Yet another cast aluminum plate topic...

dc42

@gtj0 said in Yet another cast aluminum plate topic...:

I also tried the tempered glass over aluminum route. It's going to be a bitch to get heat transfer from the aluminum to the glass unless you use a thermal adhesive or paste between them.

Also, tempered glass is frequently warped by the tempering process.

deckingman

@gtj0 said in Yet another cast aluminum plate topic...:

I also tried the tempered glass over aluminum route. It's going to be a bitch to get heat transfer from the aluminum to the glass unless you use a thermal adhesive or paste between them...............

As @dc42 said, tempering glass (or toughening it) causes is to distort - been there, done that, got the Tee shirt. So if you use glass, stick with plain non-toughened, float glass.

Heat transfer isn't a problem - if it was, I wouldn't need double glazing in my house I get 2.5 degree top between the top of my aluminium bed and the top of the 6mm glass at 55 deg C bed temperature. If that's critical, just set the bed 2.5 degrees warmer. Personally I just use a squirt of 3D lac then I can print pretty much any filament at any temperature over about 50 deg C so bed temperature doesn't really matter to me.

mrehorstdmd

If anyone lives in the Milwaukee or Minneapolis area, Howard Precision Metals sells MIC6 cutoffs for $1.50-2 per lb. My 300x300x8mm bed plate that started as 13.5" x 15" cost me $15 when picked up locally.

gtj0

@deckingman said in Yet another cast aluminum plate topic...:

@gtj0 said in Yet another cast aluminum plate topic...:

I also tried the tempered glass over aluminum route. It's going to be a bitch to get heat transfer from the aluminum to the glass unless you use a thermal adhesive or paste between them...............

As @dc42 said, tempering glass (or toughening it) causes is to distort - been there, done that, got the Tee shirt. So if you use glass, stick with plain non-toughened, float glass.

Heat transfer isn't a problem - if it was, I wouldn't need double glazing in my house I get 2.5 degree top between the top of my aluminium bed and the top of the 6mm glass at 55 deg C bed temperature. If that's critical, just set the bed 2.5 degrees warmer. Personally I just use a squirt of 3D lac then I can print pretty much any filament at any temperature over about 50 deg C so bed temperature doesn't really matter to me.

I'm just reporting what I saw with the Flir and I did try float glass as well. It took a long time to get an even distribution of heat to the surface. Actually, a little bit of mineral oil on the center of the aluminum plate before laying the glass on top made a huge difference. Anyway, moot point for me. The printbite directly on the aluminum has been working great.

TLeTourneau

My glass is NeoCeram fireplace glass that I got from a local shop. I use a .5mm layer of high temp silicone sheeting between the glass and the heat bed.

@mrehorstdmd - thanks for the pointer! I'll give them a call.

jrjones88

Here is another place that sells off cuts of cast aluminum, out of California: http://www.sandsmachine.com/alumweb.htm

mrehorstdmd

@tletourneau go to https://www.howardprecision.com/random-rack to select a piece, get a quote, and they'll send a confirmation email. Then you email back and then tell them you want it and will pick up and they'll get it ready for you.

TLeTourneau

@mrehorstdmd thanks again for the replies! I called and talked to them, nice people. They no longer have a facility in Minneapolis so no local pickup for me. They have a piece of MIC6 that was $40.00 and was $67.00 shipped. The issue was that it is 19 5/8" x 28" and I couldn't find anyone local to cut it to size. If I have Howard cut it the price goes to over $100.00 shipped. I was able to get a 19.675" square 3/8" piece of ATP5 for $95.55 shipped. I've ordered a SSR and some 184C thermal cutoff fuses. Now I just need to order a 120v silicone heat pad. Looking at the frame and thinking through it I think a slightly smaller than 500x500 would be a good idea to give me room to mount the bed to the frame, like 460x460 if I can find one in 110v.

I have also ordered enough 2020 extrusion to build a stable gantry for bed (along with MGN15 linear rails for the X and Y axis).

TLeTourneau

Would a 450x450 heater be alright on a 500x500 bed? Also, does anyone know of a reasonably priced supplier that is not in China or on a holiday?

PlasticMetal

@tletourneau said in Yet another cast aluminum plate topic...:

Would a 450x450 heater be alright on a 500x500 bed?

Absolutely. Aluminum is an excellent heat conductor, and 1 inch shy on each side is a non-issue. In fact, it gives a desirable gap to ensure the heater clears any mounts, clips, etc.

I use a 310mm diameter MIC-6 plate on my delta, heated by 3 PTC elements (like these), and the heat spreads out fine. In retrospect, 4 would have been a little quicker, but it all works.

gtj0

You could also get 4 200x200 pads and wire them in parallel.

Wyvern

Not to take over the thread, but has anyone used 3M 468MP to attach a mirror to an aluminum bed?

I hate hate hate hate hate clips or the likes, they get in the way and reduce build area.

jrjones88

@wyvern said in Yet another cast aluminum plate topic...:

Not to take over the thread, but has anyone used 3M 468MP to attach a mirror to an aluminum bed?

I hate hate hate hate hate clips or the likes, they get in the way and reduce build area.

I restrain my glass plate in 3 directions from the side. I still need to modify (improve) it since the heat cycling loosens the screws over time, but the aluminum is flat enough that after polishing it, if I lift only the glass, the aluminum sticks to it for a few seconds and is lifted up as well.
I usually have to slide the glass plate off the aluminum plate to separate them.
I was using the binder clips before but found that it warped the glass slightly because they clamped at the very edge of the glass.

Wyvern

@jrjones88
You have a nice plate then, mine, while it works surprisingly with no compensation will visibly warp if one adjustment knob is too tight, it's too thin IMHO to use alone.

I'm testing out corner clamps, they work, but they reduce build area by 10mm and seem to interfere with the bed adjustment (cocked to one side)- but prints look better.

I will leave 1 inch corner uncovered from adhesive, that way I can get a scraper under and peel- its .1mm thick.

TLeTourneau

I use Swiss Clips, they're unobtrusive but allow me to remove the glass relatively easily. I'll see how they work with the 3/8" APT5 and 1/4" glass.

https://www.dickblick.com/products/swiss-clips/

dc42

@wyvern said in Yet another cast aluminum plate topic...:

I hate hate hate hate hate clips or the likes, they get in the way and reduce build area.

That's why I use build plates that are a little larger than the area reachable by the nozzle. I don't see any point in using a glass plate on top of the aluminium if you can't remove it very easily.

Another reason to use an oversized built plate is that the edges will inevitably be a little cooler than the rest.

TLeTourneau

@dc42 OT but do you think this paint would work with the mini differential IR sensor?

Rust-Oleum Specialty 12 oz. High Heat Satin Bar-B-Que Black Spray Paint
https://www.homedepot.com/p/Rust-Oleum-Specialty-12-oz-High-Heat-Satin-Bar-B-Que-Black-Spray-Paint-7778830/202315061

mrehorstdmd

Here's what a 750W Keenovo heater does on a 300x300x8mm MIC6 plate set to 100C:

alt text

Notice that the ears of the plate read much cooler than the rest of the plate. It looks like temperature drops off rapidly as you move away from the outline of the heater, so using an oversized plate may not provide any more printable area.

TLeTourneau

@mrehorstdmd it'll be interesting to see how it turns out for me. I've ordered a 120v 1000w 450×450mm Keenovo, due to the holiday in China I likely won't receive it until the end of February. I'm going to try adapting the mount design you used. Where did you get the Teflon blocks from?

Wyvern

@dc42 The conundrum is the nozzle and cradle assembly sit very low, so I can't clip to the rear of the plate at all as it juts out 3 inches from the bed, the build plate sits very close to the the tray- so much so that the clip interferes with the adjustment of the bed, I could install larger springs however.

I only print on build mats, these require a scraper and mild rapping on the handle, this moves the plate around.

Clipping onto the this thin bed causes the mirror to warp.

I would buy a CNC'd bed, but the one available requires an expensive silicone heating mat $140 I can't justify just yet.

Glass has a lot less expansion when heated and mirrors are usually very flat, I don't use a probe, so if the build plate is warped i'm SOL.

With A/C heating mats, is there not a way to use the duet signal to turn on/off control the heat? everything I have seen uses a dedicated controller.