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Tough 1500 Resins dimensional inaccuracy

Hello,

We’ve had the Form 3+ for less than a month at my job and am honestly getting buyers remorse given how bad our experience with the Tough 1500 resin has been. It has many issues, one of which it deforms heavily under at low temperatures, but most importantly, it the worst dimensional accuracy of any resin or filament I’ve ever used. Advertised by Formlabs on their “Dimensional Accuracy Report” says they have maintained a -0.05" average dimensional tolerance on 100mm features, whereas I’m getting 2.15mm oversized after post curing in the Form Cure. Yes, you saw that right, it’s over 40x worse accuracy than what Formlabs is advertising it can hold.

This is not only a bad look for Formlabs but is also a bad look for myself as I’ve had to adamantly advocate to get a Formlabs printer in our department, and to have it fail this terribly, I mean I might as well just eye ball these part sizes with a dremel I could probably do better this is really terrible and I’m going to have to ask Formlabs for refund materials unless they can recommend a resin that can print to what they say they can.

Anyways I’m just posting this to let anyone wondering whether to buy this material to please stay far far away unless you’re just doing single piece models as it’s too inaccurate to be used in any multi-part assemblies period.

This is odd since Tough 1500 is been rock solid for me. I do find it to be slightly off but not enough in what I am doing to matter. Now if you need it to be perfect I guess you will have an issue. Same goes with Grey Pro that I have found. Depends on what you are doing with it dimensionally I have found after a certain amount of time if you leave it sit it will shrink somewhat.

Have you gotten a chance to measure your model vs. your print and compare that deviation to what Formlabs advertises like I have above?

Have you tried another resin and confirmed it doesn’t have the same tolerance error? Maybe it’s the machine and not the resin… I haven’t measured anything I’ve printed with Tough 1500, but I’ve printed a lot of parts and they all fit together as expected.

What tolerances and allowances are you using when designing your assemblies with Tough 1500?

I have not measured as well but like Randy my fitment is as expected with the obvious cleanup.

Most of what I do is smaller stuff. Typically, I’ll give myself about 0.1mm of clearance, so 0.05mm negative tolerance for each of the two mating faces.

That’s helpful. I reprinted my part given the recommended wash times Formlabs provided and curing procedures using the Form Cure again. Again all my features were over/undersized if they were an outside/inside feature respectively. On average I’m getting 0.249mm (on 2" feature) average deviation, with a good amount of variability. I’ve only done a small number of tests so don’t feel comfortable calculating the std. dev. as it’s probably not accurate at this time. But if you’re able to achieve accuracy of better than 0.05mm then why am I getting 0.249" on a 50mm (2 inch) feature? This makes me think it isn’t a resin, but maybe my printer isn’t properly tuned from the factory…

Cured resin expands with absorbed IPA. It is recommended that prints should be allowed to dry between washing and curing. This should be for at least 12 hours, and preferably 24.

Okay, well I might try this. This is what Formlabs recommended in an e-mail exchange and what I tried yesterday:

Allow parts to dry for 30-45+ minutes

So that’s what I’ve done. I might print some more basic test parts and see if there’s a significant difference in dimensions between the dry times. I won’t be able to get to that until Wednesday next week though :confused:

try to print 4 same parts at the same print batch.
Dry one for 45mins, the other for 6h, 12h and 24h, before placing them in cure. Use same cure times.
Also notice that if you use heat in Cure, the part must be placed inside the chamber at the very start so as the heat up slowly, as Cure heats up.

keep in mind, that since the resin will absorb IPA, (and some other liquids) you should minimize the amount of time the part is submerged, I generally have had the best results (with dimensional accuracy/stability) following:

  • 5 min. (or less) in the ultrasonic cleaner (simple green)
  • 3 - 5 min. in the formwash (IPA) (depending on size & geometry)
  • follow up with cleaning using alcohol wipes
  • 60 - 90 minutes (maybe more) on the drying rack (using a small fan)
    then put it in the oven to cure.

I think you should check the units you are using. Discrepancies of multiples of 2.5 usually point to the mixing of imperial and metric units.

It’s a USian thing mostly.