better hobbed bolt

Mine is a combination of both. Its does have a recess but its as wide as the one on the top.

Perhaps my bolt was badly cut, because it slips every complete turn by 2-3 teeth.

 

can you visually confirm it skipping ? try looking at it while manually extruding without filament
maybe there is something you're missing

I'm out of solutions, i solved mine by cleaning out the hot end as it was partially clogged. it couldn't push the filament through fast enough so it grind ed through it

 

I can visual and by hand.
Every full turn it skips at same spot. I have to clean same threads everytime. Cleaning doesnot help, it starts to shave the very next turn.
Nothing helped but more tension.

I have only 1 explanation. It must be warped.

 

Got my bolt swapped in and it is working better. I used a dremel to cut off the extra length so it didn't hinder x-movement towards home and get in the way of the hotend cable plugs. Works great!

 

Got my bolt swapped in and it is working better. I used a dremel to cut off the extra length so it didn't hinder x-movement towards home and get in the way of the hotend cable plugs. Works great!

 

I need my hubbed bolt replaced. Cant find anything on ebay, all of them are hubbed too far away from the bolt head.
I got around 12.5mm from the head to the cuts. I can cut the bolt if its too long but i cant find the right one :
I tried contacting ROBO support many times asking to buy another bolt but no one replied in MONTHS !

Here is my bolt.

 

did you see this post?
http://forums.robo3dprinter.com/index.php?threads/better-hobbed-bolt.846/#post-3934
if you get this one you have to turn the bolt the other way around for the hobb to line up as stated in the post.

scroll down to #12
newest link http://www.ebay.com/itm/Hobbed-Bolt...739?pt=LH_DefaultDomain_0&hash=item2a3ba2d5cb

 

I'm have some similar issues with slippage and grinding, it's making me paranoid to leave 2 hr prints alone as i have saved a few from being wasted by catching the slip when it happens and then pausing the print to fix the hob-grip. I think it's exacerbated by the cheap pla i have being extremely hard, so the stock robo3dr1 wade extruder and hobbed bolt aren't up to it.

I believe the bolt and extruder on the robo are a re-purposed 3mm filament design. the filament guide slot is way too big, and on my larger prints you can see the filament leaning either way back and forth in this slot all the time. This can't help the already handicapped 'flat' hobbed bolt.

Ive seen some parts designed to better guide the thin 1.75mm filament parrallel into the extruder, so i'm going to try a combination of something like it, with the addition of a diy hobbed bolt to solve the problem.
If it's good I'll share results.

 

i fixed my problem with better filament, the one i was using was 1.6 or 1.4 which was why it wasn't holding it properly

 

Haha, thats probably true, but i can buy an 8mm bolt today and i 'have the technolgy' to 'hob' it tomorrow at work.
This will cost me $5 to have 4 goes at it.
Although, my print bed has cracked so i'm out of commision until the new smooth rod upgrade kit arrives anyway which I have asked jerry about but havent ordered yet, i think i'll be waiting a while....

 

Ok, an update on this, the handmade hobbed bolt worked, but no better than the stock one in my case.

If I could be bothered using the mill at work I could probably do a better job, but the stock robo hobbed bolt should work fine if it is installed the right way.

I'm also finding that aggressive retraction is tightening the nut in the gear wheel on the hobbed bolt to the point that the gear stalls the stepper. Honestly, driving a bolt by a nut on it's arse end is truly, truly.. insert appropriate words.

Tesseract said he reversed his, I'm going to do the same before I lose it bigtime.

Why?
If you have a close look at the stock hobbed bolt, the 'teeth' are indeed 'directional', they are cut using an offset end mill bit with an indexing head and if you look at the side profile of the teeth, just like a shark, the teeth are angled a certain way to provide higher grip in one rotational direction.
Guess which way.
You bet, the opposite way to the stock robo assembly.

Reversing the hobbed bolt will achieve two things.

1. The teeth will grip filament as intended, most probably better.
2. The bolt will never again self-loosen or tighten.

Gargh!

 

ok, so that wont work obviously. Just tried, no spacers or washers are going to get the stock robo bolt reversed.

I need to buy a hobbed bolt with the hob further out so that it can go in in the reversed direction.

Tesseract, could you please advise what hobbed bolt you used to get the head inside the gear?

 

Tesseract used the same one I posted earlier.. if you search on ebay there are a bunch listed. So long as you follow the instructions at the beginning of this thread..

here is another that will work..
the seller even states it is for the robo3d hobbed bolt upgrade...http://www.ebay.com/itm/Robo-3D-Hob...179?pt=LH_DefaultDomain_0&hash=item338e8882eb

 

I tried a bolt with the hob at 25mm but it was 1-2mm too short. 27 or 28 should be right though you will probably need a washer or 2 at the gear end.

 

Despite the pic, this one is hobbed at 15mm so it is a direct replacement of the Robo3d and will require the nut to be in the gear.

 

http://www.ebay.com/itm/16128533581...49&var=460322489724&ssPageName=STRK:MEBIDX:IT

This looks like a good one, comes in 23,26,29mm hob position and the hob cutting looks very nice.
I think I'll try the 29mm one.