67 replies to this topic

[Cali-Nerfer]

Has anyone else finished theirs yet? I'm nearly done with mine, but the stock keeps breaking. As a community, we should try to brainstorm a way to reinforce the stock with a non-3D printed solution because I don't want anyone else to have the same problem when they go to build this thing. 

Crossbow.png

 

I used Devcon on the stock and that thing is rock solid.

[Nurf Doctor]

If this is a necro then I really do apologize. Looking through the file for the extended version, I found this piece

 

and I cannot find any mention of it in this thread. I found it in this spot in the blaster

 

and it appears to perhaps be a piece to keep the spring centered, but I'm not completely certain.

 

Again, apologies if this is a necro, but I'll be attempting to tackle this print soon and I'd rather not fuck up something that will have this much time into it.

[CaptainSlug]

You make that piece out of 1" SCH40 pipe. It keeps the spring from kinking enough to interfere with the notch in the plunger rod.

From: http://captainslug.com/durendal.html

[Nurf Doctor]

Ah, ok that does make sense. I guess if you were using a larger diameter spring then it wouldn't be as necessary, though I'm not sure if I would trust printed parts to stand up to something like my K34 pieces.

[CaptainSlug]

It's intended for a K25, but helps do the same thing with a K26 as well. Anything with a larger OD than a K25 won't need it.

 

Having it in place gets rid of the "crunchy" feeling you get during the priming stroke.

[Nurf Doctor]

My PETG print is coming along nicely. Little cleanup and it's basically perfect. Also got the internals from McMaster-Carr today, so I need to figure out a good way to get my aluminum tube cut down with a decently straight cut.

[Lucian]

The front end of [k26] +Bow length variant just shattered after ten shots. Just wanted to give fellow builders a heads-up. I do not have a plan for this issue. Hypothetically the front could be entirely printed in TPU (flexible filament)... that might absorb some of the shock. Could be interesting!  

[CaptainSlug]

There's an optional front plate I had included in the model that can be machined out of polycarbonate or aluminum that is intended to act as a load spreader. If it's not there for some reason you just need to print out a template based on the front of the printed end cap.

 

Edit: Alternatively I need to apply the lesson learned from the Caliburn project and add significantly thick buttress material around the ends of the part to stiffen it.

Edited by CaptainSlug, 11 June 2017 - 11:30 PM.

[CaptainSlug]

By request I added some through-holes in the stock assembly so that it can be reinforced with threaded rod.

 

https://www.thingive...m/thing:2721329

[stuck by stefan]

Have you considered trying to integrate some sort of polycarbonate frame inside the shell? In my opinion a purely 3D printed shell will never be able to hold up to the forces of priming and firing.

[TantumBull]

Have you considered trying to integrate some sort of polycarbonate frame inside the shell? In my opinion a purely 3D printed shell will never be able to hold up to the forces of priming and firing.

 

The post directly above yours addresses that issue.

 

Or did you read that and still think it would need an internal polycarb frame? If so, see caliburn.

 

I was similarly hesitant right after the machined caliburn was released. Meaker and others were developing a 3D printed variant, and I poo-poo'd on the idea for exactly your reasoning (lots of experience with 3DP and seeing shear and tension induced failure, never fully realized how good PLA is in compression with sufficient infill). Then I disappeared for 2 yrs in grad school. Now I come back to find that I was clearly proven wrong.

Edited by TantumBull, 19 January 2018 - 06:17 PM.

[stuck by stefan]

 

The post directly above yours addresses that issue.

 

Or did you read that and still think it would need an internal polycarb frame? If so, see caliburn.

 

I was similarly hesitant right after the machined caliburn was released. Meaker and others were developing a 3D printed variant, and I poo-poo'd on the idea for exactly your reasoning (lots of experience with 3DP and seeing shear and tension induced failure, never fully realized how good PLA is in compression with sufficient infill). Then I disappeared for 2 yrs in grad school. Now I come back to find that I was clearly proven wrong.

I actually didn't see slugs post before I posted mine, my bad. But I'd still have to see one of these printed and thoroughly tested before I believe in it's durability.

[Meaker VI]

I actually didn't see slugs post before I posted mine, my bad. But I'd still have to see one of these printed and thoroughly tested before I believe in it's durability.

Read through the comments; Lucian has one.

[stuck by stefan]

When your X axis belt skips 90% into the print   

Not that upset cause it came out crap, anyone have any theories on why my layers look so inconsistent / pushed out?

Edited by stuck by stefan, 02 February 2018 - 05:14 AM.

[Geric2004]

When your X axis belt skips 90% into the print   

Not that upset cause it came out crap, anyone have any theories on why my layers look so inconsistent / pushed out?

 

 

 

A guess would be stepper motor voltages. But would need to see your print settings first. Also, what's you're printer?

[Meaker VI]

Looks like overextrusion to me.

[stuck by stefan]

Do files exist for a normal (Non-extended) length stock that still has the through holes for threaded rods?

[CaptainSlug]

I have not gotten around to doing that yet.