One of the parts I print is a fitting for attaching a carbon fibre rod to a PCB probe. In use it should be always under compression, it is printed with the Z axis aligned with the shaft axis, and has proven robust in field use over several months. However recently we have had a few failures, where the part has been sheared along the layer boundary. I've had various reports as to the cause, from "someone fell on it", to operators using the device to "hook" down into position multi-ton equipment suspended from a gantry crane, to what looked liked someone had used it as a golf club. I can't comment on these failures occurring around the time the company announced reduced Christmas bonuses due to low profits! A quick way to overcome the weakness in tension/shear would be to incorporate a couple of 3mm ID tubes running through the Z axis, then inert 3mm screws and pretension, as is done with pretensioned concrete beams. However I need to reduce the weight at the head as much as possible. It occurred to me that it should be possible to print the strengthening tubes in the Z axis, perhaps around 1mm ID, and then have the printer go back and inject plastic into them to tie the layers together. Unfortunately I'm overseas in Brazil and away from my workshop for some time, and so can't carry out the necessary testing, but perhaps someone had tried this idea before? My visualized sequence, just picking some numbers, which obviously would require testing. Say for a 0.1mm layer build, using a 1mm ID pinning hole, if we found we could inject plastic 5mm deep: 1. Build the layers with the pinning columns up to 5mm 2. Increase hotend temperature as required for more fluid plastic 3. Move to centre of each pinning hole in turn, drop head/raise bed to seal against layer 4. Inject plastic of calculated volume 5. Step and repeat to next hole An enhancement would be to stagger the start/end of each pinning hole in the Z axis, so as to avoid any single weak layer. If this were incorporated into Slic3r, there is then the question of whether the program selects the pinning locations itself, as with support material, or whether the information can be added manually to the stl model. In the latter case the designer has better control of location and depths - the pinning could be done as internal tubes of set diameter, with a Slic3r option to recognize these and add the pinning fill. Further ideas welcome! David https://reprap.org/forum/read.php?263,173202,173202#msg-173202 Mon, 12 Oct 2026 06:07:14 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?263,173202,174055#msg-174055 https://reprap.org/forum/read.php?263,173202,174055#msg-174055
Printing does give you the ability to quickly modify the design, which I like. We had a few PCB breakages, and it only took an hour or so to come up with a modified version that provided more support for the board. At this stage the most we have had to build is a batch of five, but if quantities go up I think the molding approach will be the way to go.]]> leitor Slic3r Mon, 31 Dec 2012 06:31:30 -0500 https://reprap.org/forum/read.php?263,173202,174006#msg-174006 https://reprap.org/forum/read.php?263,173202,174006#msg-174006 tmorris9 Slic3r Sun, 30 Dec 2012 23:20:41 -0500 https://reprap.org/forum/read.php?263,173202,173974#msg-173974 https://reprap.org/forum/read.php?263,173202,173974#msg-173974 Free nozzle dropout not neccessarily go straight downwars, maybe put nozzle lower but then it sticks with great amount of plastic after "injection".
Difficult maybe to move away without dragging with nozzle.]]> Tertzoid Slic3r Sun, 30 Dec 2012 17:04:25 -0500 https://reprap.org/forum/read.php?263,173202,173919#msg-173919 https://reprap.org/forum/read.php?263,173202,173919#msg-173919
However I would still like to trial my pinning/injection idea, as I think it could greatly increase part strength.
A couple of problems I foresee are:
1. The hot-end bonding to the plastic when pressed down to make a seal. This could perhaps be overcome by using a non-stick/thermal insulating material washer around the hot-end tip, or perhaps a full seal would not be required.
2. Air locked in the tube unable to escape. This could be avoided by design, leaving a path for air to escape at the bottom of the tube, or perhaps by using a slit-trench design rather than a tube.]]> leitor Slic3r Sun, 30 Dec 2012 09:49:56 -0500 https://reprap.org/forum/read.php?263,173202,173242#msg-173242 https://reprap.org/forum/read.php?263,173202,173242#msg-173242
And as you mentioned, using higher hot end temp.]]> tmorris9 Slic3r Wed, 26 Dec 2012 16:29:09 -0500 https://reprap.org/forum/read.php?263,173202,173202#msg-173202 https://reprap.org/forum/read.php?263,173202,173202#msg-173202
A quick way to overcome the weakness in tension/shear would be to incorporate a couple of 3mm ID tubes running through the Z axis, then inert 3mm screws and pretension, as is done with pretensioned concrete beams. However I need to reduce the weight at the head as much as possible.

It occurred to me that it should be possible to print the strengthening tubes in the Z axis, perhaps around 1mm ID, and then have the printer go back and inject plastic into them to tie the layers together. Unfortunately I'm overseas in Brazil and away from my workshop for some time, and so can't carry out the necessary testing, but perhaps someone had tried this idea before?

My visualized sequence, just picking some numbers, which obviously would require testing.
Say for a 0.1mm layer build, using a 1mm ID pinning hole, if we found we could inject plastic 5mm deep:
1. Build the layers with the pinning columns up to 5mm
2. Increase hotend temperature as required for more fluid plastic
3. Move to centre of each pinning hole in turn, drop head/raise bed to seal against layer
4. Inject plastic of calculated volume
5. Step and repeat to next hole

An enhancement would be to stagger the start/end of each pinning hole in the Z axis, so as to avoid any single weak layer.

If this were incorporated into Slic3r, there is then the question of whether the program selects the pinning locations itself, as with support material, or whether the information can be added manually to the stl model. In the latter case the designer has better control of location and depths - the pinning could be done as internal tubes of set diameter, with a Slic3r option to recognize these and add the pinning fill.

Further ideas welcome!

David]]> leitor Slic3r Wed, 26 Dec 2012 09:59:10 -0500