Automated tap hole measurement

You have an uphill climb, but good luck. The torque is a good idea, but flawed in the sense that if the thread is cut oversize, you won't detect it that way. Are you planning on having a simular test with the no-go side of the gage or is this a simple pass-pass test, I mean if the thread exists it's good with no lower limit? If that's the case, you need to ask your self why are you doing the test at all? Inspection does not add value and 100% inspection will only catch 80% of the errors.

Optical comparer on a robotic arm to take photo images. With a computer to compare the images to known good holes. Some type of marking device on robotic arm to mark holes good or bad.

I agree with Labyguy, the system would be quite complicated. Evenifyou could operate it on a CNC coordinate measuring machine, you would still have the issues of go versus no-go gages as well as positional accuracy issues. It woud have to operate similar to a tapping head, only with a gage. Then since it would be automated, you would have to find a way to deal with checking if the hole and the gage are clean. You would probably end up rejecting a lot of good parts which would creat a whole new set of problems.

Take a look @ SMAC actuators. www.smac-mca.com

They make a variety of different sizes of linear with rotary motion actuaors.

Here is a link directly to a videoclip of one version of thread inspection wiht a custome thread gage tip(not neccassary) on their website.
http://smac-mca.com/thread-check/threadcover.htm

These actuaors are used for a variety of applications do to the speed, precision, adn feedback they offer. The thread inspection appliciation you are discussing is a typical appliciaton.
one of the nice thing about these are that the hardware componets remain the same and you can program these to do the various check you would like to do.
using the GO plug gage (in a thru or blind hole) you can check the following:

- No Threads
- Undersized Threads
- Shallow Tap,
- Dull Tap
- Broken Tap
- Oversized Threads

Additional checks that can be done are
- number of turns (threads)
- depth & # of threads in a blind hole
- Initial(First) Thread Depth
- Counterbore Depth/ Presence
- Double Tap Thread

All of the above functions are programmable(no additional hardware required), and are not required unless the user cho0ses to implimnet them.

If you would require further information, contact me and I can provide you wiht it, as I have experince with this product & application.

Welcome to the forum PROG. It appears that you have a lot to contribute.

Would you use this actuator on a programmable CMM or a robotic arm? If the robotic arm, what would the positional accuracy be? Could it maintain perpendicularity with the surface that the tapped hole is in, or could the actuator compensate? Could you use the go and no-go on one actuator or would it require a "tool change"?

In the video it appeared that the pitch was being checked by bumping against the sides to check like a CMM. If so that would require very close positional accuracy. This must go on my list of things to see at IMTS next year!

I always amazed at haw fast the technology is advancing in the manufacturing field, and this is a particularly interesting challenge. I just had a part rejected from a customer because an operator failed to tap 2 holes during production on one part. Taking the part back, tapping the holes, having the anodize stripped, replating the part and delivering the part, plus the negative reaction of the customer is very costly. In a high volume production situation the cost savings of automated inspection could be huge.

Hello garyceng,

Basicly you can think of these actuaros as miniture CMM's or more than that depending upon the application. These actuators have the "ability to do work & verify it at the same time".

In the midwest they are used mainly for production QC appliciaotns in the automotive field and are implimented on inline processes either doing assembly & QC check or just QC checks.

They are suited for high speed, high accuaracy (from 5um - 5 nanaometer resolution in a direct drive linear motion zero backlash), excelent repeatabiltiy both for force & distance.

It is hard to describe in an e-mail on all of the benifits that these units offer. A live demonstration/ disscution does much better. These will be at the upcoming QC/ Assembly Show in Chicago next month. IMTS as well.

The thread inspection applications use the linear /rotary actuator. |
If multiple threads (internal or external type) are to be inspected the actuator can be shuttled on a pneumatic slide to the various positons.

As for allignment, there are a few ways this can be handled.
The shaft can be allowed to float and give some. This works for most customers. For additional float a floating coupler can be implimented between the go thread gage member and the shaft of the actuator. these allow for the alignment compensation.

As for the plug gage, yes you could do pretty much anything. A GO gage could do all of the checks (Go/ No-Go) or if desired a custom Go/ No Go plug gage could be used.

Yes, in the video you are seeing a push/pull routine that is measuring the amount of movement this is checking the pitch/ clearance in microns.

These actuators are very affordable espicially in these QC applicaonts as they alos provide measurement data for SPC colloection..Easy Gage Corrilation between an automated process and a manual metheod, and eliminate the humane error effect.
They are in a clean & simple package.

Other QC appliciaotns would be:
Hieght Gage
Plug Gage
Bore Gage
Run out/ Concentricity/ Tri-lobing Gage
Effort Testing (Force & Postion measurment)
Many more..............

Thanks for sharing the info. I just went to EASTEC so my trade show quota is used up until next Sept. for IMTS.

I try to stay away from really close tolerence work. My mill can interpolate to hold +/-.0003. Any closer than that and I head for the honeing machine. When you start talking about tolerences closer than 50 millionths my brain goes into overload. However I will seek this out at IMTS because I am curious as to how they can hold nano-tolerences on a piece of equipment with so many motion variables. They must have some new technology to overcome the tolerence stackup bettween the different axis.

Quick and dirty way to measure thread depth would be to put a small prox switch (3-5mm dia) at end of a probe and use this to measure contact depth with a quill tape(i.e. basically just a ruler like you would see on the side of a drill press) attached to side of probe to give depth travelled. As for thread size, need more time for an eloquent, cheap solution.

Keep me posted.

Maybe a functional Thread Gage, attached to a simple CNC-CMM or some other kind of motion controller?

The Starrett #1141 does internal thread and has an optional mechanical drive unit.

http://catalog.starrett.com/catalog/images/objects/3000/2902.pdf

I've created some automated thread inspection using the Starrett thread system and Testar-Marposs module gage system. www.testar.com.

Our system checks Pitch, Function, Location and Depth of both internal and external threads.

I wouldn't recommend this for anything that will have short production life, (it wasn't the cheapest way to go) but it sure has saved inspection time.

Another cost savings are the ergonomic factors. Although harder to quantify as a direct reflection to these system, is the decline in Repetitive Motion Trauma.