RappiDelta Jr. Ultra low price 3d printer for everyone
The RappiDelta Jr. is a low component count 3d printer, no belts, bearings or pulleys meaning low cost and high reliability.
The RappiDelta Jr. is a low cost, high quality 3d printer for everyone. It was born from a meeting I had with a good friend of mine while showing him my previous printer design. The idea was to produce a printer that was easy to assemble and set up that had as few parts as possible.
The delta design that I had used previously fit these criteria, all that needed to be done was to refine what I already had and scale it to have mass market appeal.
There are various delta designs available that all use 3 linear rails for carriages to slide on. These require belts, pulleys, bearings and can be a little fiddly to set up and master. My design is much more in line with the delta type robots that are used in industry pick and place applications due to their high speed, accuracy and reliability. The arms are connected directly to the output shaft of the gearbox, and it is this simplicity that separates the RappiDelta Jr. from the rest.
Over the last few months I have refined the design with the help of a few of my engineering friends and colleagues to the point that the RappiDelta Jr. has been through many iterations and is now ready to be released to the world.
The printer is entirely made of plastic, which was one of the prime drivers behind the project. Sure the all aluminium look is great, but it comes at a price especially when it comes to shipping!
All of the prototype plastic parts were printed using the RappiDelta that I built at the start of the year which has a build volume large enough to handle these big components.
Here are some of the early prototype parts that were printed on the large format printer during the design stages.
The advantage here is that no metal parts are required, no pulleys and belts, no bearings (save the rod ends). This ultimately results in a cheap to manufacture low component count printer.
The unique top frame of the printer has integrated motor mounts for the 3 motion steppers as well as 'sockets' to snap the upright sections in to. The uprights simply snap in to the 'sockets' of the lower frame. It really is as simple as that - 5 pieces that can be put together to form the main frame in under 30 seconds! As fast as it can be assembled it can be disassembled for transport with no fiddly nuts and bolts to contend with. Once assembled the main frame is extremely strong and rigid - one of the tests involved stacking 75kg of weights on top and it remained rock solid.
Rather than mechanical endstops the RappiDelta Jr. utilises slotted optical sensors which prove more repeatable homing and ultimately better prints. One of my stretch goals is to be able to offer auto bed leveling to further enhance the functionality and ease of use.
The remainder of the mechanical parts can be assembled quickly and easily with a couple of hex keys.
Once assembled the printer can print on a 17cm diameter circle and up to 17cm tall. These dimensions have been chosen based on my experience of what is actually reasonable to print as well as being based on a similar size to other entry level printers. In future you can increase the build volume by using longer uprights, and if required longer delta arms. The basic model has no bed heater and as such is limited to printing PLA (this is actually my preferred plastic!) but other options are available to allow the printing of ABS and other plastics that need bed heating. There is also an option to have an SD Card reader and LCD control panel to allow printing without a PC, something that I have found invaluable when developing my prints as it allows on the fly adjustments.
As soon as I had assembled the first prototype I couldn't wait to get it moving. I was still missing a few bits (namely the hot end and bed) but temptations got to me. I couldn't believe the speed that it moved!
I have done extensive testing with the prototype and have had great results. It is much easier to set up than its Daddy due to a smaller bed and I have been able to produce some interesting prints. The following were all done with a 0.5mm nozzle and printed at 200 microns.
Over the last 6 months I have been working with suppliers to establish the best deals possible for the component parts of this style of printer. These relationships alongside the simple design have meant that I am able to offer kits at an incredibly low price.
It is simple! In order to bring the RappiDelta Jr. in to production and provide you, the customer, with the best value possible Kickstarter provides the ideal platform. The funding received will enable bulk purchasing deals to be made, and investment in tooling to benifit not only those that back the project but those who are keen to have access to affordable 3d printing in the future.
What will the final design comprise?
The prototype printer used in this video is almost exclusively printed using the larger RappiDelta which is great but not all that suitable for mass production. There are several options for each component depending on demand, and I have detailed these below:
The main part of the kit is the top frame, this single piece component includes motor mounts and sockets for assembly as well as cut outs for the Delta arms and provision for mounting the endstops. This is the biggest challenge to manufacture, and the funding level will determine that method of manufacture for this part.
The base is a much simplified version of the top frame, and again the method of manufacture will depend on funding. In any event it will be a plastic component.
The uprights were an exercise in producing a fully printed printer, and it is likely that the production models will made from 20mmx20mm stock plastic section or aluminium slot 6 section.
The delta arms will remain made from plastic and will either be printed or cast.
The rods again were printed because I could but I will replace them with more conventional carbon fibre rods in the production kit.
The end effector plate is a simple part that can be waterjet cut with ease.
Finally the mechanical parts have been selected and comprise readily available components.
The control board is a Sanguinololu running a modified version of the Marlin firmware which is specific to this style of delta printer. The firmware will be provided with your kit so you can make changes if you desire.
Motors are Nema17 with planetary reduction gearboxes which offer massive holding torque and high accuracy.
Shipping will be available anywhere in the World, but due to varying costs the price of shipping is not included in the price. I will work with each backer to get the best deal possible for shipping closer to the delivery date.
Risks and challenges
The biggest risk to the project is success, as this is one of the variables that I cant control. This will change the way in which the kits are produced, in lower volumes I will be able to meet the demand 'in house' but if the kits sell like hotcakes I will need to change the manufacturing process involved with making the main framework to suit the demand.
The other major risk is the supply chain, although this will be minimised by using reputable suppliers for major components, and by spreading the load by using multiple suppliers if necessary. Having been through the process once already with the larger RappiDelta I am confident that I am aware of the pitfalls and able to mitigate them appropriately.
The prototype that I have printed still requires a couple of minor modification to become production ready, but with the Christmas break coming I will have more time for a little more R&D to perfect the final product. For instance the rubber bands seen in the videos will be replaced with torsion springs providing a more aesthetically pleasing and functional solution.Learn about accountability on Kickstarter
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