It seems easy enough to add if I feel strongly about it. I think the motivation is that any weight slows things down, so why not use a bowden? I’ve never used one, so I’m excited to use it as is.
I didn’t want to carry the weight on the x axis. more mass, more potential for ringing at speed. also, less mass = greater speed. so far, I’ve really liked the bowden system. all my previous printers were direct drive. it’s not without downsides, like inability to print things like ninjaflex. but I only ever did that once and wasn’t that impressed. you also need to tune your k-factor (linear advance) more carefully to get clean corners.
It’s easy enough to adapt the head for direct drive, if that is desired.
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Cool. The railcore has a bondtech attached to the hot end. I have the parts for a flex3drive, but haven’t purchased the hardware yet. I’m zipping along at a max of 100mm/s now, and sometimes hear the extruder skip because it can’t melt fast enough. My rostock max had a bowden and was kind of a pain to get the retractions right.
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I routinely print around 120mm/s with non-printing moves around 160mm/s to 180mm/s. Obviously this works better with larger parts because acceleration is a factor.
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Which hot end are you using?
e3d v6 https://e3d-online.com/products/v6-all-metal-hotend (24v) … for faster printing you have to crank the temp to 230+ depending on the material. also, for the last 3 years I’ve been printing almost exclusively in Ziro Carbon fiber . It is hands-down the best filament I’ve used in 7+ years of printing.
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Does the carbon fiber filament tear up your nozzle?
it’s not that aggressive. it shows little to no warping or oozing with excellent layer bonding and strength. basically, it’s just incredibly reliable. i start and run prints and almost never check on them.
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Never used it myself but here is a CNC Kitchen test result of 300 g of carbon fiber filament. Link takes you directly to results in the video.
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the carbon filament in that test is high temp petg-based so quite abrasive. the ziro CF is PLA and much less aggressive. I think the CF in the filament serves more to give it admirable reliability characteristics than super strength. it’s just not that brittle compared to others i’ve tested (and largely disliked). one exception is that I tried super expensive ($150/kg) markforged CF (true CF filament) which requires a temp of 280C just to get started. prints beautifully but will destroy a non-hardened nozzle.
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Amen to Carbon fiber PLA. all parts look so good!
I also been printing wth Polycarbonate CF filament with extremely good results.
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Jeff I will be watching your build very close. I love the design…Thank you @stewart.
Once I’m done with my basement I will start a build. I can use another printer…(don’t tell my wife)…
OK. I ordered some ziro. You’ve convinced me.
I went to Home Despot and they didn’t have the 1/2" square tube, but they did have some C channel. So I am just gonna try hard and not look at it from the bottom. I think this will work fine. It is plenty stiff. It was $13 with tax, for anyone who’s keeping track. I haven’t measured it with the calipers yet, but lucky for me, I have the CAD if I need to change it slightly. 
I used 1/2" square wood dowels in early prototyping tests. Works just fine. Just not as pretty. Don’t remember where I got it. Maybe Amazon.
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Hey @stewart. I really like the design. LOVE the OnShape document. I made a copy and will probably make a build of my own in the next few months.
I have an OnShape user tip that you may find helpful. Instead of adding hundreds of parts into a single assembly and connecting each one individually. You could create smaller sub assemblies with many repeated parts. Then add/insert the sub assembly into a larger assembly one or more times. For example: The corner pieces with the bolts could be a starting assembly. 9 Bolts, plus one corner piece. Get that all attached then create another assembly for the box frame. It would have the 2020 extrusions and 8x of the corner assemblies. That way each sub-assembly could be reused as often as needed. This makes it SUPER easy to update and maintain. If you needed to change the length of the bolts you would have to update about 50 pieces in your current assembly. But if you had them in sub assemblies you would only need to replace 9. Hope that makes sense. It might be difficult to explain in text.
Here is one of my files that uses sub assemblies if you want an example of what I mean. Look in the Assemblies folder. The full assembly just uses the sub assemblies.
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@mordiev great tips. I think the document as it stands represents a design that evolved and changed significantly over the years. If (or when) I rebuild it from scratch, I will use the techniques you describe.
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So far, I have shied away from assemblies at all. I see now that I need to really embrace them a lot more. I should probably spend some time watching some onshape tutorials. I watched a few when I started to get some simple things done, but then as soon as I was dangerous, I stopped. Now I see that even though I can generally do what I want, I could be doing a lot more if I learn some more.
Do I need the Z spacer part from the z parts? Is that to determine how close to one edge the X top/under pieces go so they are vertical?
yes, it provides a consistent offset from the back of the printer so that the z axis is aligned perfectly. use top and bottom. can be printed quickly and light. it isn’t attached to the printer.
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OK. I’m not finding that on the drawing (95mm doesn’t seem to be a measurement to the 2020 or the angle bracket). There is also the electronics on the bottom. Should that be 95mm from the rear of the 2020, the front of the 2020, or the front of the angle brackets?
Unless I’m missing it, I don’t see the part fan on the BOM either. It looks like it will accept a 40mm fan, but you’ve also drawn a 30mm fan adaptor? What does the chef recommend?
I’m almost done printing the bottom right z. This has warped a little and pulled the spring steel sheet up in the lower left corner. The bottom left Z just barely fits, wish me luck! I will be making the Z middles on the CNC. Should be an interesting aesthetic. They won’t fit on my existing printer.
The cross bar spacers are soo close. If I remove my bltouch I can fit them, but I can’t print them on this bed without the bltouch. I am considering just skipping them until I can print them on the gridbot. Printers should be able to take care of themselves, right?