3D Model - When Calibration is a Bad Thing

3D Model - When Calibration is a Bad Thing

Equipment and instrument calibration is not an acceptable substitute for process feedback.

I once worked with a very intelligent Quality Assurance (QA) engineer. In a discussion where he was espousing the virtues of mandatory periodic equipment calibrations, he made the statement "I never buy tires from a company that doesn't provide alignment services. I always have my car alignment checked when I buy new tires." He was quite certain that this analogy supported his argument that periodic equipment and instrument calibrations were essential.

The concept argued by the QA engineer is that all things that may require adjustment or calibration have to be checked and adjusted on a periodic basis by qualified technicians using specialized equipment. Belief in this concept is ubiquitous in today's QC systems and is even dictated by many regulatory bodies including the United States FDA.

Back to the car analogy: Let’s suppose that I'm taking my car in to get new tires after having gotten 60,000 miles on my old ones. Further, let's say that the tires all wore evenly, that the car drives straight and true and that the car's gas mileage has been constant and is acceptable. Should I have someone check and adjust the wheel alignment?

The purpose of wheel alignment is to insure that the tires track true to the vehicle's path so that the car drives straight, the tires wear evenly, the tires last a long time and the vehicle gets good gas mileage. If these conditions are true, why let someone adjust the alignment? No matter how well trained and no matter how specific their equipment, they are not going to make things any better and they might make things worse. If these conditions are not true, why did I wait until now to do something about it?

A successful process requires timely feedback. Waiting until my tires are worn out to check my alignment is not timely. I should visually inspect my tires as I walk up to the car, not only for wear, but for proper inflation. When I drive, I should be aware of unusual or unacceptable behavior like pulling or drifting. And when I fill up at the gas pump, I should check my gas mileage to verify that nothing’s amiss with the engine or drive train.

Time and time again, I've seen processes go haywire after mandatory equipment calibrations. I’ve also seen "validated" processes, using calibrated equipment, drift out of specification. Measurement processes are especially vulnerable. It's common to see measurement processes go unmonitored and reliant solely on periodic calibrations.

Do not rely on equipment calibrations to insure process integrity. Find timely feedback mechanisms and use them to monitor processes. Use calibrations as diagnostic tools, not as process controls.

3D Model Overmold Scanning

3D Model Overmold Scanning

3D Scanning can be a very powerful tool for correcting overmold problems.

Flash and/or failure to shut off in overmolding is often caused by a poor fit between the part and the mold. Scanning can provide an easy and straightforward method to correct the fit.

The part to be overmolded is scanned and enough data is collected to accurately describe the part. Software such as Rapidform is used to create a solid model (CAD model) of the part including all the shrinkage, warpage, etc. The end result being a CAD model that accurately represents the part to be overmolded. The model is then used to redesign and modify the overmold tooling to fit the part precisely.

3D Model Dimensional Inspection

3D Model Dimensional Inspection

X-ray CT scanning and 3D Laser scanning are ideal for dimensional inspection of components, especially when ergonomic or freeform shapes are involved.

Modern CAD software is not limited to prismatic features. Designers are able to incorporate a wide variety of shapes that often defy inspection without the use of scanning. This is especially true with injection molded components.

When diagnosing overmolding problems or assembly issues on parts with complex surfaces, scanning is often the only way to collect enough data to accurately characterize the components and find the problems. Sometimes it's even beneficial to "reverse engineer" the molded component and create a solid model (CAD model) with shrinks, checks, warps, etc intact.

3D Model AVAST XP 64-bit Problem

3D Model AVAST XP 64-bit Problem

"There could be an issue with your operating system probably" is the AVAST support response to this issue.

Due to the nature of my work, I run Windows XP 64-bit. I've been using AVAST anti virus software for 3 years and until recently, I've been a big fan of their product. But starting with the release of version 6, I've been having problems with updates. Some virus database updates corrupt my system and prevent the system from booting, causing it to hang during the boot process.

To fix this issue I have to:
1. Boot in Safe Mode
2. Un-install AVAST
3. Boot normally
4. Re-install AVAST

After the above, the system will behave normally until another AVAST update. Not every update causes a problem. In fact, most don't, but 4 times in the last month I've had to recover using the above procedure.

A Google search on this issue reveals that I'm not the only one with this problem. If you're running XP 64-bit and looking for anti-virus software, you might do well to look at something other than AVAST.

3D Model Rapidform XOR Certified

3D Model Rapidform XOR Certified

I just got word that I'm certified in Rapidform XOR. I'm not completely sure what the certification means other than that I passed the 2.5 hour long on-line proficiency test. The test was also a prerequisite for attending the advanced training classes at this year's Rapidform Success conference, which I did.

So if I was already certified before I took the advanced classes...

3D Model Rapidform Success

3D Model Rapidform Success


I just got back from the Rapidform Success 2011 conference in Denver where I completed the Rapidform Advanced XOR training - great experience, learned a lot. I was impressed with the software before and I’m even more impressed now.

Rapidform XOR is software for processing 3D scan data. Rapidform uses the Parasolid modeling kernel and creates parametric solid CAD models. The modeling tools are comparable to the major CAD packages plus the software has great tools for processing scan data.

I’m looking forward to applying what I’ve learned...

3D Model CNC Machining STL

3D Model CNC Machining STL

Many shops are reluctant to machine parts using STL CAD models. Shops that embrace STL have an advantage over those that don't.

I recently surveyed a number of contract manufacturers with CNC machining capabilities. Only one shop responded positively. And they didn't say that they could or did machine from STL, but that they thought they could. I provided them with an STL file of part of an avocado to see if they could tool path it. They sent me a picture of the partial avocado machined from foam. I thought that was a pretty impressive response given that all the other shops either just said "no" or didn't respond.

Why is it important to be able to machine using STL files?

Most additive type rapid prototyping methods (SLA, SLS, FDM, EBM, 3DP, etc.) rely on CAD models in STL format. When going from prototype to production, I think there's an advantage to using the same file for both.

Many 3D laser scanners and X-ray CT scanners output STL files. If the purpose of scanning is to be able to machine a replacement part for a +20 year old aircraft, legacy tooling, patterns, etc, why add the burden of creating solid models from the STL output by the scanners? Why not just machine the STL? The concept is already established in rapid prototyping as "scan to print". If modifications are needed, software like Rapidform's XOR Redesign have tools for modeling with STL.

For more advantages to STL, see Tom Beard's Modern Machine Shop article.