Clamp Foot Plate

[Doddy]

A bit of thread revival, I'll admit. I've been playing in the shed trying to recover my old star mill back into operation (so many tales of woe, but that's water under the bridge now). Fitted with a 2.2kW Chinese water cooled spindle I thought to try a bit of isolation routing. Previously results for me were varied... from terrible to bloody terrible, and I'd written the technology off (I blame the previous 3020 style MD router that I had before). Anyway, this time the results were very encouraging - good enough for one-off prototypes of unexotic components. But, the one area of weakness is always getting the laminate flat on the bed. So, I'm here googling for "pressure feet" and up comes this thread. Has anyone in the last 5 years since this thread died come across an affordable pressure foot for a 80mm dia spindle, or knocked up a diy alternative? Any experience, good or bad of the results on PCB with fine (for routing... maybe 10 thoa) geometries.

[phill05]

Doddy,
In my pre cnc days I had and used a few engraving machines and on one I made a spring loaded nose cone for the spindle that worked very easy if you don't have a large qty' of units to make would be a simple option for you.

Phill

[m_c]

In all honesty, if you've got a compressor, get a vacuum table.

Small vacuum table kits can be had for not that much money - https://vacuumtables.co.uk/diy-cnc-kits
Or if you have some other method of generating the required vacuum, the basic tables aren't expensive - https://vacuumtables.co.uk/vacuum-ta...rking/r-series

I've got 3015 R and 4030 RAL table from that website, and they do the job. I was surprised by how little air they actually use. My 3HP compressor runs less than 50% of the time when using either of the tables.

[Neale]

I haven't yet tried milling PCBs but one comment I've seen is that even if the table is flat, the laminate might not be, at least to the precision needed. I know that there is some level-correction software around that probes the surface then applies a correction to Z while engraving. Might be worth a look? Quieter than a compressor!

[Doddy]

Neale: Cheers - you're right, you're optimistically trying to keep to within a few microns (hah!) under a varying surface. But, by far the worst effect is the warp on what is a flexible board. Flattening is the first tool in the armoury. (Re. first.... this is definitely not the first time I've tried, but the first time I've had what I consider good success. Driven on by eyeing up a £1750 PCB router on flea-bay the night before, I figured (a) don't have the space, (b) wtf am I doing with the Starmill.... turns out the star mill can be pretty precise, once I've had it in many bits, and replaced the crashed limit sensor).

m_c: Agreed - in principle, I gave my vacuum table (bought for this purpose when I had the MD router) away. I would say that I could easily adapt my PCB fixture plate to be a vacuum table. I'm curious about using the compressor - I do have a 50l silent compressor (recent casuality of the failing pub trade... collateral damage of Covid), but curious how to change a blow to a suck??? Besides, I do have a vacuum pump somewhere... and if all else fails then I have Henry (or the Wicks equivalent).

I was thinking more about this last night. I have the luxury that the StarMill is.. a mill. I don't have to chase the spindle around, I just need a device that is referenced to the column. so this might be easier (and cheaper) than I previously thought. Certainly a spindle-mounted device (where I started thinking) is entirely the wrong approach.

[m_c]

but curious how to change a blow to a suck??? Besides, I do have a vacuum pump somewhere... and if all else fails then I have Henry (or the Wicks equivalent).

Venturi vacuum generator - https://vacuumtables.co.uk/vacuum-pu...compressed-air
The first link I posted includes them in the kit, but they are a pretty simple thing, and I'm sure there are plans available to make one for not much money.

If trying the vacuum route, main thing I would add is a manometer/vacuum gauge, so you can see the vacuum is working as intended, which the kits linked don't include.

It's worth mentioning that vacuumtables.co.uk were reselling a German company's kit. I can't remember who, but I did find them when I was looking at what tables to buy, and my orders were directly shipped from Germany. Price was comparable to buying direct from Germany, and VacuumTablesUK answered any questions I had before buying quickly, so they got my business.

[Doddy]

Venturi vacuum generator - https://vacuumtables.co.uk/vacuum-pu...compressed-air
The first link I posted includes them in the kit, but they are a pretty simple thing, and I'm sure there are plans available to make one for not much money.

Ah, I ignored the kit link on the basis I have a pump (I'm currently overed from head to foot in Ali-oxide from dremelling 4 years of oxidation from the pump - motor was stalled from lack of use but generally banging it about it's sprung back to life). I have a manometer - came with the pump.

Venturi?, need a continuous airflow?, I suppose a NRV could help, but think I'll stick with the pump and a low-pressure switch. I've looked at the tables in the link - I think they'd work very well with sheet materials that would cover the vac table but I'm likely to want to play with fairly small boards (100x75) - think I need a table with smaller vacuum zones, so already looking at aquatic 4mm adjustable manifolds, miniature pipe benders and brazing kits. Well... it is the holiday season!

[m_c]

Ah, I ignored the kit link on the basis I have a pump (I'm currently overed from head to foot in Ali-oxide from dremelling 4 years of oxidation from the pump - motor was stalled from lack of use but generally banging it about it's sprung back to life). I have a manometer - came with the pump.

Venturi?, need a continuous airflow?, I suppose a NRV could help, but think I'll stick with the pump and a low-pressure switch. I've looked at the tables in the link - I think they'd work very well with sheet materials that would cover the vac table but I'm likely to want to play with fairly small boards (100x75) - think I need a table with smaller vacuum zones, so already looking at aquatic 4mm adjustable manifolds, miniature pipe benders and brazing kits. Well... it is the holiday season!

Have a look at the video on the table page - https://vacuumtables.co.uk/vacuum-ta...table-vt2012-r
They come with a length of black beading/gasket that you fit to the slots, so you can reduce the vacuum area to just the size you need.

Pierson Workholding have some good videos on how to use vacuum tables - https://www.youtube.com/playlist?lis...D1tNNi9COAyVlt

It's worth noting, you don't need to butt the gasket end to end. If you're not using the maximise size of the table, you can get away with running the two ends through the same corner from opposite directions.

[Kitwn]

I think this may be the software Neale is thinking of...

http://www.autoleveller.co.uk/

[Neale]

That's the one - couldn't remember the name. I've looked at it but never actually used it as my router did not have a suitable probe. For small pieces where height was critical (typically engraving) I've skimmed a spoil board but that can't cope with an uneven workpiece.

Kitwn - good to see telepathy working at such a distance!