Fixturing or clamping devices are necessary to assure absolute quality when inspecting parts in a warped state. This method has long been the traditional technique but can be costly and challenging to implement.
Mechanical clamping fixtures are used to place parts in a physically constrained position for measurement. These fixtures can cause unreliable or inconsistent results with each measuring procedure.
Warpage of injection-molded plastic parts is particularly problematic for achieving precise quality data. How can these parts be properly and accurately assessed without producing the hassle of fixturing? ZEISS’ De-Warp software package is the virtual clamping solution you need to measure parts unclamped and generate precise measuring results.
Injection Molding Scales with Your Production Needs
Injection molding is one of the most popular processes to produce high-quality and cost-effective plastic parts. This production method is utilized for several parts and products, including plastic bottles, toys, electronic housings, agricultural parts, household containers, machinery and automotive components, the healthcare industry and more, says Industrial Equipment News.
According to the International Journal of Innovative Research in Science, Engineering and Technology, injection molding has been so embraced because it facilitates producing thin-walled parts for a wide variety of applications. Injection molding enables the creation of geometrically complex parts at low cost in a single process step, explains Tristan Koslowski and Christian Bonten of the University of Stuttgart.
The main advantage of injection molding is the ability to scale according to production needs. Once the initial costs have been paid, the price per unit during injection molded manufacturing is extremely low. The price also tends to drop drastically as more parts are produced.
Mechanical Clamping — Unreliable, Expensive, Not Worth It
Delivering injection-molded plastic parts near net shape to the end-user without warpage can be challenging. Warpage is when the part’s shape is distorted and has a slight twist, bend or bow. This common issue for plastics manufacturers results from suboptimal production process parameters, fast cycle times with corresponding short cooling times, and forces during assembly.
Warpage imposes several constraints on quality assurance.
“Measurement of warpage is of great concern in injection molding operations because warpage affects the surface qualities and dimensional accuracy of the molded components,” says the International Journal of Innovative Research in Science, Engineering and Technology. As well, parts won’t correspond with CAD data or end up out of tolerance dimensions.
However, warpage is not a functional problem to a certain degree, as plastic parts do not always act alone and are part of an assembly. Clamping or fixturing devices during inspection are needed to determine if the parts will function when assembled, even with deviations.
Non-contact, non-destructive optical measurement technology, such as ATOS 3D scanners, is also the preferred inspection method when using fixtures on warped parts. The high-resolution 3D measurement data they collect is accurate and provides the ability to measure difficult-to-reach regions of a part.
There are several benefits to using clamping devices for parts during the inspection process, including:
- Simulation of later mounting conditions with fixed points when using non-contact optical metrology.
- Measurement of parts with a compensated warpage.
- Measurement data can be correctly interpreted.
- Part rejection rate can be diminished.
Unfortunately, clamping fixtures also cause their own issues with parts measurement:
- Lack of process stability and time-consuming operation.
- Conventional clamping fixtures can’t be used altogether with computed tomography (CT); this method can cause disturbances in the measuring process, such as the fixturing itself touching parts and preventing measurement and fixture materials creating noise/artifacts that make data unreliable.
- Fixturing can be very expensive and needs maintenance.
- Fixtures can take up to three to four times as much space as metrology systems.
- Information from the unassembled state of the part is lost.
- Metal fixtures interfere with the acquisition of the measuring data when using some forms of non-contact measurement.
How can manufacturers hope to thread the needle of compensating for parts warpage without imposing the problems of mechanical fixtures?
De-Warp Solves the Problem of Fixturing
Manufacturers need a way to digitally de-warp parts after easily scanning them in an unassembled state. De-Warp is an innovative software solution to this common manufacturing problem. By leveraging accurate 3D measurement data, De-Warp allows users to simulate parts in a clamped state. As part of the ZEISS Quality Suite, the software package is available with GOM Inspect Pro and GOM Volume Inspect Pro software.
This new module addresses the problem of fixturing when assessing warpage through several robust functionalities:
- Virtual compensation of warpage of parts with a powerful and efficient built-in finite element analysis (FEA) algorithm.
- ‘Remove Warpage’ function applies virtual force to a part by defining virtual fixing points and evaluating data of unstressed parts.
- Automatically generates complete, parametric measurement results of the part in its virtually clamped state without a clamping fixture.
These capabilities enable plastic manufacturers to optimize several production tasks, including:
- Accelerating the product development process.
- Reducing costs resulting from time-consuming measurement processes and complex clamping devices.
- Minimizing the rejection rate of totally functional parts.
De-Warp can complement measuring applications across a broad range of industries:
ATOS ScanBox is an ideal solution for part verification and continuous quality control in automotive part production. This family of automated 3D scanning inspection cells can easily identify and analyze warpage, shrinkage or displacements for body-in-white and flush and gap inspection using an ATOS blue light 3D scanner mounted on a robotic arm.
Plastics manufacturers can overcome these deformations using ATOS full-field 3D measurement data inside the ZEISS Quality Suite. The De-Warp software module of GOM Inspect Pro uses algorithms for the virtual compensation of warpage and shrinkage. These algorithms make it possible to detect over-constrained datum conditions without mechanical fixtures.
Plastics on CT
The ZEISS METROTOM industrial CT line particularly excels at simultaneously measuring interior and exterior features of small to medium-sized plastics parts for digitalization. Demand for these parts is growing in many end-user industries, such as automotive, packaging, additive, electronics and medical.
From tool correction to series inspection and optimizing first article inspection with GD&T analyses, De-Warp will automatically compensate warpage when using ZEISS METROTOM.
Easily scan your parts in a tension-free state using the T-SCAN hawk 2, then use the data it collected to digitally assemble the parts. GOM Inspect Pro uses the scan data to generate a mesh. The De-Warp package mimics the part assembly virtually within one software. The software checks the dimensions in a few steps as if the part is already in its final position.
For more information: www.zeiss/metrology