Welcome to the SeeMeCNC Community

I've got two hobbed rollers, and one felt a bit rough on my fingertips, so I zoomed in to take a look... The simplest things look so much cooler up close.

[img]http://i.imgur.com/POjM8bg.png[/img] [img]http://i.imgur.com/2usgJIC.png[/img]



You can see that the first one was cut a little deeper and has more "bur" to it, so it feels rough and is packed with plastic grindings.
The second one has the same recesses from the tapping/cutting process but smaller, and it's a lot cleaner (and also doesn't have plastic crud in it yet since it's new).

That's a pretty rough cut! Was that done with stone knives?

Looks like others have processes that yield cleaner results. http://store.makerstoolworks.com/extrud ... -8mm-bore/

Not apples to apples with Brass, though.

[img]http://cdn1.bigcommerce.com/server3200/ ... 0.1280.jpg[/img]

interesting
the rough cut grooves probably are not good for reliable consistent feeding.

I have one of the Makers Tool Works hob rollers, it is beautifully machined with clean deep consistent grooves. I have not tried it yet, but now you have inspired me to get it installed !!
The SeeMeCNC roller on my NEMESIS printer is having issues feeding PLA, hopeful this hob will work better.

The brass should not be a issue, some alloys of brass I have machined are surprisingly hard. I think brass could be better than steel for these.

I'd like to try one of these too. Just today my ezstruder started skipping again. It hasnt done that in months. What size do we need...8mm or 5mm.

heathenx wrote:I'd like to try one of these too. Just today my ezstruder started skipping again. It hasnt done that in months. What size do we need...8mm or 5mm.

5mm for ezStruder direct drive.
8mm if you have a geared stepper motor.

I'm not an expert on hobbing stuff, but I think this is a manufacturing defect caused by one or two things;

1) Low quality cutting tools. If they are hobbed with a tap, the tap should be PVD or CVD coated for smoother cuts.

2) Wrong alloy. If it's stainless steel, it should be either 303 or 17-4 pre-hard, DEFINITELY NOT 316 or 304. Brass should be 360, aluminum should be 7075 or 7068.

That kind of rough, ripped looking cut is probably from using a soft metal.

Thanks, Brian. I ordered the 5mm.

Generic Default wrote:I'm not an expert on hobbing stuff, but I think this is a manufacturing defect caused by one or two things;

1) Low quality cutting tools. If they are hobbed with a tap, the tap should be PVD or CVD coated for smoother cuts.

2) Wrong alloy. If it's stainless steel, it should be either 303 or 17-4 pre-hard, DEFINITELY NOT 316 or 304. Brass should be 360, aluminum should be 7075 or 7068.

That kind of rough, ripped looking cut is probably from using a soft metal.

I'd assume that the SeeMe guys cut these on their Mazak... Might be with a tap, I'm not sure. Maybe one of the guys will chime in.

HOW WE MAKE! a knurled drive roller: http://youtu.be/S432wz9C76w

Seems awfully slow for that machine.

Generic Default wrote:1) Low quality cutting tools. If they are hobbed with a tap, the tap should be PVD or CVD coated for smoother cuts.

2) Wrong alloy. If it's stainless steel, it should be either 303 or 17-4 pre-hard, DEFINITELY NOT 316 or 304. Brass should be 360, aluminum should be 7075 or 7068.

I'm going to look you up the next time I need a lot of abbreviations and numbers.

heathenx wrote:HOW WE MAKE! a knurled drive roller: http://youtu.be/S432wz9C76w

I wonder if they've changed their process since then. That video is of them making parts for the old Steve's extruder.

I am pretty sure they still cut teeth with a tap.
Jim, looks like you got a pretty rough one... their tool could have been getting dull, or they are just getting in a hurry.

So...I received and installed my new brass makerstoolworks hobbed gear. It's quite nicely cut. Unfortunately, it doesn't feed my filament. It just churns and eats away at it. It's too late in the day to figure out what's different with this brass one but I suspect it's either deeper cut or maybe the channel is too wide. Just a guess. For now I removed it and stuck the stock one back on. Perhaps next week I can figure out the differences between the two.

I got to take a picture of Brian's hobbed roller, and they're as nice in person as the website makes them look.

[img]http://i.imgur.com/sAhzNIF.png[/img]


That's unfortunate that you didn't have a good go with it. Does it seem like it doesn't have the same amount of "tooth", or is it not getting enough purchase for some other reason (spring tension, maybe?).

Im not quite sure what's wrong. Im almost thinking that the groove is too deep or something and maybe the bearing doesnt have enough pressure on the filament...idk, just a hunch. Ill have to save it for Monday.

My gear looks exactly like your photo. Its made very well.