Roto Molding vs. Blow Molding, Cost and Process

Rotational molding and Blow molding are unique processes which offer a number of process advantages. However, it is important to consider the advantages and disadvantages of Roto Molding vs. Blow Molding process when choosing which is right for you.

Contact us to discuss your requirements of 50L Plastic Extrusion Automatic Blow Molding Machine. Our experienced sales team can help you identify the options that best suit your needs.

Rotational molding is versatile process which offers significant design flexibility and a low startup cost. Therefore, the process allows production quantities ranging from 50 units per year going up to 20,000 units per year.

Blow molding is a manufacturing process with shorter cycle times for parts with more limited design flexibility. Initial startup costs are relatively very high.

This article is going to discuss the key aspects of Blow Molding vs. Rotomolding.

See Also Infographic About Rotational molding vs. Blow molding.

Rotational Molding Products

Rotational molding, also referred to as rotomolding is a low pressure thermoforming process which produces seamless small and large hollow plastic products with uniform wall thickness. As a result, the low startup costs make it an ideal process for thermoplastic products.

Products that are rotomolded include single and double wall parts such as kayaks, ice coolers, chassis for electromechanical equipment and marine products. Useful features can be designed into rotomolded parts such as molded-in inserts, spinwelds, colored graphics, foam filling, structural ribs and undercuts. All without welding or bonding pieces together. The ability to produce parts with complex geometry with undercuts and molded-in inserts makes working with rotational molding companies desirable.

See also: 7 Major Plastic (resin) Types for Roto Molding

Blow Molding Products

Blow molding, is a high pressure process which has low cycle times and is ideal for parts with low complexity. Products such as fluid containers, fuel tanks and small plastic toys use the blow molding process. Even though production capacity is high, expensive tooling cost can be a barrier to entry.

In addition, blow molding process has the ability to mold more complex parts, however additional processes such as infra-red welding and heat amplification are required therefore adding cost to the process.

What are the advantages and disadvantages of Blow Molding?

Advantages of blow molding:

• Short cycle times: the cycle time for a blow molded part can range from 5 to 20 minutes but secondary processes such as infra-red welding can sometimes take longer.
• Uniform wall thickness for small parts: parts will have a uniform wall thickness for parts with a small diameter however that can change as the size increases.
• Seamless hollow parts: hollow parts are seamless and do not require any bonding.
• Ideal for manufacturing simple shapes such as bottles: Simple shapes such as bottles can be produced at a fast rate and low cost.

Disadvantages of blow molding:

• Part geometry is limited and restricted to basic forms: blow molding is ideal for parts with simple geometry
• Tooling cost is very high: tooling is high and is approximately 6-10 times the cost of rotational molding tooling.
• Low volume production quantities are costly: due to setup costs, producing lower quantities drive prices higher.
• Surface finish is not aesthetic: parting lines can be pronounced and surface texture is not always desirable.

What are the advantages and disadvantages of Rotational Molding?

Advantages of rotational molding:

• Low cost tooling: tooling cost is low in comparison to blow molding due to the low pressures involved.
• Consistent wall thickness: because the process uses gravitational forces to spread the plastic inside a mold, parts form with uniform wall thickness.
• Double wall construction: double wall parts can be formed which are ideal for cases and containers.
• High strength and durability: structural features can be designed into parts providing additional strength and support for large flat surface areas.
• Seamless hollow parts: the parting lines on rotationally molded parts are discrete.
• Ability to mold complex geometry: design flexibility provides the ability to mold very complex and detailed assemblies.

Disadvantages of Rotational Molding

• Cycle times: the only disadvantage of rotational molding vs. injection molding and blow molding is the cycle times, however this can be overcome with multiple low cost tools.

See Also: Advantages and Disadvantages of Rotational Molding

Is Rotomolding Right for You?

When deciding whether rotomolding is the right process for you it is important to consider the following.

• Is low cost tooling an important factor?
• Does the design have a degree of complexity to it that prevents it from being blow molded?
• Does the project require a short production run to begin with and then ramp up afterwards?

If the answer to any of those is yes then rotomolding is the right process for your project. That is to say, if you are looking for a rotomolding company in California, contact us today for a free quote.

Most importantly, blow molding is ideal for simple tanks, however when it comes to manufacturing parts with more detail there can be additional tooling and process costs for secondary processes.

Roto Molding vs. Blow Molding

Specifications

Blow Molding

Are you interested in learning more about 5 Gallon PC Special Blow Molding Machine? Contact us today to secure an expert consultation!

Rotational Molding

Uniform wall thickness Wall thickness become inconsistent as the part diameter increases Walls thickness is uniform throughout the part Tooling High quality CNC tools High quality CNC tools or lower cost cast tools Tooling Cost Usually 6-10 times the cost of rotomolding tooling 3 tooling grade options all lower than blow molding tooling costs. Tooling Maintenance Mold is under pressure and requires costly maintenance. Modifications come at a high cost. Mold is under low pressure and may require minor maintenance. Modifications are relatively low in cost. Tooling lead times 11-12 weeks 7-8 weeks Cycle Times Low cycle times provide a higher output per tool cavity Higher cycle times provides lower output per tool cavity Design Flexibility Limited design flexibility and simpler part geometry Flexibility in the design allows for undercuts, threaded inserts, graphics and various other complex features

See also: Rotomolding Design Guidelines

Roto Molding vs. Blow Molding Cost Case Study

Case Study – 50 Gallon Trash can

Roto Molding vs. Blow Molding Case Study – 50 Gallon Trash Can

Cost Factors Roto Molding Blow Molding Tooling Cost $20,000 $210,000 Tooling maintenance Cost $1000 / yr. $5000 / yr. Part Cost $110 $90

Design Flexibility in Rotomolding

The diagram below shows a design guideline for the Rotational Molding process.

• Features: There are various features that can be incorporated into a product. These include, male/ female threads, threaded inserts, graphics, raised lettering, ribbing structures and undercuts.
• Cost considerations: When making a part cost efficient it is important to take into consideration the quantity of inserts, tool pieces and part weight have an impact of the average cost of the final product.

Conclusion

In conclusion, rotational molding has a clear advantage with design flexibility and low cost tooling. Certainly, now that you have ready more about Roto Molding vs. Blow Molding, read more here about Rotational Molding vs. Injection molding.

If you are looking for a roto molding company and need expert advice contact our California headquarters at (877) 768-6585.

See Also Infographic About Rotational molding vs. Blow molding.

Extrusion Blow Molding Machine Production Fixed Cost:

Fixed cost refers to the cost of whether the factory is open or not, regardless of whether it is produced or not.

Calculated in chinese yuan: one extrusion blow molding machine CNY / day, three places after the decimal point.

Fixed Cost Estimates Are Only Available For Pure Blow Molding Machine Company.

If the company covers production content such as blow molding, mold manufacturing, and finished product assembly, the infrastructure and other expenses should be reasonably divided and calculated.

1. Factory depreciation (own factory): total cost / 30 years / 255 days, leased factory: annual rent / 255 days;
2. Extrusion Blow Molding Machine equipment depreciation machinery and equipment total price / 10 years / 225 days;
3. Infrastructure maintenance cost, annual maintenancecost / 225 days;
4. Extrusion Blow Molding Machine and equipment maintenance costannual maintenance cost total / 225 days;
5. Financial year total interest / 225 days;
6. Total management expenditures per year / 225 days
7. Total annual expenditure of electric transformers / 225 days
8. Unforeseen expenses
9. Other

Subtotal 1+2+3+…9=X CNY/day.

One Extrusion Blow Molding Machine Production CostX / ( Total blow molding capacity (g) * utilization rate of 75%) = Y CNY/g/day.

Y * One machine (g) = Z CNY/day

Description Of Content And Formula:

• 30 years: The design life of a general factory building is 50 years, which is reasonable according to 30 years.
• Total blow molding capacity: the sum of the blow molding volume of all blow molding machines in the factory.
• 225 days: One-year effective working day is calculated in 225 days.
• 10 years: The life of extrusion blow molding and related equipment is 10 years.
• Infrastructure maintenance costs: generally estimated at 2% of total infrastructure value
• Extrusion Blow Molding Machine and equipment maintenance costs: generally estimated at 3% of the total value of machinery and equipment.
• Management cost: the sum of administrative staff salaries, hospitality expenses, travel expenses, transportation expenses, certificate costs, etc.
• Electric transformer apportionment: fixed expenditure for independent transformers.

Extrusion Blow Molding Machine Production Variable Cost:

Variable cost description: Variable cost refers to the cost directly incurred in the product itself. In units of CNY.

Calculated to: CNY / PCS (delivered qualified products), decimals reserved for three.

Processing Cost: CNY/ EACH MOLD

10. The number of mold times for one extrusion blow molding machine can be produced every day (24 hours) * the rate of qualified products 95% A
11. Workers’ wages total / A
12. Electricity cost * 0.75 * 24 / A
13. Fixed cost amortization Z / A
14. Blow molding machine processing costeach mold. 11+12+13=B CNY/EACH MOLD

Original And Auxiliary Materials Cost:

Raw material weight unit price × product gross weight D CNY/PCS

Auxiliary material consumption total / A = E CNY/PCS

Packing Cost:

Single blow molding machine product packaging cost measured F CNY/PCS

Freight Cost:

Transportation cost measured G CNY/PCS

Secondary Processing Cost: Assembly, Printing, Etc.

The second processing cost is measured and calculated H CNY/PCS

Extrusion Blow Molding Machine Production Total Cost:

Self-operated products B+C+D+E+F+G+H==K CNY/PCS

Proprietary products B+C+D+E+F+G+H==K CNY/PCS

Profits and taxes, etc.:

The contents of each enterprise depending on the specific circumstances.

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