Delta printer with simpler structure


I am interested in building a 3D printer for producing objects bigger than the normal 200mm cube (initially in chocolate) without requiring a lot of mechanical engineering. The precision need not be up the standard of the conventional desktop printer but it will be interesting to see what are the limitations. I have a simple extruder which works with chocolate so my current thoughts are on positioning the extruder. The bed needs to be stationary as wobbling warm chocolate will cause a collapse. The current extruder weighs about 200g but will need an extra cooling pipe as my first attempt worked in 2D but not 3D.

My current thoughts are to suspend the extruder on 3 wires, with the same geometry as the delta printers, but with another 3 wires to the top of the extruder to hold it vertical. It avoids all the sliders and parallel bars of the conventional delta. Click to see my simple diagram. The diagram shows six stepper motors, each with a pulley. I have not yet thought a good way to use the fixed pitch of a toothed belt to pull the wires.

If this works, the printer could be made to almost any scale. A downside is that the printer will be much bigger than the product being printed as the wires need to be kept well away from vertical and horizontal, but the frame is only three columns and a base so could be easily assembled when required.

Any thoughts?



I really love the idea, but I would worry about the torque those motors would need to have.

In a conventional delta the majority of the weight is taken by the structure and the motors just move the brackets. In the wire version, the entire weight of the extruder and everything connected to it would need to be supported by the motors - as well as additional torque for tensioning against the top set.



Thanks for the thought. To check this I will start the project with a simple test with just 3 motors, a weight for the extruder and thin cord to a pulley on each motor.



Here’s one with the same geometry as that which you’re considering - i.e. being able to change the angle of the chocolate nozzle:

A version with a fixed nozzle angle:



Beefy NEMA 17 steppers have quite a lot of holding torque. A delta also does rely on the motors to take up the majority of the weight of the moving parts - though for performance is usually designed to have as little weight at the effector as possible (carbon rods, bowden extruder etc) which negates this issue.