Molded product and its manufacturing method

Abstract

A method of making a molded article is disclosed. The method includes forming a body comprising a polymeric material. The method further includes polishing a portion of the body with an abrasive element to smooth out at least one defect. The abrasive element includes a polymeric material different from the polymeric material of the body.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a molded article and to a molded article. In particular, but not exclusively, the present invention relates to a method for manufacturing a molded knee implant and to a molded knee implant, which may be a femoral knee implant component. [Background technology]

[0002] Typically, polymeric articles may be formed by molding techniques such as injection molding or compression molding. The mold results in a shiny surface, but surface defects may occur. In addition to surface defects, it may be necessary to remove areas where the polymer is injected into the mold, such as gates. Removal of parts of the article may cause a dulling of the surface and an increase in roughness, which may be quantified as an Ra value. Ra is the arithmetic mean of the absolute values ​​of the profile height deviations from the mean line recorded within the evaluation length. Simply put, Ra is the average of a set of individual measurements of the peaks and valleys of the surface.

[0003] Additionally, molding techniques can result in articles having parting lines, also known as parting lines, which are the boundaries where the draft angle changes direction, i.e., the boundary line that separates the core and cavity halves of a molded part.

[0004] Methods for reducing defects on polymeric articles include using abrasive media to remove the defects. Drag abrasion is a method in which the article to be abraded is pulled through a mass of media, honing and polishing the article in the process. The article is then "dragged" through a work bowl filled with grinding or polishing media. Vibratory abrasion involves placing specially shaped pellets of abrasive media and the article to be abraded in a vibratory tumbler. The vibration causes the media to rub against the article, abrading it.

[0005] Drag polishing and vibration polishing have been found to be inappropriate for polishing polymeric articles intended for surgical purposes or that include a bearing surface that may rub against another surface during use. This is because during polishing, the abrasive particles of the polishing media may break free from the matrix to which they were bound and become embedded in the surface of the polymer. The final article may contain impurities in the polished surface. For example, in the case of surgical implants or other medical devices, the embedded media may cause adverse effects on biocompatibility, either with toxicity to the surrounding tissue or mechanical irritation of the surrounding tissue. In addition, the embedded abrasive particles may cause excessive wear of the surface of the article or of the corresponding surface of the further article with which the first article is in contact.

[0006] Non-abrasive rotating polishing wheels can also be used to polish articles. This is an advantageously simple method. However, this method is not suitable for polymeric articles because it utilizes friction to polish the surface of the article. The friction generates heat that softens the polymer. The softened polymer is applied to adjacent surface areas rather than removed. In addition, this method can change the crystallinity of the polymer at the surface. This can create excess stress that can lead to defects in the article during use.

[0007] Flame polishing is a method of polishing a polymeric article by exposing it to a flame or heat. The heat briefly melts the surface of the article, and surface tension smooths the surface. The method relies on melting the surface of the article, which can create localized stresses on the surface, thereby affecting wear properties. Melting also changes the crystallinity of the polymer at the surface. The method can typically only be applied consistently to flat surfaces, with less accuracy on uneven surfaces.

[0008] It is an object of certain examples of the present invention to at least partially solve, mitigate, or eliminate at least one of the problems and / or disadvantages associated with the prior art. Particular examples are directed to providing at least one of the advantages set forth below.

[0009] In particular, it is an object of certain embodiments of the present invention to provide techniques for polishing molded articles that reduce the amount of particles embedded in the surface.

[0010] It is a further object of certain embodiments of the present invention to provide a technique for polishing molded articles that provides a smooth transition between the machined surface and the molded surface.

[0011] It is an object of certain embodiments of the present invention to provide a technique for polishing molded articles that reduces the Ra value of the article compared to known techniques, while maintaining biocompatibility. Summary of the Invention

[0012] Aspects of the present invention provide methods of making molded articles, molded articles, and implantable devices as set forth in the accompanying claims.

[0013] According to one aspect of the present invention, there is provided a method for producing a molded article, the method comprising: forming a body comprising a polymeric material; abrading a portion of the body with an abrasive element to smooth out at least one defect; An abrasive device, wherein the abrasive element comprises a polymeric material different from the polymeric material of the body.

[0014] Preferably, polishing the portion of the body comprises: rotating the abrasive element; and supporting a rotating abrasive element against a surface of the body such that the abrasive element abrades the at least one defect.

[0015] Preferably, the difference in Ra value between the polished portion of the body and the unpolished portion of the body is less than 0.8 micrometers.

[0016] Preferably, rotating the polishing element includes rotating the polishing element at a spindle speed of 1000 rpm to 20000 rpm and a feed rate of 100 mm / min to 5000 mm / min, and the molded article has an Ra value of 0.2 micrometers to 1.0 micrometers.

[0017] Preferably, the different polymeric material of the abrasive elements has a higher hardness than the polymeric material of the body.

[0018] Preferably, the polymeric material of the body comprises polyetheretherketone (PEEK) and the different polymeric material of the polishing elements comprises annealed PEEK or barium-filled annealed PEEK.

[0019] Preferably, the method further comprises machining the body to form a machined edge, and the polishing step comprises smoothing the machined edge.

[0020] Preferably, machining the body includes cutting a path with a cutter to remove a portion of the body, the abrasive element following the path of the cutter.

[0021] Preferably, prior to polishing the body, the method comprises: Abrading a portion of the body with an abrasive medium; or and smoothing a portion of the body with an etched glass rod.

[0022] Preferably, the body is formed by injection molding and the at least one defect is a mold gate.

[0023] Preferably, the molded article is an implantable device, optionally a femoral knee component.

[0024] According to a further aspect of the invention there is provided an abrasive element for use in a method of producing a molded article.

[0025] Preferably, the abrasive element comprises a bull nose for contacting the body.

[0026] According to a further aspect of the present invention there is provided a moulded article produced by: forming a body comprising a polymeric material; abrading a portion of the body with an abrasive element to smooth out at least one defect; The abrasive element comprises a polymeric material different from the polymeric material of the body.

[0027] Preferably, the difference in Ra value between the polished portion of the body and the unpolished portion of the body is less than 0.8 micrometers.

[0028] According to a further aspect of the present invention there is provided an implantable device formed by: forming a body comprising a polymeric material; abrading a portion of the body with an abrasive element to smooth out at least one defect; The abrasive element comprises a polymeric material different from the polymeric material of the body.

[0029] Preferably, the difference in Ra value between the polished portion of the body and the unpolished portion of the body is less than 0.8 micrometers.

[0030] Preferably, polishing the portion of the body comprises: Rotating the polishing element at a spindle speed of 1000 rpm to 20000 rpm and a feed rate of 100 mm / min to 5000 mm / min; and supporting a rotating abrasive element against a surface of the body such that the abrasive element abrades the at least one defect; The formed implantable device is polished so that its Ra value is 0.2 micrometers to 1.0 micrometers.

[0031] Preferably, the implantable device comprises a femoral component for a knee implant. [Brief description of the drawings]

[0032] Embodiments of the invention are further described below with reference to the accompanying drawings. [Figure 1a] 1 is a schematic diagram of an abrasive element according to an example of the present invention. [Figure 1b] 2 is a schematic diagram of a body according to one example of the present invention formed during a process for manufacturing a molded article. [Diagram 2] 1 is a flow chart of a method for producing a molded article according to an example of the present invention. [Diagram 3] 4 is a further flow chart of a method for producing a molded article according to an example of the present invention. [Figure 4] 4 is yet another flowchart of a method for manufacturing a molded article according to an example of the present invention. [Figure 5a] FIG. 3D view of a femoral knee implant. [Figure 5b] FIG. 3D view of a femoral knee implant. [Figure 5c] FIG. 3D view of a femoral knee implant. [Figure 6] FIG. 5B is a schematic diagram of the femoral knee implant of FIGS. 5a-5c. [Figure 7a] 1 is a scanning electron microscope (SEM) image showing the surface of a femoral knee implant. [Figure 7b] 1 is a scanning electron microscope (SEM) image showing the surface of a femoral knee implant. [Figure 7c] 1 is a scanning electron microscope (SEM) image showing the surface of a femoral knee implant. [Figure 7d] 1 is a scanning electron microscope (SEM) image showing the surface of a femoral knee implant. [Figure 7e] 1 is a scanning electron microscope (SEM) image showing the surface of a femoral knee implant. [Figure 7f]1 is a scanning electron microscope (SEM) image showing the surface of a femoral knee implant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Prosthetic implants can be used to partially or completely replace diseased and / or damaged joint tissue. Such implants can include articulating surfaces that replace the natural articulating surfaces of the bone. For example, an implant for a knee replacement can include a femoral implant and / or a tibial implant. The femoral implant can be implanted on the distal end of the femur and can replace the articulating surface of the femur. The tibial implant can be implanted on the proximal end of the tibia and can replace the articulating surface of the tibia.

[0034] During operation, the articulating surface of the femoral implant articulates against the articulating surface of the tibial implant. Various materials have been used for the femoral and tibial implants. For example, the implants may be made of metal, e.g., cobalt-chromium. Metal implants may have significantly higher stiffness and tensile strength than bone. As a result, metal implants may have an increased tendency to protect the underlying bone from the stresses normally applied to the joint during use. According to Wolff's law, bone remodels in response to applied loads. If the bone is shielded from these loads, it is not exposed to the stimuli required to maintain bone mass. This may lead to, for example, a loss of bone mass that may increase the likelihood of the implant loosening. In recent years, there has been increased interest in knee implants formed from polymeric compositions that can be formulated to have mechanical properties that are more compatible with those of bone.

[0035] The following description describes a femoral knee implant as an example of a molded article, but any article formed by molding is contemplated. Exemplary articles include, but are not limited to, implantable devices such as femoral or tibial knee implants and spinal implants, and manufactured components such as bearings and gears.

[0036] Throughout this specification reference is made to polymeric materials. Preferably, the polymer is a polyaryletherketone (PAEK) material.

[0037] Suitable polyaryletherketones may have repeat units of formula (I):

[0038] [ka] In the formula, t1 and w1 independently represent 0 or 1, and v1 represents 0, 1, or 2.

[0039] The polyaryletherketone preferably comprises at least 90, 95, or 99 mole % of repeat units of formula I. The polyaryletherketone preferably comprises at least 90, 95, or 99 weight % of repeat units of formula I.

[0040] The polyaryletherketone may comprise or essentially consist of repeat units of formula I. Preferred polymeric materials comprise (or essentially consist of) the repeat units described above, where t1=1, v1=0, and w1=0. t1=0, v1=0, and w1=0, t1=0, w1=1, v1=2, or t1=0, v1=1, and w1=0. More preferably, the polyaryletherketone comprises (e.g. essentially consists of) repeat units I, where t1=1, v1=0, and w1=0. Or t1=0, v1=0, and w1=0. Most preferred polyaryletherketones comprise (particularly essentially consist of) the repeat units described above, where t1=1, v1=0, and w1=0.

[0041] The polyaryletherketone may be selected from polyetheretherketone, polyetherketone, polyetherketoneetherketoneketone, and polyetherketoneketone. In some examples, the polymer is selected from polyetherketone and polyetheretherketone. The polymer is preferably polyetheretherketone (PEEK).

[0042] Polyaryletherketone has a resistance of at least 4KJm -2 , preferably at least 5KJm -2 , more preferably at least 6KJm -2 The notched Izod impact strength measured as described above is 10 KJm -2 Less than 8KJm -2 The notched Izod impact strength, measured as described above, may be at least 3 KJm -2 , preferably at least 4KJm -2 , preferably at least 5KJm -2 The impact strength can be up to 50KJm -2 Less than 30KJm -2 It may be less than.

[0043] Polyaryletherketone has a resistance of at least 0.06 kNsm -2 and preferably has a melt viscosity (MV) of at least 0.09 kNsm -2 , more preferably at least 0.12 kNsm -2 , especially at least 0.15 kNsm -2 Advantageously, the MV is at least 0.35 kNsm -2 , especially at least 0.40 kNsm -2 May be 0.45kNsm -2 MVs of may be particularly advantageous.

[0044] Unless otherwise stated, melt viscosity (MV) is measured at 340 °C and 1000 s according to ISO 11443 using a Bohlin Instruments RH2000 capillary rheometer. -1 The viscosity is measured at an incidence angle of 180° using a die of 0.5 mm (capillary diameter) x 8.0 mm (capillary length). The granules are loaded into the barrel and allowed to preheat for 10 minutes. Viscosity can be measured nominally 5 minutes after the start of the test, after steady state conditions have been reached and maintained. Polyaryletherketones have a viscosity of 1.00 kNsm -2 Less than 0.5kNsm -2 Polyaryletherketones may have an MV of 0.09 to 0.5 kNsm -2 in the range of 0.14 to 0.5 kNsm -2 in the range of 0.4 to 0.5 kNsm -2 The MV may be in the range of

[0045] The polyaryletherketone may have a tensile strength of at least 20 MPa, preferably at least 60 MPa, more preferably at least 80 MPa, measured according to IS0527 (specimen type 1b) tested at a speed of 50 mm / min at 23° C. The tensile strength is preferably in the range of 80-110 MPa, more preferably in the range of 80-100 MPa.

[0046] The polyaryletherketone may have a flexural strength, measured according to IS0178 (3-point bending test on 80 mm x 10 mm x 4 mm samples at 23 °C at a rate of 2 mm / min), of at least 50 mPa, preferably at least 100 mPa, more preferably at least 145 mPa. The flexural strength is preferably in the range of 145 to 180 MPa, more preferably in the range of 145 to 164 MPa. The polyaryletherketone may have a flexural modulus, measured according to IS0178 (3-point bending test on 80 mm x 10 mm x 4 mm samples at 23 °C at a rate of 2 mm / min), of at least 1 GPa, suitably at least 2 GPa, preferably at least 3 GPa, more preferably at least 3.5 GPa. The flexural modulus is preferably in the range of 3.5 to 4.5 GPa, more preferably in the range of 3.5 to 4.1 GPa.

[0047] The polyaryletherketone may be amorphous or semi-crystalline. The polyaryletherketone is preferably crystallizable. The polyaryletherketone may be semi-crystalline. The level and degree of crystallinity in a polymer can be measured by wide-angle X-ray diffraction (also called wide-angle X-ray scattering or WAXS), for example, as described by Blundell and Osborn (Polymer 24,953,1983). Alternatively, crystallinity can be evaluated by Differential Scanning Calorimetry (DSC).

[0048] The level of crystallinity of the polyaryletherketone may be at least 1%, suitably at least 3%, preferably at least 5%, more preferably at least 10%. In particularly preferred embodiments, the crystallinity may be greater than 25%. It may be less than 50% or less than 40%. The main peak of the melting endotherm (Tm) of the polyaryletherketone (if crystalline) may be at least 300°C.

[0049] Figure 1a shows a schematic example of an abrasive component 100, and Figure 1b shows a simplified representation of a molded body 150. In this example, a surface imperfection 152 is shown on the molded body 150. Once polished, the body 150 comprises the manufactured molded article, which may be an implantable device and may suitably be a femoral knee component.

[0050] The body 150 is formed from a polymeric material. Any suitable polymer may be used to form the body 150 of the molded article of the present disclosure. Preferably, the polymer is polyaryletherketone (PAEK). Suitably, the polymer is polyetheretherketone (PEEK).

[0051] The abrasive component 100 includes an abrasive element 102 adapted to abrade a portion of a body 150 and a drive element 104 capable of rotating, actuating, vibrating, or otherwise moving the abrasive element 102 .

[0052] The polishing element 102 may include an attachment end 106 that is attached to the drive element 104 and a contact end 108. The attachment end 106 may be releasably connected to the drive element 104. For example, the attachment end 106 may be threaded. Thus, the polishing element 102 may replace an existing drive element or be retrofitted to an existing drive element. The contact end 108 of the polishing element 102 is the portion of the polishing element 102 that abuts the article body 150 in use. The drive element 104 may drive the polishing element 102 to move when the contact end 108 is in contact with the body 150.

[0053] In this example, the contact end 108 of the polishing element 102 may have a bullnose or be otherwise rounded. The contact end 108 may have a diameter of 2 mm to 8 mm, suitably 4 mm to 5 mm. In other examples, the contact end 108 may be any suitable shape or size, for example a flat plate or a pointed cone.

[0054] 1a, the polishing element 102 is an elongated rod, i.e., the polishing element 102 has an elongated extension between the attachment end 106 and the contact end 108. It should be appreciated that in other examples, the polishing element 102 may be plate-shaped or any other suitable shape.

[0055] In an example where the molded article is an implantable device such as a femoral knee implant, the abrasive element 102 may be rod shaped and have a bull nose contact end 108 having a diameter of 2 mm to 8 mm, suitably 4 mm to 5 mm, and may be approximately 4 mm.

[0056] The abrasive component 100 may also include a controller (not shown), which controls the path of the contact end 108. In other words, the abrasive component 100 may use an automated system to control the abrasive elements 102, which reduces variation between or across articles. Thus, the controller may include a program including code for controlling the path of the abrasive elements 102, and a machine-readable storage device that stores such a program. Moreover, such a program may be transmitted electronically via any medium, for example, a communication signal carried over a wired or wireless connection.

[0057] The abrasive elements 102 are a polymeric material that is a different polymeric material than the polymeric material of the body 150. Any suitable polymer may be used to form the abrasive elements 102 of the molded articles of the present disclosure. Preferably, the polymer is a polyaryletherketone (PAEK). Suitably, the polymer is a polyetheretherketone (PEEK).

[0058] For example, the polymeric material of the body 150 may be a first PAEK material, and the different polymeric material of the polishing element may be a different PAEK material. In some examples, one or both of the polymeric materials may include a filler, such as an abrasive filler, for example, barium sulfate. That is, the barium sulfate may be present in the polymeric composition in an amount of up to 20% by weight of the total weight of the polymeric composition. Alternatively, or in addition to including a filler, the polymeric material of the polishing element 102 may be annealed. An annealed PEEK material is a different polymeric material than an unannealed PEEK material in the sense that the PEEK material has been hardened by annealing. In other words, the body 150 may be formed from an unannealed PEEK material, and the polishing element 102 may be an annealed PEEK material. Thus, the polishing element 102 is harder than the body 150.

[0059] By having the polymeric materials of the body 150 and the polishing element 102 as different polymeric materials of the PAEK family, such as PEEK in the unannealed and annealed states, respectively, the polishing element 102 allows the required Ra value to be achieved without the use of polishing media that embeds abrasive particles in the surface of the body. In this sense, the Ra value throughout the body of the article is reduced overall when compared to articles polished with alternative polishing techniques. As a result, the final article does not contain a significant amount of impurities in the polished surface. This can result in an increase in the lifespan of the final article, especially due to reduced wear on the bearing surface that rubs against another surface during use. Furthermore, in the case of implantable devices, the biocompatibility of the article is not compromised.

[0060] 2 illustrates a method of manufacturing a molded article using the abrasive component 100. The molded article may be suitable for use as a femoral or tibial knee implant. First, in step S210, a body 150 is formed that includes a polymeric material.

[0061] A polymeric material is provided in liquid or pliable form and shaped using a mould to form the body 150. Typical moulding techniques include, but are not limited to, rotational moulding, injection moulding, blow moulding, compression moulding, extrusion moulding or thermo moulding. Suitably the moulding method may be injection moulding.

[0062] Once the body 150 is formed in step S210, at least a portion of the body may include one or more surface defects 152. The surface defects 152 may include surface bubbles, discoloration, parting lines, machine edges, etc. To remove the surface defects, the portion of the body is polished in step S220 with polishing element 102. Polishing the portion of the body 150 may include removing a plurality of surface defects 152.

[0063] By polishing a portion of the body 150, defects are smoothed out such that the difference in surface roughness between the polished and unpolished areas is small. That is, since the injection molded surface is shiny (except for the defects), most of the surface does not require polishing. For example, the injection molded surface may have an average Ra value of 0.01 micrometer to 0.1 micrometer, suitably 0.025 to 0.075 micrometer, more suitably 0.05 micrometer. The polishing step S220 buffs out the defects 152 such that the polished portion of the body 150 more closely resembles the roughness of the unpolished portion of the body's surface. For example, the polished portion of the body may have a difference in Ra from the unpolished portion of the body of less than 0.8 micrometer, suitably less than 0.75 micrometer, more suitably less than 0.6 micrometer, more suitably less than 0.28 micrometer.

[0064] The Ra value of the polished portion of the body after the polishing step S220 is less than 1.5 micrometers, suitably between 0.1 micrometers and 1.2 micrometers, more suitably between 0.2 micrometers and 1.0 micrometers.

[0065] 3, a method of manufacturing the molded article described in FIG. 2 is shown with an additional step. After forming a body including a polymeric material in step S310, the method further includes rotating the polishing element in step S315. Rotating the polishing element 102 may include rotating the polishing element 102 using the drive element 104. That is, the contact end 108 of the polishing element 102 may rotate about a longitudinal axis of the polishing element 102.

[0066] In step S315, the abrasive element 102 may be rotated at a spindle speed of 1000 rpm to 20000 rpm and a feed rate of 100 mm / min to 5000 mm / min. Suitably, the abrasive element 102 may be rotated at a spindle speed of 5000 rpm to 15000 rpm and a feed rate of 500 mm / min to 2500 mm / min. The rotation speed of the abrasive element may be optimized for a particular molded article. For example, for a femoral knee implant (shown in Figures 4 and 5), the spin speed may be optimized at a spindle speed of about 10,000 rpm and a feed rate of about 1000 mm / min to give a Ra value for the femoral knee implant of 0.3 micrometers to 0.5 micrometers.

[0067] Then, in step S318, the rotating polishing element 102 may be brought into contact with the surface of the body of the molded article such that the polishing element 102 polishes at least one defect 152. In this manner, the contact end 108 of the polishing element 102 contacts the defect 152 and polishes away the area of ​​the body 150 containing the defect 152. In some examples, the polishing element 102 may be set at a height below the surface of the body to polish the surface defect 152. That is, the contact end 108 may be set at a height lower than the height of the surface of the body such that the contact end 108 applies pressure to the surface of the body of the molded article. For example, the polishing element 102 may be set at a height of 2 micrometers to 15 micrometers below the surface of the body. Suitably, the polishing element 102 may be set at a height of 5 micrometers to 12 micrometers below the surface of the body, and more suitably, 10 micrometers below the surface of the body.

[0068] To achieve a smooth transition between the polished area and the surface of the body 150, the polished area may be larger than just the defect 152; that is, the area around the defect 152 may also be polished by the polishing element 102. The polishing element 102 being a different polymeric material than the body 150 means that the contact end 108 polishes the defect 152 without embedding a large amount of material into the surface of the body 150, as compared to abrasive techniques.

[0069] Referring to FIG. 4, a method of manufacturing the molded article described in FIG. 3 is shown with additional steps. For example, when an injection molding process is used to form the body (S310), the area where the polymeric material enters may form a gate. Similarly, molding processes that involve attaching two or more parts of the article together may form parting lines. These defects may be machined out. In this example, the method includes a step S412 of machining the body of the article. The step S412 of machining the body 150 may include using a cutter to cut a path to remove at least a portion of the body. That is, using a cutting machine to cut the defect 152 from the body 150.

[0070] Machining the body 150 forms a machine edge, which is an area of ​​the body 150 that is blunted or roughened by a machine. This machine edge may be a defect 152. Thus, the polishing element 102 may polish a portion of the body 150, including the polishing edge, to smooth it in step S420. In some examples, the polishing element 102 may follow the path of a cutter. In some examples, a controller may be used to automate the machining and polishing steps S412, S420. This allows for consistency of surface Ra values ​​across the part.

[0071] In addition to or alternatively to the step S412 of machining the body, a step S413 of polishing the body 150 with an abrasive medium can be performed before polishing the body in step S420. The step S413 of polishing the body may have a further subsequent step S414 of smoothing a portion of the body 150 with an etched glass rod. The etched glass rod may remove embedded particles of the abrasive medium from the previous step. Thus, polishing the portion of the body 150 with the abrasive element 102 may be the final step S420 to provide an overall smooth finish. In addition, the step S420 of polishing the portion of the body 150 may also remove embedded particles of the abrasive medium from the previous step.

[0072] In some examples, micromachining may be used for at least one of the cutting step S412 or the polishing step S420. One example of a suitable cutter is the Hurco™ 5-axis machine manufactured by Hurco Companies, Inc. of Pleening, Germany, and described at https: / / www.hurco.eu / products / 5-axis-machining-centers / . It will be appreciated that any suitable machine capable of orienting polishing elements to follow the profile of the surface to be polished may be used.

[0073] 5a-5c show a 3D model of an exemplary part, where the part is a femoral knee implant.

[0074] The polymer body 550 of the femoral knee implant is shaped using injection molding. To form the required shape of the femoral knee implant, the polymer is injected through a gate and split into two parts: a medial condyle 554 and a lateral condyle 556 on either side of the intercondylar slot 558. The area of ​​the body 550 formed as a result of the gate is machined to remove a portion of the side from the intercondylar slot 558. This portion may be 0.1 mm to 1 mm, suitably this portion is 0.2 mm to 0.4 mm, more suitably 0.3 mm. This machining process also cuts into the radius, creating a sharp edge 559 on the slot radius, this radius may be 2 mm to 5 mm, suitably 2 mm to 3 mm, more suitably 2.5 mm.

[0075] The sharp edges 559 may be sharpened using the methods described above to form a smooth transition along the intercondylar slot 558 .

[0076] Figure 6 shows a schematic diagram of the exemplary molded article of Figures 5a-5c. The intercondylar slot 558 of the implant includes a separation line 660 that must be machined away using the polishing methods described above.

[0077] The Ra value may be measured at three locations, for example, the apex 670 of the intercondylar slot 558, and the edges 672, 674 of the intercondylar slot 558 on both the medial 554 and lateral 556 condyles. This can therefore determine whether the polished portion is sufficiently smooth for use in surgical applications. For implantable devices, the above method provides a smoothed article with reduced biological incompatibility compared to methods using abrasive media.

[0078] The method of manufacturing a molded article as described above advantageously results in a molded article with reduced wear over its life due to a smoother surface. In addition, the molded article may have a significantly improved appearance in the sensed areas with removed defects consistent with the gloss of the molded surface. EXAMPLES

[0079] The femoral knee implant specimens were made of PEEK material. The specimens were machined using a Hurco™ 5-axis milling machine, and then polished using a barium sulfate-filled and annealed PEEK rod. The Ra values ​​were measured for multiple femoral knee implants of the same size and deformation for the medial and lateral condyles. The results are shown in Table 1 below.

[0080] [Table 1]

[0081] The average Ra value for the implants without polishing was 0.657 micrometers. After polishing with the barium-filled PEEK rods, the average Ra value was 0.377 micrometers. This indicates a significant decrease in the Ra value after polishing, resulting in an improved surface finish. EXAMPLES

[0082] The femoral knee implant samples were made from PEEK material. The samples were machined using a Hurco™ 5-axis milling machine and then polished using annealed barium-filled PEEK rods or annealed PEEK-only rods. The Ra values ​​were measured at the medial and lateral condyles. The average Ra value of the samples polished with annealed barium-filled PEEK rods was 0.751 micrometers, and the average Ra value of the samples polished with annealed PEEK rods was 0.7509 micrometers. This indicates that there is no significant difference between the samples polished with annealed PEEK-only rods or annealed barium-filled PEEK rods. EXAMPLES

[0083] Femoral knee implant specimens were made from PEEK material. The specimens were machined using a Hurco™ 5-axis milling machine and then polished using annealed barium-filled PEEK rods or annealed PEEK only rods. The spindle speed and feed rate were optimized to a spindle speed of 10,000 rpm and a feed rate of 1000 mm / min.

[0084] The Ra values ​​on the machined and polished areas of the medial and lateral condyles were measured to determine how rough the machining and polishing process with each rod type roughened the surface. The average Ra value for the samples polished with barium-filled PEEK rods was 0.36 micrometers, and the average Ra value for the samples polished with PEEK rods was 0.39 micrometers. This indicates that there is no significant difference between the samples polished with annealed PEEK only rods or annealed barium-filled PEEK rods. EXAMPLES

[0085] Femoral knee implant specimens were made from PEEK material. Some specimens were machined using a Hurco™ 5-axis milling machine and then polished using annealed barium-filled PEEK rods. Other specimens were machined using a Hurco™ 5-axis milling machine and then hand polished using P800 paper, followed by P2500, then a felt pad.

[0086] The machined and polished samples were analyzed using a scanning electron microscope (SEM). The results are shown in Figures 7a-7f. Figures 7a-7d show the surfaces of samples polished using a barium-filled PEEK rod. Figure 7e shows the hand polished surface and Figure 7f shows the surface with grain separation.

[0087] For the sample polished with the annealed barium-filled PEEK rod, a small number of barium sulfate particles were found on the surface. The largest particle found was 2.63 micrometers, with the majority being submicron. In contrast, for the hand polished sample, a significant number of aluminum oxide, iron, and sodium particles were found. The largest particle was measured to be 40.829 micrometers.

[0088] Thus, although a small amount of debris was introduced by the annealed barium-filled PEEK rod, the amount and particle size was extremely small when compared to alternative polishing methods.

[0089] Throughout this specification, the terms "comprise" and "contain" and variations thereof mean "including but not limited to" and are not intended to (and do not) exclude other components, integers, or steps. Throughout this specification, the singular includes the plural, unless the context requires otherwise. In particular, when the indefinite article is used, the specification should be understood as considering the plural as well as the singular, unless the context requires otherwise. Throughout this specification, the term "about" is used to provide flexibility to the endpoints of a range by providing that a given value may be "a little above" or "a little below" the endpoint. The degree of flexibility of this term can be specified by the particular variable and can be determined based on experience and the relevant explanations in this specification.

[0090] Concentrations, dimensions, amounts, and other numerical data may be presented in a range format herein. It should be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly to include numerical values ​​expressly recited as limits of the range and to include all individual numerical values ​​or subranges subsumed within the range as if the numerical values ​​and subranges were recited. For example, a weight ratio range of about 1% to about 20% by weight should be interpreted to include the expressly recited limits of 1% and about 20% by weight, and also to include individual weights such as 2%, 11%, 14% and the like, and subranges such as 10% to 20%, 5% to 15% and the like.

[0091] It should be understood that features, integers, or characteristics described in connection with a particular aspect or embodiment of the invention are applicable to any other aspect or embodiment described herein, unless inconsistent. All of the features disclosed herein, and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel feature or combination of features disclosed herein. It will also be understood that throughout this specification, language of the general form "X for Y" (where Y is some operation, activity, or step, and X is some means for performing that operation, activity, or step) encompasses, but is not exclusive to, means X that are specifically adapted or arranged to perform Y.

[0092] Each feature disclosed in this specification, unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

[0093] The reader's attention is directed to all articles and documents related to this application that are filed contemporaneously or prior to this application and that are open to public inspection together with this application, and the contents of all such articles and documents are incorporated herein by reference.

Claims

1. A method for manufacturing a molded article, the method comprising: forming a body comprising a polymer material; polishing a portion of the body using a polishing element to smooth at least one defect, wherein the polishing element comprises a polymer material different from the polymer material of the body.

2. Polishing the portion of the body comprises: rotating the polishing element; supporting the rotating polishing element against the surface of the body such that the polishing element polishes the at least one defect. The method according to claim 1.

3. The difference in Ra value between the polished portion of the body and the unpolished portion of the body is less than 0.8 micrometers. The method according to claim 1 or 2.

4. Rotating the polishing element comprises rotating the polishing element at a spindle speed of 1000 rpm to 20000 rpm and a feed rate of 100 mm / min to 5000 mm / min, wherein the Ra value of the polished portion of the body is 0.2 micrometers to 1.0 micrometers. The method according to claim 2.

5. The different polymer material of the polishing element has a higher hardness than the polymer material of the body. The method according to claim 1 or 2.

6. The polymer material of the body comprises polyetheretherketone (PEEK), and the different polymer material of the polishing element comprises annealed PEEK or barium-filled annealed PEEK. The method according to claim 5.

7. The method further comprises machining the body to form a machined edge, and the polishing comprises smoothing the machined edge. The method according to claim 1 or 2.

8. Machining the body comprises cutting a path with a cutter to remove a portion of the body, and the polishing element follows the path of the cutter. The method according to claim 7.

9. Before polishing the body, the method further comprises: polishing a portion of the body with a polishing medium; or smoothing a portion of the body using an etched glass rod. The method according to claim 1 or 2.

10. The body is formed by injection molding, and the at least one defect is a molding gate. The method according to claim 1 or 2.

11. The molded article is an implantable device, optionally a femoral knee component, according to the method of claim 1 or 2.

12. A polishing element for use in the method of manufacturing the molded article according to claim 1 or 2.

13. The polishing element according to claim 12, comprising a burnish nose for contacting the body.

14. A molded article, forming a body comprising a polymeric material, polishing a portion of the body using a polishing element to smooth at least one defect, produced by the polishing element comprising a polymeric material different from the polymeric material of the body.

15. The molded article according to claim 14, wherein the difference in Ra value between the polished portion of the body and the unpolished portion of the body is less than 0.8 micrometers.

16. An implantable device, forming a body comprising a polymeric material, polishing a part of the body using a polishing element to smooth at least one defect, formed by the polishing element comprising a polymeric material different from the polymeric material of the body.

17. The implantable device according to claim 16, wherein the difference in Ra value between the polished portion of the body and the unpolished portion of the body is less than 0.8 micrometers.

18. Polishing the part of the body rotating the polishing element at a spindle speed of 1000 rpm to 20000 rpm and a feed rate of 100 mm / min to 5000 mm / min, supporting the rotating polishing element against the surface of the body such that the polishing element polishes the at least one defect, The implantable device according to claim 17, wherein the Ra value of the polished portion of the body is 0.2 micrometers to 1.0 micrometers.

19. The implantable device according to any one of claims 16 to 18, wherein the implantable device comprises a femoral component for a knee implant.

Images