Buying filter panels at wholesale volume looks like a price decision and is really a consistency decision. A supplier who is cheap and variable costs more than one who is slightly dearer and identical every time, because the variability lands on your assembly or your maintenance team.
Consistency between batches
This is the first thing to establish, and you have to ask directly: will the tenth order match the first? Specific questions get specific answers. What cutting method is used? Is the specification held on file? Is there a retained sample from the last batch to compare against?
Where the answer is vague, expect variation. Panel dimensions that move by a millimetre or two between batches cause intermittent fit problems that are very hard to diagnose later, because nothing about the panel looks wrong.
Stated tolerances
A supplier who quotes a tolerance is telling you something about their process. One who quotes only nominal dimensions either has not thought about it or is not going to hold to anything. Ask for the tolerance on the dimensions that matter for your assembly – usually the ones that determine fit, not the overall size.
Material honesty
Polypropylene is recyclable and recycled content is common, which is fine where it is declared and consistent. What causes trouble is recycled content that varies between batches, because it changes colour and mechanical behaviour. Ask whether the material is virgin or recycled, and whether that is held constant.
The same applies to additives. UV stabiliser, colour, flame performance: if these are part of the specification, ask whether they are present in every batch or only when requested.
Lead time and what happens when it slips
Ask for the production lead time separately from the shipping time, and ask what happens at peak. Filters are seasonal in some markets and a supplier who is reliable in February may be stretched in June. Knowing that in advance is the difference between a planned buffer and a stockout.
Questions worth asking directly
- Is the specification held on file, or re-created from the drawing each time?
- Is there a retained sample from the last batch to compare against?
- Is the material virgin or recycled, and is that constant between batches?
- What is the production lead time separately from shipping?
- What happens to the lead time at your peak season?
- What is the tolerance on the dimensions that determine fit?
Suppliers who answer these specifically usually have the process to back it up. Vague answers are themselves the answer.
Freight, packing and damage
Filter panels are bulky and relatively light, so freight cost is driven by volume and damage by packing. Ask how they are packed and whether there is any protection against edge crushing – a pallet of panels with crushed edges is a common and avoidable loss.
Agree who bears the risk of transit damage before the first order. It is an unglamorous conversation that prevents an unpleasant one later.
The awkward questions
Ask what happens when a batch is wrong, and how quickly. Every supplier gets it wrong occasionally; the difference is whether the correction is immediate or argued over weeks. Ask for a named contact for specification questions, and whether technical queries reach someone who has seen the production line.
And ask for two references from customers ordering repeat quantities of custom sizes, which is the situation you are actually in. References from large standard-size orders tell you much less.
What we can do
We supply honeycomb filter panels direct from the factory, with the specification held on file and a retained reference sample from each batch. Tell us your sizes, volumes and what varies if it varies, and we will quote against a written specification rather than a nominal size.