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PP-MP0205 E3D Aero Steel Pinion Gear - Issue - Set Screw Hole Location
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Description

Specification Document Pathway:
/home/aleph/shared-j/devel/lulzbot/TAZ/accessories/yellowfin/production_parts/machined_parts/pinion/22_tooth_gear_revc.pdf

A shipment of PP-MP0205 E3D Aero Steel Pinion Gears from PO# 31773 has a dimensional issue regarding the location of the set screw hole. Of 100 units checked only 14 were spec-conforming with 84 having a set screw location above the maximum spec tolerance of 2.75mm. The highest set screw hole location measured on these was 3.18mm. The difference between these units is shown on Picture 1, with the non-conforming gear on the left and the conforming gear on the right(correction made).

Checking how this could interact with the delrin gear, which aligns with the tooth on the opposing side from where the set screw location is (see picture 2), it appears that the 4mm wide delrin gear when aligned parallel with the pinion gear is sufficiently far from the set screw hole on the non-conforming units that there shouldn't be an issue. The gears that have a hole position of 3.18 have hole edges that are 4.66mm from the opposing side, while the gear itself is only 4mm. That leaves .66mm of extra space separating the delrin gear from the set screw hole, with full teeth interlocking(see Picture 2). If this is an accurate description of the interaction of these two parts(feedback needed), then I would suggest that the upper tolerance on the set-screw location be increased from 2.75mm to 3.25mm to reflect the limits of manufacturability.

I'll work with @jperry to inform E3D of the issue. I'll be holding these 2000 units in QC pending feedback on my findings. If we do need to reject them, having an estimated 84% fallout rate would be cause for a batch rejection.

Picture 1

Picture 2

Event Timeline

AOJAS created this task.May 30 2019, 10:38 AM
AOJAS triaged this task as High priority.
west added a comment.May 30 2019, 10:43 AM

@AOJAS you are using an aero gear, those are 4mm thick. The yellowfin gear is 6mm thick

AOJAS updated the task description. (Show Details)May 30 2019, 10:43 AM
AOJAS updated the task description. (Show Details)
AOJAS updated the task description. (Show Details)May 30 2019, 12:26 PM
AOJAS added a comment.May 30 2019, 1:21 PM
In T7529#138033, @west wrote:

@AOJAS you are using an aero gear, those are 4mm thick. The yellowfin gear is 6mm thick

If that's the case, doesn't the gear overlap with the set screw area even if the set screw hole is in spec? It would overlap by .75mm to 1mm under current conditions.

AOJAS added a subscriber: Steven.EditedJun 6 2019, 9:02 AM

@Steven
The current plan with MER is to release 20 units to have built out and tested for issues.

A detail that wasn't mentioned earlier: The grub set screws that are currently shipped with these gears is the smaller type which seats fully recessed in the hole, so it doesn't have the issue of interaction with the gear teeth of the Delrin gear that we had in the past.

kent lowered the priority of this task from High to Normal.Jun 11 2019, 1:18 PM

This is e3d's drawing:

and here is a control chart of the set screw hole location with the LCL and UCL specified in the e3d drawing:

This is our drawing:

and this is the same dataset but with the LCL and UCL from our drawing:

I think we can use almost all of these if we separate the parts in the first peak from the parts in the second peak and then use the parts in the first peak for V3's and the parts in the second peak for Aeros.

@tutley @samantha do either of you know which drawing we should be inspecting these to? @jperry can we verify which drawing e3d is building these to?

@kent I believe it is Baldwin's drawing so that the interference between the tooth profile of the spur gear and the hole for the set screw in the pinion gear is minimal. this will help prevent broken spur gear teeth. Ideally there would be no interference between the hole and the spur gear teeth.

with the gears that are in Baldwins drawing, the center of the hole can be 2.75mm from the edge, meaning the edge of the hole would be at the 4.25mm mark, this would leave at most 1.25mm overlap with the 6mm thick spur gear (~1/5th the width of the gear)

with the gears from the aero, the center of the hole can be 3.2mm from the edge, meaning the edge of the hole would be at the 4.7mm mark, this would leave at most 1.7mm overlap with the 6mm thick spur gear (~1/3 the width of the gear)

AOJAS added a comment.Jun 24 2019, 8:41 AM

@jperry
Has the data that Kent created been communicated to E3D?

I'm not entirely sure what has and hasn't been communicated yet. I have contact E3D about this and requested a drawing. Sam from E3D provided their drawing which was passed along to the appropriate parties at Aleph. I haven't heard anything after that.

kent added a comment.Jul 2 2019, 10:44 AM

To avoid this issue in the future, I recommend creating a new part number for the V3 pinion gear using our drawing, https://devel.lulzbot.com/TAZ/accessories/yellowfin/production_parts/machined_parts/pinion/22_tooth_gear_revc.pdf

jperry added a comment.Jul 5 2019, 9:25 AM

I've created part PP-MP0282: E3D, V3 Aero Steel Pinion Gear w/ Set Screw. We will need to update AS-TH0055 BOM to have this part instead of the PP-MP0205.

AOJAS added a comment.Jul 8 2019, 9:52 AM

Just to clarify, of the units with holes closer to the edge, and the units with holes farther from the edge, which are going to be used for which assemblies?

What is the new part number being created for one of these assemblies?

jperry added a comment.Jul 8 2019, 9:59 AM

The new part PP-MP0282 is for the V3 version only

bowman added a comment.Jul 8 2019, 1:01 PM

@jperry @tutley Please start a change order for the BoM to be changed. Thanks

I created a change order under T8547

adam added a subscriber: adam.Jul 9 2019, 10:56 AM

Are we sure E3D can get this gear to us at the same or comparable cost to the aero pinion gear?

AOJAS added a comment.EditedJul 9 2019, 2:21 PM

An additional note on changing the specifications for this part is that we need them to come with the M3x3 grub screw preinstalled. We are having issues with shipments not having bags of the grub screws accompanying them, and even when they are shipped with the screws, that bag of screws has to be kept track of without existing in inventory. Just having them be preinstalled would solve the problem.
@tomc
@MichaelM
@jperry

AOJAS added a subscriber: tomc.Jul 9 2019, 2:21 PM
kent added a comment.Jul 15 2019, 9:55 AM

@adam They are capable of making it, since a good portion of the batch was made that way. I don't know if they will need to re-quote it or not. We will find out when we make our first RFQ with the new part number and drawing.

The alternatives are as I see it:

  1. Proceeding with buying pinion gears made to aero spec to use on the V3 and hoping that enough are defective in this particular way to meet the design requirement of the V3.
  1. Using the aero spec pinon gears on the V3 and have less tooth engagement and possible interference where the set screw is.

I can't currently recommend either of those alternatives.

tomc removed a subscriber: tomc.Jul 15 2019, 2:19 PM
AOJAS added a comment.EditedJul 16 2019, 3:34 PM

I've released the units to Tom. Here are the numbers:

ct | Part# | Name
950 | PP-MP0205 | E3D Aero Steel Pinion Gear w/ set screw
1050 | PP-MP0282 | E3D, V3 Aero Steel Pinion Gear w/ Set Screw

The 1050 PP-MP0205 will be adjusted out of QC inventory, then 1050 PP-MP282 will be adjusted in to replace them. (per @tomc )

Everything is labelled to make sure people know the PP-MP0205's are for Quiver only. While the PP-MP0282 can technically be used for either the Quiver or V3 assembly, I don't believe that the BOM allows us to have the flexibility of "Either Or" when it comes to tracking usage, so we probably want PP-MP0282 on the BOM for V3 only right now.

Does anything more need to be done to close this ticket out?
@kent
@jperry

AOJAS added a subscriber: tomc.Jul 16 2019, 3:35 PM
tomc added a comment.Jul 17 2019, 11:51 AM

I don't think so I made the adjustment and sent them off to toolheads so we should be good

DaniAO added a subscriber: DaniAO.Jul 17 2019, 11:55 AM

@kent @Jperry- do we have a drawing already for the new part? if so where is it stored?

The file path is below. I've also logged this path in the product card for part PP-MP0282.

https://devel.lulzbot.com/TAZ/accessories/yellowfin/production_parts/machined_parts/pinion/22_tooth_gear_revc.pdf

kent added a comment.Aug 2 2019, 8:12 AM

from E3D:

We have now been through our stock and segregated out batches of gears that have the grub screw hole nominally 2.5mm in the the edge and ones that are nominally 3.0mm from the edge. We have split these out into the following SKU's:

CC-AO-TITAN-GEAR-SMALL-250 (4000PCS available and only for AO)
CC-AO-TITAN-GEAR-SMALL-300 (13000PCS available although are also use for general E3D stock)

I think we should update the drawing that @jperry linked because it has the old part number. This will break that link in the product card since the filename will be different unfortunately. Maybe we should just post a link to the directory? like https://devel.lulzbot.com/TAZ/accessories/yellowfin/production_parts/machined_parts/pinion ?

jperry added a comment.Aug 2 2019, 9:01 AM

I've updated part PP-MP0205 to have CC-AO-TITAN-GEAR-SMALL-300 and PP-MP0282 to have CC-AO-TITAN-GEAR-SMALL-250. I also updated PP-MP0282 to have the link to the parent directory. The link is https://devel.lulzbot.com/TAZ/accessories/yellowfin/production_parts/machined_parts/pinion/.