better hobbed bolt

Just make sure you trim off all the excess bolt end. Looks matter. I have a 15mm one but reversing the 29mm one really sounds like a good idea. Remember to secure the bolt head in the gear recess with something like red Locktite on the sides of the bolt head. All the nuts I have found have back and forth play in the gear recess. I definitely had delayed retract/extrude cycles before I did that (to the nylocknut in my case.) I never had problems with the nylocknut tightening. It might be due to a rougher finish on my bolt.

 

My nut will be hard to extract from the gear as its a press fit, I used soda can aluminum to shim it in evenly on all sides.

I'll do the same for the head of the bolt, or print a new gear that's a friction fit.

 

I think the fact that the nut is so well bonded and aligned in the gear is part of the problem, the torque of the motor drive is super-direct, plus i do a lot of honeycomb infill on complex organic shapes with difficult perimeters.
I'm on the 'ragged-edge'. Once the gear is driving the head of the bolt, that will be one more green tick on my list.

 

It's in the mail, I'll post a few pics of how that particular hobbed bolt works out regarding spacing etc when i get it.
I should also get around to posting the stl file of my modified wades hinge. It's made a big help in guiding the 1.75mm filament into the bolt area 'vertically' the filament doesn't wave around sideways right in the hob like the 'stocker'
.

 

That looks great Peter. I always have to take the screws off because I cant find the hole to feed it through, is it up yet? Egar to try it

 

Hi Guys, here's the modded wades hinge with guides for 175 filament.
I really think it makes at least a little difference in the hob area as it prevents the filament from levering sideways in the hob during X travel.
The part needs to be printed on its 'back', ie, with the 'guide slot' up in the air.
No warranties expressed or implied, proceed at your own risk.
ABS would be best as PLA is so hard and inflexible that i had a little trouble getting the bearing axle to 'pop' in, but it did, mine's PLA.

Other hinge mods,
M4x50 hex stainless bolts go pretty nice. Especially with the 3D printed thumb screw head. Use a nut to hold the bolt in the plastic head though.
The springs are 1/4" x 1/2" x 0.038" (0.9mm wire) and work great, lots of pressure, I usually wind them in till the bolts stop behind the nuts then undo them 1-1.5 revs as 'fully home' is a little too much compression.

 

Oh, and forum mods, please consider allowing the native rotation of attached images, they keep rotating on me to weird positions when i upload them, or is it just me doing something wrong with my jpgs?

 

Peter, you should modify it to add a thumb tab like this:



With the thumb tab and bolt caps from thingiverse I can easily squeeze the guide open with one hand while feeding with the other. I never need to take the screws off. I just loosen them a few turns. I also don't get a sore thumb anymore.

I also beefed up the guide a bit but it looks like you already did that.

 

I used these bolt caps: http://www.thingiverse.com/thing:194184

 

Steve, when you use the thumb tab, do you use your hooked index/middle finger on the tab and your thumb on the bolt heads in a pinch grip to compress the springs? if it's convenient, please post a pic of how you grip it in operation. As long as the vertical rods aren't being yanked on it sounds like a cool idea to include so I'll probably mod it to include it.

I think I like undoing the screws personally (since they are so much easier now anyway with the thumb screws) as the opportunity to inspect the hobbed bolt for plastic shavings and a quick squirt or canned air duster to clean is something I regularly do when changing filament or even just between prints, especially if the prints are long, infact, if the print is going to take more than 2hrs i think a hobbed bolt inspection is almost mandatory, but then i've had alot of problems with the stock bolt and my new one is still on its way.

 

Thumb on the tab, hooked index side on the bolt heads and pinch. Probably could pinch it the other way but I am right handed and the right side of the printer is accessible. I check it every few spool changes but I have had no plastic shavings since I replaced the hobbed bolt and added a bunch of washers to the springs. My old (November delivery) stock one was really bad. The hobb grooves were angled backwards! I had good retraction but very bad extrusion.

 

Printed mine out just then with colorfabb xt.

 

Same, if the stock hob teeth were the correct way around, there would probably be no complaints about feed grinding.

I just realized that I've been using my robo essentially 'sideways' so i could access the front and back with equal ease, so yeah, i get the thumb side now! haha .
It would probably be nice to mod the carriage so that the feed side was facing the front, but i'm pretty sure things will be in the way.

 

I found that a little squirt bottle of hairspray works alot better than the scotch blue edge hold tape for me, PLA printing with no heated bed at all.
Might be worth a try.

 

Thanks for the tip, I used the tape plus hairspray with this print (didnt want to waste the tape from the previous print). Because my heated bed clip burnt I am printing on a cold bed, when I fix the problem I will probably print straight onto the heated bed.

 

Darkhunter, My guide is printed in ABS. It looks good in XT. I have not tried my spool yet. Is the XT a lot more flexible than ABS? My son and I had trouble with a model rocket base in PLA where the fins shattered on a bad landing when the parachute got stuck. We'll try the XT next.

Hint on posting photos - select "insert thumbnails" works great to insert expandable thumbnails.

 

Thanks for the tip Steve. XT is an amazing material and I find it very easy to print in, easier than ABS! XT is very strong, I havent done much printing in ABS so I will not be able to give you such a greatly accurate answer but what I do think is that they flex about the same, its just that XT is stronger and more wearable.
I think you should definitly try XT for that base.
If your looking for flexibility and strength in one awesome material, I would recccommend Nylon Bridge as well. Just a bit of PVA and there is no warpage what so ever. I really do love printing in both xt and nylon

 

Thanks guys, I'll try XT for the base next and post the results in the projects area. The rocket is really pretty neat, http://www.thingiverse.com/thing:8754. We designed one segment to hold a small ClipHD video camera and another to hold a 10 DOF IMU and a Teensy Arduino for logging altitude. We have a good video of the parachute failure so far.

 

Sounds good, make sure you do post it on the projects thread, I would love to see the final product!