The additive lathe is a 3d printer that prints on rotating objects.
It is using FDM (fused deposition modeling) to deposit ABS plastic on the object.
The project integrates 7 systems:
Chuck mechanism
Rotating Spindle
X-axis movement
Extruder
Heating element with control
Microcontroller
User interface
All of the systems work independently.
What is left to do is fine tune the synchronism of the motors and the software and makes small improvements in mechanical design so things will go more smoothly.
Systems review
Chuck mechanism
just like in a regular lathe ,the chuck hold circular objects with its 3 arms.
It is made out of a single 3D printed object with all the gears and parts printed together as a assembly.
All three arms move together toward and outward of the center axis.
The other side of the check has teeth for the timing belt.
The is press fitted into a big bearing that lower the friction and stabilized the chuck.
The part took 52 hours to be printed and it worked on the first try (yehh!) – the only one I had.
Rotating Spindle
The rotating spindle is rotating with a stepper motor. It is connected to the motor with timing belt and there is a pulley that keeps the belt stressed.
X-axis movement
For the X movement I used rack and pinion mechanism (mainly because it was too expensive to by such a big acme Threaded rod and all the accessories).
The motor is located on the extruder head and the pinion is connected with a set screw. The extruder head moves easily especially in the middle part of the lathe and it’s hard for it to reach the ends. I did the M2M trick for holding the rods and I need to work on that a little more to make the rods parallel so the extruder will move freely.
I made two versions of the rack and pinion. The second one I used solidworks tool for making gears which is very easy and create very good gears.
First genetation rack and pinion - not working
Extruder
For the extruder I made two version. The first version was naïve I didn’t use any spring and the gear contact with the wire was either too weak or too strong- both cases there was no extrusion. In addition there was a lot of friction from the pushing plate.
The second one had a bearing instead of a plate and the gear was smaller for more torque. I added a spring (with adjustable force) that ensure constant between the gear and the wire.
First generation extruder
Heating element with control
The heating is done with nichrome wire. The nicrome wire is control with mosfet and the microcontroller pulses with modulation to it to control the amount of current that heats it.
It is programmed to head rapidly (full power) until it reaches 120 C and then the mosfet and the microcontroller preserve that temperature.
The temperature measurement is done with thermocouple.
User interface
The first application for the late is making plastic springs. I wrote a code in procession to allow the user to decide the height and pitch of the spring. He can also control the direction of the spring.
