Frequently Asked Questions
Technical & Project Related Questions
What tolerances can you achieve?
A very common questions we are asked is: “What tolerances can you generally achieve?”. However, giving out a-one-tolerance-fits-all answer would be unrealistic and too far away from manufacturing reality. Nevertheless we would like to give you a rough idea about tolerances.
Tolerances depend on numerous influencing factors such as
- The size of your part
- The design
- The number, type, and size of features
- 3D surfaces
- Materials used
- Surface Finish
For that reason our engineers and technicians will need to carefully review each individual design. You will then be advised if we can or cannot achieve your desired tolerances and how you may need to alter the design to achieve your desired tolerances. If you have particular tolerance requirements, please feel free to get in touch with us today.
Below, please also find some further information on tolerances:
SLA and SLS models are typically +/- 0.1mm in X & Y and +/- 0.3mm in Z (XYZ as per the build orientation, not per your design orientation). This varies up or down for various geometries and sizes. If a customer needs a tight tolerance in a particular area, they can specify this in a 2D PDF, and we will machine or finish the part to suit.
Vacuum casting of polyurethane parts is primarily dependent upon the tolerance of the master model (see SL tolarances), then a tolerance of +/- 0.15% is applied as a general rule. This varies depending upon weak geometry. To ensure the accuracy of Star Prototype’s polyurethane parts, we usually machine a Tufnol fixture for post-heat-treatment. This ensures that the part does not shrink upon heat treatment.
Unless otherwise specified, we comply with the DIN 16901 standard tolerances for plastic injection moldings. It is possible with careful thermal, time, and pressure control to have very accurate parts. We need to know your requirements in advance so that we can manage key features in the tooling and molding process. As a general rule, you should never make more than one feature very accurate in the design. That feature can be repeated across the part, but to make a whole series of very different features very accurate is impossible for any molding company to achieve – you end up chasing your intolerances around the part. You get one feature right only to find another one slightly off.
Our general tolerances for CNC machining of metals is DIN-2768-1-fine and for plastics DIN-2768-1-medium. Tolerances are greatly affected by wall thicknesses, material choice, and geometry, so we will seek to advise as to achievable tolerances for each part. We pride ourselves on wishing to help our clients achieve their desired tolerances that are better than DIN-2768-1, but we work on a “best effort basis only” if the tolerances stated are tighter than our stated standards. The reason we refuse to be held accountable for very tighter tolerances is that we are a prototype factory and very tight tolerances present a huge risk due to the nature of our work.
All manufacturing and technical specifications need to be clearly specified in the 2D drawings in order to be followed.
How do delivery times compare to the West?
Strictly speaking, Star Prototype’s time frame for delivery is similar to Western suppliers. For raw SL & SLS parts we typically take two days for production plus three days for shipping. In the USA there is overnight shipping. We cannot do that.
Can I get 'rapid injection molded' parts in days in the USA and Europe?
Yes, you can. Rapid tooling for plastics is a service that appears to be slow in China when compared to some ‘rapid injection molding’ services. Some Western rapid tooling companies claim to take one day to produce molds and moldings – compared to two weeks for the same part at Star Prototype. But there is a fundamental difference: the Western suppliers that have a one to seven-day turnaround are not producing quality parts. These rapid injection molded parts are poor quality and the designer often has to greatly modify his design to suit the supplier’s processes. Star Prototype can make most parts, no matter how complex, so long as they conform to normal international molding standards. In fact, the more challenging the better!
Also differentiating Star Prototype from the ‘other guys’ is the fact that the customer owns the mold from Star, and the parts can be as complex as you like. You can also have any material you desire for your prototype – even if we have to import it. Projects from Star Prototype typically take two to four weeks to produce. All of Star Prototype’s molds are made from tool steel and therefore last 50,000 plus cycles. Additionally, all surface finishes are possible, including chemical-photo etching.
How do you ensure your quality?
In order to deliver on our quality promise we take the following actions for every project:
- Full Design-for-Manufacturing (DFM) review at enquiry stage by skilled engineering team
- Full contract review by shop-floor managers upon receipt of purchase order (PO)
- Pre-manufacturing material identification using in-house OES & XRF equipment
- Thorough in-process inspection routines including first article inspection (FAI)
- Post manufacturing inspection & reports
Pricing Related Questions
How does STAR compare to Western suppliers on price?
This is a complex question. China’s greatest advantage is its labor cost. Zhongshan City workers’ pay is, on average, one-sixth compared with the USA. Imported technology, however, can cost as much as double the USA/Europe. Electricity in China is on par with some of the highest prices in the US and Europe, and imported materials can be much higher, but domestically produced much lower.
As a general rule, labor-rich work is considerably more competitive than technology and material-rich work. But this is not always true. Price can vary greatly depending on the type of prototyping service. Some general guidelines to consider include:
SLA & SLS prototyping are not competitive from China unless you start to do full cosmetic finishing to the raw SL/SLS model. Then, production can be about substantially less than Western prices.
Vacuum casting of polyurethane is normally 30-50% less than Western prices. The expensive material here is the imported Axson resin. That said, vacuum casting and the subsequent finishing are very labor intensive.
Rapid tooling for plastics is consistently nearly half the US/European price.
Pressure die manufacture and die casting of aluminum and zinc can be as little as 25% of the Western prices, but can range up to 50% of the cost. This is an uncut gem in the Star Prototype portfolio. There is no way of short cutting the process of pressure die casting. There are no ‘rapid’ ways of producing die cast tools, as the process is far too violent for soft materials. They must be HRC 43 to 48 H13 tool steel.
How does STAR compare to other Chinese suppliers on price?
Star Prototype products are typically 50-100% more expensive than other Chinese suppliers. This is because we employ the very best skilled workers, exceptional English-speaking graduates, high-quality imported materials, and advanced technology equipment. Star Prototype aims to deliver service and quality that is far superior to other Chinese suppliers. In that respect: quality is priceless.
How financially secure is STAR?
In 2011, Star Prototype increased sales by 45% to USD 7 million with a pre-tax net profit of USD 800,000. All company machines and equipment have been bought with cash. There is no debt in the business and cash hovers around USD 500,000. On top of this, Star Prototype is self-financing a working capital requirement of about USD 700,000. Star’s balance sheet value at the end of 2011 was about USD 2.1 million. Gordon Styles has a strict policy that the company must remain debt free and have approximately one month’s sales value as cash in the bank. Any funds above that can be spent on new equipment.
Can my company get credit with STAR?
Except in very exceptional circumstances, all new rapid prototyping customers must pay in advance for the first three orders, after which we will consider giving 30 days credit. Except in very special cases, all tooling orders require a 50% deposit in advance, even for clients who have credit terms. Typically the balance must be paid after T1 approval of samples. Terms are negotiable with each individual customer.
How can I pay Star Prototype?
Star Prototype accepts payment in two ways:
- Bank to bank wire transfer. STAR has accounts in Hong Kong and Zhongshan, China.
- Paypal. Star Prototype can send you a PayPal invoice and you can use your PayPal account or credit card to pay.
Company Related Questions
How do I know my design will be kept confidential?
Anyone that says they can protect your intellectual property completely is a liar. In today’s Internet world, it is impossible for even the most powerful governments to keep anything secret. Even companies the likes of Apple are beaten to market by copy houses, even when there appears to have been no breach of security at all. How is that? Well, maybe some Apple guy leaves the latest iPhone on a bar table while he goes to the bathroom. Whoops.
Star Prototype will sign your NDA and we will work to keep your IP secure. We promise not to take your prototype to any bars and leave them it on the table for people to take home.
When your product is a financial success, you will be copied. In a way, it is a testament of commercial success. Unless you have huge financial resources to hire lawyers and chase infringers, there will be nothing you can do to stop them, even in the USA and Europe. The best advice anyone can give about staying ahead of the copy houses is to build an exceptional brand, wear the fastest running shoes in the product development arena, and always be one step ahead. By the time your competitors are copying you, you should have the next product in the market. That is why Apple comes out with so many new models and is so successful – they run faster.
What if we are not completely satisfied with the parts we receive?
If it is practical to do so, we will replace free of charge any parts that you are not completely satisfied with. If that is not practical, then we will credit the customer a negotiated sum.
Regarding T1 samples from tooling: T1 samples are never completely satisfactory. For example, T1 samples never carry the final finish as the customer often finds the need to modify the design and have tooling changes made.
Who owns STAR?
Star Prototype China Limited of Hong Kong is 100% owned by British engineer Gordon Styles. The subsidiary factory Star Prototype Manufacturing is 100% owned by STAR HK, and therefore owned 100% by Gordon Styles. There are no Chinese investors or shareholders.