Movable-shaft design for adjustable gear teeth engagement

[Flying Whale]

I have a geared motor bolted onto a moving plate supported by rollers standing on a fixed base. The same fixed base has a rack on the bottom. There are 4 rollers, 2 on each side of the fixed base, and they're on separate shafts (there's material between the two sides, and it cannot have holes). The moving plate assembly can get up to a mass of 1,000 kg.

Sizes and materials here are quite large (plate is 600mm wide, made of 12mm laser-cut steel, and the fixed base is a standard beam profile) so no tolerances can be reliably specified to get the correct mesh engagement. This has been built and tested, it failed because the gear teeth didn't fully engage, then solved with a not-so-repeatable nor time-efficient method for a long-term product line. (Having to shim the rack to push it into the pinion is not a solution, at least for our requirements)

I've tried to find some existing designs where gears are designed with adjustable centers, but my research has led me nowhere. One idea I've had is to mount the rollers on shafts with offset centers (one of which is threaded and tightened to the plate by a nut), but that adds complexity to the assembly pretty quickly, since the four rollers have to be adjusted independently.

Any help is appreciated, thanks.

 

[mfgenggear]

OP
ouch when designing gear train , even a rack and pinion. center distance must be maintain. there is variable tension out there.

however my suggestion is to machine the centerline of the rollers to the center line of the pinion. and the top of the plate where the rollers rest must be machine flat and straight. and parallel to the rack pd with in .001 tolerance. .
the mounting face of the rack and the fixed base must be flat and parallel.
the pinion must be fixed position mounted with a housing. where the motor can be mounted and a coupling to assemble with
the pinion shaft.

if this is to expensive and complex
then let us know to try an other suggestion.

 

[mfgenggear]

OP
this may be a better option

 

[CWB1]

I've tried to find some existing designs where gears are designed with adjustable centers

Many gear trains have an idler gear on an adjustable/offset pivot, similar to an automotive belt tensioner or multispeed bicycle chain tensioner. Instead of applying constant spring tension, techs manually rotate the pivot to set mesh depth and tighten a few bolts to lock the mechanism. Typically the center pivot has a flange with slotted holes for the locking bolts. A bit of care needs to be taken in design and stackup analysis to ensure reasonably equal mesh between the idler and gears upstream and downstream, bc obviously the pivot/idler swings in an arc but its not particularly challenging.

 

[Flying Whale]

must be machine flat and straight. and parallel to the rack pd with in .001 tolerance. .
the mounting face of the rack and the fixed base must be flat and parallel

Ideally this would be the definitive solution. However, I live in a country where the manufacturer will laugh if you tell them laser-cutting isn't precise enough. They'll take offense when you specify tolerances, they'll claim they're unnecessary and ask you to remove them, because they can get all the dimensions "exact" anyway.

But my personal rant aside, I'm not about to argue against or break the trust that my company has with their manufacturer (mainly because there isn't any better locally, I've checked). So if you do have any other ideas, I'd be happy to hear.

As for the mechanism, I believe a powered screw would run into the same issue, where the nut needs to be precisely located relative to the rollers. I wouldn't prefer a screw mechanism anyway since my travel is 6m and I don't have space for a fixed motor.

 

[Flying Whale]

techs manually rotate the pivot to set mesh depth and tighten a few bolts to lock the mechanism.

I like your idea, though I am somewhat concerned about relying on bolts in slots to lock the mechanism, especially when they're right next to motor and under intense vibration. I appreciate the input, I'll sleep on it and see if I can solve the issue.

 

[mfgenggear]

Ideally this would be the definitive solution. However, I live in a country where the manufacturer will laugh if you tell them laser-cutting isn't precise enough. They'll take offense when you specify tolerances, they'll claim they're unnecessary and ask you to remove them, because they can get all the dimensions "exact" anyway.

But my personal rant aside, I'm not about to argue against or break the trust that my company has with their manufacturer (mainly because there isn't any better locally, I've checked). So if you do have any other ideas, I'd be happy to hear.

As for the mechanism, I believe a powered screw would run into the same issue, where the nut needs to be precisely located relative to the rollers. I wouldn't prefer a screw mechanism anyway since my travel is 6m and I don't have space for a fixed motor.

It is not, thus why your are here posting with an issue. 1000 kg load with laser cut surface.
I am retired gear engineer for aerospace applications.
There are 3 classes of machines . Regular, precision and super precision.
Your manufacturing method is inadequate.

 

[MintJulep]

Are the rollers rubber?

The problem you're trying to solve isn't clear.

Set the engagement once, how does it change?

 

[mfgenggear]

Are the rollers rubber?

The problem you're trying to solve isn't clear.

Set the engagement once, how does it change?

Mint
With the current design objective would be to maintain a center distance of the pinion to the rack , unknown module or DP. However It requires backlash. And a constance center distance. The rollers should be precision bearings. Holes should be precise true position
To the center of the pinion. The gear train should be sufficient quality class.
The assembly requires sufficient stiffness and robust to minimize moment.
To my opinion the laser may not be able to achieve the precision required.
So the option would be a total redesign.

 

[mfgenggear]

So the objective would be to use a stiff spring or actuator to maintain pinion contact with the rack.
And it would be set as not to apply full contact.
Which full mesh would cause premature wear from interference.
A lead screw would require bearings on each end and could be adjusted to keep the assembly level and prevent jamming. May be a better option.
Since the nut could be brass.

 

[mfgenggear]

AI Overview



+6

A lead screw assembly, used to convert rotational motion into linear motion, typically consists of a threaded shaft (the lead screw), a matching nut with internal threads, and optionally, components like end supports and thrust bearings.

Here's a more detailed breakdown of the components:

• Lead Screw (Threaded Shaft):
  This is the cylindrical component with external threads that spiral around its length.
  
  
• Nut:
  The nut is a cylindrical component with an internal thread that corresponds to the external thread of the screw shaft.
  
  
• Lead Screw End Supports:
  These are used to fix the lead screw in place and ensure proper alignment.
  
  
• Thrust Bearings:
  These bearings help to reduce friction and wear, especially when the lead screw is subjected to high loads.
  
  
• Self-Aligning Thrust Bushing:
  This type of bushing allows for some misalignment between the screw and the nut, which can be helpful in certain applications.
  
  
• Optional Lubricator:
  Some lead screw assemblies include a lubricator to help reduce friction and wear.
  
  
• Anti-Backlash Nuts:
  These nuts are designed to eliminate or reduce backlash, which is the play or looseness in the system.
  
  
• Materials:
  Lead screws and nuts can be made from various materials, including steel, aluminum, and plastic, depending on the specific application and requirements.

 

[dtimberlake]

https://imgur.com/ltoISGM

Steering backlash adjustment

My 03 M3 has some backlash in my steering. When moving the steering wheel side to side at a dead stop, I could hear something in my steering knocking. I'm pretty sure that it is the rack. FCAB and the steering coupler have already been replaced. I inspected the front control arm and the tie rod...

www.e46fanatics.com

 

[mfgenggear]

https://imgur.com/ltoISGM

Steering backlash adjustment

My 03 M3 has some backlash in my steering. When moving the steering wheel side to side at a dead stop, I could hear something in my steering knocking. I'm pretty sure that it is the rack. FCAB and the steering coupler have already been replaced. I inspected the front control arm and the tie rod...

www.e46fanatics.com

Lol brings back memories
I would calculate change gears for phuater and barber Coleman manual gear hobbers.
For index and feed gears..

 

[mfgenggear]

 

[dvd]

not sure what the issue is, but I have used this approach with these types of motions

U.S. Tsubaki Pin Gear Drive Units

Tsubaki Pin Gear Drive Units (PDU) can replace gears and racks, offering new design possibilities for rotating and linear drives. Learn more.

www.ustsubaki.com

Roller Pinion Racks deliver constant positional accuracy

Nexen's patented rack and pinion system, with bearing-supported rollers, delivers constant positional accuracy over multiple rack sections at any length.

www.nexengroup.com