We've written this guide to help make the often complicated process of buying a checking fixture easier. We'll cover how to reduce the cost of your checking fixture, how to produce the best RFQ for your checking fixture supplier and how to avoid common fixture buying mistakes.
We've also included a list of useful questions to ask your supplier for your next checking fixture project, helping you get the right information to ensure the best quality, cost and value.
We've also compacted this guide into a free download should you want to save it and come back to it later, or take it with you on the go.
- Checking Fixtures - An Overview
- How Much Does A Fixture Cost?
- Case Study: Reducing The Bottleneck On CMM
- How Can I Reduce The Cost Of A Checking Fixture?
- How To Produce The Best RFQ For Your Supplier
- Common Fixture Buying Mistakes (And How To Avoid Them)
- Great Questions To Ask Your Fixture Supplier
- How To Balance Checking Fixture Cost vs. Benefit
CHECKING FIXTURES - AN OVERVIEW
Checking fixtures are an essential measuring tool in the production process. They ensure repeatability, accuracy and reliability for parts with often complicated geometries.
The precision measurements obtained with a checking fixture ensure control of part dimensions for mass production. Using checking fixtures in the right stage of process can also help to control production costs by reducing scrap.
Balancing cost, delivery and quality
Checking fixtures help increase profitability by reducing scrap, as well as assuring product quality, but they do come at a cost.
As a buyer, balancing the factors of quality, cost and delivery can be a difficult task. There are many considerations to take into account to determine this balance, including:
- Initial outlay
- Tool life
- Intended tool life
- Aftersales support
The cost of a checking fixture is impacted by many factors including:
- Materials used
- Design specification
- Location points
- Level of inspection required
HOW MUCH DOES A FIXTURE COST?
Checking fixture cost depends on a number of factors, and will be specific to each project.
Some of the factors that influence the cost of checking fixtures include:
Dimensions & Complexity of Form
In most cases, the larger the component, the larger the fixture is required to hold the component, consequently increasing cost. The geometric complexity of the component will also be a major factor in the design and type of the fixture required. More complex forms will, naturally, require more complicated, (and costly) checking fixtures.
Material of Component & Product Lifespan
Steel pressings, plastic mouldings, aluminium castings and fabrications are just a few of the products that may require quality inspection. The material of the component will influence the type of checking fixture needed- and the type of tooling board used.
Are you using standard or bespoke parts in your checking fixture design?
One of the biggest influencers of checking fixture cost is whether you're using standard or bespoke parts in your fixture. Bespoke comes at a price and it's often not needed in a fixture. Your supplier will be able to advise you on the parts you can buy 'off the shelf', helping reduce the cost.
CASE STUDY: REDUCING THE BOTTLENECK ON CMM
We were approached by a first tier automotive supplier to discuss how they could reduce the bottleneck on their CMM, with components waiting for first off / last off inspection as well as mid process inspections. They reported that, due to the number of different components and the routine checks required on each, they were falling behind on inspection verification prior to production approval. Initially, the customer requested a set of fixtures for operator use and a further set of fixtures for CMM inspection.
Having discussed this with the customer, we focused on reducing the number of fixtures required, as well as creating a dual-purpose design to allow both accurate in-process control beside the machine for operator use and further use as a CMM fixture.
The result: saving time and cost while boosting production
The result was a suite of fixtures which incorporated up to 30 dial test indicator positions on each tool, allowing RPS & SPC points to be checked during the manufacturing process by the operator. The same fixtures could then also be used for CMM inspection.
The result was a reduction in the the number and cost of fixtures required, whilst maintaining full process control, reducing the overall CMM time required and so boosting production.
HOW CAN I REDUCE THE COST OF A CHECKING FIXTURE?
Reducing the cost of a checking fixture is often a priority for a buyer, and your supplier will work with you to achieve the most cost-effective fixture.
Some effective ways to reduce costs include:
Supply a sufficiently detailed specification
Often, checking fixture suppliers are simply sent a drawing of the component to be checked, without clarification on form, hole positions, datum locations or the type of inspection to be undertaken. Not supplying enough information at the start of the process can actually end up costing you more. Limited (or non-existent) information within the specification runs the risk of extra requirements only becoming apparent during fixture production, causing budget overruns and timing plan extensions.
Simplify your fixture design
Be receptive to proposed design simplifications – the fewer the individual parts to be made, the lower the cost of your fixture will be. Examples of these could include:
- Combining handed component fixtures on to a single, common baseplate;
- Producing the fixture from a single billet of material, rather than constructing from multiple parts assembled on to a separate base;
- Do away with the baseplate. A tooling board body with lifting handles secured directly to it may be all that is need for simple, visual inspection fixtures.
Don’t overcook the inspection functionality
Take time to think about the type of inspection you’ll be undertaking - you can add additional, unnecessary time and cost to the production of your checking fixture if you overdo its functionality. For example, requesting a full RPS 'in car line' inspection fixture when all that is really required is a simple gap and flush check will dramatically (and needlessly) increase the price.
Set the manufacturing tolerance at an appropriate level
Consider your component inspection requirements, and then tolerance your checking fixture accordingly. Chasing microns takes time and will cost you money. Loosen the manufacturing tolerance of your checking fixture, if you can, and it’s cost will also drop.
HOW TO PRODUCE THE BEST RFQ FOR YOUR SUPPLIER
Providing your checking fixture supplier with the best possible RFQ is always a good idea – you’ll get back a proposal that is tailored to your unique requirements, and you’ll save yourself time and money too.
Below are some of the considerations and additional information we recommend discussing with your checking fixture supplier.
1. Do you have CAD data for your component?
The more information regarding your components geometry and dimensions the more accurate the quotation. Most suppliers will prefer CAD data to be available with the RFQ, as this enables them to view the full geometry of the part and establish dimensions for the fixture.
2. What is the material specification for the fixture ?
Depending on the application of the fixture, different materials can be used. Tooling board offers a cheaper alternative to aluminium but your product and / or schedule may require the more robust option of aluminium or steel. If you are unsure, it is worth discussing with your supplier.
3. How is the component to be held and positioned during inspection?
Indicating features of the component you require to be used as datum positions is critical, and must be included in your RFQ. They could be holes, slots or other features on the component, used to ensure that each individual part can positioned on the fixture with assured repeatability.
Components can be requested to be inspected “In Car Line” which requires the part to be positioned in the same plane as it is situated in the vehicle. This may require towers to be included in the fixture design to hold the component in position, with additional cost implications.
4. Include and check additional manufacturing considerations
It’s important that the sketches of the proposed design are available from the supplier to make comparing like-for-like quotes much simpler. These will give you a good indication of how your RFQ has been interpreted by your supplier, and allow you to view the quotation with more clarity.
5. What are the checking fixture finishes needed?
Specifying the finish needed, for example whether the fixtures require painting or anodising, is important to include at the RFQ stage. This will reduce the need for unexpected add-on costs.
COMMON FIXTURE BUYING MISTAKES (AND HOW TO AVOID THEM)
Making mistakes when buying your fixture can cost you both time and money. To help, we've put together a list of common buying mistakes, and how to avoid them.
1. Information overload
Whilst a comprehensive specification is required by your supplier to ensure accuracy in the initial quotation and subsequent checking fixture production, too much information can be a mistake. For example, sending over multiple component CAD files risks your fixture being made to the wrong revision level, with expense required to resolve both cost and timing. To avoid this, make sure you control the information you send to your suppliers.
2. Presuming your specification is obvious
Invest time at the start of the RFQ process to create a thorough, in-depth specification. This will reduce the risk of any errors, or best-guesses to fill in the gaps, leading to over or under specified quotes. Include information on specifics such as fixture construction, component location points and inspection level needed. Also, make sure any instructions to your supplier are confirmed in writing or detailed in schematics.
3. Over/ under specifying
Balancing the specification and requirement of your fixture with your budget is not an easy task. A fragile specification may save you money initially, but if the fixture won’t last the duration of production you’ll be paying out again for a replacement. Conversely, a costly aluminium body isn't necessary if you only need to be holding - or inspecting - a few plastic parts. Your supplier will be able to advise you on the best choice for your fixture.
4. Assuming ISO accreditation guarantees quality
Choosing a supplier with an ISO accreditation will give you some comfort, but relying on this alone to give you the quality of supply and service that you require can be a mistake. If your supplier truly is quality focused then they really should be offering you more - other key considerations should include the potential for customer buy-off, and aftersales support to iron out any post-supply issues.
5. Choosing the 'cheapest' supplier
Whilst we know that cost is a key driver for any checking fixture buyer, going for the cheapest option available can be a mistake. While it can minimise your initial outlay, going 'cheap' can also lead to compromises in functionality and tool life. You can also incur further costs for unforeseen extras such as additional clamps, design changes or increased manufacturing time.
GREAT QUESTIONS TO ASK YOUR FIXTURE SUPPLIER
When choosing a new checking fixture supplier, it’s important to have confidence in their ability to manufacture your fixture on time, within budget and to the high standard you expect. We’ve put together some useful questions to ask your new supplier, helping you make an informed decision.
- How experienced are you?
- Are you ISO accredited?
- What lead times do you offer?
- Have you ever worked with a customer to reduce the cost of a checking fixture? If so, can you give me more information on this?
- What inspection/ verification processes do you use?
- What are your aftersales procedures?
- Can I visit your facility?
- Do you need any further information to generate a RFQ?
- Do you have any suggestions to improve our checking fixture specification?
- Can I send you another RFQ?
It can be difficult to thoroughly assess a potential new checking fixture supplier. Asking the right questions is essential, and gives you the best chance of finding a new supplier that is the best fit for you.
HOW TO BALANCE CHECKING FIXTURE COST VS. BENEFIT
When buying a checking fixture, cost is an understandable key driver for any buyer. But it's also important to consider the cost vs benefit balance, ensuring you buy the best quality and value checking fixture for your project - and that's not always the cheapest.
Buying a checking fixture simply on price can lead to difficulties further in the process, either with hidden, unexpected costs or through additional costs needed in an under-specified quote.
Going for the cheapest option available will minimise your initial outlay but may mean you are compromising on functionality and tool life. Inevitably, a fixture is going to be ‘cheap’ for a reason. Make sure you fully consider the following before going down the low cost route:
Skimping on the specification can mean not including steel contact points in a tooling board body, or including smaller (and fewer clamps) than are needed to properly secure a part, or going for 10mm thick aluminium baseplate when it’s obvious that 20mm is the right choice. Once you’ve made your purchasing decision, you don’t want the CAD review stage to be the first time that you find out about the 'cheap' solution your supplier is proposing.
A 'cheap' quote can mean the quality of your fixture is not what it could, or should be. Cutting corners, for example by going for a lower grade, less robust tooling board, not reviewing the CAD design thoroughly, rushing fixture manufacture or limiting the quality assurance process can end up costing you time and money.
Long lead times
If you’re on a compressed time scale, and on time delivery is critical, then going for the cheapest option may not be the right choice for you. Short lead times can be costly for a supplier. Overtime is expensive, and your cheapest supplier will want to avoid out of hours working.
That four-week lead time you needed may become five or six. The delays to your programme caused by your fixture not arriving when promised could ultimately end up costing you more.
A cheap supplier will be more resistant to providing further after sales support, which can mean that changes such as light weighting or clearance adjustments come with extra, unplanned charges.
Balancing benefit versus cost may cost you more at the start, but you'll be confident that you've made the right choice long term.