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Tool Changer

Tool-changer

Info

Discord forum thread: Tool-changer License: CERN-OHL-S-2.0

Overview

The tool-changer is a system that allows tools (in our case a micropipette) to be mounted reversibly to the Z-axis.

It consists mainly of two main mechanical parts:

  • The docking interface: we re-use Jubilee's interface, a Maxwell kinematic coupling.
  • The locking mechanism: this is a custom REL (remote elastic lock), inspired by Jubilee's, but redesigned with simplicity in mind.
    • Active mechanisms use a motor (such as ours and Jubilee's).
    • Passive mechanisms do not (e.g. Pipettin Zero's, Prusa XL's, and DAKSH-V2's tool-changer systems).

Throughout this section you will find general guidelines for building the Pipettin bot's tool-changer, such as the tool-changer's drawings, manufacturing instructions and other options and ideas you could consider for your Pipettin bot.

tc3-photo-608zz-front

Demo video

Usage

Our tool-changer is based on Jubilee's Tool-changer, but we implement some essential changes. It's placed on the bottom end of the Z-axis, and it's attached with some screws to the 20x40 V profile.

alt text

The Jubilee's tool-changer (an also ours) is based on the concept of a Remote Elastic Lock (a.k.a. REL).

  • The motor isn't mounted on the tool-changer (is remote).
  • Constant holding torque ('elastic').
  • Admits mis-alignment (± 1-2 mm).

In our tool-changer, a spring keeps the lock engaged, providing a constant tension (sort of like the 'normal closed' concept in electronics). When we want to park the tool, we move the tool to its parking post and release the lock by pulling from a Bowden cable. Find a complete explanation in the design section.

alt text

Remote actuator

The tool-changer's actuator is remote, meaning that its motor is somewhere else. We have mounted it to the back-panel, to keep it close to the control electronics.

The remote has three important parts: the top and bottom bases, and the carriage.

The only piece that will have a degree of motion is the carriage (at the middle). This component is secured to the Bowden wire via a screw, and can pull from it by moving downward. Pulling on the wire will cause the tool-changer to unlock, while moving upwards will allow the tool-changer to unlock (pulled by its spring).

alt text

The base parts will be affixed to the electronic casing using four screws, rendering them immobile relative to each other. Otherwise, the motor would not produce any useful pulling force.

The motor, as we said before, is remote, in order to save space and weight. and is mounted on the "backpanel". The bowden cable has one mount point on it, and another on the top of the Z-axis.

Tip

To manually release the lock, you can grab the bowden cable by hand at the top of the Z-axis, and pull upwards. Note that any loaded tools are likely to fall off, so make sure you catch them before releasing the lock fully.

Assembly

Required skills and resources

As other systems, you must have access to a 3D printer. All custom parts were printed in PLA.

Other option is to make metal (or plastic) pieces with a CNC router (or laser). It will be more expensive, and require several operations.

Step 1: Gather the parts

TO-DO

The instructions here are for an old version, and has already been replaced.

Documentation is pending, models can be found here: https://gitlab.com/pipettin-bot/pipettin-bot/-/tree/master/models/all_models-v3/AS-TOOLCHANGER-3?ref_type=heads

Parts and materials:

3D printed parts:

  • tool-changer:
  • BRAKE_BASE.V1
  • KEY.V1
  • TOOL_PLATE.V1
  • HEADPLATE.V1
  • KEY_PLATE.V1
  • GERAR_H_DW29.6-1 + BREAK_ARM_GEAR.V1
  • GERAR_H_DW29.6-2 + BREAK_ARM_GEAR_MIRROR.V1
  • Motor base:
  • BASE_V1
  • MOT-MID.V1
  • TOP_V1

Of-the-shelf-parts:

  • tool-changer:
  • 1x 2040V-490.V1 profile (you used it in Motion System)
  • Bowden Wire x Ø2 mm x 1 m
  • 6x Cap Screw x Ø4 mm x 30 mm
  • 2x M5 screws x 25 mm
  • 2x M3 screws x 12 mm
  • 2x M3 nuts
  • 3x M5 screws x 10 mm
  • 5x M5 nuts
  • 1x compression spring number f34
  • 4x M4 screws x 12 mm
  • 2x slider nut M5 bosch profile 20x40-V
  • 4x slider nut M4 bosch profile 20x40-V
  • 1x M5 washer
  • 1x M3 screw x 6 mm
  • Motor base:
  • 5x M5 screws x 20 mm
  • 1x M5 nuts
  • 2x M5 washers
  • 4x M4 screws x 20 mm
  • 2x M4 nuts
  • 4x M3 screws x 20 mm
  • 4x M3 screws x 12 mm
  • 4x M3 nuts
  • 1x Lm8uu
  • 1x threaded rod
  • 1x tempered rod
  • 1x stepper motor
  • 1x coupling for the stepper motor
  • nut THSL
  • KFL08 (pillow block bearing)

Tools for assembly:

  • Alen Wrench screwdrivers:
  • 5 mm
  • 4 mm
  • 3 mm

toolchanges_parts_tools_materials.jpg

Step 2: tool-changer Machining Instructions

Parts and materials:

  • PLA filament
  • Aluminum 20 x 40 V profiles

Tools:

  • 3D printer
  • Seals
  • 3D Printer
  • Band-Saw
  • Screwdriver
Instructions

Info

Most models are not yet linked to this website. Find the FreeCAD files at: https://gitlab.com/pipettin-bot/pipettin-bot/-/tree/master/models

  1. First, you must print the 3D parts. Do the adjustments that you need to do in case of using other type of profiles.
  2. For profile machining, look steps 2, 3 and 4 on this link.

Step 3: Assemble the structure

We recommend get out the profile of the Motion System.

Additionally to this, you have to do a square hole on the end of the profile. The key will pass through it.

Assemble the actuator
  1. Place the belts on the HEAD_PLATE.V1 as shown in the image. Then, place the M4 x 12 mm screws next to the nuts to attach the piece to the profile.

toolchanger_assmebly.png

  1. Position the KEY_PLATE.V1 on the TOOL_PLATE.V1. Then, insert the 3 button-head M5 screws into the holes indicated in the figure, securing them with their respective nuts.

toolchanger_assembly_2.1.png toolchanger_assembly_2.2.png

  1. Place the KEY.V1 on the KEY_PLATE.V1, using M3 screws and nuts.

toolchanger_assemly_3.1.png toolchanger_assembly_3.2.png

  1. Check that everything fits properly. That is, ensure that the toolplate and head_plate fit snugly, and the screws align with the corresponding bolts. Additionally, verify that the key fits into the hole in the profile.

toolchanger_assembly_4.png toolchanger_assembly_4.1.png

  1. Now, place the break arms with the gears engaged, placing the base on top, and connect everything using the M5 screws and profiles nuts.

toolchanger_assembly_5.png

  1. Next, attach the spring to the end and connect the Bowden cable. You can use a screw, a nut, and a washer to secure a lock on the Bowden cable.

toolchanger_assembly_6.png

Assemble the Motor base
  1. Place the BASE_V1 on the position with the stepper motor as shown on the image. Then, place the M3x12 mm screws to the BASE_V1. Finally, put the stepper motor coupling.

pas1_base.png pas2_base.png

  1. Insert the THSL nut and the LM8UU in the MOT-MID.V1 as shown in the image.

medio1.png

  1. Secure the THSL nut with the M3 x 20 screws and locked them with the nuts.

medio2.png medio2.2.png

  1. Finally, insert the M5 x 16 mm and its nut in the shown place.

medio_3.png

5) On the bottom of TOP_V1, insert the KFL08 and adjust it with M4 x 20 screws with its nuts.

top1.png top2.png

6) Once you have the three parts assembled, place the threaded rod and the hardened rod as shown below to bind the parts.

assemble.png

7) Finally, secure the hardened rod in the BASE_V1 and in TOP_V1 with the M4 x20 mm screws.

assemble2.png

Connection between tool-changer and motor

The connection between them, as mentioned earlier, is through the bicycle cable. We will thread the cable through the groove of the Z-axis profile and secure it with zip ties, ensuring that none of this affects the vertical movement of the axis.

toolchanger_wire_2.jpg toolchanger_wire_1.jpg

Additionally, we will use this cable to guide some electronic cables to this area of the robot.

Assembly Video

To do

Record assembly video for the latest mechanism.

Interactions

As we mentioned before it is connected to many parts:

toolchanger-assembly.png toolchanger-perfil_union.png

  • To the micropipette, through a plate. The plate is going to change depending on the size and the type of connection you can do to the tool:

toolchanger_interactions_1.png toolchanger_interaction_4.png

The blue part is the plate we used for the Electronic Micropipette. And the grey part is the base you can use to adapt the tool-changer to any other tool.

  • To the toolparking. Here, the tool-changer is going to leave the tool:

toolchanger_interaction_2.png toolchanger_interaction_3.png

Maintenance

Daily, it is essential to clean the tool-changer to ensure the proper functionality of its moving parts. Failure to do so may result in potential sticking.

If any 3D-printed components are broken or deformed, they can be reprinted.

The stepper motor does not require maintenance, as it does not have brushes that need replacement.

Design

As we said before, we wanted to create a system that adapts to the Jubilee system, to be able to exchange tools without major changes. Based on that, we modify some jubilee's parts. One of our main objectives was to design something as simple and compact as possible, minimizing space occupancy and allowing for maximum freedom of movement along the Z-axis.

If you want to modify or create a new version of the actuator, you must have in mind the following:

Tool Changer

  1. For the design of the 'KEY.V1':
  2. The key has, laterally, the shape of an arrow (green lines). Thanks to this shape, it will engage between the teeth of the brake arm gears. These teeth need to have as close to a vertical angle as possible so that the resulting force from the interaction is primarily horizontal (red lines).
  3. On the other side, it will be secured to the key plate, which will be inserted into the tool plate using 2 M3 screws (yellow holes).

toolchanger_interactions_key.png

  • The length of the key must take into consideration the width of the profile, the width of the brake arms, and the width of the head plate.

toolchanger_design_key.png

  1. For the design of the 'TOOL_PLATE.V1':
  2. This piece serves as the mounting point for the tools.
  3. It has three holes to connect the tool plate and the key using screws (yellow marks). Additionally, there are three holes for attaching round-headed screws for the kinematic system (red arrows).
  4. The tool parking wings are also located on the side (blue marks).
  5. The green hole is to facilitate the key assemble, and the triangle hole (in purple) is to put the keyplate.
  6. In future versions, it will have holes to prevent the tools from falling down (we're still working on it).

toolchanger_design_toolplate.png

  1. For the design of the 'HEADPLATE.V1':
  2. It features a square hole for the passage of the key (red arrow).
  3. There are 4 holes for securely fastening it to the profile (blue arrows).
  4. Additionally, there are 6 holes for inserting pins to support the heads of the screws from the tool plate that are part of the kinematic system (purple arrows).

toolchanger_design_headplate.png

  1. For the design of the 'KEY_PLATE.V1':
  2. This piece connects the key with the tool plate. It is attached to both using nuts and screws.

toolchanger_design_keyplate.png

  1. For the design of the 'GEAR_H_DW29.6 + BREAK_ARM_GEAR'
  2. This piece is the one that engages the key and ultimately holds it.
  3. It has a gear to coordinate the opening between both teeth (Δx/Δt same for both arms, green arrows). The parameters of the gear were adjusted until the separation between the two axes was sufficient (red arrow). It also has that shape to withstand higher pressures.

toolchanger_design_breake_1.png toolchanger_design_breake_1.png

Parameters we used:

  • BASE:
  • numpoints: 6
  • simple: false
  • height: 10 mm
  • module: 0.8 mm
  • teeth: 37
  • COMPUTED:
  • da: 31.2 mm
  • df: 27.6 mm
  • dw: 29.6 mm
  • HELICAL:
  • beta: 45°
  • double_helix: true
  • INVOLUTE:

  • pressure_angle: 20°

  • The center of this gear is the axis around which the brake arm will move (red lines). The axis will be a screw, and by using a nut, it will help attach the brake arm to the profile.

  • The tooth has a cut so that, during the opening, the key can pass through completely (yellow marks).

toolchanger_design_breake_1.png

  • At one of the ends, there is a protrusion (red arrows). This will be used to place the spring. Its size can vary depending on the type of spring and how easy it is to handle.
  • At the opposite end, there is a through-hole where the cable of the sliding cable will pass through (green circles). The thickness of the brake arm must be wide enough to withstand the pressure generated by the spring and the cable. Due to this, it is also important that, if PLA is used, it is printed with a high infill (we print with a 90% infill), and that the hole on which the system will pivot, that is, where the screw passes through, is well-reinforced.

toolchanger_design_breake_1.png

  1. For the design of the 'BRAKE_BASE.V1':
  2. This component adds stability to the system, preventing the teeth from separating when the spring expands (highlited piece).

toolchanger_design_basebreak.png

Motor base

We needed to create a system for remote control of the actuator. To achieve this, we considered utilizing a mechanism that pulls the internal wire of the cable, similar to a pulley system, as explained earlier.

The motor base is affixed to the back panel, and we secured it using nuts and screws on the top with the top.v1 and base.v1 parts (indicated by the green arrows). Additionally, we incorporated a template road to enhance stability (blue arrow).

The cable wire will pass through the holes marked in yellow and will be secured with the screw indicated by the red arrow in the image

toolchanger_design_motor_base.png

The cable used will extend to the tool changer actuator through the guides of the profiles, and it will also assist in routing the electronic cables towards the Z-axis.

toolchanger_wire_2.jpg toolchanger_wire_1.jpg

Models

The latest versions of all files will be available at this link

Tool changer parts

  • BRAKE_BASE: custom part
  • Material: PLA
  • CAD: BRAKE_BASE.V1.FCStd
  • Part number: BRAKE_BASE
  • KEY: custom part
  • Material: PLA
  • CAD: KEY.V1.FCStd
  • Part number: KEY.V1
  • TOOL_PLATE: custom part
  • Material: PLA
  • CAD: TOOLPLATE.V1.FCStd
  • Part number: TOOLPLATE.V1
  • HEAD_PLATE: custom part
  • Material: PLA
  • CAD: JUBILEE.FCStd
  • Part number: HEAD_PLATE.V1
  • KEY_PLATE: custom part
  • Material: PLA
  • CAD: JUBILEE.FCStd
  • Part number: KEY_PLATE.V1
  • GEAR_H_DW29.6-1 + BREAK_ARM_GEAR.V1: custom part
  • Material: PLA
  • CAD: BRAKE_ARM_GEAR.FCStd
  • Part number: GEAR_H_DW29.6-1 + BREAK_ARM_GEAR.V1
  • GEAR_H_DW29.6-2 + BREAK_ARM_GEAR_MIRROR.V1: custom part
  • Material: PLA
  • CAD: BRAKE_ARM_GEAR.FCStd
  • Part number: GEAR_H_DW29.6-2 + BREAK_ARM_GEAR_MIRROR.V1
  • M2 Screws and nuts: off-the-shelf parts.
  • Bowden Wire x Ø2 mm x 1 m: off-the-shelf parts.
  • Cap Screw x Ø4 mm x 30 mm: off-the-shelf parts.
  • M5 screws x 25 mm: off-the-shelf parts.
  • M3 screws x 12 mm: off-the-shelf parts.
  • M3 nuts: off-the-shelf parts.
  • M5 screws x 10 mm: off-the-shelf parts.
  • M5 nuts: off-the-shelf parts.
  • Compression spring number f34: off-the-shelf parts.
  • M4 screws x 12 mm: off-the-shelf parts.
  • Dlider nut M5 bosch profile 20x40-V: off-the-shelf parts.
  • slider nut M4 bosch profile 20x40-V: off-the-shelf parts.
  • M5 washer: off-the-shelf parts.
  • M3 screw x 6 mm : off-the-shelf parts.

Motor base parts

  • BASE: custom part
  • Material: PLA
  • CAD: MOT-BASE.FCStd
  • Part number: MOT-BASE.V1
  • MID: custom part
  • Material: PLA
  • CAD: MOT-MID.FCStd
  • Part number: MOT-MID.V1
  • TOP: custom part
  • Material: PLA
  • CAD: MOT-TOP.FCStd
  • Part number: MOT-TOP.V1
  • M5 screws x 20 mm: off-the-shelf parts.
  • M5 nuts: off-the-shelf parts.
  • M5 washers: off-the-shelf parts.
  • M4 screws x 20 mm: off-the-shelf parts.
  • M4 nuts: off-the-shelf parts.
  • M3 screws x 20 mm: off-the-shelf parts.
  • M3 screws x 12 mm: off-the-shelf parts.
  • M3 nuts: off-the-shelf parts.
  • Lm8uu: off-the-shelf parts.
  • threaded rod: off-the-shelf parts.
  • tempered rod: off-the-shelf parts.
  • stepper motor: off-the-shelf parts.
  • coupling for the stepper motor: off-the-shelf parts.
  • THSL: off-the-shelf parts.
  • KFL08 (pillow block bearing): off-theshelf parts.

Development

These 3D-printed parts were designed in FreeCAD 2.1 and 2.0, then exported in the FCStd format for slicing. They were printed on an Original Prusa i3 MK3 using STL files.

Most pieces were inspired by Jubilee's designs for compatibility between these CNC machines tools.

If you want to dive into file formats visit here.