Smooth PEI Spring Steel Sheet 257x257mm

Springs · 1 option in stock

Compression, extension and die springs for printers and machine builds. The parameters are listed in order of importance: the one at the top decides the most, and no amount of care further down makes up for getting it wrong.

This page lists 1 option, from ¥20.8.

What this part is

257×257 mm smooth PEI spring steel sheet, PEI coated on one or both faces, held to the bed by magnets. PEI grips when hot and releases when cold, which is why it is the default build surface on Ender 3 and CR10 class machines.

The parts of this item

Figure 1 — A spring needs five numbers: wire diameter, OD, free length, coils, end type — miss one and it will not match

The parameters that matter

Not every number on a part like this is worth the same. These are the ones that decide whether it fits and works, and what to look at for each.

How to choose, step by step

1. The three sizes — Outside diameter has to fit the bore, inside diameter has to clear the rod, free length sets the travel. All three, not two.

Reading the part numbers

You can order by part number or by selecting the parameters. The part number is fastest, but it does not always encode every parameter — the selector on this page is the authority.

7 common mistakes

1. Compress past solid height and it stays short. A spring taken to coil bind never comes back. Work out the travel before you fit it.
2. OD and ID have to both work. It has to drop into the bore and still clear the rod.
3. Do not mix rates in one set. In a die with four pockets the stiffest spring takes almost all the load and the others do nothing.
4. The seat has to be flat. A spring sitting on an uneven face bends sideways and breaks at a few tens of thousands of cycles.
5. Extension springs need initial tension checked. Two springs that look identical can differ by 20% in preload.
6. Measure before you order. Take the old part off and measure it, or send us a photo with the caliper reading — that beats guessing from a model number every time.
7. Everything here is in millimetres. Where a size is imperial, convert it: 1" = 25.4 mm, 1/4" = 6.35 mm, 3/32" = 2.38 mm.

Telling it apart from lookalikes

Against a glass bed: glass is flat and cheap, but adhesion depends on glue and you have to wait for it to cool to get the part off. PEI grips hot and releases cold with no glue, but the coating ages and dislikes scrapers and acetone.

Confirming it is the right part

This page has one configuration, so there is nothing to choose — which makes confirming that it is the right part more important than studying the specification. Three steps is enough:

1. Measure the mating dimension — the one place this part touches something else: bore, shaft, thread, tube OD, or hex across flats. It is the number people get wrong, and half a millimetre out means it will not fit.
2. Measure the outline and the mounting hole spacing. Two parts that do the same job from two makers often differ by 2–3 mm between holes: it looks like it will fit, and it goes on crooked.
3. Send us two photographs: one general view showing the machine and where the part sits, and one close-up with the caliper reading in shot. If the machine has a nameplate, include it — plenty of these parts are specific to one machine, and the model number locates them faster than dimensions do.

When to replace it

You do not replace this until it fails — but "still looks usable" and "still reliable" are two different things. Any one of these and it is time:

• Free length noticeably shorter than new — more than about 5% means it has been compressed past its limit.
• Cracks or a broken coil.
• Force clearly down, so ejection or return no longer completes.

Fitting and use

Check before assembly

• Wipe every mating surface with a lint-free cloth. No chips, no burrs, no old grease. One chip is enough to make a bearing noisy.
• Measure the fits — shaft, bore, centre height — against nominal. More than 0.02 mm out and you should check whether you have the right part.
• Check the orientation: the side with the shoulder, step or oil hole has to face the right way. Fitted backwards, it is usually scrap on removal.

Assembly

• Press if you can; do not hammer. If you must tap, use a brass or nylon drift and put the force on the ring that is being fitted, never through the raceway.
• For an interference fit, heat to 80–100 °C first (oil bath or hot plate — never an open flame on a bearing). Hot fitting is easier and safer than cold pressing.
• Tighten fasteners in a diagonal pattern in 2–3 stages. Taking one down fully first distorts the housing and cocks the shaft.

Running in

• Turn it by hand first. It should be smooth, with no tight spot and no axial play. If there is a tight spot, loosen and reseat — do not run it in.
• Run it slowly and unloaded for 10–20 minutes, then feel the temperature. A clear rise means too much preload or poor alignment.
• Re-torque the fasteners after running in, then apply load.

Three things not to do

• Do not hammer. It brinells the raceway, you cannot see it, and it whines forever afterwards.
• Do not mix brands or precision classes in a matched pair. The load shares unevenly and the poorer one always fails first.
• Do not skip lubrication on parts that need it. A few hundred hours dry and it seizes.

Matching parts

• Guide rods — 1–2 mm smaller than the inside diameter
• Flat washers under the seat

Lead time, custom work and shipping

• Stock sizes: dispatched in 1–2 working days, subject to stock
• Custom: non-standard sizes, materials and treatments are possible — send quantity and drawing
• Shipping: from Shenzhen; domestic courier by default, DHL or dedicated line for export
• Volume: quantity pricing available, contact us for a quote

If you cannot find the size you need, or you are not sure which one fits, send us the problem you are solving — what machine it goes on, the dimensions of the part you have, what it has to achieve — and we will match it.