20mm Plastic T-Slot

by ProtoParadigm, published

20mm Plastic T-Slot by ProtoParadigm Dec 14, 2011
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20mm Plastic T-Slot - Rev 2
Completely redesigned; the new beam prints faster and is stronger both against deflection and torsion.

UPDATE: Added DXF of Profiles. Naming convention is [dimensions]-[bolt size]-[Wall Thickness]-[Multiplier]. We are starting to prefer 1pt6 (1.6) wall thickness profiles and find printing them No Infill, 1 Extra Loop, No solid Layers, with a trace thickness of .8mm results in a quick and adequetly strong beam.

These beams are being designed as the main structural component for a 3d printer though arguably they are of more use as a general hobby framing and mounting set. That said they are designed with both printing and commercial extrusion in mind.

If printed in ABS, they can be solvent welded with the aid of a T-Slot Welding Jig http://www.thingiverse.com/thing:13598 and ABS Glue http://www.thingiverse.com/thing:14490 . A center hole increases the beams second moment of inertia while aiding in fusing beams.

PLA beams are more rigid though they are not as easy to fuse into various lengths.

An example of Friction Fit hardware is located -
Here - http://www.thingiverse.com/thing:9797
& Here - http://www.thingiverse.com/thing:13599

The standard beam profile is meant to accommodate both M3 hardware as well as 6-32 nuts and bolts. Both bolt heads or nuts will fit in the slot with an insert provided to help guide and captive M3 nuts. 6-32 Nuts will captive natively.

Alternative profiles are provided for M4 / 8-32 hardware as well as dedicated M3 and 6-32. All profiles are located in "20mm Profiles - Printing.skp" Use the 'Push/Pull' tool to create a profile of the desired length.

If the printing instructions are followed, these beams can be printed fast (going at even a moderate pace we're able to produce all the beams needed for a Prusa in under 12 hours). While the beams can technically be printing with any working profile, they will not print as quickly and may not perform as intended structurally.

100mm Beam.stl - actual height is 101mm to allow for loss during welding
20mm Test Beam.stl - shorter for testing settings
M3 Nut Insert.stl - use with metric hardware
20mm Profile-Printing.skp - profile faces for printing and creating different heights
20mm Profile-True.skp - diagram of a properly printed profile
20mm Profile-Printing-pt4.skp - profiles based on 0.4mm widths, contains a M5 profile
M3 Nut Insert.skp - source file for insert

Check Back For
T-slot Profiles for Thing-O-Matic, Ultimaker & Mosaic at various resolutions, speeds.
OpenScad version to ease design of compatible hardware and accessories.


These beams are designed with 2mm wall thicknesses to be printed with zero infill using consecutive loops of 1mm trace widths. There are also also a set of beams with 1.6mm walls for .8mm trace widths located in "20mm Profile - Printing - pt4.skp" though the standard profiles are more tested.

When printing correctly, the nozzle will trace out 2 (3 for stronger) consecutive loops making a single jump as it jumps layer. The center hole is absent in the profile and created as an artifact of having zero infill. If you plan on printing many of these beams it will be worth your time to create a dedicated profile adjusting Flowrate (or what-have you for your skeinforge version) to give the best looking and strongest beams.

General Tips
If you go to fast printing a single beam the print can start to mash about from overheating. Use a cooling fan or print multiple beams at once to give each layer time to cool. You can alternatively turn on the 'Cool' plugin to slow everything down...but who wants that, we're making T-Slot!

It is possible for T-slot printed in a thingomatic to warp ever so slightly towards the back of the bot. If this happens, enclosing your bots open sides with board or tin foil will help. I have a piece of cardboard that clips to the Z-stage that shrouds to the front of the bot in much the same way as the z-stage shrouds to the back of the bot. This helps the most.

If your nozzle is too low on the first layer you will get a small flange at the base of your beam. It can be taken off with a razor or better, change your Z-height slightly to give your nozzle a little more room for that first layer.

Profiles are being put together for various printers and extruders for a more plug and play printing experience but the following should help you get setup making a dedicated profile.

Settings ReplicatorG 27
1) Create New Profile
a. Top Menu: GCode > Edit Base Profiles...
b. Select the Profile you want to start from ie. SF35-Thingomatic-HBP-Mk7
c. Hit Duplicate and name something descriptive ie. T-Slot ABS
d. Your done! Skeinforge should open. If it does not, repeat steps 'a' and 'b' selecting your new profile and click the 'edit' button

2) Edit Toolpath
Top Menu: Gcode > Edit Base Profiles.. > 'Your new profile' / click 'edit'
Under 'Fill' tab -

Extra Shells on Alternating Solid Layers = 1 (or 2, just be consistent)
Extra Shells on Base =1 (or 2)
Extra Shells on Spares Layers = 1 (or 2)

Infill Solidity = 0

Solid Surface Thickness = 0

(I find this to make them look nicer)
Thread Sequence Choice = Perimeter - Loops - Infill

3) Adjust Width (if necessary)
Under 'Carve' -
Layer Thickness (mm) = 'Whatever your comfortable with, I use 0.3 so its a little faster than my standard 0.2 or lower)

Perimeter Width over Thickness (ratio) = 1 / (the Layer thickness used previously) ie. If I used 0.3 for my Layer thickness, I perform 1 / 0.3 = 3.3333 This ensures that the perimeter trace width will be 1mm

Under 'Fill' -
Infill Width over Thickness = The same value used in the previous step, in my case it would be 3.3333

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what do you suggest opening these files in? when I open them in sketchup make (despite having selected "mm") it's opened as meters, and it just makes things extremely tedious to work with.

could you possibly upload the double width version of this, i would prefer to use that for parts of a project i'm working on, otherwise i need to make one myself

Hi, nice approach and easy printing here thanks for this. But I am missing a collection of connectors with and without threaded support for different arcs and directions and extenders, do you know some?

1.5" x 1.5" plastic t slots extrusions are now available at http://modularextrusions.com/
They will make some great printer frames.

Does enyone have a profile for slicing it so the outout looks like the one on the picture ?
I mean printing it using consecutive loops.


im wanting to print this to build a foldarap but the slot width is not big enough if any body could edit this and give me the stl it would be greatly apreciated it needs to be a 20mm x 20mm m6 slot with a slot width of 6mm

Has anyone tried to slice this with slic3r?, i set 0 infill, 2 perimeters, auto wall with and they come hollow. Im printing the 20mm test piece at thins moment, but it looks good (and hollow). Also, anyone did any load testing of this beams?, they might be very useful to build printers and geek toys down here (Argentina) where aluminum extrusion is really expensive.

Nice! Is this design based on any commercially available plastic beam design, and if so which one? I would imagine that extruded parts are stronger and can be used for longer beams but combined with printed custom parts.

like this idea but I would like a printed joint if possible, like little plastic pieces that would go in the slots to join them together besides welding them


We tried several versions of something like this. In the end creating a secure connection ended up consuming too much of a beam's useful length to be material efficient to make beams of any appreciable length. Secondarily you lost the use of the slot in the beam for most of the beams length.

We have built fairly large structures using individual small beams latticed with the friction fit hardware. Very stable, very strong.

is there any way you could upload a 200mm, 50mm and a 75mm beam?

I have tried making them from the sketchup files but nothing that i export out of sketchup prints the same as the 100mm beam stl that i downloaded. (i get a box on the inside of the tslot that is not connected)

i have make a pretty great profile in skeinforge that will print the 20mm and the 10
0mm stl files i downloaded here perfectly now.

thanks for uploading these, I have been printing a ton of them

You're using the push/pull function in sketchup correct? Would you email a copy of that beam to
lt; contact (AT) ProtoParadigm (DOT) com
gt; and maybe we can see what the problem is. If you are familiar with DXF, they are also available in that format. If we can't get that figured out we can put up an stl of the length and beam to use.

Looks really awesone; do you have any load testing results?

We are setting up a run of testing for Rapid Prototyped T-Slot with an engineering department at a local University. Using some of the lab equipment from the Civil Engineering department we plan on comparing different materials, grades, tool-paths, joining methods, etc.. We should also have a Stratasys join the games and see how it does against the hobby class.

Still can't get over how clean these printed using the custom profile settings included. Making me rethink my settings on everything I print now!

This looks great! I was wondering what shell value did you use?

I used 3 shells and the profile settings given...only way I could get it to completely print solid.

Any chance you'd consider throwing together a panel for these? It'd be awesome to kick it off before going to bed and coming out with 12 sections :) It runs me nearly 2 hours a 100mm section currently.

That can happen. It may be an easier route using Skienforge's multiply plugin and just have it make a grid. If you are going for fast it might be worth a dedicated profile. With a layer height of 0.4mm and a trace width of .5mm (or .4mm depending on T-slot breed) we're below 20 minutes a 100mm beam without needing a fan at the nozzle. Less time if doing multiple beams at once and the beams have a chance to cool before they are hit again. Packing them tight together you can get a couple meters from a single press of the 'build' button.

blah. Those numbers are incorrect. They should have said:

Layer Thickness - 0.4mm
Trace Width - 1.0mm (or 0.8mm depending)

These have given us good fast results. Just make sure if you're using a Thing-O-Matic that the filament feeds oh-so-smoothly, or else you can get waves in the beams from the cantilever raising up a miniscule amount as it tries to pu
ll in more filament.

What extruder/nozzle diameter/flowrate are you using that allows you to print at 0.4mm layer height and 1mm thread width fast enough to get a 100mm beam to print in 20 minutes? I'm having trouble getting my ToM MK7 to push ABS that fast... The best I have come up with takes about 45 minutes.

We were using a Makergear Extruder; 3mm plastic, .4mm nozzle. Just now starting on profiles for MK7. What linear speed are you moving at?

I've been printing 2 at a time as I've been trying to get a good fast skeinforge profile worked out... I had to slow my profile down because I was occasionally getting failures where it would jam at about 80-90mm tall... so now it's taking me a little under 2 hours to print 2 using an Mk7 at feedrate 30 and 0.4 layer height and 0.5 thread width (and 3 extra shells to print the 2mm thick beams) I'm having difficulty printing at 1mm thread width unless I slow it down to like 20 feed rate.

Printing these is making me want to try the experimental 1.5 mm diameter nozzles that MakerBot sells. :)

i am running a .35 MG nozzle with .3 layer height so that probably explains the 50 min per beam i am getting. I am running 50mm/sec on an old cupcake.

i cant get them to print any faster than about 50 min each (i have been printing 9 at a time), mine dont have any holes on the internal structure of the beam except for the center hole. they are turning out really nice but without seriously affecting the structural integrity i cant figure out how to get them to go faster.

My Prism mendel uses misumi extrusion. Have you tried a printing profile that is compatible with misumi or 80/20?

Or have you tried an m4-sized channel? I could remove the 'tongue' on the prism parts that goes into the 6mm channel on the misumi rails and make a 'fully printable frame' branch.

We did look at some of the popular aluminum T-Slot extrusions. The concern was the increased cost of the bolting hardware and thinner wall thicknesses needed to accomodate it.

There is a profile in the 'pt4' (which will probably be renamed 1pt6 to reflect wall thickness) that is meant for M4 hardware. I tried some hex and square nuts in the channel and they work well.

I do like some of the profiles associated with aluminum extrusion that have larger corner cavities, b
ut sadly, they do not lend themselves to the quick and sturdy method we're using for printing. Requires to many jumps.

I have yet to find a use for these, but they look terrific. Any chance of a dxf so I can extrude in openscad? I don't know how to get them from sketchup.

Yes, we'll throw that up here in a little bit. Any preference on DXF format?

wow those are pretty