loop() {
   //PWM signal values were adjusted manually by trial and error, the main aim was to have the temp being maintained at around 220 degree Celsius.         
 {analogWrite(H1, 172); //PWM signal set 172, to heat the cartridge H1
 analogWrite(H2, 172);//PWM signal set 172, to heat the cartridge H2
 analogWrite(H3, 172);//PWM signal set 172, to heat the cartridge H3
 delay(15000); //Rest period of 15 seconds for the heating cartridge
 analogWrite(H1, 20); // PWM signal set to 20, Does't let the cartridge cool Down completely
 analogWrite(H2, 20);/ PWM signal set to 20, Does't let the cartridge cool doewn completely
 analogWrite(H3, 20);/ PWM signal set to 20, Does't let the cartridge cool down completely
 }
 //Below is the temp input code
 
  Vo = analogRead(ThermistorPin);
  Serial.println(Vo);
  Serial.println(Vo);
  R2 = R1 * (1023.0 / (float)Vo - 1.0);
  logR2 = log(R2);
  T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
  T = T - 273.15;
  T = (T * 9.0)/ 5.0 + 32.0; 
  Serial.print("Temperature: "); 
 // Serial.print(T);
  float C= (T-32);
  float P= 0.5555;
  float temp= C*P ;
  Serial.println(temp);
  Serial.println(" C"); 

  delay(500);

Closed Loop Code

• Here the heaters are turned on and off Digitally. Two temperature are compared so that the system does’t behave eratically.
• The two temperature values have a difference of 4 degrees or you can say that there is a range between which the heaters will be turned ON otherwise OFF.

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int ThermistorPin = A2; //Thermistor attached at analog pin A2
int Vo; 
float R1 = 10000; //voltage divider resistor value
float logR2, R2, T; 
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07; //thermistor co-efficients
#define H1 10
#define H2 9
#define H3 6

void setup() {
Serial.begin(9600);
pinMode(H1, OUTPUT); //setting pin H1 as output, goes to the first mosfet which controls the Heat Cartridge.
pinMode(H2, OUTPUT);//setting pin H2 as output, goes to the second mosfet which controls the Heat Cartridge.
pinMode(H3, OUTPUT);//setting pin H4 as output, goes to the third mosfet which controls the Heat Cartridge.
}

void loop() {

  if(T<248)
           
  {
 digitalWrite(H1, HIGH);  
 digitalWrite(H2, HIGH);
 digitalWrite(H3, HIGH);
 }

 else if(T>252)
 {
 digitalWrite(H1, LOW);  
 digitalWrite(H2, LOW);
 digitalWrite(H3, LOW);
  
 }


 //Below is the temp input code
 
  Vo = analogRead(ThermistorPin);
  Serial.println(Vo);
  Serial.println(Vo);
  R2 = R1 * (1023.0 / (float)Vo - 1.0);
  logR2 = log(R2);
  T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
  T = T - 273.15;
  T = (T * 9.0)/ 5.0 + 32.0; 
  Serial.print("Temperature: "); 
 // Serial.print(T);
  float C= (T-32);
  float P= 0.5555;
  float temp= C*P ;
  Serial.println(temp);
  Serial.println(" C"); 

  delay(500); }
  
 

Programming the board

• Programming the board is pretty simple. I used a 16mhz clock with 22pf resistor to make sure that the Arduino IDE recognises my board as Arduino UNO which it did.
• I used FabISP to programme the board. Here is the picture of my board marked with the ISPheader pins; MISO MOSI VCC GND RESET SCK. Connect these to the respective ISP pins on the programmer and you are good to go.
• After that You need to burn the bootloader. The fuses are set when the bootloader is dumped to the MCU.
• The final step is to programme the board, You ned to upload select upload using programmer in order to burn the code to the MCU.
• Done Uploading.

Assembly

• Mechanical Assembly :

Here is a time-lapse of my assembling the mechnical structure of the filament producer. In this video the following parts are being assembled :

1. Housing
2. Barrel
3. Nozzle
4. Auger bit
5. Hopper
6. Motor
7. Motor coupling

• Electronics Assembly :

Here is a time-lapse of me makein connections of various sensors and output devices to the electronic board. Also i added a fan to keep things cool.

In this video the following parts are being assembled :

1. Circuit Board
2. Cooling Fan
3. Heat Catridge
4. Thermistor

Walk-Around

Left :

The left profile is simple and minimilist, there is nothing mounted on the left, I plan to put a sticker of the proudct name.

Right :

On the right side you can see the electronics board tucked in smartly, it does not add to the height and lenght of the machine and this is efficienctly placed.

Test Runs

Auger Bit & motor test Run :

• In the video, first tets run for the auger bit is shown.
• Here the motor is given power from a power supply, the test was performed to see how the motor and auger bit coupling is performing and also to see if the bit is turning without any disbalance and is centered about the motor shaft axis.
• Also I tested the feeding of the material and weather it’s being pushed forward or not.
• The test was a succes.

PVC Granules feeding test Run :

• This test was performed to see whether how PVC granules are transported.
• Since i was at my home i used a cordless drill to power the auger bit.
• This test was done after I turned the barrel, it was mainly to test the clearance b/w the bit and the barrel.
• I made 2 barrels onw with a bore of 16.2mm and one with 16mm. The 16mm bore barrel worked perfect.

Findings :

• Auger bit diameter - 16mm
• Barrel Bore diamter - 16mm

This came as a bit os a shocker, since having both the diamters same would result in an interfarence fit, but that was not the case. After a couple of dry run of the auger bit in the barrel it would break in.

First time filament extruded :

• This was 4 am in the morning, this was my tbird try at extruding the filament , it came out very good but not perfect, mainly since because i was pulling it with my hand which was not consistent.

Findings/ Parameters

• After running few test runs and playing around with the values, I finally found the right setings for my PVC.
• There are no set values for a particular material, every material behaves different since it’s from a different manufactures or in a different condition.

• You might want to start with looing at the melting pint of the the material you are using from the net and using that values as the initial avalue. And after that play around the initial value unitll you get the desired result.

• In my case,

– Temperature of hotend - 245 degree Celsius

– Motor Speed - 10 RPM

These are the two values that you have to set to get the filament.

License

• To generate the license head over to Creative Commons
• I wanted to use a simple and straightforward license, so that anyone can modify my work and develop on it while giving me due credits.

• I have chosen the NON - COMMERCIAL since I see my project as more of a DIY project which would act as an accessory to one’s 3D printer.

• 

• 

• 

• 

The following code was generated :

<a rel="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png" /></a><br /><span xmlns:dct="http://purl.org/dc/terms/" property="dct:title">TAPAS Filament Extruder</span> by <a xmlns:cc="http://creativecommons.org/ns#" href="http://fab.academany.org/2018/labs/fablabakgec/students/abhinav-garg/" property="cc:attributionName" rel="cc:attributionURL">ABHINAV GARG</a> is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License</a>.<br />Based on a work at <a xmlns:dct="http://purl.org/dc/terms/" href="http://fab.academany.org/2018/labs/fablabakgec/students/abhinav-garg/blog/final/" rel="dct:source">http://fab.academany.org/2018/labs/fablabakgec/students/abhinav-garg/blog/final/</a>

which lookes like this :

TAPAS Filament Extruder by ABHINAV GARG is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Poster

Final Video

Future Scope & Improvement

• My project lacks a Puller & Winding assembly, so that is on he list. They help to control the diameter of the filament and also Wind the filament.
• Also I would like to eliminate the 3D printed base/housing and replace it with aluminium/ms plates.
• A LCD with rotary encoder to set temperature and motor RPM are on the list too.
• Add a wheatstone bridge for the thermistor.
• Write a PID controler programme.