I often hear questions about Moldflow，Here I would like to provide professional answers to some of these questions：

Q: How accurate is warp analysis in Advisor package
A: The accuracy of any simulation software will be dependent on what you use for inputs. In general RTP Company does not use the Autodesk Moldflow Adviser series for analysis because we’re often doing analysis of complex geometries and unique, complicated engineering resins. Under those circumstances Autodesk Moldflow Advisor makes some assumptions and simplifications that will compromise the accuracy of the results. For simple parts and basic unfilled thermoplastics, Adviser may accurately predict warpage. However, because you cannot view the mesh and assigned wall thicknesses used for calculations, it may be difficult to know when the analysis is accurately representing your geometry and when it isn’t.

Q: Does the sink analysis work for elastomers?
A: We do not have any direct experience using Autodesk Moldflow to predict sink in elastomers. However, there is no reason why this analysis wouldn’t be accurate provided you had good material data. In analyses in which you’re concerned with sink and voids and other issues related to packing the part, good PVT data will be critical to getting accurate results.

Q: What is the typical charge for the analysis?
A: RTP Company offers CAE analysis services to our customers, and the cost, if any, is dependent on several things including the material volumes and the relationship with the customer. Our services are frequently free of charge, but occasionally if the volume is low and the amount of time required for analysis is great, there could be a charge. If you have an application you’d like reviewed, contact your RTP Company Sales Engineer.

Q: Time to generate the solid model (warpage example) with 1 million elements?
A: The 3D model shown during the webinar was a fairly simple model with many of the irrelevant radiused edges removed/suppressed and no other significant complex features, so this model did not take long to build at all. The Dual Domain model was likely built in less than a few hours. This includes some time cleaning up free edges, overlapping elements, disconnected nodes and high aspect ratio elements. Once we had a clean Dual Domain model with consistent low aspect ratio elements, we used that outer surface mesh and meshed through the thickness. That is a process that is automatic and relatively easy within Autodesk Moldflow, so this entire 3D model was likely translated from the original CAD solid model in less than half a day.

Q: How long it takes to have the rheological data for simulation and who pays for this data?
A: How long it takes to generate the data necessary for analysis will depend on the type of analysis you’re doing and the material. If we already have a material tested (but not listed in the public database) we can send you data very quickly. If we need to send out data for rheology testing only (for a filling analysis) we can generally get results in 48 hours to a week. If you need data for packing and warpage analysis and we needed to also do PVT testing, that would require us to mold samples and then do rheology testing along with PVT testing. That can also generally be done within a week. CRIMS data (the shrinkage testing done at Moldflow Plastics Labs) requires a significant sample of material (which we may need to make) and several weeks of testing, so that can take anywhere from 6 weeks to 3 months. As with all of our analysis services, the cost to the customer is dependent on several things, but we typically pay for basic testing for Moldflow analysis data.

Q: What are the differences in elements used in dual domain and 3D. They look similar to me.
A: I answered this during the webinar.

Q: How to determine v/p switchover point
A: Autodesk Moldflow Plastics Insight allows you to set up your processing just as you would on an actual molding press. You can transfer by volume, ram position, injection pressure, hydraulic pressure, clamp force, a pressure control point or injection time. If you run the analysis with the V/P switchover set as automatic, Moldflow will transfer when any of your limits is reached.

Q: We are limited with the types of resins we have to use. High viscosity, high temperature, and frequently glass filled. Is a Moldflow Advisor Analysis particularly warp analysis useful to us?
A: Based on my experiences with fiber-filled semi-crystalline materials and the complex flow behavior with these materials, I would not suggest using the Moldflow Part Adviser to accurately predict warp. You may decide to use it to see filling concerns, and if you see flow patterns and other issues that concern you, you would know a more in-depth analysis using Insight might be warranted.

Q: Which type of Mesh to be chosen to predict exact warpage of part?
A: The geometry of the part and the available material data will dictate what type of mesh you use for analysis. For typical thin-walled injection-molded plastic parts, a midplane shell mesh used for analysis with CRIMS data will give you the most accurate warpage predictions.

Q: How much does cooling change the results?
A: For all of the analysis shown in this webinar, cooling was assumed to be uniform. Autodesk Moldflow Plastics Insight does allow you to model inserts and cooling channels and to perform a cooling analysis of the tool, but in general if a tool is designed properly analysis of the cooling system isn’t necessary. If you’re doing analysis BEFORE you cut steel on a tool, you want to minimize warpage due to all causes. In Thursday’s webinar Bob Sherman will discuss the primary causes of warpage in detail, and although non-uniform cooling is frequently used to offset warpage due to other effects, cooling is usually not a concern when we’re doing analysis during design.

Q: How to prepare a model for the midplane analysis? is it a plane that goes along the middle of thickness of the part?
A: A midplane model is exactly that, a plane midway through the thickness of the part wall. It is created by finding the point equidistant to the two sides of the thickness and assigning an attribute thickness. This is simple enough with a flat plate, but with complex geometries and intersecting shafts, bosses and other features, finding the exact midplane can be complicated.

Q: How accurate are the results? How closely do they reflect real life?
A: Garbage in, garbage out. The more accurately you can represent the geometry and the material and the molding conditions, the more accurate the results will be. The software has evolved a lot over the past 25 years so that it now accounts for some of the most complex polymer behavior including things like viscosity entrance effects and long fiber flow development and variations in properties due to fiber alignment. If you’re accurately representing your geometry and you’re using Gold standard material data for the exact material, you can trust the results. I’ve seen some customers cut tools with windage based on analysis results.

Q: Why not use an H pattern to balance the runner (to enter at the same time)?
A: If you’re referring to the gaming grill example, there are a few reasons to use Moldflow to artificially balance the runner system. First the runner layout we used allowed the tool to fit within a smaller mold. An H-pattern runner would require additional turns in the runner system and that would mean the part would need to be further from the sprue, making the mold bigger and the injection pressures higher. Another reason to layout the runner this way is to save on material usage. An H pattern runner would use significantly more material, and depending on whether regrind was allowed a smaller runner can mean significant cost savings.

Q: Can mold flow simulate in-mold inserts?
A: Yes. Molded-in inserts can be modeled within Moldflow Plastics Insight and they can be assigned their appropriate material properties. This is another advantage of the Moldflow Plastics Insight software which allows you to analyze complex molding operations such as molded-in inserts, overmolding, 2-shot molding, and gas assist molding.

Q: How do you account for fiber orientation in FEA originating from Moldflow?
A: There are two ways to do this. We can run Moldflow filling, packing and cooling analysis within Moldflow, and then within Autodesk Moldflow Plastics Insight we have the ability to apply loads to this molded part and do some simple stress analysis. The FEA would analyze the structural load using the material properties determined during the filling and warpage analysis. Another option is to do a Moldflow 3D filling and warpage analysis and then export those fiber orientation mechanical properties results for use in another FEA software.

Q: How do you feel about using a surrogate material for mold flow analysis when characterization data isn’t available?
A: It’s better than nothing; as long as you’re confident they are equivalent or near equivalent materials. Most experienced analysts do this all the time, there are many more than the 9,000 materials that are in the Moldflow public database

Q: is the CRIMS Data, available in UDB File?
A: All Material data in the Moldflow database is utilized via the binary .udb format. Any publicly available data from RTP Company is available as a .udb file, although use of the current database is preferred over because it is always automatically updated.

Q: on your 4 gate/runner, don’t the two center runners hesitate and cause problems?
A: Balancing the pressure drop has to be done with care and sufficient runner length is needed to prevent hesitation effects from creating problems. As long as there is sufficient flow length, only small diameter differences are needed to balance pressure, and severe hesitation isn’t an issue.

Q: can you account for the Beaumont effect?
A: The thermal instability from successive runner branching can be detected but only with 3D analysis and a very finely meshed model. Success in predicting flow behavior to date still lags what happens in reality, but according to Mr. Beaumont himself (he presented @ Autodesk University 2011), he has gotten his best results to-date with the latest version of AMI. When predicting high shear heating in AMI, you also have to modify the parameter “Absolute Maximum Melt Temperature” as the software caps all shear heating calculations @ 30°C above that value.

Q: Would you do Moldflow for most micro molds
A: Molding analysis has been performed for micro-molding, I recently saw a published article on that subject. Care would need to be taken on tolerances when generating the mesh to make sure that nothing is compromised from merging of nodes, etc. But the physics still apply even on such a small scale.

Q: Does Long fiber modeling take into consideration fiber tumble, or does it assume linear orientation?
A: The latest version of Moldflow software (AMI 2013) does have the first generation of development in trying to predict orientation in the “thickness” direction. Not a lot of validation that I am aware of, but it is a start. In most injection molding geometries there will still be very little orientation through the thickness.

Q: Could a customer just contract with RTP Company for the Moldflow analysis (if they are not a material customer)?
A: RTP Company analysts generally only do analysis for customers using our materials, but if you have an application that you’d like to examine with one of our materials, contact your RTP Company Sales Engineer.

Q: can the mesh be adjusted to get a more detailed flow or smaller incremental flow front?
A: A finer mesh can be utilized to create better flow front definition and flow front results can be scaled to look at smaller increments of flow. Additionally, flow front progression parameters can be reduced so that each time step in the analysis is for smaller increments, but that will also run up the analysis times.

Q: Contact for material data?
A: Contact either you RTP Company sales engineer or Barb Matousek or Bob Sherman in our CAE Technical Services group.

Q: Is it offered to non Moldflow users?
A: RTP Company material data that has been tested for Moldflow inputs can be made available to Moldex and Sigmasoft users also, but we cannot create input files for the database as we can for Autodesk Moldflow. We will have to supply you the analyst with thermal and rheological information and creating a personal database will be up to the analyst.

Q: who should do moldflow analysis? Part designer or tool designer?
A: Preferably at both stages, but generally before you are ready to cut steel. Mold Adviser is useful where a part designer can do early preliminary analysis to make sure wall thickness requirements are reasonable, and then later a tool designer might be able to predict warpage results once the geometry is better defined and gating options need to be explored.

Q: who provides the material properties? Material suppliers are usually reluctant to provide this data
A: We are not reluctant to provide material data for our materials if we have it. Contact your RTP Sales Engineer or RTP Company CAE group and we can determine whether we have the material data you need. If not we can look at options for providing you the best data for your analysis needs.

Q: how much does mesh size interferes with the final results? Is there any relation between the part size and mesh size?
A: The mesh size should mainly be determined by part features and changes in thickness. General rules of thumb are 1) 3-5 elements across any thickness variations to be sure any potential hesitation is predicted, 2) at least 3 elements minimum in the height of ribs, and 3) at least 3 elements or more between features. A relatively uniform mesh size should be utilized when that is reasonable, but exceptionally large parts may not allow that. There are exceptions, such as if ribs are extremely short, but execution times are quick enough now that it is best to refine the mesh in these regions just to be sure.

Q: Is it possible to predict in-mould stress when over-moulding a metal part?
A: Yes, but only in a 3D analysis. The metal insert will need to be meshed in tetrahedrons and assigned the proper properties, and then the molding analysis will predict shrinkage around the insert and the insert stiffness will be included in the warpage analysis also.

Q: Please note that both Midplane as well as Dual Domain will use CRIMS data, if available.
A: Yes, that was a “slip-up” on our part. The dual domain is essentially also a midplane analysis with results mapped to the two exterior surfaces so it can utilize the CRIMS data in shrinkage and warpage analysis. To date, the CRIMS is not utilized in 3D analysis, but rumor has it that Autodesk are working on coming up with a way to incorporate it into 3D analysis. The dual domain even though it utilizes CRIMS data, can fall short in predicting warpage instabilities, that is where a midplane model works best, as long as the geometry is well defined by the midplane model.