cooling and drifting

ok. When i first started calibrating things i did not have my heatsinks installed. I got it to the point that i was getting fairly decent quality prints. Had some tweaking to do here and there. So then i installed the heat sinks and fan. Now i get huge drifts along the x and y axis. The drifts can be as much as a total shift of 3-6mm between layers. I thought at first maybe my stepper drivers were at fault and thought about adjusting them. But i did not make any changes to them and it does not seem to me like adding a heat sink and fan would result in them needing to be changed. Am i correct about that?
I disabled my heated bed and am doing a print right now. The shift is not so bad. The part being printed almost looks like it should with the exception of the first layer. I am detecting though when the X and Y axis have to move at the same time that the motors sound strained.
This makes me wonder if i just need a power supply with a few more watts. Im at 550W right now.

I am noticing that whenever x and y have to move at the same time that both of them vibrate and jerk a bit (if thats the proper terminology).

okay i turned off the heated bed and things improved big time. But I still did not make it through the entire print without a shift. But It makes me think my powersupply is not big enough to run my heated bed and the motors. And probably i need to readjust the trim pots on my X axis.

550W seems high enough for a pure 12V power supply, providing a total of about 45A.
Are you using an ATX power supply? If yes, the power on 12V rail is probably going to be lower than 550W, probably at least less than half (It has -12V which will not be used, and also the unused 5V rails).

Can you share the wiring of your setup?

Edited 1 time(s). Last edit at 08/20/2014 01:08AM by alvinhochun.

Also, if it is an ATX, have you got a dummy load on the 5v line?

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Waitaki 3D Printer

I had shifts on my Mendel until I lowered the acceleration settings. Send an M501 command and paste the resulting display here.

What was happening was the motors cannot start and stop as fast as the firmware was trying to move them.

I'm using a 250 watt ATX power supply for my electronics and steppers and a separate 72 watt power supply for the heater and it works fine.

You also want to make sure your stepper current is adjusted correctly. For NEMA 17 steppers the current should be around 1 amp. epending on your electronics, there is a test pad where you measure a voltage and adjust the potentiometer to read the proper voltage.

Thanks for all the input. Tonight I will get back to you all.

Email guy.... For whatever reason M501 is giving me nothing. But I can tell you my configuration.h setting for acceleration.
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,1000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION 1000 //X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 1000 //X, Y, Z and E max acceleration in mm/s^2 for r retracts

Ok. I have readjusted my stepper drivers. All drivers have a vref of aprox .4V Doing the math Vref=Imax*8*rs using a imax of 1amp and rs of .05 ohms thats what i calculated they should be.
My ATX supply is rated at 25A on the 12V rail.

So first attempt to print after adjusting the steppers i set the bed to 60 degrees (printing pla) and the hot end to 185. Right way the X axis went off track.

Then turned off the heated bed and ran the same print and it was doing great except for the edges were not sticking. I let it print for a few minutes just to see that it was not drifting.

This time i am heating the bed to temp then i will turn it off and start the print and see what results i get.

Ok.....
Heated the bed then turned the bed off. Started print job and it successfully finished.
Noted problems i still have. X axis motor feels a bit warm. Y and Z are cool to the touch.
Need to check the level of my bed. one side is soooo slightly lower than the other. But not enough to make a noticeable difference.
I stated in another thread my heatsinks seemed too large. I had installed them anyway using kapton tape to keep them from shorting anything. I ordered smaller ones that should be here tommorow. So tomorow night I will install them and double check the Vref on my x axis and get to printing.
Longer term plan is to investigate why my ps wont keep when heating the bed or just use a different set up. I have a few PSU's from other unused projects laying around and may just have one that will fit the bill.
Im pretty stoked that i have got it up and running at least. Maybe a few kinks to work out but i can print now.

Try measuring the voltage output of the 12V supply when you print with heated bed on. You may observe a huge voltage drop and if that is the case, your power supply is not good enough.

Note that you say the 12V rail is rated at 25A. I am not familiar with ATX power supply ratings but this might mean +12V and -12V combined, which makes +12V only 12.5A, probably just barely enough for the heated bed itself. I am not sure about that, but I would recommend you to post more information on your power supply and the connections you've done.

Also, some power supplies may have multiple 12V rails, If it does, supply the heated bed by the rail with higher power rating and use a separate one to power other electronics.

Edited 2 time(s). Last edit at 08/21/2014 02:23AM by alvinhochun.

Good point about the amperage being combined +12 and -12. I will look into that tonight when i get home.
Will check the voltage while heating also.

When the bed and hot end are heating it drops to about 11.2 volts.

Grabbed one of my spare psu's and all is well now. Super stoked. Some tweaking to do with the calibration but happy to say things are working now as expected.

I cant thank any of you enough that took the time to offer assistance.

Edited 1 time(s). Last edit at 08/21/2014 11:15PM by Thelandofthedave.