Friday, 14 November 2014

Accurately Printing Holes Parallel to The Build Plate

Broadly speaking my 3D prints fall in two categories: aesthetic or functional. Aesthetic prints just need to look good. They typically do not need to be accurate. If they look correct to the naked eye, then that is enough. Functional prints perform an engineering role. The print finish is not important. Accuracy is. To print objects accurately it is often necessary to adjust the model and print parameters. 
Functional prints are typically combined with hardware, usually nuts and bolts. The majority of designs require such hardware to be installed vertically or horizontally, often both within a single print. I endeavor to create an accurate print that requires little clean-up. 
Note that the example print in this document would ordinarily be printed flat on the build plate. Whilst there are issues printing holes perpendicular to the plate, printing an overhang should be avoided if possible.  The holes in the example print have diameters; 20mm, 10mm and 5mm. 

Printing Without Supports
An overhang can be printed without supports. A cylindrical hole can support itself, however, the resulting print is poor.

Print settings: Maker Ware high-res default settings with no supports.

The following time-lapse images shows how some of the inaccuracy occurs.

As the depth of the overhang reduces, it begins to curl upwards. The top of the print is no longer horizontal; this causes print media to build-up on the overhang. When the printer begins bridging, this build-up distorts the hole. Subsequent layers force the build-up downwards, creating more distortion.
The largest hole in the example print has a diameter of 20mm. This is within the printer’s parameters for bridging. However, as the hole is completed it overhangs more and becomes weaker. This results in sagging. In addition, the bridging elements of the print are untidy. The build-up and bridging can be cleaned-up, but this won’t reverse the distortion of the print.

Printing With Maker Ware Default Supports 

Supports are the solution to collapsing overhangs, but the default Maker Ware supports are not adequate. The hole still collapses. (EXPLAIN)

Print settings: Maker Ware high-res default settings with default supports.

The Maker Ware Supports are untidy. They, and the bridging, are still distorting the print despite cleanup.

Support and bridging parameters can be adjusted in a custom profile. However, the design of the supports and the presence of bridging is the real problem. 

Custom Support 
Modelling supports into the print object give the operator complete control. Supports, and equally as crucial, their spacing, can be accurately defined. I create supports 0.4mm wide and 2mm apart, placed from the centre of the hole outwards. The supports are placed across the hole.
The width of the support is one print line width of the extruder at default settings. It can be easily removed with a finger. Spacing supports 2mm apart creates support across the entire hole, preventing any curling during the print and avoiding any bridging.

Modelling supports into the object creates a tidy print that is accurate (enough) and requires little cleanup.

I do not model the support into my working object, instead adding them to a duplicate when my design is complete. A support template can be imported, adjusted and combined. This is fast and non destructive. Below is a summary of the support design
that can be used for all overhangs.

Support width: 0.4mm 
The default line width of the extruder.
Support spacing: 2mm 
Working from the centre of the hole outwards. If the space between a support and a vertical edge is less than 2mm it is omitted as it typically creates a support that is hard to remove.

Dead Holes 
Dead holes do not pass entirely through an object, they have an, ‘end’.
The same approach to supports should be applied here. A space of 0.4 mm (if possible) from the end face aids removal of the support. This is an effective approach to printing nut recesses perpendicular to the build plate 

Modelling supports into an object is more time consuming as regards preparation and print time,  but the results are better quality and require less cleanup.

Friday, 24 October 2014

Levelling The Build Plate

There is a wealth of techniques for leveling the build plate documented on the Internet. Many of these require interactive prints or additional tools. I’ve achieved good results, with relatively little preparation, by refining the steps outlined in the Maker Bot documentation.
I level the build plate at the beginning of each session. I level again if I’ve interacted with the plate. For example, longer prints create a stronger bond with the plate due to the prolonged heat exposure. Removing these prints requires some wrestling which in turn disturbs the plate.  If I’m executing short prints that snap easily from the plate then I tend to level every three or so prints. 

1.) Remove any frayed bits of Kapton tape.

It doesn’t matter if there are holes in the Kapton tape. However, the size of the hole is relevant. If the hole is as big as the print, then offset the print. If it’s comparatively small then it should be fine.
Frayed bits of Kapton tape are a problem. They catch on the print head or get stuck inside a print. I use a Swann Morton scalpel with a 10A (straight) blade to trim the frayed tape. Raising the build plate above the memory card reader aids access.

To raise the build plate, choose: Jog Mode Y -> Z -> Z-

2.) Remove any bits of print media from previous jobs (I use my finger nail) then clean the build plate with Acetone. 
Ideally this is done when the build plate is cold and never when hot. Aside from getting covered in your chosen print media the build plate also gets greasy. Cleaning with Acetone gets the build plate pristine, aiding adhesion of the print. 

3.) Remove any bits of print media from the extruder nozzle.
Print media often runs through the extruder nozzle as it cools. If the nozzle is cold, then the media will be brittle and is easily snapped off with a fingernail. 
If you are leveling after a print then allow the extruder nozzle to cool sufficiently to remove the print media without discomfort. Aside from burning yourself more print media will leak out by the time you begin the leveling procedure. 

4.) Heat the build plate to your preferred temperature.
Choose: Utilities -> Level Build Plate. 
I only print with one extruder nozzle (because this is all I require) Consequently I adjust the build plate to that nozzle only.
I use a 3M Post-it note as a gauge rather than the business card supplied by Maker Bot (which is ridiculous) Post-it notes have a reliable thickness and conveniently stick to your fingers while adjusting the plate bolts. They are also disposable.

Note that the first pass is just to get the build plate in the ball park. The second pass is where fine adjustment should take place. I skip the final step where the extruder nozzle is centrally positioned. I usually cannot get the Post-It note under the nozzle in this position. Furthermore there is no logical way to adjust the plate if you are not happy at this stage.

Friday, 3 October 2014

Format an SD Card FAT 16 on Windows 7

1.) Insert the SD card.

2.) Open Windows Explorer and make a note of the cards drive. In this example it is: H.

3.) Open a Command Prompt. 
Click the Start button and type: cmd. Cmd.exe will be listed under programs. Click to execute.

4.) Type the following in the Command Prompt.

format(SD card drive):/fs:FAT
In this example: format H:/fs:FAT

5.) You will be prompted, "Insert new disk for drive H: and press enter when ready..." As the disk is already present, hit enter.

6.) When the format is complete you will be prompted to name the disk. Provide a name or hit enter to skip this step.

7.) If the command is successful it will return something similar to this...

It is clear that the card has been formatted FAT16. Note that right-clicking the card in Windows Explorer and choosing, "Properties", will display the file system as: FAT, not FAT16.

Saturday, 20 September 2014

Format an SD Card FAT 16 on OSX

Note that  formatting the card will rename it: NONAME.

1.) Insert the SD card into the reader. 

2.) Open Disk Utility.

3.) Select the SD card by clicking on it.

4.) Right click the SD card and choose: Unmount
The card name will become greyed out.

5.) Open a Terminal window.

6.) Type: diskutil list
This command gives information on all connected devices. The relevant information in this instance is the path to the [SD card] device and it's name. In the example below the path is: dev/disk3 and the name (identifier) is: disk3s1. Note that the actual card 'name' in this example is, "TMP_NAME_SD1".

7.) To format the SD card, type:

newfs_msdos -F 16 (path to the SD card device) / (SD card device name)

In this example:

newfs_msdos -F 16 /dev/disk3s1

*Note the underscore in the command is necessary.

If the command is successful it will return something similar to this...

8.) In Disk Utility, right click the card and choose: Mount
The card will now be shown as: Format: MS-DOS(FAT16) The card is name is: NO NAME  



Command returns: Permission denied.
  • Is the card right protected? Check switch on side of card.
  • Do you have the required permissions? Type: sudo -s to get a full root shell.
 Command returns: Resource busy.
  • Is the SD card mounted? Unmount in Disk Utility as documented above.

Makerbot Replicator 2X SD Card Conventions

The Makerbot Replicator2x only reads SD cards that are formatted FAT16. The maximum partition size of  FAT16 is 2GB. You can format a card with a larger capacity than 2GB as FAT16, however,  the partition will only be 2GB. Furthermore, the Replicator2x won't recognise it, instead returning the message, "SD card read error". So, a 32GB SD card formatted FAT 16 will *not* work.

SD Cards for the Replicator 2X must be 2GB in size and formatted FAT 16.