Print white text flush on a black surface?

[terrypin]

I've not yet made a print including text wiith my Ender 3 V2. But I'll soon need to do so and would appreciate some advice on a few practical points from more experienced users please.

The 10 text labels will be on the top surface of a rectangular box lid, which has dimensions of 175 x 95 x 3 mm. Maybe a bit thicker if necessary. The labels (like On/Off, Up, Down, etc) will be near holes made for various buttons and switches. Each label will therefore be fairly small. I want them to appear flush with the surface, white on my black PLA filament.
One option might be to carefully paint the 'valleys' with a fine brush, and hope to wipe off excess. Another would be to fill with something like 'Hard As Nails' glue, again wiping the surface clean before leaving it to set.

But ideally I'd like to do it by stopping the printer just once, changing to white filament, and resuming. If I go that route, I'll obviously have to displace them downward in my OpenSCAD code text. What changes do I have to make in OpenSCAD and/or Cura, so that the stop occurs at exactly the right place?

Would another idea be to make each label say 1 or 2 mm high and push them into place? I suppose they could be printed collectively, joined by a thin line, easily removed?

All suggestions/tips/advice will be much appreciated.

 

[andy_mk3]

One option I saw on Youtube recently. Print them in white with the text ever so slightly proud of the surface, paint them black then sand the top down to take the black paint off leaving the white behind.

From this video: https://www.youtube.com/watch?v=e7K3BXWmipk

 

[Scougar]

Note that in the video he is using a resin printer for the buttons. This means he gets lettering MUCH nicer than a regular printer.

I would be inclined to do this (I've already done a test for this):

Print the lettering hollow where possible. Then put tape across the face (seal well!), put them face down, and fill from the back with a thick paint or paint and glue mix so when Dry you get nice thick flush lettering.

Trying to do raised lettering that is sanded down that requires a mass of bridging from underneath may be difficult, hence what I am suggesting here.

 

[terrypin]

Thanks both. Think I'll pass on the sanding idea (hey, what a complex project in that video!) but will definitely try the hollow lettering. Similar to the 'Hard as Nails' option I mentioned.

But I'm still hoping for an almost hands-off approach (apart from changing the filament) if that can be achieved with OpenSCAD and Cura - by a novice!

Just seen this, which looks very promising, although I don't want to have to switch from Cura to Prusa.

https://help.prusa3d.com/en/article/insert-pause-or-custom-g-code-at-layer_120490

 

[terrypin]

"Print the lettering hollow where possible. Then put tape across the face (seal well!), put them face down, and fill from the back with a thick paint or paint and glue mix so when Dry you get nice thick flush lettering."

Spent most of yesterday experimenting with that promising method, but without much success. These are my best so far!

Leaving aside my likely clumsiness, one factor is probably that 'Hard As Nails' is too sticky. (What did you use for your test?) But I reckon the key issue is the small size of the text I'm using. With the panel dimensions I described, and two rows of five labels each works out at roughly 29 mm per label, including space between them. So they have to be quite small. Font will of course be another factor. (What did you use?) I haven't given up yet but I'm leaning towards two other possible methods.

The first is the 'push fit' approach. IOW, print the black panel, with empty holes for the text. Then change the PLA on my Ender 3 V2 to white and print the solid text, at a slightly smaller size. I made a start but (apart from my rather old and brittle filament snapping, unobserved, during the test!) I forgot to add what Cura calls a 'raft' to the text characters. (Did I mention I'm still a novice?) Aiming to try this again today.

All advice will be much appreciated thanks.

 

[terrypin]

My first attempt to make the 'hollow' version of a label is shown here in Cura's preview:

But I failed:
- to mirror the text (a silly mistake)
- to realise that parts like the inner hole of an 'O' will just fall off the panel, as it has nothing supporting it.

The first is easily corrected. And I think the 'loose bits' issue could be fixed if I add a thin 'support' layer at the back of the panel and push the solid (mirrored) text into the hollow equivalents from the front. Does that seem reasonable?

I printed the solid text 'Off-On' with Cura's 'raft' setting enabled. First time I've ever needed one. It seems unnecessarily large for this tiny object and in future I'll just add a much smaller rectangle layer in my own OpenSCAD model instead. It remains to be seen whether either 'raft' could be neatly removed; important if the text is to look OK. FWIW

I mentioned that I was focusing on two methods. The second was resorting to printing the whole thing on my Canon inkjet. Perhaps on glossy paper. Probably laminating it. Then gluing it onto the panel. A cop-out, but the 3D approach is beginning to look more challenging than I expected!

 

[PardonTheWait]

Make the box as one STL and the labels as the other, with the labels one layer high. Add some sort of registration marks to the STLS that are placed identically so that they are perfectly the same size.

Centre each STL on the build plate, print the white labels, then leave them on the plate and print the black part while they’re still there. It’ll just go around them.

If your build plate has a texture as well it’ll help it look nice.

I can’t remember where I found out about this but I tried it and it worked. As long as you can be 100% sure they’re aligned, which you can do by including something around the edge of the object like a brim/skirt basically, only even needs to be in the corners. If you do opposite corners you won’t even have to remove it after the first print and it’ll still centre them perfectly.

 

[terrypin]

Thanks a lot, sounds promising, although I’m having trouble visualising or understanding it.

A typical test objective would be a white label size 8 Arial Narrow Bold ‘NEXT’. Flush with the surface of a black rectangle about 30 x 15 x 3, or even protruding 1 mm above it as second best.

How can I print the 1 mm high text on the bed without a base to support it? Each individual small letter would slide around. And I don’t really understand what you mean by ‘registration marks’? Also, presumably the second STL would be hollowed out for each character?

I’m currently struggling with the Arduino aspects of the project (using the DfRobot MP3 Mini Player), but if/when I surface from that I’ll restart the 3D printing experiments and report back. If you can recall your original source meanwhile, which probably had some hard code example, that would be good.

 

[PardonTheWait]

A bit hard to explain just in words so I've made some pictures but for some reason that's completely beyond me, even though my second STL has the same font, when I slice it, it changes to a totally different one! I'm mystified.

Basically you print the text only one layer deep. Then you print the box, with the text missing and it will print the first layer around it, leaving you with a now solid layer with a white text in it, then the rest of it will print on top of it.

The registration marks are just corners, if you make four corners, put two on one of the prints, and the opposite two on the other, it will let you centre it properly, and they won't clash so won't need removing.

First print plate:





Here's that rectangle from below - like I said when I slice it it changes the font, bizarrely, so this is un-sliced which is a shame, as if I could slice it I could show you just the first layer.



Just print the first one, leave it on the bed, change the filament, and print the second one.

If small text is going to come off the bed then you have adhesion problems - maybe try printing that first layer very slowly or lower your nozzle height a bit.

The other option is flip it the other way up and put a pause in your print for the filament change. I use PrusaSlicer which has this built in, but prior to that there was a tool on the Prusa website called, I think, PrusaColor, which would let you load a gcode file into it and it would add the code for you. The text would have to sit proud of the box in that case. I print quite a lot of stuff that way though and it works well.

 

[Scougar]

@terrypin Sorry you didn't have success I cannot see your pictures btw.

Good luck with the other suggestions. Interested to see the result.

EDIT: I used JB Weld Plastic Bond. It would be very easy to tint.

@PardonTheWait : Those look really good!

 

[terrypin]

@Scougar: Can you explain what the problem is? All three images look OK here. Can others display them OK?

I'm an habitual user of Araldiite, but never tried mixing it to get a nice white. If you've done that with JB Weld Plastic Bond, what did you use as the colourant? Would it flow freely to fill the small text cavities under discussion?

 

[terrypin]

@PardonTheWait: Briilliant! Thanks so much for taking the time to prepare such a thorough explanation. It'll be a day or three but I'll definitely be trying it.

 

[Scougar]

@Scougar: Can you explain what the problem is? All three images look OK here. Can others display them OK?

I'm an habitual user of Araldiite, but never tried mixing it to get a nice white. If you've done that with JB Weld Plastic Bond, what did you use as the colourant? Would it flow freely to fill the small text cavities under discussion?

Ah.. i was accessing through my work VPN which blocked the images. Now on my own network it's fine.

I'm fell in love with JB Plastic Bond. Incredible stuff. Hmm... it would flow, but into everything small? maybe not. It can be squished down after though.

 

[Scougar]

Ah.. I think I didn't explain myself very well.

EMBOSS the letters. then fill from the back. The front should already be flush.