Ini adalah peralatan presisi untuk mengukur Permeabilitas Pasir Pengecoran. Secara default, alat ini dapat mengukur permeabilitas absolut spesimen AFS (Diameter 2”X2”) atau Metrik (Diameter 50mmX50mm).

Dengan bantuan attachment juga dapat mengukur

• Permeabilitas Relatif Cetakan (Lihat 4.2.1)
• Permeabilitas Mutlak Inti (Lihat 4.2.2)
• Permeabilitas Absolut Pasir Tak Terikat (Lihat 4.2.3).

Nama Produk:	Pengukur Permeabilitas Digital
Kode Produk:	VPD1
Kode Referensi Pesanan:	V0000107
Pasokan Listrik yang Diperlukan:	Tegangan 230v 50Hz AC (Standar) 110v 60 Hz AC (Opsional) Fase Tunggal, Distabilkan dengan pemutus Tegangan Lebih/Kurang.
Steker Listrik:	Tipe M: Steker 15 Amp
Arus Maksimum Khas:	2,2 A pada 230V
Pasokan Udara Terkompresi:	Diperlukan Udara Terkompresi Kering 2 Kg/cm2 untuk membuat operasi sepenuhnya otomatis. Opsional jika Air Drum dapat diangkat oleh Operator.
Komunikasi:	Modul RTU RS485 Serial RS232 Ethernet (Opsional) CloudSync menggunakan V-Sync
Ukuran:	500 X 320 X 460 mm (P x L x T)
Dimensi Pengepakan:	600 mm x 450 mm x 625 mm (L x L x T) Khas
Berat Bersih:	Sekitar 25 kg
Berat Kotor:	Sekitar 30 kg
Warna:	Standar Pabrik
Rentang Pengukuran:	0-100 mmWC dan bacaan terkait Bagan pengukuran permeabilitas AFS ditampilkan secara digital.
Dapat dilacak ke:	Standar Produsen
Hitungan Terkecil:	1 mmWC
Persyaratan Spesimen:	Spesimen tipe kompresi
Suhu Operasional:	0-50 derajat Celcius
Standar Pengujian:	BIS: Standar AFS: Opsional
Frekuensi Kalibrasi:	22500 nos. Siklus Pengujian atau Sekali dalam Setahun

• Pengukur Permeabilitas Digital.
• Lubang Besar.
• Pompa Sifon.
• Sertifikat kalibrasi.
• Buku petunjuk.

Pemisah Pasir : Untuk mendapatkan sampel yang representatif

Peralatan persiapan spesimen untuk membuat spesimen AFS standar atau Kompresi Metrik.

Ada empat jenis kit kalibrasi yang dapat dipilih:

VKPA: Dengan tipe spesimen standar untuk lubang kecil

VKPB: Dengan tipe spesimen standar untuk lubang besar

VKPC: Dengan tipe Rubber Boss untuk Lubang Kecil

VKPD: Dengan tipe Rubber Boss untuk Orifice Besar

• VPR: Penguji Cetakan Perm
• VD: Tabung Permeabilitas Inti
• VBP: Tabung Permeabilitas Dasar
• Lubang Kecil

• Permeability Meter VP (Untuk Tujuan Pendidikan)
• Pengukur Elektropermeabilitas VEP
• Penguji Multi VCAT
• Pengukur Permeabilitas Digital VPD
• Alat Pengukur Permeabilitas Digital VPD II

• Air Demineralisasi
• Rakitan Bos Karet (Bagian # V4500259)

The Unseen Pillar of Casting: A Deep Dive into Sand Permeability

Permeability. This is the measure of a sand mold's ability to allow gases to pass through it. It is a fundamental requirement for producing sound, defect-free castings. A mold that cannot effectively vent the massive volume of gases generated during pouring is a recipe for disaster, leading to defects that can render a casting useless.

The Theory and Importance of Permeability Testing

At its core, permeability is a measure of how easily a fluid—in this case, gas—can flow through a porous medium like compacted sand. The scientific principle governing this is Darcy's Law, which establishes a relationship between the flow rate, the properties of the fluid, the pressure gradient, and the permeability of the medium.

In a foundry setting, the standard method for quantifying this property is the American Foundry Society (AFS) Permeability Test. This test involves taking a standard cylindrical specimen of prepared sand (2 inches in diameter and 2 inches high), ramming it with a standard force, and then measuring the time it takes for a specific volume of air (2000 cc) to pass through it under a constant pressure. The result is expressed as a Permeability Number. A higher number signifies a more permeable sand, meaning gases can escape more easily.

The importance of this test cannot be overstated. When molten metal enters the mold cavity, it rapidly heats the sand and any moisture or organic binders present. This process generates a significant volume of gases, including steam, hydrogen, carbon monoxide, and carbon dioxide. This gas volume can be many times greater than the volume of the mold itself. If these gases cannot escape through the sand pores quickly and efficiently, they will become trapped, building up pressure within the mold. This pressure can resist the inflow of metal, leading to incomplete castings, or it can force its way into the solidifying metal, creating a variety of gas-related defects.

Therefore, permeability is a critical balancing act:

• Too Low Permeability: Traps gases, causing defects like blowholes and pinholes.
• Too High Permeability: Can lead to a poor surface finish on the casting and may cause defects like metal penetration, where the molten metal seeps into the large pores between sand grains.

Factors Influencing Sand Permeability

Permeability is not a fixed property but is influenced by several interconnected factors related to the sand and the molding process. Understanding these factors is key to controlling the final outcome.

• Grain Size and Shape: This is the most significant factor. Coarser, more uniform sand grains create larger voids between them, resulting in higher permeability. Finer sands pack more densely, leading to smaller voids and lower permeability. Similarly, rounded grains will have larger pore spaces than angular grains, which can interlock more tightly.
• Grain Distribution: A sand with a wide distribution of grain sizes will have lower permeability. The smaller grains will fill the voids between the larger grains, reducing the overall porosity. Foundries often aim for a sand with three to four sieve distributions to create a balance between strength and permeability.
• Binder Content and Type: The type and amount of binder (such as clay or chemical resins) directly impact permeability. An excess of binder can fill the voids between sand grains, drastically reducing permeability.
• Moisture Content: In green sand systems, water content is critical. A small amount of water is necessary to activate the clay binder, but excessive moisture generates more steam during pouring and can also reduce permeability by filling pore spaces.
• Ramming Density: The more a sand is compacted or rammed, the smaller the voids between the grains become, and the lower the permeability. The ramming energy must be carefully controlled to achieve the desired mold hardness and permeability.

Permeability of Different Sand Types:

• Silica Sand: The most common foundry sand. Its permeability can be easily controlled by managing grain size and distribution.
• Zircon Sand: Being finer and having a different grain shape, zircon sand typically has lower permeability than silica sand but offers higher refractoriness and a better surface finish.
• Chromite Sand: Similar to zircon, chromite is used for its high thermal conductivity and chill effect. Its angular grain shape can lead to lower permeability if not managed properly.

Permeability as a Diagnostic Tool for Casting Defects

An out-of-spec permeability reading is a major clue when diagnosing casting defects. By analyzing the permeability number in conjunction with the type of defect observed, foundry engineers can pinpoint the root cause.

• Blowholes and Gas Porosity: These are cavities within the casting caused by trapped gas. They are the classic symptom of low permeability. If the sand is too fine, has too much binder or moisture, or is over-rammed, gases cannot escape, and they form bubbles in the metal.
• Metal Penetration: This occurs when molten metal seeps into the sand mold, resulting in a rough, sandy surface on the casting. This is often a sign of excessively high permeability, where the pores between sand grains are too large for the surface tension of the metal to bridge.
• Scabs, Cuts, and Washes: These defects, where a portion of the mold surface breaks away and is embedded in the casting, can be indirectly related to permeability. Low permeability can cause high gas pressure at the mold-metal interface, which can lift or erode the sand surface.
• Incomplete Fill (Misrun): If the back-pressure from trapped gases due to low permeability is high enough, it can prematurely halt the flow of molten metal, preventing it from completely filling the mold cavity.

The Modern Approach: Online Testing and Automation

Traditionally, sand testing has been a manual, batch-based process performed in a laboratory. While essential, this method has a time lag; by the time a problem is detected, a significant amount of defective sand may have already been used, resulting in scrap castings.

The modern trend is a move towards online and automated sand testing. Advanced systems are now available that can be integrated directly into the sand preparation and molding line. These systems automatically sample the sand at critical points (e.g., after the muller or before the molding machine) and provide near-instantaneous readings for key properties, including permeability, compactability, and moisture.

Pentingnya evolusi ini sangat besar:

• Kontrol Waktu Nyata: Sistem kontrol dapat menggunakan data langsung untuk membuat penyesuaian otomatis dan segera pada campuran pasir, seperti mengubah air atau penambahan bahan pengikat.
• Stabilitas Proses: Otomatisasi meminimalkan unsur manusia dan memastikan bahwa sifat pasir dipertahankan dalam jendela kontrol yang sangat ketat, batch demi batch.
• Pencegahan Cacat: Dengan mendeteksi penyimpangan saat terjadi, sistem ini mencegah produksi cetakan yang cacat, sehingga secara signifikan mengurangi tingkat pemalsuan.
• Peningkatan Berbasis Data: Pengumpulan data yang berkelanjutan memungkinkan analisis yang canggih, membantu pabrik pengecoran memahami interaksi kompleks antara variabel pasir dan hasil pengecoran, membuka jalan bagi pengoptimalan proses lebih lanjut (Industri 4.0).

Cara Tepat Mengontrol Permeabilitas

Pengendalian permeabilitas yang efektif merupakan disiplin ilmu sehari-hari di industri pengecoran. Hal ini membutuhkan pendekatan sistematis yang mencakup material, proses, dan pengujian.

Pemilihan dan Pengelolaan Pasir: Mulailah dengan pasir dasar yang memiliki angka kehalusan butiran (GFN) dan distribusi yang sesuai untuk jenis coran yang akan diproduksi. Lakukan analisis saringan secara berkala untuk memantau perubahan distribusi butiran akibat degradasi atau kontaminasi.

Kontrol Pengikat dan Aditif: Kontrol penambahan lempung, resin, dan aditif lainnya secara tepat. Gunakan uji seperti uji lempung Metilen Biru untuk menentukan jumlah lempung aktif dalam sistem. Hindari penambahan berlebihan yang dapat menyumbat pori-pori.

Manajemen Kelembapan: Hal ini sangat penting untuk pasir hijau. Gunakan uji pemadatan sebagai metode utama untuk mengontrol penambahan air pada muller. Hal ini memastikan "temper" yang konsisten dan membantu menstabilkan permeabilitas.

Kontrol Pemadatan: Standarisasi dan kendalikan energi pemadatan atau pemampatan yang diterapkan selama pencetakan. Hal ini memastikan kepadatan cetakan yang konsisten dan, oleh karena itu, permeabilitas yang konsisten.

Efisiensi Mulling: Pastikan muller beroperasi dengan benar. Mulling yang tepat akan melapisi butiran pasir secara merata dengan binder tanpa merusak butiran secara berlebihan, yang akan menghasilkan lebih banyak butiran halus dan mengurangi permeabilitas.