The scalability issues of various types of FDM 3D printers

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MacroMAKEiT: Affordable Large Scale 3D Printer launched on kickstarter September 18, 2018

One of the major concerns with owing and operating a large format 3D printer, is that you would prefer to get the largest possible build volume for the smallest possible foot print; where footprint is the volume of space that has to be allocated to the printer and can be expressed as an imaginary cubic bounding box around the outside of the printer. It is best visualized if you had to build an enclosure around the 3D printer to keep out drafts, dust or “curious fingers”. Since in some facilities/homes space is at a premium, this build ratio would have to be as large as possible.

The build ratio is defined as the build envelope / the space required to enclose the printer.

There are several variations on the two main co-ordinate systems; Cartesian and Delta.

The RepRap style

(or as I call them: traveling beds, because the bed travels back and forth)

RepRapPro Mendel, the progenitor of modern desktop 3D printers, uses a traveling Y axis bed within a gantry style cartesian system.

Core XY, Floating Bed

HyperCube Evolution by SCOTT_3D. An example of a CoreXY Floating Bed 3D Printer

Core XY, Static Bed

The voron2.1 An example of a CoreXY with a static bed

Delta Printer

Monoprice MP Delta Pro

All delta printers have a static bed. They also tend to lend themselves to being scaled in the Z axis very easily. They also have the worst build ratio of any style of printer.

The problems of trying to print big

The main problem with scaling up a 3D printer is having to increase the size of the build plate. Additional heating requirements can be overcome by switching to an AC mains heated bed, however having to move that bed either up and down or front to back exposes a problem that becomes all to clear when the full build volume of the machine is being used: The build plate becomes heavy.

Very heavy. It is expected that a large format 3D print will require many kilograms of filament to build the entire model. In the case of the world’s largest 3D printed object, as produced by the US Department of Energy’s Oak Ridge National Laboratory in 2016, the final part weighed in at around 750 Kg. That printer, incidentally was a gantry style cartesian with a static bed. In addition to which, the bed itself must be robust enough to carry that mass without itself warping. This would mean even more mas in the form of the build plate just to to keep from warping under the strain.

The Keenovo Integrated Silicone Heater; available on Amazon

Most 3D printer filaments require a heated bed. One notable exception is PLA. Aside from PLA, everything requires a heated build platform. At larger scales, it can be expected that just heating the platform will require a thousand watts of power (depending on size and target heat). Drafts and other sources of heat loss, from a non enclosed printer will cause an increase in that power requirement. Keeping the bed insulated from all heat losses is paramount. With a non static bed insulating it is non-trivial.

Since the prints are expected to be large, it is understandable that the user would not want to wait weeks for a single print, even if it is of high value. Print times on a large format should be comparable to desktop printers. The biggest limiting factor to print times is the rate at which the filament can be heated and extruded. A powerful hot end will be required so that enough thermal energy can get into the filament before it is extruded. If it is extruded at the wrong temp, then the print could fail.

A Maxiwatt, hot end. Its main feature is that the heating element surrounds the filament as it passes through

Multiple heating elements are needed to bring the filament to temp at prints speeds above 60 mm/s (desktop 3D printers generally operate at 30 mm/s). Additionally, large format 3D printers use a large diameter nozzle; around 1mm or more. Since time is of the essence there is no need to print a large object at with a .4mm nozzle unless the design calls for it.

Finally, there is the cost concern. Large format 3D printers typically cost two orders of magnitude more than desktop printers. The Anet A8 set the bar at the absolute lowest cost 3D printer that a person could buy. To achieve this, they had to cut back on some creature comforts that should not normally be left out (e.g. a power switch). At $150 USD it sets the benchmark as the lowest cost point that a machine could cost and still be considered a compete 3D printer (and it didn’t come with filament).

The 3D printer shown at the start of the article, the MacroMakeiT, kickstarted at $7,000 USD for a print area of 12 times that of the Anet A8 at 46 times the price; and this is one of the lowest cost large format printers you could obtain. A reasonable desktop printer, with the creature comforts such as the Ender 3, costs around $220 USD. At that price point the MacroMakeiT cost around 31 times for a 12 times build area. I are comparing the area as opposed to volume because most of the printer styles tend to scale well in the Z axis anyways.

What is needed is a print mechanism that starts at a reasonable point scales linearly with the build area. Doubling the print area should not cost 10 times the price.