This is my Anet A8 carriage modification to allow me to quickly change between different tools, thus increasing the versatility of the printer. In this build I will show the making of the plate that all of the tool heads will mount to, as well as a few different tool heads that can be printed.
This will outline the main plate that mounts to the carriage that all the different tool heads mount to. The plate mounts to the A8's three X carriage bearing/mounting blocks. The plate is made with four 10mm recessed holes in the back that hold four 10mm x 3mm neodymium magnets that are used to hold the tools to the carriage. On the front side of the plate, there are four tapered recessed holes that sit just over the magnets in the back. These holes are to align the tool on the plate and to keep it from shifting when in use.
One thing i forgot to mention was that you will need to print one of the X axis belt holders le this one: https://www.thingiverse.com/thing:2125082. There are holes in the back of the plate to schw this on using some 3mm tapping screws.
Front face of the carriage mounting plate.
Example placement of the neodymium magnets on the back side of the tool plate and on one of the tool mounting plates.
The universal tool mounting plate is a generic plate design that is used with any tool head that is made. This plate has the alignment tabs and holds the magnets that mate the tool head to the carriage. There are four 3mm screw holes in the plate that are used to mount the plate to the tool head. The heads of the screws should be on the front side of the plate. There are recessed holes in the carriage mounting plate that let these screw heads recess in to the plate for it to mount flush.
Front side of the tool mounting plate with alignment tabs.
Back side of the tool mounting plate with recessed holes for the magnets.
The tool head connector is used to connect those tool heads that need to be electrically connected to the 3D printer electronics in some way. When I designed this, I had to think of different tool heads that I wanted to build and make sure that I had wiring needed for each head. So far the only tool heads that use this are the 3D printer head and the laser engraver head.
The connector mounting bracket seen in the picture below has been designed to be mounted to one of the acrylic uprights on the A8 that originally mounted the main controller board. If you are still using this for that purpose, you may need to change your screws in a couple places to longer ones to get it to fit.
The connector that I used is a 10 pin (2 x 5) Molex connector set purchased from Amazon.
The second pic in this section shows how the connector is wired. The top two 12 volt pins get wired directly to the PSU and are used to give power to the laser engraver assembly that I purchased. The next two are for the part cooling fan for the 3D printer head. These wires are also used for the laser engraver module to control the laser using Gcode commands. Next is the wires for the small 30mm cooling fan that blows on the E3D heat sink. The next two sets are for the hot end. First is the connections for the 100ohm thermistor for the hot end, and the next ones are for powering the heater cartridge that brings the heat block up to temp. That is all the connections that I could figure would be needed for any tool heads that would be used.
This is the 3D printer hot end tool. The hot end tool for this uses a bowden style hot end to rreduce weight. This tool head also has a bracket on it for mounting the stock centrifugal part cooling fan. When removing this tool from the carriage, it is necessary to remove the bowden filament feed tube from the pneumatic fitting.
This tool head uses a 10 pin Molex connector to wire the electronics for easy disconnect when switching tools. Only 8 of the 10 pins are used for this as this head does not use the constant 12v feed. The connections used should be the heat sink cooling fan + and -, the part cooling fan + and -, the wires for the heater cartridge for the hot end and the termistor wires. When making the cable harness, make sure to leave enough slack in the cables for the print head to reach all corners of the print area.
Unfortunately because of the design, this will not be able to handle a direct drive 3D printing head due to the weight of that type of setup and how the head attaches.
I created a short youtube video clip showing the 3D printer head in operation. This was prior to having the connector completed, which is why the wiring in the video looks a little messy.
3D printing tool head assembly.
The pen plotter tool is designed to give your printer the ability to draw using a pen or a marker. The pen/marker is held in the tool holder using two thumb screws. To do this, home your carriage assembly and then disable your steppers. Move the pen to the left front corner of your print bed and place the pen in the holder letting it rest on the bed, Give it a slight bit of downward pressure and tighten the two thumb screws to lock it in place. You can then home your printer again and you are ready to go. Below is a picture of the tool head with a pen mounted. Below that is a sample print that I did using the pen plotter tool.
I also made a short video clip showing the pen plotter working. Tht tool head in the image was one of my first designs for the pen holder, but I found out that there was just a little too much wobble in the pen when printing.
Pen mounted in the pen plotter tool head
Sample print done with the pen plotter tool.
For the laser engraving tool head I purchased a 6 watt laser engraver module from Ebay. The module had 2 sets of wires. The first set was for 12 volt power for the laser. The second set was for the TTL/analog signal for controlling the output of the laser. Making the tool mount was pretty straight forward, but when it came to connecting the wiring, which I thought would be pretty straight forward, I found that it was not as easy as it seemed. I had wired the connections to the 12v + and - connections, and the signal wires I connected to the part cooling fan output + and -. When I plugged in the module, the laser came on at full power right away. After doing some testing with my volt meter, I found that on the laser module, the two black negative wires were common and for the TTL signal should have been a 12v PWM signal. What I found out though is that on the A8, the controller modulates the negative line for the cooling fan, and the positive remains constant, thus causing the laser module to fire right away. The solution I came up with was to use a transistor switch like this one shown in figure 1. Using this allowed me to use the switched negative from the A8 to control the positive line to the laser module. For the resistor values for R1 and R2 I used 10K and 100K respectively. This was the circuit board I made to handle this task. I mounted the boardnext to my main board and connected it between the power and the part cooling fan lines. I tested this on the laser module and it worked perfectly. I was able to use the M106 and M107 Gcode commands to turn on and off the laser. When I tried it with the 3D printer head though I found that it didn't control the part cooling fan like I had hoped it would. I think I just need to rebuild this using different resistor values to drive more base current to the transistor. Since I am not using the part cooling fan so much lately, I can put this off for a while.
As with the other tool heads, I made a couple sample videos of the laser engraver tool working. This is just engraving a small black and white image onto a thin piece of plywood.
Below is an image showing the final results of two test runs. One at a low resolution (center), and the other at a high resolution (right). The original image is shown on the left.
The laser engraver module mounted and connected.
If you are looking to use this design and make additional tool heads for other tasks, the first thing you should print is the tool_plate.stl file. This is the plate that is common to all tool heads. From there, you can create a new plate using the Anet_A8_multi-tool_carriage.scad file and copying something like the "laser_engraver_tool" module to a new module block as a starting point, and build your tool head from there. This is a mostly flat plate module that will get you a good starting base plate that will bolt on to your tool plate that you should have already printed. The tool plates mount together with small M3 screws and nuts. As mentioned earlier, you will sandwich four 10mm x 3mm round neodymium magnets like the ones linked below in between the tool plate and your new tool mount.
When mounting the magnets, make sure that the polarity is correct so that when you put the tool plate against the carriage plate that the two pull together. If the magnets are not correct, some or all of them may repel each other.
I hope you enjoy making this mod for your Anet A8 printer or similar model. As always I welcome feedback on my designs and would be interested in seeing any makes of this, or any new tool heads that people come up with.