Yet another cast aluminum plate topic...

Wyvern

It's a little self-contained heat controller and timer, no wiring to the Duet at all.

The problem I see with it is the inability to set the bed temp with G-code, the upside is the reduction in wiring and since it's remote, no chance of it damaging the due... unless it decides to start on fire.

TLeTourneau

@wyvern I went with a SSR, I prefer to let the Duet control the temperature. It is really useful for prints like some of the ABS where I drop the bed temp after a few layers.

Wyvern

I've heard of the SSR throwing high peak voltages during SSR deactivation/off cycling.

But usually that is with shutting down actual coils- so maybe that is bad information.

Phaedrux

@wyvern I'd go with a Duet controlled SSR. Something like:
https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=288

I'd worry about forgetting to turn on or off a seperate controller. Might as well let the Duet automate it with Gcode.

Wyvern

Any success with PID tuning?

Phaedrux

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

Any success with PID tuning?

Me? Yes, I have a 310mm ish square 6mm MIC6 plate with 600w 290mm ish silicone heater RTV siliconed to the plate and SSR. PID tuning it had no issues.

TLeTourneau

I'll be interested in how my PID turns out. Mine will be a 500x500mm and 3/8" (9.525mm) thick ATP 5 cast plate with a 450x450mm 1000 watt 120v SSR controlled heater with a 1/4" (6.35mm) glass plate on it.

gtj0

Keenovo sells versions of their heaters with a controller ...
https://www.keenovo.com/Keenovo-Digital-Controller-Manual.pdf

I don't know what the temperature tolerance is on them but it'd seem like extra expense and just one more point of failure. I'd stick with an SSR and let the Duet control the temperature.

oops, this was a late response

Wyvern

So I got's the stuff, I ordered a 13X13 ATP-5 1/4 cast plate from Midwest metals for $45 shipped. The MIC6 was more expensive $35 BUT another $35 to cut + $10 shipping, one other place wanted $93 just for a slice!

I ordered the 300W mat and a SSR. So it's like $115 for the setup, but there is no way I'm spending another $40 on a replacement heated bed that will warp in a month.

My question now is do I use the 8 mounting holes that was stock, or just 4? I feel the use of extra thumb screws was due to the warp of the cheaper heated bed.

I will not be probing this bed, and I don't trust myself to accurately drill a 3 hole setup, so the most accurate manual leveling is a must.

I just hope all my hardware for the 12mm Z rods come at the same time (ditching the wimpy 8mm crap)

Phaedrux

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

My question now is do I use the 8 mounting holes that was stock, or just 4?

The FT5 mounting holes are trying to make up for a flimsy bed. With a stiff bed a 3 point system is ideal. Don't worry about drilling accuracy, it really won't matter as long as you're in the ballpark. It's far easier to get 3 points level than 4 points.

Wyvern

I'm thinking of forgoing the counter sunk holes, I think using them may cause things to be over restrained when it heats up.

Instead I'm thinking of using slightly oversize holes and aluminum washers (the washers are countersunk and the bottoms are flat) so long as tension and weight are enough to keep it from wriggling around.

Phaedrux

@wyvern I've done a 3 point countersunk mount on mine. It's not up to the level of a kinematic mount, but it hasn't seemed to have a noticeable impact on first layer printing.

Originally I had intended to have two of the holes along the side to keep the pivot point along the center of the bed, but then there was a bit of instability, so I went with two corners and the opposite center. I was also going to use bolts with round heads to allow for some adjustment, but the screws were expensive and when the M4 bolts worked fine I didn't bother.

One corner is set static as reference, and the other two are pitch and roll.

Drilling wasn't too bad. It just took some patience. I used progressively larger bits and slowly reamed out the holes. I used a drop of oil each time which helped keep the chips from getting everywhere if nothing else.

Wyvern

I see. The stock setup on mine is a tapered screw and countersunk hole, so they fit flush- but it's unnecessary when the nozzle doesn't come anywhere near them.

I haven't worked with this type of Aluminum, it's supposed to be easier to work with than Mic6, I have a really nice IR hand drill, or, access to a really tired POS drill press, I just hate drilling crooked holes.

Is it really that hard of an alloy?

Phaedrux

@wyvern I just used a hand drill. I oversized the holes slightly to give the bolt heads some space to self adjust. I used a piece of tape to judge the depth of the hole to leave 1mm at the bottom. I didn't find the MIC6 hard to drill.

Wyvern

Ok good, I've drilled through some serious steel that might as well been diamond, nightmare fuel when you only have one shot to do it right.

I will just pick up some new bits.

Looking forward to a bed that's flat, my machine is unusable ATM.

TLeTourneau

@wyvern ATP-5 is harder than MIC-6, I'd say take your time, use lubricant when drilling and as mentioned use stepped sizes. I'm going with a kinematic mount for mine, at least I'm going to try to. My plate is a bit thicker so I have a little more material to work with.

Clinton Aluminum has good article online that discusses the differences between ATP-5 and MIC-6 but the forum marked it as spam for some reason.

Wyvern

Thanks,

I was reading that last night, but half asleep.

If I'm reading specs correctly, Mic6 is stiffer, and slightly more conductive.
ATP is slightly more elastic, less prone to taking a set and grows slightly less than Mic6 under heat.

TLeTourneau

@wyvern that's kind of what I got from it as well, along with the ATP being a little harder. Given the sizes we're dealing with I don't think the nominal difference in stiffness will have an impact.

TLeTourneau

So the next question, 1/4" glass on top of the 3/8" cast aluminium or something like BuildTak or PEI directly on the aluminum? The glass seems flat but when I apply glue I can feel ripples in it. I haven't actually done anything with the cast plate yet, the heater should be here tomorrow, but the surface feels smooth.

dc42

@TLeTourneau, you will find different opinions on that. I prefer to use a removable glass plate so that I can swap print beds easily. The main benefit is that if a print sticks too well to the bed, I can put the bed+print in the fridge or freezer to help it to come free. Also I can swap plates and start a new print after one has finished, without waiting for the bed to cool down (which can take a while if you are using a thick aluminium plate). Finally, I can experiment with different print surfaces (plain glass, PEI, PrintBite etc.) on top of the glass plates.

The disadvantages of using glass on top is that you need to have space at these margin for bed clips (which loses a little print area unless you included a margin in your bed design), and the temperature on top of the glass will be lower than on the aluminium by 5 to 10C.

If you do use glass then I suggest 4mm thick not quarter inch. Ordinary float glass is usually flatter than toughened glass.