MakerBot Replicator Original Stepper Replacement

[Eric Schimelpfenig]

Hey everyone! I've got a MakerBot Replicator Dual (the wooden one) that's got over 1500 hours of printing on it. The other day after a marathon of printing one of my axes stopped moving. I checked all of the wires and they were good, then I took my stepper motors off and swapped them. Turns out whatever motor was plugged into my X axis didn't move. This ruled out wiring, and the motor. It now meant that something was wrong with my board.

Turns out I had a bad stepper driver. I thought these were readily available online, and it turns out that the ones you can buy for most of the other Rep Rap based printers won't work because while Makerbot used and off he shelf chip, they flipped it over for some reason. The only way I found this out is that I know someone who used to work at MakerBot and knew that.

So, in my quest to repair this thing one last time, the only stepper driver I could find was from a sketchy website for $50 when all the other ones were under $10 (they just had the pins wrong)

There's hope though! I was able to find two cheap sources for these:

Turns out Flashforge copied them and you can buy them from their site for about $15 each. You can also build your own. It only requires a basic level of soldering. The hardest part is finding the chip. Thankfully I've figured this all out for you and posted it in a handy guide which can be found here:

http://sketchup.dozuki.com/Guide/How+to+replace+a+stepper+driver+in+a+MakerBot+Replicator/31

This guide will show you how to identify which of your drivers is bad, how to source the Flashforge ones and how to build your own if you want.

At the end of the guide there's a step where you tune the voltage of the stepper driver. My method was crude, but effective. If anyone has a better way to tune the driver I'll happy fold that into this step by step guide.

[Jetguy]

If you haven't fixed the regulator on the mainboard, that stepper driver is the least of your issues.

Just giving you a gentle but firm warning.

[Jetguy]

Again, a non upgraded Rev E is a ticking time bomb. You fix it now, maybe $10.

You fail and let it blow, and it's not if, it's when, you just cost yourself about $200 in replacement parts because everything blows faster than you can blink.

https://www.flickr.com/photos/90025904@N04/sets/72157639842879535/

https://groups.google.com/forum/#!searchin/makerbot-users/regulator/makerbot-users/kRfWxHLah4U/UtpYRLS_e-wJ

Another user guide http://www.akeric.com/blog/?p=2836

[Ryan Carlyle]

Yep, thanks for posting your findings, kind of unfortunate that you didn't ask here first though, we could have saved you some research time :-)

For the record, the "upside down" way that Makerbot designed the Botstep driver board is superior to the standard Pololu/Stepstick orientation. The driver chip dumps its heat into the PCB through a dedicated thermal via on its underside, so a heat sink on the opposite side from the chip is much more effective for driver cooling than putting the heat sink on top of the chip. The only reason the "normal" (Pololu) way has the driver chip facing "up" is because it's a few cents cheaper per unit to put all the components on one side of the board, and that would hide the trim pot if oriented "correctly" like Makerbot Botsteps. Makerbot's way is arguably the best way to use a removable driver -- digital current control and better heat sinking -- but the community standardized on the Pololu format basically out of inertia.

In addition to using a FlashForge driver (which uses the Mightyboard digital current control but outputs slightly more current per digipot setting) or flipping upside down a Pololu (which requires soldering and annoyingly adjusting a trim pot) you can also solder up the adapter PCB I made for using alternate drivers in Mightyboards: https://oshpark.com/shared_projects/0jqJEimG  This lets you use a stock Pololu 8825 with trim pot up (meh) or a Panucatt SD6128 with full digital current control (awesome). Either will greatly increase the allowable stepper current capacity. 

Note that if you use the SD6128 adapter with digipot connection, you need to drop your slicer's digipot settings (via the G130 command in your start gcode) to 28 to output the correct current for stock Replicator/clone Moon's 17HD-4063-0xN steppers. 

[Eric]

I actually wasn't even aware of this forum, after I did all the work my MakerBot friend recommended that I post my findings here. Jet Guy: My board has "the fix" on it already. I bought this as a refurb from MakerBot and they made sure it was all set before I got it.

I probably should have used a better term than "upside down" The only reason I described it that way is that any replacements I could find were opposite of the original Makerbot ones.

I wanted to put this guide out for people that just want to get their printer running again easily. There are a lot of these hanging out in schools and makerspaces and if people go on Amazon and just grab what looks to be the right part they could burn stuff up. Knowing how to at least identify the pinouts and not do something damaging was the main goal here. I suspect that most people will just buy the flashforge parts. At some point flashforge is going to stop making those. I suspect that the Pololu drivers will hang around longer. For the price, I stocked up on a bunch of them just in case.

Ryan, I like your driver board, but I would have no idea how to get that up and running without detailed instructions.

Also, would you have any insight on how one could mount a stock Botstep into a breadboard, test the voltage, and then check it against one of these Pololu hand made setups so that they could do the tuning without having to install, remove, and reinstall over and over? And also tune them in a better way than I did, which was by ear...

--

-Eric

[Ryan Carlyle]

On Friday, June 24, 2016 at 9:39:24 PM UTC-5, Eric Schimelpfenig wrote:

Ryan, I like your driver board, but I would have no idea how to get that up and running without detailed instructions.

Some photos here: https://groups.google.com/d/msg/3dp-ideas/8XPAonL27ug/YCO23mlHAgAJ

BOM of parts to order from Digikey is in the OSHPark link: https://oshpark.com/shared_projects/0jqJEimG

To assemble:

• Stick two 8x1 male header strips into the socket on your board.
  
• Stick the adapter PCB onto the header pins so that BOTDIR is next to the regular DIR pin, as shown in the picture, and solder up all 16 pins. (You can take it out of the board socket once you tack a few pins to fix the alignment.)  
  
• Stick two 8x1 female header strips onto your Pololu style driver.
• Stick the male side of the female headers into the adapter PCB, and solder up all 16 pins. (Again, you can take off the driver after you tack a few pins for alignment.)
  

It's a lot of simple soldering, only a little worse than soldering pins on two Pololus.

As an alternative to the female headers, you can solder a Pololu style board directly to the carrier. If you do that, you will need to trim down some pins to keep them from hitting stuff. There are photos of both ways in the link above.

If desired, the SD6128 can utilize the optional vref pin so you can use the Mightyboard digipots rather than the trim pot. To do this, you will need to de-solder a blob jumper, and add an additional male header pin to the external vref hole on the SD6128. Refer to Panucatt's driver info sheet. Also make sure you adjust your digipot setting in the start gcode if you do this so you don't melt your motors. It should be [AMPS = DIGIPOT / 33.4].

 

Also, would you have any insight on how one could mount a stock Botstep into a breadboard, test the voltage, and then check it against one of these Pololu hand made setups so that they could do the tuning without having to install, remove, and reinstall over and over? And also tune them in a better way than I did, which was by ear..

The voltage probably shouldn't be the same, because the current sense resistors will usually be different. You need to find the correct equation for the driver you're using, and use that to calculate what the trim pot voltage should be. But I think it's easier to measure the trim pot resistance instead with the driver unplugged. It's a simple voltage divider circuit, although to be honest it's been so long since I've made one that I've forgotten exactly what the target resistance is. Jetguy may recall off the top of his head. 

The motors are rated 0.84 amps, so you can calculate the necessary vref voltage to output that. Or you can do it by feel -- the motors should be HOT to the touch after being on for a while, but still touchable without burning yourself. Or measure a temp around 60-70C if you have an IR temp gun or something. It's ok if they're a little cooler, just don't go much hotter. 

[Jetguy]

Wait a minute. No, MakerBot never ever to my knowledge did this mod factory. Either you got the internal "friend" special deal, and since a very close friend, very close to makerbot and got his replicators directly from them and I personally had to do this fix on all of his printers, I think you better check and post a picture of your board. Again, they never ever, ever, ever, ever did this. If they did, yours is the one in a million.

Trying to protect you from a disaster lying in wait.

As to how to adjust, if we are talking A4988s, you only need to connect the ground and logic voltage (5V) on a breadboard and then measure the pot to the ground as reference. Vmotor is the 24V pin and on A4988s, no other pins need connected for vref adjustment since the pot is just a voltage divider on the logic voltage to ground.

[Jetguy]

Again, just get why I'm harping on this.
The thread is about protecting the hundreds if not thousands of machines out there in schools and libraries and even individuals who don't know.
By the time they know, they are totally SOL.

Even if your board blew up, you got it replaced at some point, Makerbot NEVER made this fix and never admitted the problem existed.
And the whole fan thing and cooling mods was a waste of time effort and money and was never, ever, ever the problem.

If you own this printer and did not make that specific mod, well, just say you were warned today before you turn it on even one more time.

[Jetguy]

And, years ago, Gary Crowell made this plug in style in a limited production run that never caught on, not because it was a bad idea, but just the massive ignorance of the problem and ticking timebomb nature of the fault.

http://www.thingiverse.com/thing:78598

Again, unless you made some sort of mod to replace the 5V regulator with a totally different model and brand of switching style properly rated with a safety margin of around 30-36V input, every time you flip the the power switch, that might be the one that blows it up.
The basic working theory is the low ESR capacitors under the stepper drivers along with the board traces creates a massive voltage spike higher than 24V every time the main power switch is touched (switch bounce). The stock linear regulator is very sensitive and has a 25V max input rating per the data sheet on a 24V normal system. That's not even a single volt of headroom safety. The proof is the thousands of these blown up. I have a box of 20+ destroyed boards beside me as I type this.

[Eric]

Ryan thanks for posting that. If you wrote that up with pictures in really layman's terms I could link it as another alternative in my I instructions.

Jetguy: I did have an internal friend who fixed it for me. We'll leave it at that. :) I do appreciate you making sure mine is good.

PS is there any kind of guide out there to show how to make the fix for those that don't have it?

Ok your method of checking the voltage sounds way simpler than the method that pololu showed on their page. I'm going to wire something up on a breadboard and see if I can figure it out..

--

-Eric

[Jetguy]

"PS is there any kind of guide out there to show how to make the fix for those that don't have it?"

Reposting from the previous answer

https://www.flickr.com/photos/90025904@N04/sets/72157639842879535/

https://groups.google.com/forum/#!searchin/makerbot-users/regulator/makerbot-users/kRfWxHLah4U/UtpYRLS_e-wJ

Another user guide http://www.akeric.com/blog/?p=2836

[adam paul]

There some good pics of setting up the stepper drivers on my printer's discussion, page 2.

http://www.openbuilds.com/threads/triple-c-bot.1255/page-2

[Eric]

That's awesome, thank you!

On Sat, Jun 25, 2016 at 1:40 PM adam paul <adam...@gmail.com> wrote:

There some good pics of setting up the stepper drivers on my printer's discussion, page 2.

http://www.openbuilds.com/threads/triple-c-bot.1255/page-2

--

-Eric