Frequently Asked Questions

What is a 'Module'?

The size of a rack and pinion is described by its module. For a pinion, the module is defined as the ratio of the reference diameter of the pinion to the number of teeth on it. For a rack, the module is defined as the reference pitch of the teeth divided by pi. 

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What is a 'Quality Class'?

The tolerances from manufacturing are categorized by 'Quality Class', with the tightest tolerances classified as a smaller quality class number. Naturally, since the length of a product will effects its error stack up, each 'Quality Class' has it's own maximum length for racks. For various lengths, the flatness and straightness tolerances of the racks will vary in accordance with DIN 7168 S and ISO 2768 H standards. 

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How does 'Quality Class' relate to manufacturing tolerances?

Tighter tolerances in the manufacturing process will result in more expensive, but more precise components. Finding a balance between the tolerance and cost is the purpose of various 'Quality Classes'. 

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What are the advantages of a rack and pinion system?

• Unlimited travel distance

• No "whip" over long strokes

• High dynamic performance

• Low mass moment of inertia

• Low cumulative error and high precision.

• High repeatability

• High load capability

• Allows for more compact, simpler machine design

• Maintenance free (minimal lubrication required)

• Constant stiffness over the complete travel length

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Is it better to combine several shorter section or one longer one?

Machining tolerances, by nature of the manufacturing process, additively increase as the length of the unit increases. Deciding whether to utilize multiple shorter sections or fewer longer sections requires identifying the tolerance differences for each situation. To identify the difference, the total pitch error can be calculated with the following equation:

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This shows that in this specific case 3 longer racks results in less error than 6 shorter racks. 

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What is feed force?

The permissible feed force represents the maximum transmission force that the rack’s teeth can bear without breaking because of fatigue bending stress. This force results from the mechanical properties of the material and from the working conditions. It is important to note though, that the documented permissible feed force for a rack and pinion system doesn't consider failure by pitting or seizing.

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How much feed force is permissible for various rack and pinion systems?

The permissible feed force depends on the material, heat treatment method, and module. The lengthy table shows full range of values for various rack and pinion systems. 

 

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What certifications does Gambini Meccanica have in its manufacturing process for quality assurance?

Gambini Meccanica's environmental management systems is ISO 14001 certified. In addition, their quality management system is certified in accordance with  ISO 9001:2015 and OSHA 18001. These all work together to ensure that the product maintains the highest caliber of quality. Gambini Meccanica is also an Authorized Economic Operator (AEO) which provides import/export benefits as well a minimized customs controls.