Oddness with recent MBI pinch gears

[Dan Newman]

Latest MBI pinch gears are from a new supplier and may have slightly
different geometry. I have some old ones and I measured the diameter
at their troughs around 10.53 - 10.56 mm. Not unreasonable as RepG's
Print-o-Matic used to use a default of 10.58 mm and MBI's online store
used to state 10.56 mm. (RepG 32 or so removed the gear diameter from
Print-o-Matic's menus.)

On 1 Oct 2014, I ordered 5 new pinch gears from MBI. Imagine my surprise
when they hadn't shipped by 1 Dec 2014. When I poked MBI, they went out
the next day with a comment of "let us know if the set screws are missing;
our new supplier seems to have not included them with some of the gears".
Note that phrase "new supplier".

The ones I received appear to have a diameter at the trough of 10.63 - 10.65 mm.
And sure enough, I'm having to use a different extrusion multiplier with them.

But now for the odd thing. Larger diameter and thus you might think I'd be
overextruding using my normal PLA extrusion multiplier of 0.90. (Larger
diameter means larger circumfrence means more linear length of filament fed
per revolution.) Nope, I was underextruding and needed to bump the extrusion
multiplier up, not down: somewhere between 0.92 - 0.93 seems optimal. So,
the gear may be biting in deeper; a lot deeper.

BUT, I'm also for the first time having to use an "extra restart distance"
on retractions. So, it may be biting in deeper and, after retracting, not
quite gripping as well when it restarts the feeding process?

I've seen this on the two extruders I've built so far with these new pinch
gears. And, to eliminate other variables, I pulled just the motor + pinch gear
out one of the new printers and put it in an old printer: same slight underextrusion
and retraction restart issue (using the same spool of filament). Old motor and
old pinch gear in one of the new printers, no issue whatsoever. I doubt the
motor is at fault; seems to be the new pinch gear is different.

Anyhow, just a heads up. I need to run some filament in and back out of one
of the old gears and compare to the new. However, I don't have any decent
macro lenses for taking good pictures. May need to borrow someone's microscope
-- they all have nice USB cameras these days.

As an aside, I notice that the MBI store is no longer selling their "old" stepper
motors. Temporary? Permanent? Perhaps winding down production of the Rep 2X?

Dan

[Dan Newman]

> But now for the odd thing. Larger diameter and thus you might think I'd be
> overextruding using my normal PLA extrusion multiplier of 0.90. (Larger
> diameter means larger circumfrence means more linear length of filament fed
> per revolution.) Nope, I was underextruding and needed to bump the extrusion
> multiplier up, not down: somewhere between 0.92 - 0.93 seems optimal. So,
> the gear may be biting in deeper; a lot deeper.

As an aside a couple of months back, someone posted that they had a new pinch
gear from MBI and they found that its bite wore down quickly. (And someone
a few months before that made the same comment, but it wasn't clear how new
or old theirs was.) So, if the new supplier is making the "teeth" thinner,
they might bite more deeply and wear down faster. We'll see.

My main point is to give folks replacing their pinch gears a heads up.

Dan

[Ryan Carlyle]

I just ordered 6 a couple weeks ago. To my shock, they came promptly and with set screws. I can confirm 10.65mm tooth OD on the fresh one I just grabbed.

I also grabbed an "old" one that was assembled in a backup extruder but never used, which I ordered some time around March or April 2014. Also 10.65mm. 

Some microscope shots of the gears attached. Brand new gear:

Cut profile might be slightly asymmetrical? Hard to tell.

"Old but not as old as Dan's" gear profile:

The cuts look a little rougher to me on the old one. 

[Dan Newman]

On 19/01/2015 7:54 PM, Ryan Carlyle wrote:
> I just ordered 6 a couple weeks ago. To my shock, they came promptly and
> with set screws. I can confirm 10.65mm tooth OD on the fresh one I just
> grabbed.

My "old" ones date back to 2012 and some likely back to 2011 and 2010. I had
a bag and I'd buy a couple now and then and then use them. Wasn't
until I completely ran out in Fall 2014 that I had to buy some more.
(At some point in 2013 or 2014 MBI accidentally sent me several, but
I believe I gave those all away without ever using them myself; you may
have been the recipient of one of those.)

> "Old but not as old as Dan's" gear profile:
>

> <https://lh6.googleusercontent.com/-RGz68KaEIIc/VL3RATJnrGI/AAAAAAAABEU/CLboYY4w7kE/s1600/1.jpg>
>
> <https://lh3.googleusercontent.com/-7FhQFBDd8a0/VL3RE1rGGxI/AAAAAAAABEc/YndiF1HxZhI/s1600/2.jpg>
>
> <https://lh4.googleusercontent.com/-uFsLQVHD18I/VL3RG-ALu1I/AAAAAAAABEk/nA2b2VlxxqY/s1600/3.jpg>
>
> <https://lh3.googleusercontent.com/-QnDCeguJR7U/VL3RIa1w3AI/AAAAAAAABEs/jwvyDg0O-XI/s1600/4.jpg>

>
> The cuts look a little rougher to me on the old one.

Yes, they look a little rougher. Might not cut as deep into the filament?

BTW, I did some looking at eBay: plenty of "Makerbot Mk8 drive gears". But they all seem
to have a 7mm deep trough with claims of a deeper groove for better drive "power".

Dan

[Dan Newman]

And look at the radius of the cuts on the new vs. the old. The old looks to either be a larger radius OR if
it's the same, then it flattens out as you descend the walls of the trough.

Dan

[Jetguy]

Ryan,

Thanks for those nice pictures. My thoughts are that the old gear were made via a knurling process- not entirely unlike forging the metal. A very, very hard steel (probably carbon tool steel) roller is pressed into the rotating stainless gear hub to produce the teeth. The pressure is increased until the roller cannot "bite" any more and forms the teeth. The advantage of this process is that it work hardens the teeth in the process- nearly as good as if you had case hardened the gear.

That means the teeth are highly wear resistant but also very, very ,very strong.

The new method looks like typical hobbing, meaning a rotary cutter turns and cuts the teeth as the hub rotates 90 degrees to the cutter. The same basic concept the guys use in the Reprap crowd with a tap that rotates and cuts the teeth.

But that ONLY works on soft base metal and I've said since I started this hobby, the knurled type was superior in wear and overall "bite" compared to any hobbed cut gear. The reason is tooth strength. The soft base metal is never hardened and just leaves a soft tooth that can either be bent or worse, just flat out wear down dull over time.

I read a tool and die maker and they say the opposite, that cut is stronger but I think what is not being said is choice of base metal. In other words, I think a work hardened hob is stronger than a number 5 grade soft bolt being hobbed.

If we work up to real tool steel, then the answer might well change. You could also really try a true case hardening process.

[Derry]

Wonder if they are using same supplier as Flashforge.

Some Flashforge guys recently complained that the gear shipped with out the grub screw. Beyond that no photos to compare.

Ultimately all the parts could be coming out of a few China supplier and just rebrand accordingly

[Ryan Carlyle]

No, FF's drive gears are a totally different style. They use a flat tooth profile and a grooved idler bearing.

[Ryan Carlyle]

Just for fun, here's a comparison piece. It's a "cut and hardened" drive gear from www.tridprinting.com:

[Ryan Carlyle]

And here's an ABSOLUTELY TERRIBLE gear I ordered off, I don't remember, ebay or something. That's right, the teeth are full of metal swarf of the perfect size to partially clog nozzles. 

[Ryan Carlyle]

Stock R2x gear (came on my Feb 2014 model) with about 300-400 hours on it. Notice white ABS debris from the failed print that made me stop using the stock Superstruder. 10.65mm OD.

[adam paul]

I just picked up some of those hardened Mk7's.  They do look super nice, too bad they don't fit in the 3in1's.  With the groove centered, I cant get an allen wrench behind it to release the bearing pressure.  Shouldn't be a problem to grind down the back?

[Jetguy]

Try not to heat up the gear in any cutting process you use but sure, you can change that no problem

[Ryan Carlyle]

What do you mean get an allen wrench behind it? I can't really visualize it, but surely the gear doesn't block the filament release hole?

[adam paul]

That is exactly what I mean. The remainder, after the set screw. I will take some pics

[adam paul]

I can get a 1.27mm allen behind the gear to release the filament tension,  the photo is a 2mm allen, but the 1.5 will not get behind it.  This is with the groove slightly off center.

[adam paul]

some wonkyness attaching the two gears stacked

[Ryan Carlyle]

Yeah, look at that.

I guess you could unscrew the spring set screw to release the filament, but that sucks.

[adam paul]

Looks like I need to shave off about .75mm

[Jetguy]

You can push in the plunger idler through the hole on the other side if you are not using this in a dual extruder situation. 

I cannot use the wire method because when I use a geared extruder motor or a MK6 motor for 3mm filament, the shaft is 8 or 6mm and thus interferes with the same path (just a different way)

Again, there is an alternate release by pushing in through the hole and hitting the Delrin cam on the other side.

[TobyCWood]

Interesting how all the Amazon suppliers have none available.

[DHeadrick]

I bought a hobbed gear back in Feb 2014 from here:
http://store.quintessentialuniversalbuildingdevice.com/product.php?id_product=142

I found the same problem you are, that it was closer to the motor when installed.  I sent them this email and they never responded:

"Paula,

I received the drive gear (thank you), and I had some feedback to give:

Your website states that the MK7 *Stainless* Filament Drive Gear is "identical to the drive gear that is used on Makerbot printers".  I measured the part I received from you and the overall length is 0.50" where my Makerbot Replicator 2 gear is 0.43" long.  Are all of your stainless gears 0.07" longer than the parts they replace?

If all your replacement gears are all this longer size, you may want to consider shortening it so that your buyer base will not have issues if they choose to use your replacement parts.

Just FYI"

I guess their marketing is correct now.

[adam paul]

Can an oversize drive gear cause any damage to the cam?

[Dan Newman]

On 27/01/2015 8:15 AM, DHeadrick wrote:
> I bought a hobbed gear back in Feb 2014 from here:
> http://store.quintessentialuniversalbuildingdevice.com/product.php?id_product=142
>
> I found the same problem you are, that it was closer to the motor when
> installed. I sent them this email and they never responded:

They don't answer e-mail and they don't answer their phone. (And one
of the benefits they got from changing their name was the BBB
complaints filed against QU-BD aren't easily correlated against their
new company name.)

I know of several cases where they people ordered 24V heater cores
and received 12V heater cores. Nice safety problem there. In at
least two of the cases, the people gave up getting them to respond
and send them correct units or refund their money. In the third
case, I don't know if the person tried to contact them or not.

And they're not terribly loved in some circles for doing
knockoffs of other people's extruder designs. (Complaint being
that they are inferior. I've only seen the Mk7 knockoff which
was unusable. Came with a thermistor instead of a thermocouple.
Nozzles were so poorly machined that they had to be thrown out.
Drive block needed rework.)

Basically, if you have to do business with them, purchase via Amazon
which they sell through. That way, you have Amazon on your side if
there's a problem.

Dan

[Jetguy]

"Can an oversize drive gear cause any damage to the cam?"

I'm going to say no within reason and hear's the proof- I run 3mm filament in one designed for 1.75mm.

In other words, not only am I not using a genuine MakerBot drive gear on the 8mm geared extruder motor, but I'm also running thicker filament meaning that it's effectively that much larger a diameter.

So yes, I think there is a ton of compliance and thus should not be an issue.

[DHeadrick]

You are right... there is no problem for the function of the assembly.  However, the larger depth dimension does inhibit the ability to release the bearing pressure in the planned way.  It may also not fit well with the printed guides used to support flexible filaments.

[Dan Newman]

On 27/01/2015 2:25 PM, DHeadrick wrote:
> You are right... there is no problem for the function of the assembly.
> However, the larger depth dimension does inhibit the ability to release the
> bearing pressure in the planned way. It may also not fit well with the
> printed guides used to support flexible filaments.

I just received a couple of these "Hardened Hobbed Gear MK7" from
TriDPrinting.com.

First of, they are nicely made. But, they are not MK7 pinch gears:

1. They are too tall (length along motor shaft axis). An Mk7 pinch gear is only
11.0 mm tall. These are 13.1 mm tall (well, 13.08 mm. And yes, I checked that
my caliper jaws were clean as well as the faces of the pinch gear). My genuine
MBI pinch gears are 11.0 mm tall. I also looked at the Mk7 SolidWorks file,
MP1704-MK7-Drive-Gear.SLDPRT, from the Mk7 Thing at thingiverse.com: 11.0 mm.

2. The hobbed trough has diameter of about 11.5 mm instead of the 10.5 - 10.6
discussed earlier in this thread. Now, it may cut deeper into the filament
making the effective turning diameter smaller. But that would be a lot of
bite to do that.

Owing to 1 above, you cannot use these pinch gears on a Thing-o-Matic, Replicator 1,
or a Replicator 2. If you mount it flush against the motor face, you end up with
the trough centered about 3mm too far away from the motor face for the standard
ToM, Rep 1, Rep 2 motor setup. You would need to space the motor back 3mm.
Interestingly enough, that's the standard Replicator 2X setup. In short, these
pinch gears were designed with the Replicator 2X as the target. If you try to
use them on those other printers I mentioned, then you will need to make a spacer
to move the motor back 3.0 mm. While the 3-in-1 extruder is set back 3.0 mm
and uses a spacer for bots other than the Rep 2X, there's also the report
that the pinch gear interferes with the filament release.

Dan

P.S. Attached photo shows a TriDPrinting.com pinch gear (upper) and a genuine
MakerBot pinch gear (lower).

[Ryan Carlyle]

Dan, it's definitely not designed for any Makerbots. TriDPrinting is a Delta / RepRap parts supply site. 

We could probably ask Daniel if he'll shorten them up on the next production run though. 

[Dan Newman]

On 28/01/2015 3:25 PM, Ryan Carlyle wrote:
> Dan, it's definitely not designed for any Makerbots. TriDPrinting is a
> Delta / RepRap parts supply site.

Perhaps they then should list the part as having a 11mm length?

http://www.tridprinting.com/Mechanical-Parts/#3D-Printer-Hobbed-Drive-Gear

And I guess they shouldn't have edited the RepRap drive gear wiki page and
put a length of 11 mm on it either,

http://reprap.org/wiki/Drive-gear

Change history indicates it was "TriDPrinting.com" that made that edit....

Dan

[Dan Newman]

On 28/01/2015 3:58 PM, Dan Newman wrote:
> On 28/01/2015 3:25 PM, Ryan Carlyle wrote:
>> Dan, it's definitely not designed for any Makerbots. TriDPrinting is a
>> Delta / RepRap parts supply site.
>
> Perhaps they then should list the part as having a 11mm length?
>
> http://www.tridprinting.com/Mechanical-Parts/#3D-Printer-Hobbed-Drive-Gear

I meant to write they should NOT list the part as having a 11mm length....
I now have several based upon that 11mm dimension. I'll keep one and see
about returning the others as I simply don't do Rep 2X style offsets.

Dan

[dan...@puptv.com]

Hi

I'm Daniel with TriDPrinting.com, and yes, we made a mistake with our dimensions on the MK7 drive gear. We will have it fixed shortly. (It's already fixed on reprap. We may be able to make a run of smaller gears in a few months. Regardless, we will be happy to give anyone a full refund and apologize for any inconvenience.

Mistakes aside, we are very excited about releasing the new TriDPrinting.com Flying SkyDelta into the public domain. It is an amazingly low cost string based printer. Yes, the print head is only supported by 3 sets of 2 strings coming from 3 winches mounted on the ceiling.

Daniel - http://www.TriDPrinting.com/

[Ryan Carlyle]

To my mind, this is a big flaw with community names like "mk7"... Mark 7 what? In which series? Within which fork? To whose drawings?

Posting some sort of engineering drawing along with the part is probaby the right way to go for supporting customers, but there's a very fine line between that and giving cloners the keys to the kingdom.

[Bonekollector]

So - is the best option for a current in-progress CXY build still an MBI sourced gear & just expect to have to tweak settings? I do have a 3 in 1 upgrade on the shelf for the next build.

[Dan Newman]

Yes, I think so.

Dan

[tramalot]

 turn it down? And re-drill it

[Dan Newman]

On 28/01/2015 5:38 PM, dan...@puptv.com wrote:
> Hi
>
> I'm Daniel with TriDPrinting.com, and yes, we made a mistake with our
> dimensions on the MK7 drive gear. We will have it fixed shortly. (It's
> already fixed on reprap. We may be able to make a run of smaller gears in a
> few months. Regardless, we will be happy to give anyone a full refund and
> apologize for any inconvenience.

Daniel,

Thanks much for the prompt handling. (I returned my gears to TriDprinting.com
but will be very interested should they have some which are 11mm long as the
13mm ones were very nicely made. Superior to what is currently available
from MakerBot or any of the Asian suppliers.)

Dan

[adam paul]

+1 to both


 Hopefully today the weather will clear up a little for our postman.  None of that rain, sleet, snow mantra here in Brooklyn, and I will get  my returns picked up.

I would also like to see an hardened great made to mbi's mk7 dimensions, both in length and groove diameter.  The parts I did receive were very nice.

On an aside, I think there's a market for quality rep 1/2/dual parts.  Specifically the hot end.  Stepped thermal barrier, nozzles, TC,6.3mm heaters and such.  People on these fora are always asking where to get parts and the answer in invariably China.

[Ryan Carlyle]

P3D, Fargo3D, Bilby, and Carl sell SOME of the Rep1/2 parts, or decent versions thereof.

[Dan Newman]

On 04/02/2015 4:32 AM, adam paul wrote:
> +1 to both
>
>

> Hopefully today the weather will clear up a little for our postman. None of that rain, sleet, snow mantra here in Brooklyn, and I will my returns picked up.

>
> I would also like to see an hardened great made to mbi's mk7 dimensions, both in length and groove diameter. The parts I did receive were very nice.
>
> On an aside, I think there's a market for quality rep 1/2/dual parts. Specifically the hot end. Stepped thermal barrier, nozzles, TC,6.3mm heaters and such.
> People on these fora are always asking where to get parts and the answer in invariably China.

As an aside, the heater block I'm currently fond of is the E3Dv6 heater block. However,
it requires a 6.0mm OD heater cartridge rather then the more normal (for MakerBots) 6.3mm (0.25 inches).
Plenty of eBay sellers sell heater cartridges but don't tell you the OD. Filastruder, the US
reseller of the E3Dv6, does carry the correct diameter, 24V heater cartridges for the E3Dv6
heater block.

But, since the E3Dv6 heater block is a bit thicker, you end up needing to use their nozzle which has
a longer threaded section. If you use a more typical MakerBot nozzle, then you have the thread
the thermal tube farther into the block, ending up with the thermal break partway into the block.

But with a thermowell mounted thermocouple, the proper thermal barrier tube (Carl Raffle's), and
a appropriately thick aluminum heat spreader bar, things just work for me including on some of
my troublesome test objects which I print at 120mm/s, no slow downs of any sort, only a couple
of seconds per layer, with sections that have lots of retractions and short runs, and absolutely
require a print cooling fan.

But yes, I'd love to have a single source. My one bottle neck is that Carl Raffle is the only
person outside of MBI support selling a properly constructed thermal barrier tube with the
step change in the inside diameter and good inside diameters for 1.75mm filament. (Sounds like
Fargo 3D may be updating their thermal barrier tubes to do this? I'm hopeful.)

Dan

[Carl]

Me too! :-)

[dnewman]

Perhaps in your copious free time you'll start selling heater blocks, nozzles, and single (as well as dual) extruder heat spreader bars (with a variety of carriage mounting options)?  Would be nice.

[adam paul]

I too am waiting on that infamous swiss bottleneck, for another set of stepped barriers for my CoreXY.  I would also like to see an assortment of new parts.  In particular, a single extruder width, aluminum cooling bar, threaded for both left and right side.  

Why did Dan and Carl's reply come to my email?

[Carl]

It would be even nicer if there was a single 'Gold Standard' for all of the above... There are currently so many version of practically the same thing... 

I do have my hands rather full at the moment... But hopefully I will be able to offer a few well designed parts in the 'relatively' not too distant future! :-)

[Dan Newman]

Because this group is configured such that if you read it via e-mail,
then the the mail appears as though from your e-mail address. That
is, the RFC822 From: header line has you're e-mail address as the field
value. And it has no Reply-To: header line. So, if one Replies, the
reply is (generally) directed to the From: and To: addresses. I try
to remember to remove the individual's address from my reply before
sending, but sometimes forget to.

Dan

[Ryan Carlyle]

Carl, you ever consider hiring a minion?

[adam paul]

"It would be even nicer if there was a single 'Gold Standard' for all of the above..."  

I think that's you.

[Carl]

Carl, you ever consider hiring a minion?

Minions seem to be in short supply... as would be the funds to pay them! :-)

[Carl]

"It would be even nicer if there was a single 'Gold Standard' for all of the above..."  

I think that's you.

Thanks! :-) 

[Ryan Carlyle]

No minions? Ok, how about children?  :-)

[Jake Clark]

Children are a great option, they usually work for Oreo cookies or candy. However, attention spans are very short, haha :)

[adam paul]

those tiny dexterous fingers move so fast though

[Jake Clark]

They are great for putting nozzles in little baggies

[adam paul]

or their noses