Little Monster - Printing & Construction
For the little monster I used standard PLA. OF course if you want to use other material such as ABS then thats even better. I use PLA to keep it simple and the project open to more builders.
In CURA I used (in General)
- 25-30% Infill
- 0.2mm Layer Height
- Support only turned on with overhanging parts.
For the rear wheels I used a 15% Infill to keep them light.
OVERVIEW OF PARTS
Here are most of the parts labelled so they can be identified and the positions they belong in . Please make sure you read the BUILD ORDER below before starting to construct the mower.
BUILD ORDER! **PLEASE READ**
The other mower build could be done in almost any order, but the chassis of the Little Monster is very compact and needs to be constructed in a certain order. These components should be built as shown so you have access to the hinge points on the rear cover and front hood.
1. Rear Cover and Control Panel Door
Firstly solder 40cm of wires to the Rain Sensor (5V, GND and COM). Now push the rain sensor into the Rear Cover LH print.
If you dont do this now it will be very difficult to get the part into the rear cover later on.
The control panel door hinges inside the rear cover using a 2-3mm wire hinge. The control panel door must be inserted before the 2 halves of the rear cover are assembled.
a) Ensure that the parts are well sanded and you have a 90° transition between the rear cover and the control panel door at the hinge points.
b) Insert a 2-3mm wire rod (wire coat hanger will do) into the channel using the access hole provided in the part.
As you feed the wire through the hinge point (Tip: Use a power hand drill) insert the control panel door. Ensure the holes in hinge points are wide enough by pre-inserting the wire into the parts.
Once all the parts are connected with the wire, use M3 bolts to secure the 2 parts together.
I recommended to leave a section of wire protruding from the hinge point (inside the frame at the access hole) in case you ever want to disassemble the parts.
2. Rear Arches and Wheel Motors
Once the wheels are attached or the wheel arch is assembled onto the main chassis it is very difficult to access the screws. (possible but not fun)... Please therefore follow these assembly steps.
a) The rear wheel arches and motors are 1 assembly per side. Press the wheel bearing into the wheel arch (use a small amount of heat and pressure if necessary) and secure it with the bearing clamp.
b) Now attach the wheel motor to the motor bracket. The wheel bracket with wheel motor attached is now attached to the rear wheel arch.
c) Now insert the 15mm diameter metal wheel axle through the bearing and secure to the wheel motor axle with a 6mm set screw. Use loktite on the set screw to prevent it shaking loose!! Test fit the rear wheel to ensure the wheel axle is in the correct position. Dont secure the rear wheel yet until all the other chassis components have been assembled. (The rear wheel blocks all access to the bolt holes inside the rear wheel arch)
d) Assemble the Wheel arch rain lip to the wheel arch. ( Little Flange should be away from the Wheel Arch)
Completed Assembly - Same for LH and RH
The bumper bars should be assembled in the Front Lower Skirt before its assembled on the floor pan. Springs from push pens can be used to give the bumper its "spring".
4. MAIN HOOD HINGE
The hinge point for the hood runs through the 2 rear covers and needs to be installed before installing both rear wheel arches.
Ensure the parts are well sanded in that area and that the hood has a free movement before installing the wire pin.
Again a 2-3mm wire is pushed through the hinge point (use a cordless drill on a low torque setting to get the pin installed.
4. TFT Assembly
Before you assemble the TFT screen ensure the BMP files are saved onto the micro SD card and inserted into the TFT screens SD slot. Once the screen is installed its not easy to get access to this SD card slot.
Solder the Serial 1 TX and RX wires and 5V and GND wires to the MEGA Board. Label the wires.
After the assembly is complete you wont be able to get to these pins again.
To attach the rear wheel you will first need to make the adapters . The rear wheels are then pushed over the adapters and fixed with an M4 bolt through the wheel hub (hole provided) into the wheel axle adapters.
The wheel printed at 15% make them light, but the bolt hole is not strong enough with this infill amount. Use the provided wheel bolt strengtheners printed at 100% infill to give the wheel extra strength in that area and spread the torque to the wheel spokes.
Front Wheel Casters & Wheels
The 625ZZ Bearings are pressed into the casters. The casters are then fixed to the frame using flat head M5 bolts through the M5 holes provided at the front of the mower. Spacer washers are required on the M5 bolt to allow the bearings to turn against the frame. An M5 nylon lock nut is used so the M5 bolts dont need to be over tightened. Leave them a little loose to allow free movement of the wheel.
For the front wheels I used 50mm rubber wheels fro the DIY store with an M6 axle. Front wheel STL files are provided but I have not tested them yet...