HP 97 Printer Gear

[Alevin]

Hi

I have made a couple of fixing of the printer idle gear. I want to share the experience.


I have experiment with bronze metal gears, and plastic ·3d printed public model (printed at Shapeways), documented above, from RPZ (many thanks for your generous work).

The bronze gears from Germany used, are documented in a 2014 original post:

https://www.hpmuseum.org/forum/thread-11...97+printer

The supplier web:

http://www.modellbauershop.de

part number 753030

In respect the Shapeways materials options, nowadays they have avalaible a more ample set of options than in the date of the thread opening in 2020.

https://www.shapeways.com/materials

Finally I ordered gears in MJF Plastic PA12,

https://www.shapeways.com/materials/mult...usion-pa12

MJF Plastic PA12 seemed the most resilient and less brittle for mechanical operation involving dynamic forces and wear. It can be read in the technical description:

“Multi Jet Fusion (MJF) Plastic PA12 is HP’s nylon plastic with excellent mechanical properties and a slightly grainy finish. Is an ideal choice for a wide range of applications from industrial parts to durable end-use goods. Its strength, durability and stiffness make it great for functional parts, such RC car parts and mounts. Is printed using HP’s Multi Jet Fusion technology and supports very complex geometries and thin features”

The grainy finish could not be avoided ordering the smooth glossy option, as it was not available for the size of the gear teeth. This grainy finish was more rough than I expected.

Case A.

In the first Hp-97, the bronze metal gear did not work well to me. It is required to open the bore hole to the axe proper size, done by a Dremel drilling. At first trial the bore hole got not well centered, and quarter of the circumference did not gear at all with pinon. At a second trial with another gear, the hole was better centered, but it was a bit too much (may be because of metric drills?). Then it had tendency to wobble, and move back an forth over the axe, as the gear width is smaller than the original and the circaclip is well away from the outmost external face. This caused some time to get stuck in diagonal in between the motor pinon and the printer gear. May be the motor axe an pinon were sightly deformed. Finally, it was really noisy.
Pics attached show this gear.

Then I went for the nylon printed Multi Jet Fusion (MJF) Plastic PA12 by Shapeways.

Increasing the size of the bore hole, was made turning by hand with 2.25, 2. 5 mm drills, so the inner diameter was better controlled.

The roughness of the Plastic PA12 finish, and some slight oversize may created a too much resistance, so the motor could not move the gear chain. After a patient turning the pipno idle assembly for 30 minutes or so by hand, the gear and pinon got some attrition, enough to make possible to the motor torque turn the gear chain. Finally, it got to spin smooth. Even though it is a nylon piece, the noise was also loud, no as much as in the bronze idle gear case, but similar, what surprised me.

Pics attached show this gear installed

Case B.

Given the previous experience, I started with the printed nylon Plastic PA12. Surprisingly, in this case the idle gear had more tight engage than the previous HP-97, case A. After applying the same manual procedure spinning the gears to create the wear enough to make the system turn freely, It was still stuck.

So, I went to the bronze idle gear. In this case, the idle gear did not show wobble, and stayed in place. The printer noise was louder, but not so much as in the first Hp-97 with the metal gear.

So I kept in this case the bronze one on the printer. I will try to add some spacer to keep the gear on place.

May be tolerances of the plastic idle gear or the different condition of printer components made the difference.


I conclude that, apparat from the gear material and larger tolerances in the printed gear, may be Hp-97 unit printer condition may influence in the result and the most convenient option in each case.


To end up, I ask for you guys some advice,

I have found a reference for the advance wheels substitution, a guide in a slide show format created by Ignazio Cara (Italy), cited in this old forum thread.


https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=216173

But the link is not working,.... Is there some other site where the slide show can be found? Some one kept it and can uplodad it or send it to me by mail?

Thanks a lot