ADVrider

Go Back   ADVrider > Gear > Vendors
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-31-2014, 08:28 AM   #841
Lounge
Gnarly Adventurer
 
Lounge's Avatar
 
Joined: Jul 2010
Location: COS
Oddometer: 387
Don't mean to be a downer but I'm not so confident in this method. I believe the problem is that there is no differential of pressure in the vessel so all you're really doing is compressing the bubble/s. This method will work for very small bubbles in the compound but it won't do anything to help fill a significant void. Meaning, it does nothing to help flow the compound around the PCB which I believe is the problem.

Maybe try a mold with the PCB positioned vertically. This would pose a challenge with the terminals and designing the mold itself, but I do believe this would solve the problem with the voids on the underside of the PCB. Perhaps a two piece mold?? Or as others have suggested, a vacuum.

Just thinking out loud.
__________________
My apologies to the meek and the Earth they will not inherit.
Lounge is online now   Reply With Quote
Old 03-31-2014, 08:53 AM   #842
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
I cannot do a vacuum with the current mold because I didn't do a good enough job degassing the silicone. A good vacuum now would wreck it. More silicone is in the mail along with a new mold master so we can try that if necessary.

I am actually feeling confident about the casting in the mold at the moment. Pouring the resin is carefully appeared to make a big difference.

Quote:
Originally Posted by Lounge View Post
Don't mean to be a downer but I'm not so confident in this method. I believe the problem is that there is no differential of pressure in the vessel so all you're really doing is compressing the bubble/s. This method will work for very small bubbles in the compound but it won't do anything to help fill a significant void. Meaning, it does nothing to help flow the compound around the PCB which I believe is the problem.

Maybe try a mold with the PCB positioned vertically. This would pose a challenge with the terminals and designing the mold itself, but I do believe this would solve the problem with the voids on the underside of the PCB. Perhaps a two piece mold?? Or as others have suggested, a vacuum.

Just thinking out loud.
craftycoder is offline   Reply With Quote
Old 04-01-2014, 05:30 AM   #843
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
Nailed it. 45PSI and taking great care in the pouring did the trick.

craftycoder is offline   Reply With Quote
Old 04-01-2014, 05:37 AM   #844
Big Bird 928
Beastly Adventurer
 
Joined: Jan 2012
Oddometer: 2,203
Quote:
Originally Posted by craftycoder View Post
Nailed it. 45PSI and taking great care in the pouring did the trick.

The question is is it repeatable?

sent from my phablet.
__________________
Quote:
Originally Posted by Smithy View Post
Didn't take me long to sort out the derpapotomous tactic again.
Big Bird 928 is offline   Reply With Quote
Old 04-01-2014, 06:21 AM   #845
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
I'm willing to throw a $800 Motobrain prototype into the mold now to confirm it is. That is a measure of my confidence (hubris).

Quote:
Originally Posted by Big Bird 928 View Post
The question is is it repeatable?
craftycoder is offline   Reply With Quote
Old 04-02-2014, 05:40 PM   #846
Gany
Gnarly Adventurer
 
Joined: Apr 2007
Location: Melbourne, Au
Oddometer: 302
Any thin spots in the resin? As lounge said, if there were significant voids that were compressed, all it does is trap the compressed bubble in the resin. Hopefully the careful pour prevented the void in the first place. Have you tried putting the mold alone under vacuum? Does it deform?
Gany is online now   Reply With Quote
Old 04-04-2014, 02:54 PM   #847
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
I just poured a new Motobrain in a new mold with new "Version 2" firmware on it. I even took your guys advice and vacuumed the mold to suck the air out. What could possibly go wrong?
craftycoder is offline   Reply With Quote
Old 04-05-2014, 05:57 AM   #848
Gany
Gnarly Adventurer
 
Joined: Apr 2007
Location: Melbourne, Au
Oddometer: 302
You didn't test the process first!? I hope it works for you! Did you vacuum to degass then crank it to 45psi again?
Gany is online now   Reply With Quote
Old 04-05-2014, 07:22 AM   #849
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
Quote:
Originally Posted by Gany View Post
You didn't test the process first!? I hope it works for you! Did you vacuum to degass then crank it to 45psi again?
I just did a light vacuum (20" of mercury). The positive pressure didn't seem to help nearly as much as pouring very slowly so that no air ever got trapped in the first place. I feel like I am starting to get an understanding of the resin and the casting process so I risked it. I only real concern is that the air trapped in terminals expanded and moved the electronics or pulled resin into the threaded terminals. The vacuum I used was not very high I certainly saw no movement. I'm guessing it is in good shape. I'll find out this afternoon.

More generally, the time I spend waiting on stuff is driving me nuts. For example, I made my first silicone mold but the vacuum pump wasn't up to the task of fully degassing the silicone so I didn't want to risk it by putting the finished mold under vacuum (as it might blow up). I did as much testing as I could with that mold while I waited on a new vacuum pump and more silicone. Also, the first mold master was built wrong by my prototype shop so they apologized and rebuilt it which took more time.

The new mold master arrived on Thursday and I built a new mold that evening with my new pump (99.999% vacuum). Much better. I even was able to get some custom boxes that are just the right size to cast the mold in. This allows me to use less silicone and allows the mold to fit in my bell jar so I can put the epoxy under vacuum to help reduce voids. All the steps are progressing but the are taking time. My engineering career has been in software mostly and I'm not used to having to wait on anything. It is an adjustment.

In the mean time, I've been rolling around with Motobrain on my WR² for the last 2 weeks now. It's been great to have it on a vehicle for "real world" testing. I actually found a bug that I never saw on the bench. The radio automatically was going to "sleep" to save power (because these radios are often used with coin cells). I did not realize this was happening and my solution was to reset the radio when you turned on the vehicle if the radio was not connected (a radio connection could not be established when it was sleeping). This was working but I finally figured out the radio was sleeping and I have now instructed it to stay awake. This is why I am in Version 2 of the firmware. The good news is that the older firmware was not very compatible with Android (according to the radio manufacturer) but this latest version is. That is great news because it is just about time to start writing the Android version of the Motobrain software and it would have been annoying if it didn't work because of some sort or radio incompatibility. I am using an off-the-shelf radio so Motobrain doesn't need its own FCC license. I pay a premium but unless I make 100,000 units it will save me money.

In other irritating news, I realized yesterday while I casting the Motobrian that my new epoxy arrived 5 days before its expiration date. Seriously?! This stuff is over $100 a liter and it has a 6 month shelf life. I expected that I would have been afforded the lions share of that shelf life but I only got 5 days. I'm sure it had to be an accident because that would be a serious dick move otherwise. I guess I'll be waiting on new epoxy to arrive next

craftycoder is offline   Reply With Quote
Old 04-05-2014, 02:41 PM   #850
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
So, it isn't perfect but I will repair this one and try again on Monday with a bit more vacuum. The texture is very cool. It feels velvety. I wonder that huge amount of surface area will improve its ability to radiate heat?

At this point I am just spinning my wheels while I wait on manufacturing quotes. I met with a bunch of factories (all in the USA) on the 27th and we are working our way through the quoting process to get these built by people who are better at every single production step than I am (thankfully). It is funny how being an engineer who works in abstract ideas really doesn't translate to being good at any tangible skills. Oh well, at least I can do abstract pretty well.

I am about halfway through the design of the quality system which will provide me and the manufacturer with assurances that the device functions as expected BEFORE it is potted. At that point I expect the manufacturer to warranty the device for defects so both the factory and I will have a lot of input on the quality system since they have a lot to lose if it is bad.

I'm really excited about this unit. It is just shy of perfect.

craftycoder is offline   Reply With Quote
Old 04-05-2014, 03:48 PM   #851
Gany
Gnarly Adventurer
 
Joined: Apr 2007
Location: Melbourne, Au
Oddometer: 302
High Tech Fuse Block

Damn thats a nuissance... Perhaps under vacuum with the mould half full try and tilt the bucket. Always trapping air in the same spots, makes me think a two part mould work work better with the pcb vertical...

If it makes you feel better i had my first attempt at potting some electronics in electronics grade silicon. Long story short, when the company said it was a labelling error only that i got two part A's and the mix would work, they lied. Now have to waste time trying to get all the uncured goo out :( f#*kers!

Gany screwed with this post 04-05-2014 at 05:24 PM
Gany is online now   Reply With Quote
Old 04-05-2014, 03:52 PM   #852
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
I did fill it half way and vacuum and then fill it all the way and vacuumed again. I didn't tilt it though. That makes a lot of sense. I'm really close to getting this right. You are exactly right though, this is a nuisance and not a serious problem.


Quote:
Originally Posted by Gany View Post
Damn thats a nuisance... Perhaps under vacuum with the mould half full try and tilt the bucket. Always trapping air in the same spots, makes me think a two part mould work work better with the pcb vertical...

If it makes you feel better i had my first attempt at potting some electronics in electronics grade silicon. Long story short, when the company said it was a labelling error only that i got two part A's and the mix would work, they lied. Now halve to waste time trying to get all the uncured goo out :( f#*kers!
craftycoder is offline   Reply With Quote
Old 04-05-2014, 10:46 PM   #853
Lounge
Gnarly Adventurer
 
Lounge's Avatar
 
Joined: Jul 2010
Location: COS
Oddometer: 387
What about trying to extrude the compound up through the bottom of the mold vice filling it from the top?
__________________
My apologies to the meek and the Earth they will not inherit.
Lounge is online now   Reply With Quote
Old 04-06-2014, 05:29 AM   #854
craftycoder OP
Motobrain PDU
 
craftycoder's Avatar
 
Joined: Oct 2009
Location: Atlanta
Oddometer: 2,210
Quote:
Originally Posted by Lounge View Post
What about trying to extrude the compound up through the bottom of the mold vice filling it from the top?
The quality I am getting now is good enough for me. I am in the process of hiring someone else to do all this PCB assembly and encapsulation for me and I will only have to pay them when it's done right. That means that perfect is their problem (but they are experts so I'm sure it won't be a problem). When each prototype was costing me $500 for a one time use mold I needed to find a better way. This mold cost about $20 in silicone and I can use it many times and the final output is close to commercial quality. Certainly good enough for a lab prototype.

Repairing this guy should be as easy as filling the void with resin, putting it back in the mold and turning it upside down.
craftycoder is offline   Reply With Quote
Old 04-06-2014, 07:52 AM   #855
EKinOR
Gnarly Adventurer
 
Joined: Mar 2012
Location: Central Oregon
Oddometer: 232
Can't wait to buy one!

If you need a beta tester, send one my way.
__________________
- Eric
2002 BMW R1150GS
EKinOR is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 04:17 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014