ABS replacement strut
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Published on May 19, 2011
Description
This is a derivative work from MBI's open source parts files - thingiverse.com/thing:4973.
This is a first attempt to print a replacement for one of the plywood struts which commonly get broken on the ABP during assembly.
I broke mine by fat fingering it while assembling my Thing-O-Matic in Mar. '11. I'd been trying to get this into CAD and learn how to use some idle CNC machines at a local college. But, the MBI files were hard to use several months ago. Rev. F is cleaner. If you work with their files it will help if you delete the hidden block libraries. They are useful for MBI's design efforts but, they will get in your way for use to manufacture the parts. No big deal. Just a hidden caveat.
05/05/11 - I printed the ABP strut replacement. This is the strut with bushing holes. I'd broken a small tang during our original assembly and had just epoxied it together but, my sons did not like that kluge of a fix. I told them that it was acceptable for this low stress member but, they wanted to print a new one. So, after reading in Thingiverse about Webca and others having printed their entire bots [http://www.thingiverse.com/thing:3285] we decided to plunge in with the challenge of printing one replacement part.
In my pictures - if the part looks warped it is the black paper that the part is sitting on. The part is very flat.
2/2012 - Part will and does print accurately. The file is good. My mistake as a noob. See new picture in red.
This is a first attempt to print a replacement for one of the plywood struts which commonly get broken on the ABP during assembly.
I broke mine by fat fingering it while assembling my Thing-O-Matic in Mar. '11. I'd been trying to get this into CAD and learn how to use some idle CNC machines at a local college. But, the MBI files were hard to use several months ago. Rev. F is cleaner. If you work with their files it will help if you delete the hidden block libraries. They are useful for MBI's design efforts but, they will get in your way for use to manufacture the parts. No big deal. Just a hidden caveat.
05/05/11 - I printed the ABP strut replacement. This is the strut with bushing holes. I'd broken a small tang during our original assembly and had just epoxied it together but, my sons did not like that kluge of a fix. I told them that it was acceptable for this low stress member but, they wanted to print a new one. So, after reading in Thingiverse about Webca and others having printed their entire bots [http://www.thingiverse.com/thing:3285] we decided to plunge in with the challenge of printing one replacement part.
In my pictures - if the part looks warped it is the black paper that the part is sitting on. The part is very flat.
2/2012 - Part will and does print accurately. The file is good. My mistake as a noob. See new picture in red.
Instructions
********** Note: I've not installed the part. This part prints 1mm smaller in length and the holes print smaller than the drawing also. I've since processed another 3D drawing, .stl and part from MBI's latest (rev.F) 2D files. But, my second print is the exact same size as my previous. I've not yet learned how to fix and print for tolerance on my bot. Matt at MBI told me to set shells = '0' but upon reading D. Durant's explanation and testing a print with shells = '0' this is not the parameter to adjust. I think it is 'perimeter' but, I need to do other things before I print this again. If you know or have suggestions I'm all eyes to read and try.
One of my sons tried placed the part into the laser sheet cutouts and the part fits. The holes are small though.
1. Download STL
2. Generate the gcode/s3g
3. Print.
2/2012 - Update. The file is and was accurate. The printing was by a noob, me, and was not properly setup. I reprinted today 2/23/2012 with experience. The part fits perfectly. But, then we don't need it with all the great upgrades. I just updated this for history and to unmark it as a work in progress. See picture of red part for correct size. FWIW
One of my sons tried placed the part into the laser sheet cutouts and the part fits. The holes are small though.
1. Download STL
2. Generate the gcode/s3g
3. Print.
2/2012 - Update. The file is and was accurate. The printing was by a noob, me, and was not properly setup. I reprinted today 2/23/2012 with experience. The part fits perfectly. But, then we don't need it with all the great upgrades. I just updated this for history and to unmark it as a work in progress. See picture of red part for correct size. FWIW
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License
ABS replacement strut by bstott is licensed under the Attribution - Share Alike - Creative Commons license.
More from bstott
Bare in mind that laser-cutting removes material so you often have to design-in this "kerf", aka the beam width's channel removed from the material.
Not sure why your print is shorter in total length (could be simple plastic shrinkage), but the holes likely print smaller because their radii need to be grown by the kerf amount.
Thanks - Standard practice for cutting is to cut to the outside of the object line - placing the cut (blade kerf) right to the part perimeter. Kerf would not be a factor.
Our FDM process is theoretically accounting for extrusion width so I'd expect holes to only be slightly undersize if in error? The mystery is that the part fits the plywood cut out for part perimeter including tabs perfectly. It is a direct plug in if the T-slots were larger. The interior of the p
art (square, bushing and M3 holes) are also undersize.The holes are too small - not to print by quite a margin. For example, the bushing holes are 1.7mm undersize (s/b diameter 16mm is 14.3mm). The STL is to print. I'd guess one of those SF settings? *DONT_KNOW*