Tray sensor

Has anyone changed the tray sensor on a Form2? Mine has broken, so won’t recognise any trays.

Got the part number for digikey/farnell somewhere. Its made by bourns and are just simple 3 pin battery contacts.


Disassembly, soldering, assembly and then calibrating the platform can give some headache!

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Thanks for this, I’ve just ordered some

Sure, but a challenge is always good…

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Despite what formlabs say, calibrating the platform to the same position it was before you started is not too difficult. Remember to measure the distance from the tank cradle to the build tray very carefully (in 4 corners) then simply replace it so that the distance is the same as before you dismantled it. If the relative distance is the same then there is NO way the printer knows you ever took it apart!! It might be smart, but its not that smart!!

Using that distance isn’t very accurate as the platform will be in the top position so you are at the largest possible distance to measure. It can be helpful as a start when assembling the machine again(most people don’t have a caliper that can measure >140mm). Sure, you can position the platform relative to the tank +/- 1mm, the springs below the tray will compensate for it, but the 4 corners need to be at the same height and if compression is too high, you might crack the tank.

I can recommend to print the optics test as the second step and measure the length of the 4 parts at the corner(then you’ll know the state of your optics for free as well!). They all should have the same height. If so, the platform is most level to the tank and parts printed directly on the platform will be more accurate.

We would NEVER attempt to measure accurately using a vernier caliper. There is too much chance of parallax errors with the vernier not being perpendicular to the surfaces, verniers are great for quick measurements but do not really give very accurate measurements. A micrometer is much better or in this case a digital dti. (In this case the one we use is +/- 0.001mm

We made a datum plate that covers the entire tray area. its 30mm thick aluminium so has a little bit of weight to ensure the springs have some load. The four corners have index points machined into them which allows us to move a round aluminium bar from corner to corner. The bar is 40mm diameter and has the plunger DTI mounted vertically on its centre. Before dismantling we mark index dots from the DTI with a marker pen to ensure that we are checking exactly the same point each time.

We label the dots A, B, C, D and using the DTI take comparative measurements at the four corner reference points.

When rebuild the assembly we simply replicate the four corner measurements which we took before working on it, its fairly easy with the jig to reset the tray assembly to exactly what it was when it left the factory, in fact it only takes about ten minutes.

Yes a bit of work to do, but it works very well and to date we have done four different machines, all have gone back together with no problem

A mornings work making the jig has saved many hundreds that would have have been charged by Formlabs to do the same job.

On each of the machines we ran the optics test before and after the tray / sensor contact replacements. Each time the results were with a few microns of the original result for z height.

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