Making parts 2
Starting with this page, there are 2 weeks left to the final presentation on 15 June. I am there where I had planned to be. The hardware of the LeafBot that still has to be made are related to the electronics. All the rest is finished. My focus will now be on the electronics and changes in the design of the LeafBot. All the mechanical work will be discribed in this page, the change of the leafBot, collection parts, making parts and assemble them. The electronic developments will be discribed in LeafBot electronics
On the hardware of the LeafBot I didn't had to do so much. But When I startet working on the Hooverboard motor/wheels, I soon
had a problem. I informed myself about the Hooverboard motors by my college (electronics teacher) of the electronic department of
the Saxion University of applied sience. He informed about how difficult it is to get to know how the magnetic fieds are operating
in the wheel it self. I would take a long studie of testing and measuring to analyse the Hooverboard motors. With this information a driver can
be selected. Otherwise it would be likely that the motors will not drive nicely. It was a measage I didn't liked, but I only had to
think for 5 seconds to decide that I had to surge for other, more simple to operate, electric motors.
I surged a bit on the internet and found a robot making website where they used windshield wiper motors of an car. I informed about by Luis if these would be suitable. Luis agreed with this option, because he uses them selfs also and so I went to the car scrapyard Kleine Staarman near to my home town. It is an specialist in used Japanese Car Parts. With an box full with tools I surged between the different cars. Then I stood in front of two Mazda Xedos 6 cars. I drive these cars also my self and I had a good feeling about it. I looked under the bonnet and discovered that both cars had the same windshield wiper motors.
It was time to open the tool box and start to disassemble the motors. It was a bit off an struggle to be able to reach to the 4 screws, but after an 30 minutes and paying €25,-, I took them to the FabLabEnschede.
I will now discribe the steps to build the Wind Shield Wiper Motors in to the LeafBot.(I will now use the abbreviation WSWM). The electronic assembly of the motors can be found LeafBot electronics
The Leafbot is originaly not designed to fit the WSWM but the design and dimensions of the LeafBot are made bigger that it would be possible to deal with changes in the design proces. When the design of the current Leafbot was made, the motors wheren't defined yet. In the future upgrade the Leafbot can be made more compact. But the WSWM had to be build in to the LeafBot. In the picture below the first test to have a look how the WSWM would fit. Now I could make the plan to change to Leafbot chassis.
The WSWM where drawn in Solidworks to be able to find quickly and new position in the LeafBot. Because the WSWM are not mirrored they have to be placed in an opposite position. On both sides, material must be cut away.
To fit the WSWM idealy, they had be be positioned in an angled position. To be able to drill the 4 new holes on each side of the LeafBot Chassis, 2 drilling molds where designed in SolidWorks and printed. To speed up the printing proces additional holes are implemented in the design. less material to print = saving cost and time.
The original mountings holes of the Hooverboard wheels, and the bottom side of the chassis where used to guide the drilling mold.
Works perfect on both sides
Also the other side the holes where drilled. Note that the drilling mold is different from the otherside.
Next step is to cut away some wood on the inside of the chassis and cut some wood away from the rip of the storage box.
Checking if its fits.
Appliing the screws and it fits perfectly. No additional sanding is required.
The other side wood in cutted away out of the bulkhead.
During the assembly of the WSWM, wheels that would fit on the axle diameter and would fit on the the LeafBot dimensions, have been designed in SolidWorks. The wheels are been printed on the Stratasys Dimension 1200. I first wanted to print them massif, but that would be using 900 grams of build material pro wheel. In my opiniun that was an bit much so I decided to print them not massif. Pro wheel it was 229 grams of build material. It saved also in buildingtime. Still it was 12 hours pro wheel.
Removing the support material
It looks great and fitted well. But I immediately discovered that the stiffness of the wheels around the middle hole, the position where the wheel is attached to the axle, was not great.
Picture from the backside.
Later during the testdrive the wheels broke of.
Quickly new wheels had to be designed with more stability around the WSWM axle but not using more material. Based on the first wheel design, but now using more rips I tried to add more stiffness in the material because the printer has only to print outside shell material. In this case my idea is prevent that the material can squeeze together. This is what was happening with my first wheels. I also added holes in the wheel to be able to stitch the tyre to the wheel instead of gluiing it. But the printersoftware couldn't handle this. I tried to reduced the file in Netfabb, meshlab and Rhino but the Stratasys Catalyst software kept on crashing when it had to calculate the support structure. The problem was in the amount of small holes. When I removed them the file was printable, but it took to long. The prints would be finished during the weekend (the last building weekend). In the weekends the FabLabEnschede building is closed. To be able to work on my LeafBot during the weekend, I had to design an different wheel so it it could be printed on an Ultimaker 2 at my home.
So I designed again an new wheel and now be to able to print it on a Utimaker 2. It used less support material, thinner wallthickness and it will be supported with an metal plate that is clamped over the axle. The wheel is screwed to the metal plate.
The 1e wheel was printed on an Ultimaker 2 in an fast printing setting. Layer thickness of 0,3 mm and speed of 60mm/s. The inside fill was 60%. The print was an bit rough but it looked that it would be useable. But when the wheel was assembled and the batteries where also fitted to the LeafBot, the weight was to much. Again the stiffness in the middel of the wheel was not enough and the layers started to break which resulted during the first testrides that the wheel bended and almost broke.
I like the design of the new wheels. The wheel it self was very stiff. But the layer thickness and the inside fill the hub of the wheel was not strong enough. The filament layers starting to break. The 0,3 mm layer thickness can also cause this problem, because the layers it self are a bit more rounder then a thinner layer, and therefor the area of the material that is melded to the other layer is also smaller. With this smaller connection surface between the layers it self, the the strenght of the 3D print is then also reduced.
An test on the BCND printed sadly failed to due blockage of the filament.
I took 2 Ultimakers 2 printers during the last weekend home to be able to make the last 3D printes parts, including the wheels. During the last 2 weeks it was very very busy in the FabLabEnschede with customers who also had to print a lot. The print task had to planned well and I even have printed customer prints at home. The Ultimakers have printed all weekend non stop to print my parts and Fablab customers parts.
I needed still stronger wheels to handle the weight of the LeafBot. I started during the night of Friday to Saterday to think how to make stronger wheels. I still had an peace of Beech fineer laying around at my home. I was still laying there be used to press an special shape out of it. For me now the right moment to make an mold and press the wheel spokes out of it. I made an new wheel design in SolidWorks. The Spokes made form pressed Beech fineer. The rim made with the Ultimaker 2 3D printer. The two parts joint to together with 4 screws.
On the 2 Ultimakers 2 I printed the 2 rims simultaneously. I used now an different setting to print the rims. I used an layer thickness of 0,1 mm and reduced the printing speed with 30%.
A few years ago I installed 3185 Wp on PV solarpanels on the roof of my barn and since then I can monitor als my power consumption and the amount of electricity that my solarpanels are making. When I looked to my recorded data I discovered that the two Ultimakers where using about 800 Watt of electric power. I switched on Friday evenening at about 19:30 the first 3D prints. It was an 12 hour print. You can see when the Ultimaker was finished at Saterday morning. During the day the amount of energy I am using is not so well visible because my solar panels where making more electric energy then I was consuming. But during the nights it is visible that the 2 ultimakers where using energy. In the early moring on Monday the 13 of June the last 3D print was finished.
During the 12 hour printing time I could work on the mold making and laminating of the spokes. I startet with the mold. Made it from wood pinewood beams
From this Beech fineer I cutted small strips 30 mm in width and 180 mm long
The strips are first fitted in the mold to test if the width is not to wide.
Each peace of fineer is glued and placed in the mold. I used PU glue from Bison
To press the fineer I used as much clamps that would fit.
This is how the first spokes came out of the mold.
Just near the middel of the spokes I needed to press it harder with the clamps. This is what I did. Pressed some extra glue between the layers and clamped it again. The result was an even stiffer spoke.
The first rim was ready. The spoke and rim could now be made ready to fit them together.
To be sure that the wheel will turn round and not in an oval way, spokes where grinded and I used the hole that I drilled in the middle of the spokes. If I have drilled the hole not perfectly in the middle, with the grinding the spoke ends will get the same end distances towards the middle.
The spokes needed to be grinded a bit more to fit them in the rim.
I grinded the spokes so that they would fit perfectly in the rim, to prevent that the rim would not mounted concetric over the spokes. The rims and spokes are attached with M4 srews and nuts. I took an old Ritchey megabite bicycle tyre. Cutted it and removed the sidewalls. Then I glued the tyre around the rim.
The blue rimmed wheel is the other wheel. I didn't had 2 white filaments to be used for both Ultimakers.
This was an test to be able to print the wheel on an smaller UP 3D printer by making the wheel from smaller parts but time was up to finish the prints.
Then I designed the gearing of the brushes in SolidWorks.
This is an exploded view of the assembly. The grey electric motor fits in the green 3D printed hub. The black 3D printed hub fits over the axle of the motor and will be fixed by an small M4 srew. Over this black hub the gear will be assembled and is fixed by the teeth on the black hub and is been fixed by the nut that slides over the black hub.
From the back side it looks like this.
The electric motor is fixed in the green hub. The electric motor can turn in the green hub. The outgoiing axle is excentric, and if the motor is turned in the green hub, the distance between the two gears can be adjusted, so the bicycle chain will be tigthened. This prevents that the chain will drop of the gears.
Inside the green hub, there are ribs to fix the motor. This is done to ventilate the motor. If the fixing was all around the motor, the motor can run very hot.
I took bicycle gears from Shimano spockets, I have several at home like these and designed an new hub to fit the gears on.
The axle of the brushes was still to long, and with an angle grinder the axle is shortened.
To be able to fix the black hub, a flat surface had to be grinded on the axle.
resulting in a lot of red heated sparks
The black gear hub fits well
The gear fits perfectly
Both gears assembled.
The bicycle chain assembled.
Tightening the chain by rotating the electric motor in the blue hub.
To be able to control the robot I designed an remote control where I could use the PCB made in the weekly assignment of week15 and I could use the fabkit.
The remote control is designed in SolidWorks. Is consist out of two outside casings and a chassis to fit all the electrics on to. I ordered an joystick and from Seek push buttons and an potensio meter. I draw them in Solidworks to be able to design an perfect fitting outside casing.
The 9V battery is fitted in the grip. The rib in front of the battery is holding the battery in place.
The first prototype was ready to be assembled. In this picture the fabkit is placed at the bottomside of the yellow part. On the left there is place for 3 push buttons from Seeed. I designed this already in the remote control, that in the near future I can develop the LeafBot to a next stage and use the push buttons for additional features. But it will be for the final project to much to develop. One button is there for switching on/off the battery power of the remote control and the other one is for the tilting mechanisme to emty the Leaf storage box of the LeafBox. But the one will get for the final project a function. It will be able to switch on and off the brushes of the LeafBot. Above the joystick the NRF24L01 2.4GHz Radio/Wireless Transceiver is positioned. That PCB operates on 3,3 V. The battery delivers 9 volts. On the right side of the joystick I have placed the PCB with the regular that I made in week 15. Below this the Fabkit is placed.
Next step is to make space in the yellow 3D printed part to fit the soldering pins in. They are sticking out of the PCB at the bottomside. I also started to connect the wires, but soon I found out that the height and space inside the remote control covers was not enough.
The battery connected to the regulator. the 9V goiing in, 3,3V goiing to the fabkit. The Fabkit will then run on 3,3V. But in this case the NRF24L01 2.4GHz Radio/Wireless Transceiver is connected to the 5V connector of the FabKit, which is delivering 3,3V.
Next step is in SolidWorks to create a bigger casing for th remote control.
At the bottom of the PCB chasis there is now more space for the fabkit to connect all the wires to it.
The layout is the same as with the first model.
1: NRF24L01 2.4GHz Radio/Wireless Transceiver
2: Regular from 9V to 3,3V
5: Push buttons
6: battery 9V
The differents is that I only had 2 push buttons and it looked to me interresting to control the RPM of brushes. So the 3e push button is replaced by an potension meter from Seeed.
On the Ultimaker 2 all the new parts have been printed.
This is the end of the parts making. All parts have been made and the building proces will continu with electronic production which can be read in this LeafBot electronics website.