Gear Data 2

[smwdrum]

I have question about gear data listed in the data table on a F/P. I know you can calculate things that might not be listed in the table based on different formulas, but what about the data for Shaping and hobbing, how do you get that data based on the gear data from the F/P, are there formulas or charts....

 

[mfgenggear]

smwdrum

It depends mostly on what type of equipment is to be used. and the attributes of the gears. spur vs helical and so on. most machine manuals specify the requirements.

It depends the the gear data agma or din quality class. if the class lends it self to gear cut, then
it is up to an experience operator to figure it out. most machines are CNC, with some old machines out there require gear train calcs. if it requires gear grind same difference. a good operator knows to swivel the tool spindle to allow for the correcting to obtain the correct lead. on shapers there is no adjustment. but must have the correct D+f on hobs or shaper cutters.

Please be more specific for a better answer.

Mfgenggear

 

[smwdrum]

We make gearing for the Aerospace Industry and everything is laid out for the operator to standardize the work as much as possible. So on our operation sketch we have the gear data listed for the shaping / hobbing operation with the necessary gear data (which obviously is not final size to allow for grind stock post heat treat) and then on the gear grind operation we have the gear data per the F/P requirements since its the final grind of the teeth. So was just wondering how you go about getting the data for the shaping / hobbing operation from the data table on the F/P, are there calculations to do that? Hope this better explains my question with a little more detail.

 

[mfgenggear]

Smwdrum

#1) if the parts are case harden you must calculated the circular tooth thickness, from span width & or Measurement over wires. use standard practice for the amount of stock removal vs the type case hardening required. add stock to the gears for final processing. you have to make sure that during case hardening cycle the case depth is pinched to the high limit to allow stock removal with out deviating the hardness and case depth.

#2) if it is through harden the amount of stock is irrelevant except for efficiency.
only add enough stock as needed to do the job with the most efficient manner.

what the pre grind data has to have is # teeth, DP or MOD, Pressure angle.
calculated Measurement over wires or span which is based on the pre-grind CTT.
attributes like the the pre grind lead, run out, minor diameter can ether have a protuberance or the minor diameter has to adjusted for grinding. in other-words add stock for final finishing.
fillet radii at the minor diameter.

these are just some of the millions of scenarios that can be.
every job has it special circumstance.

Does the operator have the right tools to manufacture. does he have the correct whole depth, can a hob be used or does it have a shoulder next the the gear or spline. so then a shaper cutter must be used.
Does the operator have all the machine data that is required for his or her machine. like change gears, right dressing tools, correct holding tools.
whats settings for that particular machine does the operator need. check the manuals or and ask the operators. they will thank you for it.

the pre-grind data will be very close to what the finish data has but will be more liberal on tolerance because it is roughing.

Mfgenggear

 

[tbuelna]

Great post mfgenggear. High precision case hardened and ground gears often use a fair amount of tweaking when shaped/shaved/green ground/etc to compensate for heat treat distortions. You want to make sure your case thickness after finish grinding is uniform and has the required hardness/depth profile. Getting this right can involve some trial/error, and processing some test pieces. A single spiral bevel gearset used on a large helicopter drive can cost over $40K new. During manufacture, by the time that gearset is ready for finish grinding the vendor might have $20K invested in it. The later in the manufacturing cycle the gear is scrapped, the more it costs the company.

The statement "We make gearing for the Aerospace Industry..." also makes things much more complicated. The manufacture of gears that are used for a qualified aircraft application is usually subject to a controlled production process where everything is tightly regulated. This includes the specific machines/equipment, machine set-ups, tooling/fixtures, etc. used to produce a specific part. The reason is that using a qualified and controlled manufacturing process will ensure uniform quality of the finished parts. And it usually requires approval from the customer before even the smallest change is made to the controlled production process.