Phebe is HOT!

[bvandiepenbos]

The new heated bed is working really well! Easily holds 100c, I have printed about 6 hours the last two nights without any issues.
Controlling temp with a Vellman board from SeeMeCNC.
Prints sure do stick better to bed and do not curl up.

Nice design, thanks TKL!

I have 4 spring standoffs for bed leveling, then two pieces of 3/32" glass covered with 3 layers of paper mask sandwiched together, then the PCB heater, then the clear plastic build sheet.
So far it has stayed nice and flat.
The stock bed underneath gets a little hotter than I would like, but no problems so far, prbably should insulate under heated glass with something.

~*Brian V

[TKL]

I am glad to hear that Brian. Say, are those the new X-axis timing belt rollers you are using? Are they better than the old ones?

[drew]

Brian, what thermistor are you using? Stock Velleman? Did you futz with the MK138 resistors at all?

Looking forward to my board.

Drew

[johnoly99]

Hey Drew, just put a jumper in R6 to use the heated bed. That will allow you to set the low end in line with a heated bed, not a hot end

[bvandiepenbos]

Hey Drew, just put a jumper in R6 to use the heated bed. That will allow you to set the low end in line with a heated bed, not a hot end

I put a 1k resistor in place of stock R6
( jumper R6 will work also, according to Oly at SeeMeCNC )

I am using a 4k thermistor from SeeMeCNC
Glue in place with small daub of automotive high temp silicone, clamp the thermistor in place until silicone is dry.
Make sure thermistor makes good thermal contact to board, you don't want silicone between thermistor and board, only over it to hold in place.

One thing I need to change is the board LED, it sticks up to high and the head can hit it... should have used smaller LED and/or bend it back away from table.
I also wish I would have soldered wires to come out on underside of board.

Make sure you drill 1 or 2 small holes at back edge of board for zip-tie strain relief for wires.

I wired in a plug from old PC power supply so I can disconnect it for service or whatever.


~*Brian V

[drew]

Thanks John and Brian. Has anyone tried using the thermistor that Velleman sends with their kit? I have a few of those and would like to use them if I could.

[bvandiepenbos]

I am glad to hear that Brian. Say, are those the new X-axis timing belt rollers you are using? Are they better than the old ones?

TKL,
the idlers are bearings I rigged up, not exactly as new SeeMeCNC ones, but similar.
Yes, they definitely are better.
I am working on toothed idlers with bearings...that will be even better.
Got the parts, just not the time to machine and install.

The belt teeth running over the smooth idler surface still causes uneven tension and feed.
I am hoping toothed+bearing idler will eliminate wobbly small circles and jagged angled lines.

~*Brian

[tommee10533]

Hey, has anyone had any issues with the acrylic base warping from the hot bed? Just wondering if I should make one out of Alum.

[bvandiepenbos]

Hey, has anyone had any issues with the acrylic base warping from the hot bed? Just wondering if I should make one out of Alum.

the pcb heater board should be spaced up about 1/2" from stock bed with standoffs.
I made mine spring loaded so I can adjust standoff screws to level bed.

[wildideas1]

Brian can you provide the wire diag for the bed to the vellamen and resisitor info plz

Thks

[PartDaddy]

Here's a basic wiring diagram for the Phebe I.

25926 Wiring Diagram for Phebe.pdf

(89.85 KiB) Downloaded 507 times

[michaellatif]

I have found that the location of the thermistor is not optimal, the temperature difference between the center of the bed, edge of the bed (white lined box) and thermistor location varies to greatly, up to 70C. This isn't a problem with the Velleman board but is a problem with using an Arduino board. I haven't found a way yet to compensate in the firmware for low readings from the thermistor pad, but in the mean time I have 'moved' the thermistor to be on the edge of the glass plate, its a closer reading there, within ~20C of actual temperature.

As for glass that fits the Phebe I (6.5"x7"), I used glass from a flatbed scanner cut down, figured it has to be more then just standard glass as it is meant to take some abuse . I have been cycling the temp up and down (up to 130C) on the glass and so far so good, no breakage or other issues.

[Polygonhell]

Why do you care if the temperature is correct, my bed thermister reads 20 degrees low across the board (largely because of location), I just take it into account when I slice the file. You don't need accurate temperature readings, just consistent.

[TKL]

I have found that the location of the thermistor is not optimal, the temperature difference between the center of the bed, edge of the bed (white lined box) and thermistor location varies to greatly, up to 70C. I have 'moved' the thermistor to be on the edge of the glass plate, its a closer reading there, within ~20C of actual temperature.

I see nothing that can be done with the layout to change that. There will always be a difference between the temperature of the PCB tracks and the surface of a overlaying glass plate. The only thing to do is to glue the sensor to the glass.

[michaellatif]

I see nothing that can be done with the layout to change that. There will always be a difference between the temperature of the PCB tracks and the surface of a overlaying glass plate. The only thing to do is to glue the sensor to the glass.

Agreed that the only good way to get a better reading is to glue the thermistor to the glass, and I didn't mean to insinuate that the design was flawed. Quite the contrary, this PCB heated bed works very well and if not watched it will cause ABS to 'reflow'.

[wildideas1]

ok i have another odd issue. on the phebe board i used the new wiring diagram Posted Fri night and turned it all on and vellamen led light ,triggered for split second then never cycled again. so i disconnected wiring and started a continuity check and their are two side each with its own + - with this in mind I probed both + and -got continuity as i should being a closed loop. Now as I check pos to pos from the two loops i shouldn't get continuity yet i do somewhere somehow the two side are connecting like series instead of two separate loops. I cant see anywhere that the two loops are touching, can anyone else with this set up let me know if they get continuity from the two POS or NEG I think this board is Bad .

[TKL]

If you measure the resistance from one loop to another it should show infinite on the meter when the board is not connected.

[dougmsbbs]

I just measured mine, and with no wires connected at all, there is no continuity between the two loops, either + to + or - to -.

[wildideas1]

i agree with your findings that proves that something is amiss with my board i do get full tone(continuity) when i touch the two + or both - yet i cant find where on board it would be touching to allow this issue in the traces. Now what????

[michaellatif]

i agree with your findings that proves that something is amiss with my board i do get full tone(continuity) when i touch the two + or both - yet i cant find where on board it would be touching to allow this issue in the traces. Now what????

Basic question, did you solder anything to the pads? Also, what resistance are you reading between the two +'s? What resistance are you reading between each loops + and - ends?