What am I doing wrong with the clamps?

[Dave]

When going from ink to heat, and then from heat to solder paste, I always have to completely remove one clamp and its thumbscrews, shift it away from the other clamp by one hole, and then re-secure it before the stock 2"x3" substrate will fit.

For example, if I position the clamps so that the PCB is securely held in the clamp and then swap the clamps (as shown in the embedded video), the PCB is just slightly too large and won’t rest on the inner baking cutout.

If I start from a position where the PCB rests securely between the clamps on the baking cutout, then when I flip the clamps around, the PCB is only held on by a fraction of a mm.

Can anyone please tell me what I’m doing wrong here?

[troy]

Hey Dave,

I just checked the process shown in the video on my printer and another one. It worked on both. I counted the number of screw holes between my thumb screws and got 11, your picks show 12 and 13.

I suspect that you are securing one clamp and unscrewing the other, which will lead to this problem and force you to move thumb screws – I use to do that too. The embedded video shows the ‘trick’ which is to loosen all 4 screws, swap clamps, squeeze the clamps against the board, then tighten all 4 screws.

For the record, I’m not the one who discovered this approach, but i’m happy they did!

Hope that helps!
– Troy

[Dave]

Hi Troy, thanks for your response. I’ll give it a go again, but I’ve done this numerous times already. I discovered this after watching the video and seeing the method of loosening 4 and swapping clamps. I was forced to do this because my clamps don’t have the silkscreening, and I wasn’t sure if I had to flip them over or not. So yes, I did loosen and then just swap the top and bottom clamps.

When I get home from work, I’ll try again and will video the method.

Would you mind measuring your clamp cutouts? Mine came out to about 3mm for the clamping side, and 2mm for the solder heating side. For this approach to work, assuming that the center of the thumbscrew is nominally at the center of the clamp, these cutouts should have been the same size.

[Dave]

Ah, I see – I think you misunderstood what I was explaining in my post, or I did a poor job of describing it. The first image shows what happens if I keep the thumbscrews in the same position for clamping and curing, i.e. the method shown in the video. You can see that the PCB doesn’t fit.

The second image shows what happens if I go in the opposite order, like going from a stable curing position to solder paste. If I can keep the PCB stable for curing and then follow the same process in the video to go back to clamping for solder paste, the clamps barely touch the board, and therefore it’s not secure.

[Dave]

Can any other users here please post their clamp cutout measurements and compare with mine? I’m referring to the dimensions referred to below in a model of the clamp:

In the top image, I measured 2mm, but I really would have expected the design to require a 3mm cutout.

[cborn]

Mine are the same (2mm and 3mm), original Kickstarter printed clamps.
Overall width is 13mm, slot for screws is 8mm.

[Dave]

Ok, thank you for the confirmation. I can’t figure out what I’m doing wrong, then. I guess I’ll have to make a video so someone can tell me what I’m doing wrong. I’ve followed the process outlined by the embedded videos (i.e. I don’t remove any screws, I just swap the clamps), and the standard substrate doesn’t fit. I assume it works fine for you, though?

[Dave]

I forgot to ask, what sort of material were the original clamps 3D-printed from?

[cborn]

Yes,works fine for me!

Clamps are milled Aluminium, printing on one surface says “HOT SURFACE”, “^ BAKE ^”, “v CLAMP v” etc.

[Dave]

Ah, when you said “printed”, you mean the ones that have printed text. I was thinking 3D-printed.

Ok, I uploaded a video of what I’m experiencing, so it’s clear that (I think) I’m following the expected steps from the video in the app.

https://bit.ly/2BTNM5f

[Dave]

Hi Troy, could you or anyone else on the Voltera support team please look at the video I posted a couple of days ago and let me know what I’m doing wrong? Thank you!

[troy]

Taking a look in a sec.
I just measured my clamp and a few others in the office and checked the design. 2mm and 3mm is correct. Incidentally the cutouts in the clamps that the thumbscrews slide into are slightly deeper than center, but only by 0.250mm.

let me check that vid

[troy]

Vid helps a ton, so thanks for taking the time to make that @Dave.
The procedure looks correct, so something else is off.

2 things I noticed:

• you still have 12 holes between your thumb screws – i have 11, when i use 12 the clamps do not reach my board
• you have a bit of slop before while in the clamp position – i do not

before digging in more, can you measure the size of the board. I see it is FR1, but i want to double check.

[Dave]

Hi @troy, thanks for your response. The FR1 board is 83mm x 57.8mm.

If I have 11 holes between thumb screws, it’s even worse. Tons of slop when clamping, and when heating, the board overhangs the flange by even more. My thumbscrew holes are 5.25mm center to center.

[troy]

Hey Dave,

The board I have here is 76.3 x 50.8. So that explains why the procedure works for me and not for you. I dug into why there is a difference…

We found that people were designing 3x2" circuits for the 3x2" board, and it wouldn’t work out because you need to leave some room for the clamps. So, we increased the board size so that the useable area was at least 3x2". When that change was made, the impact on swapping was overlooked. Some other folks also pointed out that swapping clamps does not work for template boards. I need to investigate more to determine how best to fix this.

In the meantime, thanks for reporting this! I appreciate the time you put in and your patience as we uncovered the source of the discrepancy! I was talking with Mike and he mentioned you’d wanted some clamps with labels. I have a spare set here, I’d be happy to send them as a thank you. Please direct message me so we can figure out details (e.g. shipping address).

Thanks again!
– Troy

[Dave]

AH! That makes a lot of sense. I really appreciate your offering a set of clamps. I’ll send you a DM.

[Dave]

I just thought I’d share with everyone that the new clamps I had machined arrived today and they work great with the two sizes of blanks that I have. I’m glad to be past this minor inconvenience!