Manual Support

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Various materials can be used as a manually placed support material when printing PLA (ABS has not been tested). While manually placing support material is only useful in a limited number of situations, it does allow for designs that cannot otherwise be printed.

The following materials are known to work as support material (that is, PLA will stick to the support):

  • Museum putty
  • Sculpey polymer clay
  • La Doll clay

Play-Doh does not work (PLA does not to stick to it).

The first two materials work well as a support surface, but can be difficult to remove after printing. La Doll clay falls apart when soaked in water and consequently is works well as support in difficult to reach locations.

Manually placed support is most useful when the design includes a small number of flat (parallel to the print surface) overhangs that are ideally connected to the main body of the design.

This approach has not been tested with heated build platforms.

Contents

Outline of Process

Skeinforge

At present there is no support in Skeinforge for manually placed support so a lot of manual work is required to prepare for printing.

When exporting from Skeinforge comments should be left in the exported file. This is done by setting:

  • Export -> Comment Choice -> Do Not Delete Comments

Also, if any of the support material extends ouside the body of the object it is often easier to place the material correctly if a tall skirt is used. This can be enabled by activing Skirt and setting:

  • Skirt -> Layers To (index) -> 100000

Preparation

When Skeinforge has finished generating the GCODE you'll need to examine the layers in the Skeinlayer window in order to identify the z depth of the layers that need support. Examine the layers and record the z-depth of the layers that have areas that need to be printed directly on the support material.

It is useful to write down a description of the area that needs support along with the z depth as a reminder of where the support material needs be placed.

Next, the generated GCODE file should be split into n+1 pieces, where n is the number of layers that need support. This is needed in order to allow the manual support material to be placed. Each file should contain everything after the previous file and up to, but not including, the comment line that specifies the next layer that needs support.

This python script can be used to split the GCODE file into multiple files. It is a command line utility that can be executed as follows:

split-at-layers.py input_gcode_file z_depth_1 [ z_depth_n ] *

The python script produces n+1 files split at the locations specified by the z_depths in the command line. The file name of each output file has "_part_n" (where n is the file number) incorporated into the file name.

It is useful to put a G1 Xa Yb GCODE command at the end of every file except the last one that moves the extuder off of the part being printed. A and B should be replaced with values that place the extuder outside of the bounds of the object being printed. Note that the python script does not append a G1 command to the end of each file.

Printing

Print the first file.

When the file is done, reposition the print surface so you can easily get to the object to place the support material. Place the support material within the needed area on the part. The top of the support material should rise to the top of the last printed layer but it should not be higher than the last printed layer.

If the support material is too high the nozzle will plow through the material. This causes problems with the PLA adhering to other layers.

If the support material is too low the PLA will not stick, or it will tend to lift off the material as later layers are placed on top.

Placing the material so that it stays in place and stays within the necessary bounds might take a little bit practice. In the case of La Doll clay, do be aware that the PLA will not stick if the clay is too wet.

Any clay that gets onto a part of the model where the next layer is supposed to bond with the current layer needs to be throughly cleaned off or the next layer will not bond solidly. The has been, for the author, the biggest source of failed prints made using this approach. Simply removing the visible clay is not, usually, sufficient. Rubbing alcohol is known not to work effectively. It is assumed that water will work effectively, but at present it is mostly untested.

Extrude a bit of plastic, clean the nozzle, and print the next file. Repeat the process of printing files and placing support until you have run every file.

Cleanup

Cleanup will depend largely on which support material you use. Museum putty and Sculpey will need to be machanically removed using a tweezers and or some other tool. La Doll clay can be significanly softened by soaking in water (remove any easy to remove external lumps first). Once softened, tweezers, a brush and bowl of water, or a source of pressurized water (outside, of course) will generally remove the remainder.

Example: A Simple Test Piece

The Media:manual-support-1.scad test file defines a simple test object that needs easy to remove support in order to print. When completed, it consists of a captured ring that is contained by a rod and bound on each end by a disk.

Manual-support-1.jpg

Preparation

This part needs support at two layers:

  • The bottom of the inner ring.

Manual-Support-1st-Skeinlayer.gif

  • The bottom of the upper disk.

Manual-Support-2nd-Skeinlayer.gif

Assuming 0.2mm layers, z=5.2 and z=9.2 are the layers that need support.

The first file should contain the text from the start of the source file up to but not including the line:

(<layer> 5.2 )

The second file should contain the text starting with the "5.2" line up to, but not including, the line:

(<layer> 9.2 )

The last file should contain the text starting with the "9.2" line and include the remainder of the source file.

This python script can be used to split the GCODE file into multiple files. The command line for this part should be:

split-at-layers.py inputFile.gcode 5.2 9.2

Printing

Apologies for the horrid white balance.

First file printed:

Layer1.jpg

First support applied:

Layer1Support.jpg

Second file printed:

Layer2.jpg

Second support applied:

Forgot to capture an image.

Third file printed:

Complete.jpg

Note the warpage along the right side of the top disk. I believe this is because I did not get the second layer of support material high enough. Consequently, the right side lifted away from the support material as higher layers were printed.

Cleanup

Skirt removed:

AfterSkirt.jpg

After mechanical cleanup

AfterMechanicalCleanup.jpg

After soaking and final cleanup

Final.jpg

At this point the center ring freely rotated and the device can be used as a tiny rattle.

Example: A Toy with a Rod and Cam

This example uses Tiny Toy Dump Truck with Cam Action Bed [1]. "Improvements" over the original Tiny Toy Dump Truck include the use of cylindrical wheels instead of conical ones, a bed axle sleeve that is no longer tapered, and the addition of a rod and cam that is used to lift the bed once with every rotation of the back axis. The file Media:toy-truck11.scad contains the Openscad design that is used below.

Toy-truck11.gif

Preparation

There are five layers in this design that need support.

WhereSupportIsNeeded.gif

Assuming you are printing with 0.2mm layers, the z-depths of these layers are:

  • 4.0 (body bridges the lower pair of wheels)

SupportLayer1.gif

  • 7.2 (cam and rod appear)

SupportLayer2.gif

  • 11.8 (body bridges cam and rod)

SupportLayer3.gif

  • 13.2 (upper bed axle sleeve appears)

SupportLayer4.gif

  • 15.2 (upper pair of wheels appear)

SupportLayer5.gif

Break the GCODE file up into 6 files, based on the z layers.

This python script can be used to split the GCODE file into multiple files. The command line for this part should be:

split-at-layers.py inputFile.gcode 4 7.2 11.8 13.2 15.2

Printing

First file printed.

Part1.jpg

First support applied.

Part1Support.jpg

Second file printed.

Forgot to capture image

Second support applied.

Part2Support.jpg

Third file printed.

Part3.jpg

Third support applied.

Part3Support.jpg

Fourth file printed.

Part4.jpg

Fourth support applied.

Forgot to capture image

Fifth file printed.

Part5.jpg

Fifth support applied.

Part5Support.jpg

Sixth file printed.

TruckComplete.jpg

Cleanup

Manually remove large lumps of clay then soak in water for a couple of hours.

After completing cleanup.

TruckCompleteClean.jpg

Video showing operational cam action.


Another example

I'm not sure of the translation of the "patafix" a sticky white gum branded by UHU (thats maybe Henkel), or if its the museum putty of the initial list.

But strategically placed it can allow you to make objects that are otherwise difficult or save a print that start to move from the bed ("emergency need for manual support!").

A must have in your "first aid" pack for reprap (often used in my early days of printing).