Castablewax printing delimma


#1

I’ve printed this twice with the same results. I get the entire print, but the middle supports at some point pull away from the model. This wouldn’t be bad, but they take a bit of the model with it and it’s enough to make the repair kind of ugly.

This is the only angle Preform will allow me to print it. I’ve tried from flat to less of an angle. I haven’t rried totally vertical yet, though.I redid most of the supports because preform either gives me too few or such a forest of them that cleaning the supports off is just a bad as trying to repair what I have. I’m using

The model is about 70mm tall and I’m using .35mm supports. I had thought of going to larger ones in the area where the model is pulling away from the supports, but I would probably just get even bigger holes where they pulled apart.

I’m really perplexed because with an earlier version of Preform I printed the model in grey with mush less support and it was fine. The castable was does seem a bit more fragile than gray, but my goodness the sharpness I get the casrable wax.

I’d appreciate any thoughts you have on this.

Kathleen


#2

Hey,

The detach happen because the force to detach the cured resin from the resin tank is greater then the force required to detach the support.

I’m recommending on two options:

  1. increase the support tip as you suggested. I will try the 0.4 or 0.45mm as this is a very small model.
  2. increase the number of support dots. If you add another dot near to each support with the same parameters as you just print, you increase the force required to detach the support from the model by almost twice. You can place them quite close to the regular model dots. If you prefer to go on less supports due to long proccess of cleaning the model, you can try to add half of the support. Like one with 2 dots of support and one regular with one dot of support and so on.

Lets us know how it went.

Ahh one last thing, make sure the glass is clean, sometimes small dust particles just weakening the small models prints as the beam is spreading a bit.


#3

We had similar failures in our early prints. Kpinhassi gave you a good advice.
I recommend two further options:

  1. Turn the supported print by 90° or 180° around the z-axis, so the sideway motion of the tank does not pull the print away from your support structure, but pushes it toward it.

  2. If possible, try to add supports on the other side of your model, so the print supported against the sideway motion of the tank from two sides.


#4

I tried adding the extra supports and using a larger support size and it was worse. THe model cracked right where I added the most extra supports.

I think I had the model so that the wiper would with the lower part towards the wiper and the long side parallel to the front of the build plate. I think that’s what you meant about rotating the model, Mancke, right? I could be backwards.

I’m going to try a cleanup on one of the other models before I print again. This just might be one of those unprintable models on Formlabs. It’s not the first time.

THanks for your help.
Kathleen


#5

Can you upload the Preform file you just printed?

I think the location of the support is not ideal, let me try to improve it (if you like).


#6

Send me an email so I can send you a link. It’s a 24M file

kk


#7

24Mb is too big for e-mail as well.

Please upload the file to the following Dropbox link:

The link is available for 24 hours.

Thanks.


#8

I sent the file. because I am always ready to learn new things so I look forward to your corrections.

Otherwise I have a fixed model I can use and I kind of need to have it at the caster by tomorrow.

Thanks
KK


#9

Hey KK,

Here is a link to the model I placed (valid for 72 hours), hope it is in time for you, we have some hours difference so I just received the part close to midnight and didn’t have the chance to work on it.

What I did is flatting the part more in order to achieve a larger surface that came in contact with the LT tank. The angle of the part with the LT tank is producing less forces applied on the model, we pay with a larger surface on the LT tank when we do it that way.

I’ve manually placed the supports mostly in the middle of each arm and not on edges as the program do, this way I’m strengthening the model to failures. I tried to have as less as possible but due to the failures you experienced I’ve placed some extra on each arm.

finally, as advised here as well, I’ve placed the model in a way that when the LT tank is moving in order to detach the model, it will be with the arms direction and not against them. I’m understanding the this is an item for fishing so consider it as an anchor, when a fish is biting the hook it smoothly inserting to the body but it is hard and required more force to take it out. I placed it the way in and not in the way out.

Hope it will helps and if you try it, let me know how it went.

Good luck!


#10

Oh Dear, sigh.

That was just what I was trying to avoid, all those supports. Do I really need to do it that way? What happens is that they break off and leave little holes before I can get in to cut them off, and it’s a mess. And do supports really have to be on the corners? Preform does that and it drives me bonkers.

I’ll try it mainly because I’ve made a small change in the design, but I’m not hopeful. But I’m moving the supports away from the edges. That’s way too many supports.

kk


#11

Got ya, let me try to do some extra effort on it.


#12

Ok, no doubt this is quite complicated, the model is not even a mirror of its self, each side have its own thickness.

I’ve flipped it over so the edges in the middle will be the last thing the printer is doing so we have no need for edges support.
I’ve changes the support to 0.4mm and build it up peace by peace taking in account the forces applied on the model while detaching.

The model is not “approved” by the Preform, I wouldn’t bother about it from one side but cant guarantee from the other as I haven’t printed it yet, got stack of prints to perform.

Give it a shot.


#13

I will definitely look at it.

I realized later that you had the model with the front facing the build platform, so I took the idea of your points and transferred them to a model oriented correctly, in other words, the support points are now on the back of the model. It was hard to tell.

I’m always fighting with preform’s supports. I appreciate the information that I should try to print even though preform says it won’t because sometimes it says it won’t print but it can’t tell me why.

I had set the model almost vertical so that I could use less support points. It’s really important that I can get to them to cut them off rather than breaking. I hate the holes breaking leave on these castable resins. But I see it caused other issues with this particular model. THat’s why I was willing to try the flat version, which is printing now.

I look forward to seeing what your new solution is. There are always things to learn.

KK


#14

@kkingcgi, are these prints for investment casting, or are you using them to make molds for waxes, or something else? If they’re for casting or molding, where do you typically attach your sprue(s) and vent(s) if any? If you haven’t already ruled it out, building your sprue into the model and using that as your support might be an option (if that would give a sprue that’s oriented right for investment and casting and so forth). Just throwing that out there.

I’m currently attempting this with a nearly vertical orientation and few supports that are hopefully placed in areas where it’s not so bad to clean them up. We’ll see how it goes.


#15

Very good question. This particular model will be molded for wax. The others I’ve done will be cast directly, but they are much simpler prints or, in one case, a one off because of stones.

I don’t do my own casting. I use about 4 different places depending on what I’m doing so I don’t know where they would need their sprues. I haven’t ever asked about that, but when I’ve asked other technical questions, they wouldn’t answer. Lots of casters in NY so competition. Now I just point to somewhere on the model and say, ‘This would be a good place for a sprue, wouldn’t it? I’ll be really unhappy if you sprue in this other place.’ That seems to work.

Kathleen


#16

Hey KK,

Yes, for complex parts I do ignore most of the time from the note that the print is not fully supported. I’m printing human vascular segments from MRI and the models are extremely hard in terms of design so the Preform cant handle it. The prints (after the machine cleaning) is pretty good now, not perfect but durable for use.

Another suggestion I will go for, especially for casting is using the “Mini-Rafts” support option. This will make a smaller individual base for each support. This will give you the ability to cut each support, or several supports individually and remove them completely, so when you moving deeper into the model, the support are not interrupting.

image

This is the result in your model:

Keep in mind the less surface base located on the build platform is less holding to the part, so in future models, if you are using this function with less supports, it might lead to detach of the model from the build platform. This is not something that happen often, actually rarely, but just keep it in mind. Its a “game” of forces, who stronger, the base or the detach forces from LT tank while printing,

Another thing that I’m using is cutting the support a few mm from the model and then smooth it with a machine like Dremel or other mechanical option. This will give you a very nice models.

Let us know how the print went.


#17

I supported it like this:


and printed it.

I overlooked the part about using 0.35mm supports, so I used 0.8, but they’re all concentrated on the larger, flatter areas of the part, where they might be easier to grind away, whether that’s on the resin part before molding or on the final metal casting. Here’s how the support marks look on mine:

Because the cross-section is small as you go up the part, you can get away with a fairly intense unsupported angle/overhang without pulling the part off the supports, or pulling the raft off the build platform. In this case, this lets us avoid a number of unsupported minima and puts the supports on what I imagine to be the back/likely sprue area of the piece. I don’t know if I’ll find time, but I’m tempted to add a simple sprue with Meshmixer and see if I can get away with fewer and/or smaller supports.

By the way, the design looks great! I hope this discussion helps you get to a workable way to print it.


#18

This has been a great discussion for me. It was sweet of you to try to print that part and a real revelation that with the 80MM supports on the bottom, I could have printed the piece exactly the way I wanted. I had been thinking that preform had gotten smarter than it actually has. Still very good, though.

I use the mini rafts with grey, but not with castable. The castable wax is beautiful but a little fragile and there are all sorts of surprises when one casts from it. I’ve had to reprint a ring because I didn’t get all the uncured resin out of these little crevices.

And thank you for the compliment on the design. That’s the bottom of a 2 part piece.

KK


#19

`given that design- I might actually split the thing down the center and print it in two halves so the think fingers can point up with no supports at all on them, and all the supports on the separation plane.

Then glue the two halves together for investment.


#20

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