Spray Up Process for the Manufacture of an Acrylic Bathtub
Method Used: Vacuum Forming and Spray Up Presented By: LAURA URENA
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Bathtub Manufacturing Using Spray up Technique
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Table of Contents
I. II.
Open Mold: Spray Up. Major advantages………………………….4 Sheet metal forming for mold……………………………………….….5
III.
IV. V. VI. VII. VIII. IX.
Mold Release……………………………………………………………………..6
Vacuum forming molding..………………………………………………..7 Spray up process description……………………………………………10 Materials and equipment used………………………………….…….13 Technical drawings ………………………………………………………...17 Cost analysis…………………………………………………………………….19 Video………………………………………………………………………………..20
X.
References……………………………………………………………….…….21
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Open Mold: Spray Up
Fibre is chopped in a hand-held gun and fed into a spray of catalyzed resin directed at the mould. With open molding, the gel coat and laminate are exposed to the atmosphere during the fabrication process. The selection of this technique for the manufacture of the bathtub was because the feasibility that open mold methods allows such as:
Most appropriate technique based on the costs of tooling due to the single cavity mold of fiberglass used for the size of the part 30x35x18 in. Portable equipment permits on-site fabrication.
This technique enable the manufacturing of hot bathtubs that requires different types of reinforcement able to tolerate heat and load.
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Sheet Metal for Bathtub Mold
Injection mold is a technique used for the manufacture of bathtubs. For small baby bathtubs, injection molding is a affordable technique because of the size, and the costs
are not so expensive.
Using Sheet metal technique is cheaper and easier to manufacture if compared with an injection molds for a big bathtub. After forming the sheet a composite mold is manufacture. Therefore, the final bathtub will
Sheet metal forming technique is used to the manufacture of this bathtub mold.
meet the required surface finished.
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Mold Release
For the application of the mold release to the cavity for easy removal of the molded sheet, commonly these materials are used:
Bathtub Manufacturing Process: Vacuum Forming
The bathtub shape is done by using vacuum forming. Vacuum forming advantages:
•
Cost-effective and high quality in tooling and resulting part. Vacuum Forming
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Aesthetically appealing while offering close tolerances which in this case is not critical.
• •
Low to large volume parts at a reasonable price. Shorter manufacturing time.
Heater
Using vacuum forming vs pressure forming was because the lack of very specific details in this bathtub. Otherwise when bathtubs for hot spas are constructed with many details and complex shapes, pressure forming is a better option.
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Acrylic Sheet
Mold
Vacuum Lines
Bathtub Manufacturing Open Mold Process
Heating Component
Acrylic Sheet
Mold
Vacuum Fixture
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Vacuum Forming Process Description
Thermoplastics most commonly specified are
ACRYLIC, ABS, HDPE, LPPE, PP PVC, PETG and polycarbonates. , This bathtub was made with acrylic.
Heating Component
The process to shape the acrylic sheet, is as follows:
Place the plastic sheet in the heating element to 140 ⁰F and
put it into the molding tool to shape it.
After, the vacuum pressure helps to the griping of the sheet to the mold.
Then, the mold is let to cool down to 70⁰ from 5 to 45 minutes before remove the shaped sheet from the mold. Time will vary on the cooling fans.
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Spray Up Process Description
After removing the bathtub out of the tooling mold, the application of the reinforcement is
the next step:
1. Gel coat is first applied to the bathtub mold prior to spray-up of the substrate laminate to
ensure the adding of the fiber glass to the mold.
2. Continuous strand glass roving and catalyzed resin are fed through a chopper gun, which
deposits the resin-saturated "chop" on the mold.
3. The laminate is then rolled to thoroughly saturate the glass strands and compact the chop.
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Reinforcement application
4. Another layer of carbon fiber vinyl wrap is applied to
increase the resistance to loads of the mold.
5. Finally, another coat of adhesive filler polyester is applied, and let to cure Additional layers of chop laminate are added as required for thickness and resistance.
Depending on the bathtub quality, the application of adhesive resin and any reinforcement material is applied.
Carbon Fiber Vinyl11
Cutting out the holes
Holes cut outs are done using a CNC machine. Mold edges and residues are removed from the mold.
Borders are cut with a CNC to clean up all the edges.
Heated acrylic sheet for placing in the mold.
Clean Edges
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Bathtub preformed
Material and equipment used to the manufacture of an acrylic bathtub
Acrylic Bathtub using Polycarbonate/Acrylic alloy (PC/PMMA)
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Thermal-formed and reinforced with fiberglass. Acrylic bathtub material is naturally lustrous like glass. Bathtubs made with acrylic are non-staining, and non-fading. Acrylic bathtubs have a non-porous finish that is easy to clean and warm to the touch. Acrylic
bathtubs are lightweight, yet amply strong.
Acrylic tubs use fiberglass sheets for reinforcement underneath vacuum-formed sheets of colored acrylic. The advantages are pretty much the same as for fiberglass, although acrylic tubs are more expensive. Advantages
High impact strength Excellent flow
Lower processing temperatures than PC or PC/ABS
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Fiberglass Strand for Reinforcement
Also known as FRP, or fiberglass-reinforced plastic, this is typically going to be
the least expensive bathtub material.
A fiberglass bathtub is made by forming layers of fiberglass into the desired shape.
Advantages:
• • •
Low cost and light weight. Ease of installation. Finish that can be repaired. High strength glass fiber strand will be used.
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Equipment and materials
Spray up process. FRP Chop System
Vacuum Forming Machine
Wax releasing agent
Carbon fiber vinyl reinforcement
Reinforcement adhesive
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Bathtub Drawing
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Bathtub Mold
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Cost Analysis
Bathtub Manufacturing Process Vacuum forming machine Mold release wax 5.5 lbs 120x80 inches PMMA acrylic sheet Carbon Fiber Vinyl Chopped Fiber Strand (1 ton min. order) Vinyl Ester Resin Adhesive (4 gals) FRP Chop System Unit price 20,000.00 $ 60.00 $ 260.00 $ 98.00 $ 900.00 $ 80.00 $ 6500.00 $ *All prices are estimates.
Total Cost: 27,898$ with machines and raw materials. If the existence of the machine is assumed the raw material total cost will be 1398$. An actual Acrylic Bathtub costs between 400 $ and 600 $. The price for the manufacturing of this bathtub was calculated as a single unit, if materials are purchased by high volume, costs are going to reduced. If material quantity is calculated with a very high precision, cost per unit is reduced as well.
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