kWeld - "Next level" DIY battery spot welder

[anishkgt]

That's a lot of work your going through frank but I guess it's part of the fun and it pays off at the end [emoji1303]


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D

[tatus1969]

it's part of the fun and it pays off at the end

Definitely the fun, but I am also learning a lot. This is my first four phase buck converter, and the amperage is also an order of magnitude more than what I did before. I am also using Infineon's OptiMOS5 MOSFETS for the first time. They are extremely fast, have integrated snubbers, and their diode reverse recovery charge (that quickly causes ringing/EMI problems) is lower than everything else that I know. I have attached pictures from one of the switch nodes at 35A load current, clean as a whistle.

And I hope that it will also pay off, not necessarily only as an accessory for the welder, but also as a high power laboratory supply. A regular 0-12V 0-80A lab supply can easily hit 1000€ or more, this one an order of magnitude cheaper.

And last but not least, I am developing an own business as an engineering service provider, and am collecting references.

[anishkgt]

Well that's good to know. To be honest, the first paragraph was like French to me but I did understand your point.

The second is quite interesting and if it can be developed into bench power supply then I would be interested to buy one from you if your selling it latter as bench PSU itself with mV resolution. That is of course once your done with the kWeld project.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D

[Fraser]

I very recently took delivery of a Tiertime UP! BOX 3D printer (from fellow forum member Toploser).

As part of my 'getting to know the printer' process I have printed various small parts that I needed. I decided to also print the kWeld case as a test of the warping on large area prints. I always print in ABS so warping is a fact of life and needs careful consideration with regard to bed temperature and object placement on the bed.

I told Frank about my intention to produce a test print of his case ad he asked that I share the results with you here.

The result is far from perfect but then I had expected that as I used all default settings without any additional precautions against warping. The print is not a basket case but it did suffer warping at two corners of the raft and this distorted the corners of the case slightly. I will list the issues I discovered with the print below. Some are due to the default print settings, my failure to adequately preheat the build plate, whilst others are likely minor issues with the case design.

1. Case top is printed inverted to avoid masses of support material. This means the top surface will not be as fine a finish as if the case were printed the other way up.

2. When printing objects with a large base area in ABS, there is always the risk of the ABS lifting at the extremities of the print. This is usually countered by pre-heating the bed for at least 15 minutes and printing in a heated chamber. I failed to adequately pre-heat the build plate and chamber ..... oooops  The result was some warping at two corners of the print.

3. The raft in the UP! series printers is usually pretty good when it comes to ease of removal from the object sat on it. The finish on the objects bottom surface is also pretty good. For some reason the raft did not come away easily from some areas of the case top and I was less impressed with the surface of the stepped down area for the LCD and knob. The 'KWeld' logo on the top of the case also presented some issues as it was not easy to remove the support material without leaving obvious tool marks on the plastic below.

4. The Case top design includes a pair of pillars. I tested their strength when formed in ABS. My conclusion is that they are too fragile and easily break away from case top. I believe these pillars would benefit from a thicker wall or a connical shape with a wider base to carry any lateral load.

I attach pictures of the printer and the parts it produced.

Fraser

[Fraser]

Pictures continued.....

(Including broken pillar detail)

[Fraser]

A picture of the excellent UP! BOX unit and some pictures of another part I just printed.

Of significance about this part is that it was printed in the vertical plane rather than horizontal where ABS warping can be an issue.
I am going to try printing the kWeld case in the vertical plane next to see how it comes out. The raft will attach at the rear so any surface blemishes are out of sight. The print will take 5 hours so may not get done until a bit later, or tomorrow.

I should state that one of the advantages of printing in ABS is that it can be sanded, filled and painted with modelling products, just like an Airfix model kit    I may sand and paint my kWeld case when I have a good print of it. The Kermet Green is just some UP! Fila that I found at half price ! Not everyones choice of colour me thinks 

Fraser

[Fraser]

Well the vertical print of the case is under way. Should be finished around 6pm.

It uses a lot of support structure for obvious reasons. The total amount of ABS used is 62g. The conventional inverted flat print uses just over 50g so the additional support material is around 12g. Worth it if the finished product is of good quality though. The ABS filament I am using is genuine higher temperature Tiertime UP! FILA that cost me £10 per 500g reel.

For info, on this print I carried out the correct pre-heat procedure and rotated the object so that the most dense area is facing away from the printers air circulation filter fan. I am wondering if the air flow towards the filter intake on the left hand side encourages faster cooling and shrinkage of the ABS on that side. It is all a learning curve on this new printer. If the print fails, no matter, I will have tried a different approach and discovered its limitations.

Fraser

[tatus1969]

4. The Case top design includes a pair of pillars. I tested their strength when formed in ABS. My conclusion is that they are too fragile and easily break away from case top. I believe these pillars would benefit from a thicker wall or a connical shape with a wider base to carry any lateral load.

I'll add that to the improvement list, thanks!

[Fraser]

Frank,

So far that is the only design issue I have found with the case. It is looking good in the printer at the moment. It is like waiting for a baby to be born

Fraser

[Fraser]

Frank,

I forgot to ask, what design software did you use to create your case please ?

Best Wishes

Fraser

[Fraser]

The print is almost done....... it looks OK with just a little warping in the front right corner. I have made a major error though. It made me laugh when I noticed. See if you can spot the error . 5 hours print time wasted    It is all good experience 

Fraser

[tatus1969]

what design software did you use to create your case please ?

Done with Sketchup :-)

[tatus1969]

The print is almost done....... it looks OK with just a little warping in the front right corner. I have made a major error though. It made me laugh when I noticed. See if you can spot the error . 5 hours print time wasted    It is all good experience 

Took me some time... Mirrored  

[Fraser]

Frank,

Yes a real  moment .... no, make that a   

I stupidly mirrored instead of rotated 180 Degrees !

Lesson learnt 

Fraser

[Fraser]

The case print has completed 

We already know it is scrap but I can learn from it and see how well the idea of vertical printing worked.

I am actually pretty pleased with the quality of print produced. The finish is very nice with only the rear panel showing the usual evidence of its attachment to the raft. Such may easily be tidied up and polished if it is an issue.

Sadly there is still an unacceptable amount of warping along the length of the rear panel where it was mounted on the raft. Such is a common issue with printing in ABS. The print bed is currently operating at 90C. Some experienced 3D ABS printers suggest 110C and I will experiment at that temperature.

Pictures of the print followed. There was a lot of support material but it came away very easily and I have no issues with that part of the print process. It worked very well indeed.

I placed the first print attempt next to the latest and I note that the latest print looks darker in colour even though it is the same ABS filament. I prefer that colour and the finish on the surface. No problems with the KWeld Logo this time.

Fraser

[Fraser]

Pictures continued.....

[Fraser]

Pictures continued.....

[Fraser]

Pictures continued....

[tatus1969]

and does it fit? I'm curious.

[Fraser]

I will check.

I can confirm that my UP! BOX printer manages to produce very accurate prints. I needed a plastic sleeve to fit snuggly around a bolt and to have a sliding fit into a tube. I used the dimensions taken from my digital caliper and the resulting 50mm long sleeve was a perfect fit, both on the 6mm bolt and inside the 10.5mm diameter tube. The UP! Software automatically compensates for ABS shrinkage after cooling

Fraser

[Zucca]

Thanks tatus1969, read everything in 3 hours or so. Understood almost 30% of it.
Just post it in the Buy/Sell when the next batch is ready.

 

EDIT: Just signed up to your newsletter.
EDIT2: You may want to edit your first post in this thread, new people like me will find quickly what the current status is. For example:
https://www.eevblog.com/forum/projects/diy-programmable-dual-channel-bench-psu-0-50v3a/msg589395/#msg589395

Thanks!

[tatus1969]

edit your first post in this thread

Thanks for your suggestions! I will do this in a few days. I am almost done with ordering 100x rev3 boards, almost everything else has already arrived.

Maybe a little sneak preview: I could again simplify the production process of the electrode system. This is now the fourth iteration, and I am quite happy with that:

[Fraser]

That is how I intend to make my probes as well. Easily removable, yet low resistance. You have done a very nice job of those probes

Fraser

[Kjelt]

Maybe a little sneak preview: I could again simplify the production process of the electrode system. This is now the fourth iteration, and I am quite happy with that:

That looks really good, almost resembles a bullet  Is that brass with a copper electrode ?
In the mean time my project has come to a standstill, I am awaiting the final results of which supercaps I need to succesfully weld the tabs, is there already a final outcome?
And my 45V/70A PSU has a major issues, which I am still trying to solve, it is still open for repair.

But I did do some new stuff, I build a jig that will help me do some other welding operation: weld two tabs together, for which I need a vertical welding jig.
So this is how that looks, I found most parts of that jig in the dumpster a few years ago and now have a good use for it.
The electrodes I got where 7mm copper bars for the staggering price of €1.- a piece at my local ironscrap yard 
On top there is a 6mm thread to mount the weldingwire and the bottom is a 5mm tapped hole for your 5mm electrodes I bought from you with the kit.

[Fraser]

At Franks request I just checked the 3D printed case for fit around the kWeld PCB. I have not printed the final top and bottom pieces but the test piece appears to fit the PCB well. Pictures attached.

I am also intending to make some simple re-enforcement 'washers' for the bases of the two fragile pillars. The rings will be glued in place to provide lateral support. The test piece shown here is just that, an ABS pillar with a snug fit thick ABS washer at its base. I have left the build raft in place for now. The washer will be glued in pace with ABS cement or plastic weld.

I do not have the original Sketchup file so cannot edit the original design.

Fraser