A 3D Printing Experience

[Rob R]

Last nights print was also a no go. There was still a little distortion - 45 deg line from headstock nearest build plate - and the top of both ends has deformed.
Another attempt printing now as per attached piccie.


If that doesn't work then it is definitely plan B - loose the floor.

At this rate I am going to need a bigger bin........

 

[mickoo]

Rob, I don't think your current print will work either I'm afraid, the additional cross bracing is at an area where you're not getting a problem in the print.

Taking the floor out will help but may not completely remove the stress line I fear.

I'd love to know how to solve this as well, it besets a lot of my shapes, even on an expensive Form 3 and seems endemic to all SLA printers in one form or another.

 

[Rob R]

Rob, I don't think your current print will work either I'm afraid, the additional cross bracing is at an area where you're not getting a problem in the print.

Taking the floor out will help but may not completely remove the stress line I fear.

I'd love to know how to solve this as well, it besets a lot of my shapes, even on an expensive Form 3 and seems endemic to all SLA printers in one form or another.

Mick,
I have printed an earlier floorless version before I drew the solebars and that came out ok

I suspect the issue is the thickness (or lack of) of the sides.
I downloaded a little QGR 3 plank off Thingiverse, designed for FDM printing as a flat pack kit, wizzed it together on TinkerCad and printed it, auto supports and all, and it came out great. Please excuse the crappy phone pic. The sides are a little thicker (1.25mm ish rather than 1mm) and it is slightly smaller.


Maybe the answer is not to over think it?
Rob

 

[Rob R]

Apologies Jim, I thought I was on my workbench thread.

 

[mickoo]

Interesting, maybe the trick is to add the solebars with a small ledge on the inside and no main floor, then print that separately.

 

[Rob R]

Interesting, maybe the trick is to add the solebars with a small ledge on the inside and no main floor, then print that separately.

This one is designed for a 40 thou styrene floor, just the floor planks, the visible parts of the curb rails and headstocks are part of the main printing. I don't reckon much to my chances of printing a floor on it's own and keeping it flat.

 

[JimG]

I did try the upside down orientation but with not very good results.



I placed an 0.8mm wide by 0.5mm high strip around the top of the body - wide enough for a medium sized support to attach to but also leaving enough of the "proper" top surface to provide a good guide to file back to. I also avoided covering the corner brackets in the hope that I could support and print them on their own.



Medium sized supports were placed around the strip and the corner plates were supported with light supports.



The result wasn't too good. The body had come adrift from the supports at the end opposite the door. It looks as though this happened when the printing was around the support/body join since the body seems to have printed out not too badly above to the end of print.



From the end view it looks as though the supports in the middle might have kept in contact, the ones at the extremities being the ones that have separated. They have separated now but that could have been my handling during the taking off the plate and the washing/curing. The dimensions for the medium supports used were exactly the same as used for the "right-way-up" orientation and I had no problems with them separating.



At the other end of the body, the supports worked very well with no hint of separation, so I'm not sure what's going on.



And just obvious in some of the other shots, the body has bowed in quite noticeably about half way up.


I ran another print and exactly the same thing happened. The medium supports are exactly the same as the ones used on the "right way up" version and I had no separation problems with that orientation.

So I want back to the "right way up" orientation and printed off some more for the SSMRS AGM. At least these prints are now predictable and all printed well.

I might go back and see if I can get any better results with the upside down orientation. I could beef up the supports to see if that improves matters or I might try just upping the exposure time to see if that does it. I've done that before if I have had support separation problems and it has worked. As for the bellying of the sides, I note what Mick said earlier about thickening the sides but I'm a bit reluctant to do that since the tops are overwide as it is.

Jim.

 

[mickoo]

Wow, I am surprised at that, a drastic change there.

The one advantage with the sacrificial strip and probably the main reason to have it, is that you can put really big supports in because the whole strip is going to be cut back. Small tipped supports are generally for areas where the tip touches a detail you want to preserve.

If the model delaminated at only one end then that might be an indication that the build plate is not level or the LED power at that end is slightly less, but if everything else is fine then I'd count that out.

Printing perfectly flat like this does put a lot of stress on the FEP and first few layers with high peel forces, you may find that by angling it like Rob R has will reduce the peel forces, not sure what machine you're using of if you use AA either, but it only has to be a few degrees to reduce the peel forces drastically.

Your bowed sides may be down to the side wall starting thin and getting thicker toward the base, a constant thickness might reduce that effect, remember this is effectively a soft plastic as it's being printed and the peel force is centered in the middle of the FEP. Therefore when the model is raised the FEP domes up in the middle and is therefore not horizontal as it moves out to the edges anymore but sloped, this can make thin sides like this deform, especially if the mass is greater than than below.

 

[JimG]

Mick,

I used the same size of supports as in the "right way up" version. I had actually worked up to that size of support from earlier efforts where supports were separating. I had also checked out out the table levelling quite recently when cleaning the FEP after a false start. Printing "right way up" after printing the "upside down" shows no problems with the model in the same position on the LCD. However I'll re-check the table just in case it's in a critical position which works for one and not the other.

I'm also going to change the FEP to NFEP. I tried to source some at the end of last year but everyone seemed to be out of stock, so I back-ordered from 3D Jake and the NFEP arrived a couple of weeks ago. I didn't fit it since the existing FEP seemed to be doing quite well with the "right way up" prints.

The machine is a Phrozen Sonic Mini 4K and the resin is Phrozen Aqua 4K which seems to work well in the machine. It's fairly new and I hope that the LCD hasn't started to deteriorate. The reason I got the machine was that it is one of the new, higher resolution printers with a monochrome LCD which is supposed to have a much longer life.

I've printed off more of the "upside down" parts for the S Scale AGM and I might go back and try the "right way up" variety when I change the FEP to NFEP. But I'm unwilling to thicken the sides since I was fighting compromises on the body to get enough side strength that would print but not look too overscale. I would actually like now to get a good look at the original white metal kit sides to see how Alan Gibson's mould maker got round the problem in white metal.

Jim.

 

[Mike Trice]

Daft suggestion. It might be worth checking the tension of your FEP.

 

[mickoo]

This one is designed for a 40 thou styrene floor, just the floor planks, the visible parts of the curb rails and headstocks are part of the main printing. I don't reckon much to my chances of printing a floor on it's own and keeping it flat.

Print it on its side with a sacrificial ledge along the bottom, I'd cant it over say 15degs so the underside faced the build plate. Mind, it's a lot of resin and print time for something that is easier in Plasticard.

 

[mickoo]

Mick,

I used the same size of supports as in the "right way up" version. I had actually worked up to that size of support from earlier efforts where supports were separating. I had also checked out out the table levelling quite recently when cleaning the FEP after a false start. Printing "right way up" after printing the "upside down" shows no problems with the model in the same position on the LCD. However I'll re-check the table just in case it's in a critical position which works for one and not the other.

I'm also going to change the FEP to NFEP. I tried to source some at the end of last year but everyone seemed to be out of stock, so I back-ordered from 3D Jake and the NFEP arrived a couple of weeks ago. I didn't fit it since the existing FEP seemed to be doing quite well with the "right way up" prints.

The machine is a Phrozen Sonic Mini 4K and the resin is Phrozen Aqua 4K which seems to work well in the machine. It's fairly new and I hope that the LCD hasn't started to deteriorate. The reason I got the machine was that it is one of the new, higher resolution printers with a monochrome LCD which is supposed to have a much longer life.

I've printed off more of the "upside down" parts for the S Scale AGM and I might go back and try the "right way up" variety when I change the FEP to NFEP. But I'm unwilling to thicken the sides since I was fighting compromises on the body to get enough side strength that would print but not look too overscale. I would actually like now to get a good look at the original white metal kit sides to see how Alan Gibson's mould maker got round the problem in white metal.

Jim.

Interesting, there should be no difference in prints in that case, but clearly there is. I'm seriously looking at the new Sonic 8K Mini, or Mega for extra build volume.

 

[JimG]

Interesting, there should be no difference in prints in that case, but clearly there is. I'm seriously looking at the new Sonic 8K Mini, or Mega for extra build volume.

There is one difference which I haven't mentioned. The "right way up" version prints with no overall raft at the bottom of the support



...whereas the supports for the other version have a full raft



This only came about because in my first version of supports for the "upside down" version I had not used a full raft, but Chitubox decided off its own bat to insert five layers of full raft 0.5mm up from the base. This caused the print to lose contact with the base presumably because the large unsupported area of raft was distorting and causing the resin to lose contact with the FEP. I get this quite regularly with Chitubox, but usually it's only one layer of full raft some way into the print and it normally doesn't affect the print overall. To get rid of the unwanted raft, I find that I have to mess around with settings to get it to go away. In the present case, adding an actual full raft on the plate seemed to do the trick. I'm using Version 1.8 of Chitubox.

Jim.

 

[JimG]

Daft suggestion. It might be worth checking the tension of your FEP.

Mike,

I'll check that out but I normally don't have a problem with FEP tension on the Phrozen bath since the method of holding the FEP appears to give a good tight tension pretty well automatically, both on the Sonic Mini and my old Shuffle. I'm about to change to NFEP so the tension will be looked at again.

Jim.

 

[Dog Star]

Always keen to learn about new technology, this topic is including mnemonics and terms that are new to me. What does FEP stand for and where is this magic item in the printer. Why is FEP tension a critical aspect of the print process?

thank you, Graham

 

[mickoo]

I would have thought a full raft would have been more stable but if it's coming away, or is loose on the build plate, then that may explain why the body deformed as well.

I used to use v1.5 and hadn't come across it adding odd layers, I didn't use the full raft option but then again in 1.5 it didn't seem to work well at all, Chitubox is a clumsy piece of software at best I will admit, I'll miss Preform if I switch back to a LED based machine.

 

[mickoo]

Always keen to learn about new technology, this topic is including mnemonics and terms that are new to me. What does FEP stand for and where is this magic item in the printer. Why is FEP tension a critical aspect of the print process?

thank you, Graham

With respect, you need to google that, writing it all out to explain here would take an age and there are other and better explanations by people far more skilled in this malarky than me

 

[mickoo]

Mike,

I'll check that out but I normally don't have a problem with FEP tension on the Phrozen bath since the method of holding the FEP appears to give a good tight tension pretty well automatically, both on the Sonic Mini and my old Shuffle. I'm about to change to NFEP so the tension will be looked at again.

Jim.

I'm guessing the Phrozen uses a securing ring around the base of the vat that pulls in the FEP as you tighten the screws?

Pretty much like Epax and you don't really get much choice in the tension setting, it is what it is. So long as it remains constant then tension isn't as critical as it can be, all one needs do is adjust exposure times to get the best results.

 

[Dog Star]

With respect, you need to google that, writing it all out to explain here would take an age and there are other and better explanations by people far more skilled in this malarky than me

Fair enough Mick... I had done a Google search and got frightened away after running down the first couple of pages of results. Maybe my KISS approach to Google search strings did not help.

"people far more skilled in this malarky than me" - pardon? surely not? to those of use looking for a seat at the back of the class you are the master.

regards, Graham

 

[mickoo]

Fair enough Mick... I had done a Google search and got frightened away after running down the first couple of pages of results. Maybe my KISS approach to Google search strings did not help.

"people far more skilled in this malarky than me" - pardon? surely not? to those of use looking for a seat at the back of the class you are the master.

regards, Graham

I've no idea what FEP stands for and quite honestly, don't need to know, much like some bits inside my automobile, they're called x, y and z but I've no idea why they're called that.

In simple terms it's the transparent plastic sheet at the bottom of the vat that holds the resin, the LED light shines through this and solidifies the resin, the length of time the LED shines determines the strength. The idea is to make the resin stick to the build plate or previous layers of the model, unfortunately the process works both ways and it sticks to the transparent film. When the layer is done the build pate lifts up and tries to peel the model off the film, if it's too loose it'll deform the model, if it's too stiff it may rip the model off the build plate or layers already printed.

It's a tug of war in simple terms and one of the biggest variables in SLA printing, your exposure times are critical and vary with resin used, temperature, type of machine and design of FEP, they're pretty much unique to each machine and can only be found by essentially filling your bin with failed prints until you hit the sweet spot.