My coreXY design is progressing to the build stage

Neat looking fan.

I suspect it's the motor or driver that doesn't like the heat.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Is there something keeping the 500W heater from melting/whatever if your blower fan has an issue? This thing looks to small to keep its temperature down by convection alone and i cant see a thermistor on it...

It doesn't have it yet, but it's going to have a TCO to kill power to the heater if the fan fails. That heater is rated up to 600C, so it won't self destruct, but if the fan isn't running the air doesn't circulate and the heat will accumulate at the top of the printer and probably cause all sorts of problems.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

On a slightly different subject, I recently pulled a CPAP machine from the hack-rack at the makerspace. I disassembled it and pulled the blower out of it. It's about 90mm in diameter, and has a 20k rpm (max), 3 phase BLDC motor. I also recently had some PCBs made for the MCP8063 3 phase BLDC motor driver chip with PWM input. I'll be testing the blower as a print cooling fan in UMMD once I get a couple of the PCBs assembled.

The blower is sort of interesting- it has a nearly flat impeller that takes air in at it's center and flings it out along its periphery. It's in an enclosure that directs all that air flow out a single, round port that a CPAP hose fits over. The hose is very flexible and light weight, so the plan is to mount the blower on top of the printer and run the hose to the extruder carriage with a nozzle to blow on the print.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Turtle blower

Patient respiration -- important --- blower plus driver electronics

Has to be very quiet, and secondly it has to respond dynamically and positively to the patient’s respiration requirements.
Its air flow and pressure must be continually adapted to the patient’s own breathing. The blower drive must therefore be able to adjust its speed with extreme flexibility. The development engineers at ebm-papst designed the blower to be suitably dynamic for a maximum operating point at which a pressure variation of four to 20 millibars is possible within the space of 200 milliseconds.

They are finding their way into micro LED / DLP projectors
and laptop coolers

Mystery impeller?

Super dynamic polymer cooler --- but what sensor?

Hey with UMMD on CPAP maybe it can get handicap parking spot!

@DigitalDentist,

Apologies if this is a silly question, but is differential thermal expansion between steel linear rails and the aluminum they are bolted to a concern? It seems to me that the higher expansion of the aluminum could put stress on the rails in a way that tends to make them bow concavely. Though perhaps this effect is too slight to cause any significant deflection.

Quote
the_digital_dentist
On a slightly different subject, I recently pulled a CPAP machine from the hack-rack at the makerspace. I disassembled it and pulled the blower out of it. It's about 90mm in diameter, and has a 20k rpm (max), 3 phase BLDC motor. I also recently had some PCBs made for the MCP8063 3 phase BLDC motor driver chip with PWM input. I'll be testing the blower as a print cooling fan in UMMD once I get a couple of the PCBs assembled.

The blower is sort of interesting- it has a nearly flat impeller that takes air in at it's center and flings it out along its periphery. It's in an enclosure that directs all that air flow out a single, round port that a CPAP hose fits over. The hose is very flexible and light weight, so the plan is to mount the blower on top of the printer and run the hose to the extruder carriage with a nozzle to blow on the print.

IMG_20171102_200724659%5b1%5d.jpg

Did this work out? I'm not happy with my current design and the berdair is sort of fussy for me, I always gotta play with those small metal tubes...

Quote
NathanaelXYZ
@DigitalDentist,

Apologies if this is a silly question, but is differential thermal expansion between steel linear rails and the aluminum they are bolted to a concern? It seems to me that the higher expansion of the aluminum could put stress on the rails in a way that tends to make them bow concavely. Though perhaps this effect is too slight to cause any significant deflection.

That's something I've been struggling to understand. It should cause the whole thing to curl, but I have yet to see any issues with it. There are multiple screws that hold the rail in place, so maybe they all allow a little sliding. OTOH, if they did that you'd expect the guide rail positions to be unstable through multiple heat/cool cycles, and I don't see that happening. I don't know exactly why, but it works.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
Qdeathstar
Did this work out? I'm not happy with my current design and the berdair is sort of fussy for me, I always gotta play with those small metal tubes...

I've been looking at it on and off for a while now. I found a chip that will drive 3 phase BLDCs (MCP8063 from Microchip) motors up to 14V @ 1.5A and had some boards made at OshPark. I assembled the boards and tried them out and found that the chips seem excessively delicate- blocking the air flow is enough to destroy the chip for some reason, even when operating at 8V. Maybe the motor I was using was trying to pull too much current, but the chips are supposed to protect themselves from that condition. So I don't know what was killing the chips but I decided they aren't going to be reliable enough. I have ordered one of these and am waiting for it to arrive from Hong Kong. I have no doubt it will handle anything I throw at it.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I've also been working on the heater for the enclosure to allow reliable ABS printing.



It uses a 500W line powered heater with power switched by a Crydom D1225 SSR. The switching input for the SSR is a 24V signal from the smoothieboard controller. I'll also use that signal to power the 24V fan that blows air across the heater. Most of the air flow is going to be under the bed, even when the bed is all the way down, so I don't expect any problems due to excessive air movement. I may add a fan to blow air downward from the top of the enclosure to get more uniform temperature distribution. The air coming off the heater mixes quickly with the enclosure air so I don't expect it to heat up the Z motor too much. The Z motor normally operates no more than 5C above ambient anyway, so it can handle a little warming from the heater. I can add a simple heat shield if needed. I'm looking at putting a perforated metal cover over the whole thing

The temperature inside the enclosure will respond slowly to the heater, so there may not be much point in PID control.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I got the heater wired and ran a PID autotune on it- it seems to be working well even though the temperature in my basement is about 15C. It takes about 20 minutes of combined bed and enclosure heaters to get the enclosure temperature up to 45C. PID control seems to hold it within +/1C.

I think I will make an insulated lower front panel for it- I'm sure it is losing a lot of heat through the 1/8" PC- it feels warm on the outside.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

That looks like a heater bar from a Stratasys printer.
I juts had to replace the blower fans in the printer at work

Winner winner chicken dinner! It came out of a scrapped Stratasys machine.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

They do have similar bars available for purchase, I’m gonna get one for my printer

Here are the markings on the heater:

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
Winner winner chicken dinner! It came out of a scrapped Stratasys machine.

Awesome! Good to see parts being reused.

My printers are full of reused stuff- 8020, linear guides, power supplies, fans, and probably a few other things.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The BLDC driver has arrived and tests fine. I'll be designing a nozzle to fit the end of the tube and work out a mount for the extruder carriage in the next week or so. That blower whose photo I posted previously can move far more air than I'm going to need for cooling a print, even blowing through a restricted nozzle.

I got a new SSR from a box of stuff that was donated to the makerspace. I'm going to use it to switch the heater- the terminals are enclosed, so I won't have to print a cover for it to protect against electric shock. The new one is rated for 125A at 660V. I may grab another to replace the one switching the bed heat. I do like the covered screw terminals, and they have LEDs that indicate the input status. No zero crossing detectors though, so they may cause the lights to flicker a bit...

I still need to make some sort of cover for the screw terminals on the heater bar.

Edited 4 time(s). Last edit at 01/14/2018 09:09AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Mark,

Can I ask where you picked up your worm gear?

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the_digital_dentist
Z axis redesign recap:

The Z axis started with a NEMA-23 motor directly driving the Z axis motion, but then the problem of bed-drop became very apparent, so I replaced the direct drive motor with a 30:1 Rino worm gear reducer this way:

Z%20axis%20rev2.png

Though it looks symmetrical, the path to the motor from each of the belt clamps on the bed support cross-bar are actually quite different. Testing indicated that it should perform just fine, but the asymmetry bothered me, so I redesigned to this:

Z%20axis%20rev3.png

Z%20axis%20rev3%20close.png

Z%20axis%20rev3%20close%202.png

I ordered a longer shaft for the worm gear reducer and a pair of 34 tooth pulleys and pillow blocks. I remade the Rino mount- much easier this way- just a couple small plates with a few relatively small holes. The switch with the roller on the lower left is the Z max limit switch- I couldn't find another one of the tiny ones in my junk box.

I'm waiting for a few parts to arrive then I'll drill the mounting holes for the pillow blocks and move the top pulleys into position. The printed parts will be done in the next day or so and ready to drop in the moment the rest of the stuff arrives.

Ebay! [www.ebay.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The enclosure heater is done except for the addition of a TCO, which will happen when I figure out how to mount it so that it will work the way it is supposed to. I also need to add some sort of cover for the electrical connections to the heater bar. I may just glop them up with high temperature silicone.



The heater assembly rests on its "ears" on the ends of the aluminum tube, between printed ABS parts (orange) that snap firmly into the slots in the frame. Zip-ties hold the aluminum tube down. I probably won't get UL approval for that mounting method.

While I was at it I cleaned up some of the wiring and tweaked the firmware. I added some custom menu items for the LCD panel that preheat the printer for different materials. When you select "Preheat ABS" it turns on the bed, extruder, and enclosure heaters and sets them to appropriate temperatures. Selecting "Preheat PLA" sets the bed and extruder to appropriate temperatures and sets the enclosure heater temperature to 0.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I'm a bit confused about the enclosure heater thing in general:
Say your enclosure is heated up by the print bed only. The environment temp would climb up to a certain level. It will reach this peak, because the bed heater will heat less and less, the higher the environment temp is.
Now you want to raise the environment temp even more, say +20°C. Wouldn't that in turn mess up the constant bed temperature we need?

IMHO, we'd have to set the priority to constant bed temp. How much higher can we heat up the enclosure without ruining the bed-temp PID settings?

Quote
o_lampe
I'm a bit confused about the enclosure heater thing in general:
Say your enclosure is heated up by the print bed only. The environment temp would climb up to a certain level. It will reach this peak, because the bed heater will heat less and less, the higher the environment temp is.
Now you want to raise the environment temp even more, say +20°C. Wouldn't that in turn mess up the constant bed temperature we need?

IMHO, we'd have to set the priority to constant bed temp. How much higher can we heat up the enclosure without ruining the bed-temp PID settings?

The heated bed will run less and less but that does not mean it will drop in temperature itself, it is still a controlled temperature source. The heated enclosure will always be lower then, or match the bed temp so if anything the bed temps will be the one to cause problems with the enclosure temperatures

Quote
o_lampe
I'm a bit confused about the enclosure heater thing in general:
Say your enclosure is heated up by the print bed only. The environment temp would climb up to a certain level. It will reach this peak, because the bed heater will heat less and less, the higher the environment temp is.
Now you want to raise the environment temp even more, say +20°C. Wouldn't that in turn mess up the constant bed temperature we need?

IMHO, we'd have to set the priority to constant bed temp. How much higher can we heat up the enclosure without ruining the bed-temp PID settings?

If the bed is the main source of heat, you can't regulate the enclosure temperature. You can only hope that the balance of heat added by the bed plate and heat lost through the walls of the printer allow the enclosure to settle at a desirable temperature. If it gets too warm, you can vent the enclosure a little. If it doesn't get warm enough you can add insulation to the enclosure walls.

In my printer, the enclosed volume and the heat lost through the walls ensures that it won't get to a good ABS temperature using the bed heater alone (though during the warm weather months I was able to print ABS because the warm air in the printer tended to stay up at the top where the printing was taking place).

I think the root of your question is really "how good does the bed temperature regulation have to be?" If I run the bed's autotune in a room temperature environment and then heat the chamber will it cause the regulation to "fail"? I haven't tried running PID autotune on the bed with the warm enclosure. It seems to be working fine anyway, based on the temperatures I see reported by the controller board.

The main point of heating the bed is to get the plastic to stick to it. The plastic will stick over a wide temperature range, so a little variation up and down isn't going to cause the plastic to let go. In some machines that have beds on poorly design supports and/or using thin bed plates that warp when heated, it may be more of an issue because the bed surface bouncing up and down with temperature can cause print defects. That's one problem I definitely don't have.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote

I think the root of your question is really "how good does the bed temperature regulation have to be?" If I run the bed's autotune in a room temperature environment and then heat the chamber will it cause the regulation to "fail"? I haven't tried running PID autotune on the bed with the warm enclosure. It seems to be working fine anyway, based on the temperatures I see reported by the controller board.

Yes, I guess that was the reason of concern. I read horror stories about how bad a bed heater is in bang-bang mode, so I thought bed temp would be critical.
I'd start bed PID tuning around half way between room- and the desired enclosure temp. That way I'd be sure to get the best compromise.

Edited 1 time(s). Last edit at 01/16/2018 04:11AM by o_lampe.

Quote
o_lampe
Yes, I guess that was the reason of concern. I read horror stories about how bad a bed heater is in bang-bang mode, so I thought bed temp would be critical.

I think the main reason why bang-bang bed control causes print artefacts is probably not the variation in the temperature of the bed that it causes, but the effect on supply voltage. When the bed heater turns on, the power supply voltage drops. Low-cost ATX PSUs are particularly prone to this because they use a single regulation circuit that monitors a combination of +5V and +12V and can only adjust both voltages together. The drop in voltage causes a drop in heater power (a 1% drop in voltage causes a 2% drop in power), and because of the dead time of the hot end, the PID control loop takes several seconds to compensate for it. The varying temperature causes uneven extrusion.

I tested this on one of my printers. In PID mode with the printer static, both the bed and the hot end temperatures are stable to +/-0.1C @ 65C. When I switch the bed to bang-bang, the bed temperature is stable to within +0.8/-0.4C, and even though this printer uses a well-regulated PSU, the hot end temperature variation increases to +0.3/-0.2C.

In RepRapFirmware on the Duet WiFi and Duet Ethernet, the heater PWM is compensated for changes in supply voltage, so the effect is eliminated. But I still recommend using PWM+PID to control the bed heater.

Edited 1 time(s). Last edit at 01/16/2018 09:33AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Do you think a total 1/2C variation in extruder temperature is going to cause a noticeable change in the print, especially something as pronounced as Z-banding?

I have run temperature tower prints on different filaments in 5C extruder temperature steps and it can be hard to see differences between adjacent temperature bands in the prints.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
Do you think a total 1/2C variation in extruder temperature is going to cause a noticeable change in the print, especially something as pronounced as Z-banding?

No, I think 0.5C is too little to get significant Z banding. For a long time I ran that printer using bang-bang bed heater control, without the heater power being compensated for supply voltage, and I didn't see any effect. But some users have PSUs with much poorer regulation than mine, especially those with cheap ATX PSUs. Also, if the hot end PID control isn't well tuned, the hot end temperature could fluctuate more as the bed heater turns on and off.

I also doubt that 1.2C variation in bed temperature would cause sufficient thermal movement to cause Z banding; but I guess it's not impossible if the bed isn't very stable. A bed with poorer coupling between the heater and the thermistor might exhibit a larger temperature variation when bang-bang control is used.

Quote
the_digital_dentist
I have run temperature tower prints on different filaments in 5C extruder temperature steps and it can be hard to see differences between adjacent temperature bands in the prints.

If you tried changing the hot end temperature by 5C and back again on alternate layers, I suspect you would see the difference more clearly.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

What about just using the enclosure heater to heat the entire enclosure and bed together - up to say 60-80C, as required to best suit the material being printed? In other words, not use a bed heater at all.

Do people think this would work for a good range of printed materials?...including TPU, PLA, ABS etc.?