Archive for Září, 2011

Guidelines For Avoiding Costly Mistakes Plastic Parts

Guidelines For Avoiding Costly Mistakes Plastic Parts

Errors, that newcomers regularly make whilst beginning to design plastic parts can often be discovered by Rapid prototype parts before commencing to construct an injection mold. I am going to point out some frequently made mistakes and present several suggestions for designing the perfect plastic parts.

The procedure of producing plastic parts differs from making other components like metal parts. An important practice in designing plastic components is to attempt to sustain identical wall thickness. Parts with uneven wall thickness are likely to cool irregularly and leave bad shrink marks which are noticeable on the outer surface. In addition, this might bring about tension at the junction of high and low shrinkage and cause the part to warp.

Given that plastic components are shaped by injection molding, they must be designed with a draft. Draft is the angle of taper of a wall. A draft angle of 0.5 degrees is considered as a bare minimum for many appliances. Draft angles of 1.5 to 2 degrees are regarded normal for plastic injection molding.

Whilst using a thin wall thickness, every so often it is required to increase the stiffness of a component. One frequently used technique is to include ribs. Yet, when adding ribs a few guidelines have to be adhered to. The thickness of the rib ought to be smaller than the wall thickness. Typically ribs are 60% to 80% of the wall thickness and spaced no less than 2 times the wall thickness apart. Don’t make the height of the rib upwards of 3 times the wall thickness. It is better to increase the quantity of ribs as opposed to the rib height.

Bosses are utilized as components need to be mounted and are now and then designed with thick wall sections that may affect the look of the final parts.  As a guideline , the wall thickness around a boss should be 60% of the nominal part thickness if that thickness is smaller than 1/8 inches. If the part thickness is more than 1/8 inches, the nominal part thickness ought to be 40% of the wall thickness. In order to avoid sink marks and voids, the next rule should be observed when determining the height of the boss. Ideally the maximum height of the boss ought to be no more than 2.5 times the boss hole diameter.

When designing plastic components, sharp corners should be avoided. Sharp corners can lessen part strength and act as stress risers. Sharp corners moreover effect plastic flow causing parts with nasty surface patterns. The internal radius of bosses and ribs should be one quarter of the part thickness, yet a minimum of 0.015. The inside radius of other corners ought to be a minimum of half the wall thickness. The exterior radius should be the internal radius plus the part thickness.

Guidelines For Avoiding Costly Mistakes Injection Molded Plastic Parts

Guidelines For Avoiding Costly Mistakes Injection Molded Plastic Parts

Mistakes, which newcomers regularly make whilst beginning to design plastic components can regularly be discovered via Rapid prototype parts before starting to construct an injection mold. I will point out a number of usually made mistakes and present some pointers for designing the perfect plastic components.

The method of manufacturing plastic components is different from producing other components such as metal components. An important practice in designing plastic components is to try to maintain identical wall thickness. Parts with irregular wall thickness are likely to cool unevenly and leave nasty shrink marks that are visible on the outside. In addition, this might cause stress at the junction of high and low shrinkage and cause the part to warp.

Given that plastic components are shaped by injection molding, they ought to be designed with a draft. Draft is the angle of taper of a wall. A draft angle of 0.5 degrees is considered as a bare minimum for a lot of appliances. Draft angles of 1.5 to 2 degrees are regarded customary for plastic injection molding.

Whilst using a thin wall thickness, now and then it is crucial to raise the rigidity of a part. One usually used technique is to add ribs. While inserting ribs, be sure to make the thickness of the ribs less than the thickness of the wall. Normally, ribs have 60% to 80% of the wall thickness. When multiple ribs are utilized, they must be spaced at the least 2 times the wall thickness apart. It is best to keep the height of the ribs less than 3 times the wall thickness and rather add more ribs instead of increasing the height of the ribs.

Bosses are another design building block used for mounting and assembly purposes. Regularly, bosses are designed with thick wall sections that can influence the appearance of the plastic component and the finished product.  As a guideline , the wall thickness around a boss ought to be 60% of the nominal part thickness if that thickness is smaller than 1/8 inches. If the part thickness is more than 1/8 inches, the nominal part thickness ought to be 40% of the wall thickness. In order to avoid sink marks and voids, the next rule ought to be adhered to while determining the height of the boss. Ideally the greatest height of the boss should be no more than 2.5 times the boss hole diameter.

When designing plastic components, sharp corners ought to be avoided. Sharp corners can lessen part strength and act as stress risers. Sharp corners moreover effect plastic flow producing parts with unappealing surface patterns. The inside radius of bosses and ribs ought to be one quarter of the part thickness, but a minimum of 0.015. The internal radius of other corners should be at the least half the wall thickness. The outer radius should be the inside radius added to the part thickness.

The Technology of Injection Molding Machines

The Technology of Injection Molding Machines

Do you ever wonder how your plastic parts are made? In the plastic industry, the system of injection molding has been an integral part of providing different sectors plastic products essentially used in healthcare, domestic areas, automotive, fashion and the like.

In the process of manufacturing plastic parts, the technological capacity of the molding machine is significant to note. Triumph in this industry is established in superior technology, reliability and customer’s satisfaction and the largest suppliers of plastic products and services such as Husky and Nissei Corporation know this as truth. As we know, these plastic providers supply the automotive market of over 40% of plastic goods and half to the medical sector.

Substantial use of thermoplastics or a polymer that melts when heated is the main material for injection molding apart from thermosets, resin pellets or rubber. A uniform melt viscosity is needed for the process and care must be given to avert degradation of the polymer through the thermal course. The process is simple to understand in which the material is initially heated to become viscous and then forced into a ready made mold. The molten plastic solidifies instantly so the machine can operate to produce one solid plastic to the next.

Injection molding is the largest quantity processing approach that massively produces plastic parts in various shapes, sizes and dimensions. The manufacturers who utilize such ingenuity supply the whole market with needed plastic components and some people argue that these components can replace existing metal, glass, wood and other synthetic elements in the make and structure of several products, equipment and devices.

The injection molding machine covers a lot of bases. They are able to produce numerous amounts of plastic parts for different purposes. For instance, the Nissei’s hybrid injection molding machine has improved molding stability, energy saving function and an outstanding injection holding pressure that provide for an excellent molding performance. Other machines such as the electric and hydraulic types offer more and are mainstreamed in the market today.

The injection molding machine has plenty of desirable features and it generates a considerable number of plastic products and this machine has developed to the more sustainable and practical equipment that greatly sustains the plastic industry as of this moment.

SPI Injection Mold Classifications

SPI Injection Mold Classifications - Where did they come from?

SPI plastic injection mold classifications (originally called “Classifications of Injection Molds for Thermoplastic Materials”) have been in place and copyrighted since 1978. They have been updated a few times throughout the years but remain largely the same as the original draft created for the Society of Plastics Industry.

The following is an excerpt from an e-mail received 3-11-2011 from Mike Noggle who helped create the standards we all use to this day.

“The original printing was in 1978 and several other revisions followed. The most meaningful change was in the 1990’s and added larger molds as we originally addressed molds intended for 450 ton machines or less.”

“The idea originated in the mid 1970’s and around 1976 Chuck Brewer Jr. gathered some friends in the industry to discuss problems frequently encountered with losing jobs to shops quoting inferior tooling. Most toolmakers, at that time, acknowledged “Class A” molds to be the finest available but there were no written standards to describe exactly what that meant. As an example, I attended an SPI led forum one night and sat int he audience while a panelist proclaimed he could produce Class A aluminum molds.”

“At that point, I knew something needed to be done since most buyers had no moldmaking expertise. I met with Chuck Brewer, Jack Kelly and Jim Atchison on numerous occasions as we hammered out what we envisioned a Class A mold to be. It was nearly unanimous that this mold, intended for high production, needed to be of hardened steel and built to exacting standards. We also recognized there was a need for prototype, low and intermediate volume molds so we discussed standards for those as well.”

“After taking copious notes and discussing the need for standards over many months, I took the bull by the horns and wrote the initial draft. I sent it to Chuck for editing since he started this entire process. We recognized Class I through Class IV molds and inserts and gave descriptions for the buyers expectations and the moldmakers reference.” (Today known as class 101 to 105).

“After completing our work, we assigned the entire effort to SPI for publishing. It was presented at a national moldmakers conference in 1978 and, to our pleasant surprise, immediately embraced by the membership. It was intended as a guideline so buyers could understand what they should expect when ordering a mold and to level the playing field by having the moldmakers quote similar tools. Later revisions changed the molds to Class 101, 102 etc. and larger molds were recognized as class 401 etc.Though copyrighted it is, as you noted, widely used for reference. And that is how the SPI guidelines came to be.”