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3D Printing for Mould Making Part 1- FEBRUARY 2021

Tue, 23 Feb 2021 09:15:00 GMT

For my new Gee Bee R2 model, I decided to create a mould for the wheel pants. The wheel pants will be created with carbon fibre cloth and epoxy resin.
I decided to 3D print a plug using PLA filament. I had seen Ramy on YouTube create 3D printed moulds but decided to create a plug instead as it would be easier to sand and finish.
A 3d model was created in Fusion 360 and this model was sliced into 4 pieces so that it could be printed on an Ender 3 printer.
The pictures below show the steps I took to create the 3D model. I couldn't find any tutorials so this is the approach I took.

The parts were glued together using CA glue. Multiple coats of filler were applied and sanded. Following this treatment, an automotive high build primer was sprayed on and sanded.

Tips

1. You should never leave the plug in a position where it is exposed to direct sunlight on a hot day otherwise it will distort and you will have to fill and resand or repaint.
2. Leave wet sanding until the plug is fully sealed otherwise the moisture will be absorbed into the plug and later on it will seep out while you are painting, ruining the finish.
3. I painted the plug using acrylic spray paint and applied a clear coat. To achieve a mirror finish I will wet sand then polish. This will also remove the orange peel from the paint finish.
Next time I create a plug I will apply an epoxy coat then sand to eliminate the painting process. I wish this video had been published before I started on my plug Making a Composite Mould for a Carbon Fibre Part from a 3D Printed Pattern
There are lots of great videos on the Easy Composites YouTube channel showing techniques for making composite parts.

In the next article, I will cover the of making the mould.

Items used

Ender 3 Pro 3D Printer
Flashforge 1.75mm PLA Filament
Sika Surface Filler
Rustoleum Filler Primer
Rustoleum Acrylic Lacquer

Weight and Balance - October 2020

Thu, 15 Oct 2020 10:36:00 GMT

Balancing a model aircraft is normally one of the last steps of the build process and in most cases, this is achieved by repositioning components or by adding some weight to achieve the desired CG position. Normally the CG for a conventional layout is 30% ahead of the MAC of the main wing.
Recently while preparing V2 of my Gee BEE R2 profile I was balancing the model prior to the flight and ran into a major balance problem.
My new design has a scale outline and the original full-scale R2 had an 800 HP 9 cylinder radial engine and the pilot was placed near the tail to achieve the required balance.

I had placed the engine in a position that puts the propeller in the correct position and used heavier high torque servos to cater to the increased performance when compared to V1 of my design.

The servos for the elevator and rudder were moved much closer to the tail to shorten the control linkages. When I balanced the model I soon found that it was tail heavy.
I thought that I could easily get around the problem by adding some lead to the nose. Unfortunately, I soon realised that the weight I would have to add was excessive. Something like 1kg would have to be added! This was nearly 50% of the weight! So it was back to the drawing board. I would have to perform weight and balance and make changes to the placement of components and modify the model. I looked up my light aircraft design textbook and created a spreadsheet to calculate the balance position. I weighed the components and entered these into a spreadsheet. Components that could be moved were weighed separately. Other components that were not able to be moved were left attached.
An example of this is the motor, receiver, and escape left attached to the fuselage. Adjustments were then made to the location of the servos. These were moved as far forward as possible. After doing this I found that the design was still tail heavy.

To solve this problem I moved the wing further aft as the wing makes up around 40% of the weight of the model. This resulted in the desired balance point and this would not significantly affect pitch stability as there was still adequate tail area and moment arm. This design uses a separate wing saddle to allow for experimentation with different wing sections and wing aspect ratios. So to allow for the wing to be moved aft a new wing saddle was constructed.

The spreadsheet I used is available at the link below.

WBCalc.zip

To add new components insert a new line and paste the Excel formulas.
The component numbers match the numbers in the fuselage diagrams.

Weight and Balance Version 1

Weight and Balance Version 2

Decals Part 2 - August 2020

Mon, 31 Aug 2020 10:35:00 GMT

After last month's success with creating my own decals, I was determined to find a way of creating clear decals with white backgrounds so that I could match the full-scale Gee Bee R2 markings.
I spent a few hours searching for a company that could print this type of decal. The company I used is called BannerBuzz and the product is their Clear Die-Cut Static Cling
There is no minimum quantity and the price is very reasonable.

The print options I chose were

Clear Cling Material
Outside Application
UV Print
Full White Ink
Size 300 X 460 mm
No Die Cutting

As the decals are being printed on a clear sheet I did not require Die Cutting.
I uploaded my Corel Draw decal sheet in PDF format and submitted my order. I paid extra for express delivery as I required delivery before I went on holiday.
The decals arrived in just over a week and this was within one day of the guaranteed delivery period. This was very good considering the delivery delays due to the COVID Pandemic.
The white-backed decals came out great and I will use this service again to create decals for my Gee Bee Z scale R/C model.

Sample Decals for Gee Bee R2 White Backed

Decal Sheet V2 PDF

Decals Part 1 - July 2020

Thu, 30 Jul 2020 10:14:00 GMT

I decided to try my hand in making some decals for my new Gee Bee R2 profile model so that it had a more realistic appearance.
I used Corel Draw to create the logos and racing numbers. Corel Draw has a large number of fonts and I was able to select fonts that were close to the originals.
These were sized to the correct scale. The printing service I used was Avery WePrint. I chose their Clear Labels which are transparent, oil, and dirt resistant.
I copied my logos and numbers to a drawing that matched the size 196 X 135mm size and saved the image as PDF. I created an account in the Avery site and uploaded my PDF files.
Within a few days, I received the labels and was immediately impressed at the quality. A day later I had another closer look and suddenly realized that there was a problem. Any of the numbers or graphics that had white backgrounds were transparent. Luckily the main graphics, numbers, and letters were to be applied to the white plastic covering. So it wasn't a total loss. I later went back to the Avery site and looked up the FAQ page and found out that they cannot print white colours on the clear labels. I recently found another label printer who can print clear adhesive labels with a white backing. I have ordered more decals and will write about this in a later blog post. If you do not need white coloured graphics on clear backing then this service is fine. The only other drawback is the minimum quantity you have to order. At this point in time, it is a minimum quantity of 4.

Sample Decals for Gee Bee R2

Decal Sheet 1 PDF

Wing Jig Part 1 - June 2020

Mon, 29 Jun 2020 11:30:00 GMT

After building two twisted wings, one which led to the loss of the aircraft, I decided it was time to start using a wing jig.

I happened to be at a local Bunnings Hardware store one day and came across a product called MetalMate. This is a slotted steel angle product that can be used to build shelving and small sheds.
MetalMate also provides hardware packs containing brackets, bolts, and nuts.
The dimensions of the slotted angle are 32mm X 32mm X 1.5mm. It comes in the following lengths 600mm, 900mm, 1200mm, 1800mm and 2400mm.
When assembled the angle which the jig brackets would be attached to, was not a perfect 90 degrees to the jig base so I bent these using a Stilson wrench so that they as close to 90 degrees as possible. I used a spirit level to check.
I purchased enough material to create a wing jig that was around 1 X 0.5 metres so that a K & S 1/4 inch Piano Wire would be able to be used as wing rods.

To keep the wing ribs perpendicular to the wing rods I used ceramic disk magnets which are 19mm in diameter and 3mm thick. They come in a pack of 6 and are fairly inexpensive. Once the spars, leading edges, and trailing edges are glued in place the wing rods are removed and the magnets slid off. The wing rods are then re-inserted into the wing for further work. When using Cyanoacrylate glues you should be careful not to get any near the magnets otherwise these will be stuck to the ribs and could lead to the ribs being damaged when you try to remove them.

I designed some wing jig brackets in Fusion 360 and printed these on my Creality Ender 3 Pro 3D Printer using Polylite PETG filament. These slip over the slotted angle and can be fixed in place using the nut and bolts provided with the MetalMate hardware pack.
The reason for using Polylite PETG was that this material is more flexible than PLA and can withstand higher temperatures. The initial design had the wing rods passing through a hole in the bracket.
The final design allows the wing rods to snap into the brackets, making it easy to quickly remove the wing and flip it over to work on the other side. The brackets need to be printed in the right orientation to allow for the rod slot to easily spread when snapping the rod in place.
I printed extra brackets so that these could be put on the inner cross braces and placed between the ribs to provide extra support for the jig rods.
I have designed brackets that can hold 5/32 inch wing rods and these will be used when I build a wing with washout. These will be used in the rear wing jig holes. This will be covered in the next blog article.

So far I have built 2 wings one for a DAS Mini Stik and another for my Gee Bee R2 Block 2 design. The Gee Bee has a semi-symmetrical MH 43 airfoil. Both wings have turned out perfectly straight with no twists.

USB CNC Upgrade - May 2020

Mon, 18 May 2020 08:34:00 GMT

When my desktop PC failed I thought that after buying a new desktop PC with Windows 10 and adding a new parallel port card I would be up and running again in no time.
Unfortunately, as soon as I started up Mach 3 on my new desktop PC I immediately found the machine would not jog and there were issues with the parallel port driver.

I Googled the CNC troubleshooting pages and quickly found out that the Mach 3 parallel port driver is not compatible with Windows 10 and I would need a USB, compatible controller.
As a temporary workaround, I tried installing Virtual Box and Windows 7. I was able to get the machine to jog but when set to the original feed rates and jogging speeds it would skip steps.
I eventually got the machine to run by reducing speeds to around 1/4 of the original. It allowed me to cut the parts out that I required however it was painfully slow.

After some research, I found that I would need a new USB Controller and separate stepper drivers.
My original parallel port board was an all in one Mechatronics 4 axis parallel port combined controller/driver board. This board worked fine with Windows 7.

The parts I settled on are

1 USB MACH3 100Khz Breakout Board
3 TB6600 Stepper Motor Controllers (1 for each axis X, Y and Z)
1 24 Volt Power Supply 360W 15 Amp
1 Enclosure to house controller and stepper drivers dimensions 250x190x110mm
1 DC-DC converter for stepping down the 24 Volts to 12 Volts for a cooling fan.
1 Terminal block to split the 24 Volt input for powering the USB controller and the 3 Stepper Drivers

Wiring was fairly straightforward. To identify the correct wiring for my stepper motors I found this site Hobby CNC Australia. I matched up the wiring colour and was easily able to identify the A+, A- B+ and B- wires.

The instructions that came with the CNC controller are in Chinese however there are plenty of sites on the web with these instructions in English.
One of the best sites is BuildYourCNC. You can purchase the board from the site and it has instructional videos on wiring up the controller and stepper drivers and configuring Mach3 for the RNR USB Driver.
You may have to adjust the motor outputs in Mach 3 as I found that initially, my stepper motors were jogging in the reverse direction.

I mounted the controller and stepper drivers in an enclosure on nylon standoffs and added a fan to help with cooling. I will at a later date mount the fan on the outside of the enclosure with an additional fan and wire the two in series directly to a 24 V output from the power supply. I will use the DC-DC converter for a limit switch circuit.

Currently, my power supply and enclosure are sitting on top of a plastic box. I will be shortly securing these to a plywood baseboard and anchoring the cables so that they can't be pulled out.

I wired up some strip LED's to the router base to illuminate the workpiece using one of the 24 V outputs. The LED's are rated at 12 Volts so I cut two strips of 6 and wired these up in series. These help greatly when zeroing the Z axis, especially when cutting a thin Balsa sheet as any inaccuracy could lead to tabs being cut through and the part separating from the sheet prematurely resulting in the part becoming damaged.

After the upgrade my CNC is up and running again and I can jog at up to 1000 mm/minute and am back to cutting Balsa sheet at 600mm/minute. I have cut out ribs for 2 wing sets and will be cutting out more parts in Balsa and Ply sheet over the next few weeks,

3D Printing for R/C - April 2020

Fri, 03 Apr 2020 11:42:00 GMT

At the time I built my CNC Router I looked at 3D printers and resisted buying one due to the price, printer reliability and durability of the printed parts.
Times have changed and prices have dropped dramatically. Reliable low-cost printers can be purchased now and a wide range of filament materials can be used to print high strength parts. These include carbon fibre reinforced filament, ABS, ASA Nylon and PolyCarbonate.

I recently purchased a Creality Ender 3 Pro 3D printer to print model parts and for other items around the home.
I watched 3D printing videos by Michael at Teaching Tech, Angus at Maker's Muse and Chuck at Chep. These videos helped me to set up my printer, make recommended printer modifications and contained lots of tips for printing with different types of filament. Some of the issues that were a problem in the past have been quickly addressed by the Creality factory to improve the quality of their product.

The printer comes as a kit with good instructions and is easily assembled in under 3 hours. One of the problems I initially had was that the belt tension on the X-axis was too loose. This caused out-of-round prints. Tightening the belt quickly fixed the problem.

The process of creating a part involves first designing the part with 3D software. The software I use for designing the 3D Models is AutoDesk Fusion 360. You can obtain a free hobbyist licence to use this software. This took some time to get familiar with but once I got the hang of it I was able to create new designs fairly easily. A number of YouTube videos helped especially ones from Stefan at CNC Kitchen.

After designing the part in Fusion 360, the design is exported as a 3D model in STL format.
The next step is to slice the model to convert it to G-Code so that the 3D printer can print the part.
The slicing software I use is Ultimaker Cura. The STL file is imported then sliced. The slicing profiles I used to get high-quality prints were obtained from Chuck. The slicer generates the G-Code file which is then copied to the Micro SD card then inserted into the 3D printer for printing.

Items I have printed in PLA filament

motor mounts
parts for my 3D Printer

I have also printed the following using PolyLite PETG filament

robot vacuum cleaner wheels
brackets for wing jig

I did have some initial problems getting the PETG filament to stick to the glass bed when printing a design that had supports.
Supports are required when printing parts that have overhangs or any kind of bridging. The supports are designed to be easily removed after printing. The solution that I found was to use a UHU glue stick on the glass bed to help the filament stick and to print a raft before the main print starts to ensure that there was a good foundation for the filament supports to stick to. I use the same bed leveling settings as for the PLA filament, paper sheet thickness between the nozzle and the bed.

Settings I use for PETG are

Temperature 230 Celsius
Build Plate 80 Celsius
Print Speed 45 mm/sec
Fan Speed 100 %
Build Plate Adhesion Raft
CHEP Cura Profile Magic0.20

Future projects include tail wheel mount, refined wing jig brackets and moulds for wheel pants.
Ramy creates moulds for scale airliner parts using PLA filament. His uses carbon fibre to make fuselage, engine nacelles and various other components.

Below is a short video of my printer printing a motor mount in PLA for my Gee Bee R2 profile model.

CNC End Mills For Cutting R/C Plane Parts - MARCH 2020

Tue, 10 Mar 2020 10:34:00 GMT

My R/C plane parts are cut from 6,3 and 1.5mm ply. I also cut wing ribs from 1.5 and 3mm Balsa and occasionally cut 6mm foam board.
For cutting accuracy and cutting slots and complex shapes I use 1.0 mm downcut End Mills.
Typical feed rates I use on my CNC Router are 400 to 600 mm/minute. The highest speed is used with foam board.

It's very important to ensure that the bed is level otherwise when cutting thin materials the part may not be completely cut out.
I milled an MDF board that is fixed on top of the bed using a 1/4 inch tungsten carbide cutter to ensure that I had a surface that was perpendicular to the cutter.
A 3mm ply spoil board is attached to this board with 1/4 inch bolts with flat heads.

The End Mills I use were purchased from www.precisebits.com. They are reasonably priced, high quality, durable, and create a very nice clean cut.

1.0mm Downcut 2 Flute Fish-Tail End Mill Part No. MD208-0394-013F

These End Mills have a 1/8 shaft diameter so I use a reducing collet adapter that goes from 1/4 inch to 1/8 inch. This works fine in my Ryobi Plunge Router with a 1/4 inch chuck.
To get push fits when creating parts that slot together I use Inside Offset cuts for holes and Outside Offset cuts for part outlines.
The SheetCam pictures are for undercarriage parts for a tricycle undercarriage mod for the RCPowers F22.

Rear Undercarriage Files

The pictures are shown below.