Printing issues - missing powder with large ojects

[Mike Francies]

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.

[rudschul]

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

[Mike Francies]

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.

[rudschul]

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.

[Mike Francies]

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

[rudschul]

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?

[Mike Francies]

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.

[rudschul]

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.

[Mike Francies]

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.

[rudschul]

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
IMG_0030.jpgIMG_0033.jpg