Printing issues - missing powder with large ojects

In general my printer works fine. Right know i have a problem with printing large objects. I want to print an area of 10cm * 10 cm. It is not possible to rotate the object. The first 3 layer are fine, but then from the middle left there is powder missing. The next 7 layer each layer is missing more and more powder. If the area is getting smaller the missing powder is filled again. But the print is not useable.
If i rezise the object to 8cm * 8cm the print is fine with no problem. All dimension bigger than 8cm*8cm have the same problem. As bigger the object as bigger the problem.
Does someone know a solution to rise the amount of powder to get from the powder reservoir to the printing area?

Hi Rudschul - I assume the layers are solid and because the sintering melts the powder into a smaller volume there is not enough powder in the next layer to fill that volume. I think you are right in thinking you need to increase the lift of the reservoir. I don't know how quickly the Sintratec software development is but it should be relatively easy to equate the lift with the area being sintered, shouldn't it?

I am surprised you are not experiencing warping with that area of solid infill. I am still getting some warping in the front left corner of my build area and I try not to use that part until I find a solution to the uneven heating.

Edit: Just a thought - can you not tilt it at a very small angle, just enough so it does not print the whole surface at any time?

Quote:

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Originally Posted by Mike Francies

Hi Rudschul - I assume the layers are solid and because the sintering melts the powder into a smaller volume there is not enough powder in the next layer to fill that volume. I think you are right in thinking you need to increase the lift of the reservoir. I don't know how quickly the Sintratec software development is but it should be relatively easy to equate the lift with the area being sintered, shouldn't it?

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Yes, you are completly right. You are able to see, that you will need more and more powder. As Sintratec told me i am able to see that sintered area is brighter than the not sintered area after a new prepared layer. As brighter you are able to see these areas as more energy was stored. In conclusion the powder ist not sintered anymore it is melting :-) For me that very good :-) But you will need more powder but it is more stable.

Quote:

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Originally Posted by Mike Francies

I am surprised you are not experiencing warping with that area of solid infill. I am still getting some warping in the front left corner of my build area and I try not to use that part until I find a solution to the uneven heating.

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My warping zone is front right. This regeon is a little bit colder with my printer. I was playing with laser speed and surfage temperatur.

Quote:

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Originally Posted by Mike Francies

Edit: Just a thought - can you not tilt it at a very small angle, just enough so it does not print the whole surface at any time?

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No that is no solution. When i am thinking about the kit i ask Sintratek about the max printing size. They told my that 11*11*11 might be possible. A lot of my parts i want to print are abotut this dimension. So i have first to fix this problem to go further on.
For me it is very importend to know what dimension i am able to print with no problems.

Another thought - last night I printed some calibration cubes and when I put the powder into the reservoir I accidentally knocked the machine. What I noticed was that the powder settled down quite a lot so I knocked the machine a few more times and the powder settled even more. If you were to do this it would allow more powder for each layer as the powder density would be higher. Just a thought.

ok very interesting. I will try.

I tried you proposal. Yes it make a diference of the packing dense. Do you have sometimes warping issues which cause the print will destroyed? I print with following parameter:

Chamber temperature : 150
Surface temperature : 171, 7
Speed 550

After about 2 cm my object starts warping at 2 pillars

Hi rudschul,

I too had warping issues until I raised the powder surface temperature to 174.2C and lowered the speed to 550mm/s. What I had noticed was that at startup, the chamber temperature and the surface temperatures were not the same and there was a difference of some 6 degrees C. They ought to read the same and both should have been at room temperature. I reasoned that this was why I needed to raise the surface temperature as this was reading low. You may have the same problem.

If I am printing a few parts at the same time I drop the surface temperature to 173.7C otherwise the powder 'cake' of the un-sintered powder seems to be too hard so I figured the laser was raising the surface temperature just that little bit more that took it past the optimum.

I still suffer from warping if I try to print within 20mm of the edges.

I also have another problem that Sintratec assure me they are working on and that is that objects printed in the far third of the print area (away from the window) are all stretched in the Y axis. So much so that a 20mm square ends up 20 x 21mm. Everywhere else seems to be within reasonable limits.

Hope this helps.

In conclusion you think it was a good idea to lower the temperature or to raise the speed?

I agree to your scaling issues. I have the same problem, but it is not so importent for my to solve it. But if you have a solution please post it.

My main problem is to print big part (9*9*9) with constant quality. I alway run in trouble. (Warping, defect endstopper, loose nut, less powder).

It is very frustrating that i have no support access anymore and there is no realy active community who share there problems and there solutions.

I think you need to raise the surface temperature to cure the warping problem. If the surface temperature is very close to the melting temperature, the part has no chance to cool down and therefore warp.

What is your problem with the endstopper and powder?

I don't have a solution to the scaling problem but Sintratec have said they are aware of it and are working on a solution.

Ok i will raise the temperatur a little bit more and try again....

The enstopper will not work because some powder or polymere get into the endstop and work like an isolator.
Do you see a little white film outside you printer? These ploymere in compination with the powder come into the endstopp.

Yes, I do get the white film on the outside of the printer but so far this does not seem to have been a problem for me. I am surprised it gets into your micro switches enough to make them stop working. Probably worth looking for some better switches. Are these the powder sled switches or the powder and build chamber switches? The latter ones are in the back of the machine so should not get too much exposure to powder.

I was surprised just how much powder finds its way into the carcass and I regularly take the machine apart to clean out the excess. Most of this seems to come from the waste powder chamber so I have spent some time sealing this area much better and I am considering making a drop in container to collect all the overflow powder so I can lift it out easily. I also think the big drop of the powder, into this chamber, contributes to the dusty atmosphere in the machine so I also want to try to make this better too.

I love the ability to be able to have such a machine but there are still a few problems to overcome. The parts I have made that do not require absolute accuracy have been excellent and I am very pleased with them but they are all quite small and fit easily within the part of the machine that gives the best results. I appreciate that you require a much larger build area and I am pretty sure that my machine could not cope with a 90 x 90 x 90 build. However, if you would like me to try and could send me a file, I am happy to do so.

Yes i am searching for better endstops. But it is not so easy. I have contacted the distributor who sell them to Sintratec. It is a German Company and it is easer to get new one directly. The problem is that they found endstop which are water proof but not heat resit able or heat resizable but not water proof.
The problem is that the polymer are condensing like water in the air at cold glass. With the powder they stick at the contact. Right know i have changed 5 endstopper. (one at the door. two left, one right, bottom left) I have opened one defect endstopper.I have seen not really much powder, but there was e very thin resistor skin at the contact. After removing this skin mechanically and rebuild the endstop, it was working again.
Right now i want to print the following part for my Ultimaker:

www.thingiverse.com/thing:175621

In general i want to print some part from the inmoov project

SkullServoFixV1.stl

That's an interesting project. I had not seen it before but it appears to be an awful lot of work! The Sintratec will be good for some of the smaller parts but I think the SkullServoFix is just a bit too big. Could it be broken down into smaller pieces? Also, it has a lot of heavy, solid sections that could be eliminated if it could be re-modelled.

I am happy to have a go at printing the cooling duct and if it works out okay, you are welcome to have it. I will let you know how I get on and I will attempt it tomorrow.

Thank you for your advice. But for me it is most imported to know you do it. Perhaps you can share all of your printing parameter and the position where you print it.

Hi rudschul,

The cooling duct printed without problem and no curling/warping at all. (see attached photos - quality of photos not too good from my phone) The part has not been post processed other than a light brush with a toothbrush. Were you having problems printing this?

My settings were:
Chamber temperature - 150C
Powder surface - 174.2C
Speed - 550mm/s

The part was aligned as shown in the two screenshots.

The print took just over five hours to print and another couple to cool down.

If you let me know your address, I will send it to you as I have no use for it at all.

Cheers,

Mike

Thank you for your effort. The print look very good. Yesterday i tried to print it again with significant higher powder surface temperature (174). And yes the print was ok, too. In the past the print stops after about 2 cm print hight. Than you have at the right side two pilars (slice-view). And the front right pilar starts warping. The main confusion was that i had warping problems after about 2 cm. I do not expect warping after about 1 hour fine printing. In past had had parping problems at beginning and not one or two hours later.
With surface temperatur of 174 it is not so easy to clean the object like with 172.
Makes it sence to reduce surface temperatur and to lower laser speed?

The problem with just lowering the laser speed is that the powder is still not hot enough to stop the warping and in fact just lowering the laser speed actually makes the warping worse as there will be a bigger temperature differential between the sintered powder and the non-sintered powder. I have tried a lot of things to stop the warping and my solution is that there is no substitute for powder temperature - get that right and the warping disappears. The next biggest problem is trying to make sure there is even temperature all over the build area. I think this is more difficult to achieve.

You are right, the parts are more difficult to clean but at least they are good parts. You could try lowering the powder temperature to 173.7c. I do most of my printing at this temperature and the parts are easier to clean but I cannot print within about 30mm of the edges. It is near the edges that we have the biggest problem of uneven temperatures. I am thinking of devising some kind of reflectors to try and get the temperature more even. I'll let you know how I get on.

Yes you are right, the uneven temperatures are a big problem. Front of the door seems to be the coldest position. And the right side is the next coldest postion. Then the left side and at last the back side. At conjunction areas warping starts first.
So the front right corner is the first areas warping starts.

Front right and left are the worst for me. Clearly the door is giving the biggest problem and it is probably the easiest to fit a reflector to. I will try some cooking foil the next time I print and deliberately put some parts near the front edge. This should give us an indication of whether the reflectors will work or not.

A thermal camera will be useful. But i have no one....and they are expensive to rent.

Here best print it is 10.5 cm long, but not so high. Pinter with 149,5 171,5 and speed 550. The small side shows to the front
Attachment 10356Attachment 10357

I am still fighting with the right temperatur. I tryed to print 2 Fischertechnik bricks with a lenght of 9cm. With the temperatur setting of the fan duct i got warping.
The folliwing values were successfull :
Chamber temperature - 150C
Powder surface - 174.6C
Speed - 750mm/s

With lower speed i got aways warping. But with this values it was very hard to get the object free from powder.

After this i tried to print an object that has less big printed areas.

Chamber temperature - 150C
Powder surface - 171.7C
Speed - 450mm/s

It was important to lower the speed. The result was great. Easy to clean and no warping.

I am still searching for the right setting to print an object. I am not shure when big printed areas makes an problem....

Hi rudschul,

I am seeing similar results. The more parts there are to print, the more difficult it is to remove the powder. I am pretty sure the reason is that the laser is adding to the surface temperature to such an extent it takes it just past the optimum. For single, small parts I set the temperature to 174.6C but for the occasions I print many parts at once I set the temperature to 172.4C. I have not yet tried experimenting with the laser speed too much but it looks like you may be getting close to something that works. Now we need to make a sliding scale of temperature and speed against volume to be sintered.