3D Printer Files for Guide Blocks

Now that J&R and Midget have closed, it appears we no longer have any way to get the guide blocks that follow the tracks on the lower half to control the movement of the upper half in an even manner. But, one of our members, RahnA has a Daughter that created 3D printer files to fabricate new guide blocks. The ones she designed are identical to the OEM ones except for a groove down the center that was a weak point in the original design. This new design does not have that groove, and I cannot see any reason for it except to make it easier to break.

The files are in the links below, and there are four of them because different 3D printers use ones with different file extensions (.obj, .stl, glb, and .mtl). If you have access to a 3D printer, the owner's manual should tell you which file to use. RahnA had his printed using a Carbon Fiber filament, such as NylonX, PA12-CF, PETG CF or PLA CF. (there are possibly others, but I've never used a 3D printer, so I'm just talking about things I've researched). And, if you use one of these files, it must be preprocessed with a printer app called a "slicer", which is designed to be used with a particular brand of printer. Finally, a carbon fiber filament requires a special printing head that is hardened steel, not brass, because the filament is abrasive. Not all printers have this hardened head as an option and some printers may not be able to use every CF filament available.

I'm sure those of you who own 3D printers know all this already, but for those thinking of getting one, these are things you should know about and research before you take the plunge.

Again thanks to RahnA and his Daughter for this valuable resource.

- Jack

OK, now that I have my printer up and running, I've learned a few things. But first , my printer is a Flashforge Adventurer 5M which was on sale for $299 through Amazon ($100 off) and I'm pleased with it. My impressions:So, those are my thoughts on the printer.

I partially printed an HiLo guide block using the Flashprint 5 slicer. A picture of it is shown below and I printed it using PLA filament. As you can see, the block is NOT a "solid", but is honeycombed. Naturally, that saves on printing filament and in my opinion does not seem to weaken it appreciably. The part was stopped when it was about 1/4" thick and I find it is quite "rigid". It does not bend easily and I suspect even printed in PLA, it would be strong enough to use on the trailer

Rahn, if you read this, can you find out if the blocks your Daughter printed were honeycombed similarly? My guess is, looking at the picture you posted of your block, she used a very high quality carbon fiber filament and probably a high end printer. Consumer grade carbon fiber has particles that are too short or the carbon is "powdered" which makes for pretty prints, but is not strong. Industrial grade or Aircraft grade carbon fiber adds strength, but is expensive.

Hope these thoughts and observations are helpful to everyone.

- Jack

And, I went ahead and printed a complete guide block using PLA. It took about 24 minutes as I remember and used surprisingly little filament. It feels VERY strong and since PLA is generally somewhat flexible and elastic (does not permanently deform unless stressed severely), I suspect it would be strong enough to use on the trailer. I'll still print one using PETG-CF when that filament arrives and will do the same with ordinary PETG, just for comparison.

The picture shows how cleanly it printed. You can see a faint "groove-like" effect on the slanted surface which are the edges of the filament layers laid down by the printer head. These show the actual thickness of those layers that stack up on the angled surfaces. This is a bit like the "pixelated" effect you get on slanted lines that are drawn in a computer painting program. They don't bother me and don't effect the strength.

I think the inner two opposing curves might have to be cleaned up a bit at the top. The area near the inner edges is not supported during printing, so the filament kind of sags a bit there. I can easily sand it to remove the defect.

The guide blocks printed by Rahn's Daughter don't show either of these artifacts. This may be because she's using more professional equipment or is more skillful than me (or both). Interestingly, I see diagonal lines on the front surface of hers, which make me think she may have printed hers "on edge", rather than from the bottom up like I did. I can't see how else those diagonal lines would appear.

The left and right edges of my guide block appear to be slanted out - they are not, they are parallel and vertical. The camera angle produced that effect.

- Jack

Guide Blocks

Jack amazing work and write up. Thanks.

And, I've learned some more facts that may help you if you need to print guide blocks.

The Slicer program you use will have settings that position the object in the printer and this position can effect how well the object prints.

In the first two pictures below, I show a somewhat defective block printed the way it was oriented in the .stl file in this thread. The first picture is a screen shot of the block in the slicer. The second is a picture of the resultant block. As you can see, the lack of support in the top overhangs allow the filament to "sag" there, and this weakens that area and may interfere with its movement on the track. You can also see a kind of "stairstep" effect in the inside curvature, which is an artifact produced by the layering process of printing.

In the last two pictures, I show the block oriented on its back side in the slicer, which printed it that way in the printer. I simply rotated it on the "X-axis". Now, the interior portion of the block does not suffer from a lack of support and there is no sag. In addition, there is no stairstepping. I suspect Rahn's Daughter printed his blocks this way, because I now have the diagonal tracing on the front edge. It is a much better result.

I won't go into other specific options in MY slicer, because your slicer will probably be different but will probably still have these options, which will further improve the strength of the block. I printed both of these blocks using "default" options, which gave me a wall thickness of 2 layers (fairly thin) and an infill pattern that was composed of squares. You can see this in the second post in this thread. I discovered the slicer will allow you to increase the outside wall thickness and you can change the inside pattern. I will set the thickness to 8 and the infill pattern to "hexagonal" in any future blocks that I print. In my research, I've learned that these values supply better strength to weight ratios and should produce superior guide blocks.

- Jack

Looks like you are doing great Jack!! I checked in with my daughter and this is what she said: “ I printed them on their sides without supports.
This direction gives the best strength, laying it on the flat bottom would make a significant weak spot on the overhang parts as they would be stand alone layers.
PLA-CF (carbon fiber).
I used the Bambu Lab X1 Professional Carbon printer with hardened steel hotends for heat control and Hardened Steel Extruder Unit.
I printed at 70% infill. “

I added a picture of the texture for you.

So you are doing a really nice job with it Jack!

Thank you Rahn, it's about what I guessed after doing my first print. The Bambu Labs printer is certainly a much more high end unit than mine, but I suspect mine will give good results too. I printed another one using PETG filament and it came out great too. I used the 8 layer setting for the surfaces and the hexagonal infill. But, my infill percentage was only 15%, I wonder how much difference the 15 vs 70% infills make? I know, from the tests I reviewed, that the 8 layer walls just about double the strength, but those same testers did not see huge differences in the strength caused by different infills.

- Jack

I haven’t studied 3-D printers and methods much but I think the infill percentage depends on the purpose and function of the object. Higher percentage means more strength, but also more filament and print time. Lower percentage means less strength, but also less filament and print time.

RahnA said:

I haven’t studied 3-D printers and methods much but I think the infill percentage depends on the purpose and function of the object. Higher percentage means more strength, but also more filament and print time. Lower percentage means less strength, but also less filament and print time.

Click to expand...

Yes, I would agree with that statement, but what I was saying is that the infill change does not seem to have as much effect on overall strength as does changes in the wall thickness. The designs of most of the infills are very "truss-like" and a truss is a very strong engineering shape, which it achieves while using a minimum of material.

And again, in studying the way these blocks work, they should be subjected to very little stress as long as the top is not "twisted" on the tracks or they are not subjected to the stress that would occur if the trailer is towed with the top up.

- Jack

Yes, that does make sense and the truss system could very well be as strong.

The lateral twisting, as you mentioned, is what will break them.