Parameters required for a ZK worm gear

[RichardWattUK]

TL;DR

Measurement parameters required for a ZK worm

I apologise for cross-posting - I've already posted this question on CrazyEngineers but have had no replies after a few days and I was wondering if someone here could help me:

In my current job, I am responsible for maintaining an existing software application that generates a dressing program for a CNC external thread grinding machine which includes the ability to grind worms (ZI, ZA, ZN, ZK forms). I am trying to confirm the input parameters that are actually necessary for the ZK form worm because the software was written using a worm definition dialog box with the following input fields:

• Worm Data:
  • Worm Name / ID
  • Worm Type (Single Lead / Dual Lead)
  • Lead Hand (RH / LH)
  • Number of Starts
  • Reference Circle Diameter (in mm)
  • Tip Diameter (in mm)
  • Root Diameter (in mm)
  • Spindle Setting Angle (in degrees)
  • Thinnest GROOVE to REF distance (in mm)
  • Workpiece stock allowance per side (in mm)
  • Lead (in mm) (Lead 1 and/or Lead 2)
• ZK Tool Data:
  • LH Flank Angle (in degrees)
  • RH Flank Angle (in degrees)
  • Spindle Setting Angle (in degrees)
  • Tip Fillet Radius (in mm)
  • Root Fillet Radius (in mm)
  • Tip Width (in mm)
  • Tip Diameter (in mm)

I've got a copy of the DIN 3975 standard and it has the following diagram as Figure 10 in section 3.6.7 for a ZK worm:

Now the calculation process creates a profile for the grinding wheel (generating tool) and the worm profile on the axial plane (so along the worm component) which is summarised in the diagram below:

The code I'm trying to check is the part that generates the cutter tool profile as our CNC machine grinds the worm gear itself and not the worm wheel.

We check the parts we grind in-house on a Wenzel GearTec machine that accepts a number of parameters but it only asks for the grinding wheel diameter and the grinding wheel thickness - both of these are as measured at the reference (pitch) circle diameter on the worm profile, but the code accepts more parameters than this.

I've tried to find this information on the internet, but to no avail so far, so it may be that I'm using the wrong terms.

What I'm trying to find out is what parameters would you take from a ZK worm drawing to generate the profiles? I do have a copy of MITCalc I can install on a trial basis and check out what they have, but they do have a lot of detailed information they can accept and calculate to give a full picture of the worm design and characteristics.

Many thanks in advance.

 

[jedishrfu]

I think you are unlikely to get any help on your problem here as this seems like proprietary knowledge that a manufacturing company would want to keep secret.

 

[Baluncore]

I am trying to confirm the input parameters that are actually necessary for the ZK form worm because the software was written using a worm definition dialog box with the following input fields:

You cannot rely on a CAD system to perform a verification. The ZK profile was defined so that a wheel and a worm manufactured by different processes would work when brought together.

At some point you must put your feet on the ground, grind the first worm and mount it with a wheel. Only then will you be able to close the design loop and verify mechanically that both are probably correct.

If they are not compatible you must question both the worm and the wheel in an attempt to identify what may be multiple reasons for the discrepancy. Have you reached that stage?

The parameters for a ZK worm profile may be over-determined and redundant. Do you know that your Wenzel GearTec measuring machine is capable of measuring a specified ZK worm without a software upgrade ?

 

[RichardWattUK]

I think you are unlikely to get any help on your problem here as this seems like proprietary knowledge that a manufacturing company would want to keep secret.

That's a shame - I know there are several different standards (DIN, ISO, AGMA, British Standards, Japanese Standards) for the ZI, ZA, ZN and ZK worm gears and I thought there'd be something somewhere that would help me define what data would be required off the part drawing (since our customers tend to grind/machine worm parts for their customers and are given a drawing of the part with the measurements on it).

 

[RichardWattUK]

You cannot rely on a CAD system to perform a verification. The ZK profile was defined so that a wheel and a worm manufactured by different processes would work when brought together.

At some point you must put your feet on the ground, grind the first worm and mount it with a wheel. Only then will you be able to close the design loop and verify mechanically that both are probably correct.

If they are not compatible you must question both the worm and the wheel in an attempt to identify what may be multiple reasons for the discrepancy. Have you reached that stage?

The parameters for a ZK worm profile may be over-determined and redundant. Do you know that your Wenzel GearTec measuring machine is capable of measuring a specified ZK worm without a software upgrade ?

The Wenzel GearTec system already has the ZK worm software option included and it has been used - what's worse is that it seems a lot of the documentation that my predecessor would have created seems to have been not requested when he left or lost when the company has moved buildings (this has happened at least twice in their history).

I'm also relying on the most senior person in the company who has the knowledge about the machining, but he's retiring soon and even he isn't sure what/why our software asks for the data that it does.

It's a frustrating problem to be honest.

 

[Lnewqban]

I would recommend you asking your questions at this site:
https://www.eng-tips.com

 

[Tom.G]

I'm way out of my field here but "MACHINERY'S HANDBOOK" has about 30 pages devoted to Worm Gearing. A quick look shows that names of some of the variable names may differ but all seem to be pertinent.

My 23rd ediition is from 1988, so the following address may have changed.

MACHINERY'S HANDBOOK
Industrial Press Inc.
200 Madison Avenue
New York, New York 10016-4078

Hope this helps!
Tom

 

[RichardWattUK]

Hi Tom, I've seen that book come up a lot in my searches, and we may have had a copy at one point, but it's probably been lost now.

Also, our office firewall seems to be blocking Google Books as a copy of that book is available with a substantial preview on that site but I can't see it, so I'll get in touch with that publisher next week.

 

[jrmichler]

I see that Machinery's Handbook is available on Amazon. The current edition has 3000 pages, way more than my 20th Edition which has less than 2500 pages. A person who asks questions like the OP should definitely have a copy on their bookshelf. It's cheap at the price.

 

[RichardWattUK]

jrmicheler - and since it's for work, it's not coming out of my pocket, heh heh :)

(Seriously, I wouldn't be surprised if we did have a copy in the company at some point, but it's a much older version, it's been lost during the moves or my predecessor kept it.)