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View Full Version : Hold down clamps, what do you use?



Web Goblin
13-04-2012, 09:37 PM
I had been toying with the idea of making my own clamps and after much looking at what was available on the market I decided to modify something to suit my needs.

This is what I have came up with.
57095710

They are cut from 25mm thick aluminium and should be able to suit differing thicknesses of material. Although not quite finished yet Im sure you get the idea.

So what do you use? Readily available kit or have you came up with your own?

Ian

Tenson
13-04-2012, 09:49 PM
I'm not sure I see how that works. Can you explain please?

Web Goblin
13-04-2012, 10:06 PM
The top section in the first photo will have a slot milled in it to accept a screw which is used to clamp the section down on to the workpiece. If you imagine the right hand top surface of the right hand part in the second photo having the slot. The screw goes through here and clamps the "hinge" part down to the work table. The hinge part will allow the clamp to hold down different thicknesses of material.

Ian

Hi-Spec
13-04-2012, 10:18 PM
I tend to use Lenkze's clamps (http://www.lenzkes.com/index.php?newlang=eng), these things are rock solid and they have a good range...shame they're a bit on the expensive side. The mitee bite product range is also very inovative for different clamping solutions

Tenson
13-04-2012, 11:10 PM
I should probably get some clamps. How about this?

http://www.ebay.co.uk/itm/52-pc-CLAMPING-KIT-MILLING-MACHINE-METRIC-M12-STUD-/330666875329?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item4cfd4819c1#ht_2258wt_829

Hi-Spec
14-04-2012, 08:52 AM
they do the job, we still use this style in my workshop on a daily basis although the studs break with the constant use

HankMcSpank
14-04-2012, 11:43 AM
I mainly mill copper fr4....for clamps I just use ali strips ....about the same length as the copper board (therefore 160mm long) and about 40mm wide (the ali is 3mm thick). So basically one long clamp either side of the copper board...I have my CNCUSB tool sensor wire permanently connected to one of these clamps...& becuase it is ali, when I clamp the board down it makes electrical contact with the copper FR4 surface - which means I can then use the FR4 copper surface itself to touch off for Z auto tool zeroing.

Tenson
14-04-2012, 05:21 PM
That's clever! How do you implement such a an auto-z sensing circuit for Mach3?

HankMcSpank
14-04-2012, 05:41 PM
That's clever! How do you implement such a an auto-z sensing circuit for Mach3?


It would be similar (I don't use Mach3 now but have in the past)...normally with Mach 3 there's a Z auto tool zero vbscript where you need to enter the thickness of your touch off sensor (a lot of people use PCB material so therefore a thickness of 1.6mm), so you'd just use that same VBscript for a thickness setting of 0 (on account there is no 'sensor' height in play becuase your stock copper pcb surface is now your touch off sensor surface!). So when I change tools, I send my axises to X0Y0 (which is never milled and therefore always has electrical conductivity back to the aluminium clamp) and touch off.....you can't get any more accurate than touching off on the surface you are going to mill!! I'lll take a piccie later.

Re the tool sensor wire itself ...you just run the wire back to a free 'pin' on your board (which has a pull up resistor on it) & then configure Mach3 on the ports/pins page. Plenty of how tos wrt auto tool zero & mach3 on the net.

JAZZCNC
14-04-2012, 06:32 PM
I made these simple longish slimline clamps from scrap 10mm Ali plate, they work well and allow for some akward positions.
I can also use them in different ways for either single material clamping or if I need or want to cut a few jobs at same time from differant materials pieces using offsets, like for small jobs out of offcuts.!

I also have some stupidly expensive Swedish Kopal clamps that I use for things like surfacing jobs due to the way they clamp the sides of material.

The pics should give you an idea, they are just for show purposes here but it's not unusal for me to use similiar setups while working and setup some work offsets,G54 G55 etc then combine the code for several jobs in one G-code file set it off and walk away. Thats the beauty using work offsets with small jobs and a large bed.

Lee Roberts
14-04-2012, 06:55 PM
That's clever! How do you implement such a an auto-z sensing circuit for Mach3?

Some links for you Tenson: Mach3 CNC Probe Tool (http://www.mycncuk.com/forums/media.php?do=details&mid=57), Laser Zero finder (http://www.mycncuk.com/forums/media.php?do=details&mid=24) < this one has the touch off plate featured.

Let me know if you need any more help on this.

.Me

Lee Roberts
14-04-2012, 07:11 PM
I've just posted this if anyone would like to make a set of clamps:

Link: Step clamp design - Hold down thin or irregular shaped objects while milling! (http://www.mycncuk.com/forums/showthread.php/4427-Step-clamp-design-Hold-down-thin-or-irregular-shaped-objects-while-milling%21)

HankMcSpank
14-04-2012, 07:23 PM
Here's what I've implemented (the green touch off sensor wire is bottom right of picture) & the croc clip attached to Jonathan's spindle mount!)...

http://www.hostmyjpg.com/images/03241b2c_5.jpg (http://www.hostmyjpg.com)

the beauty about a long clamp is that you don't need a lot of force to hold down the board, which means less warp upwards in the middle of the board.


it's very simply, but if you mill pcbs often, it's definitely the way to go

Web Goblin
14-04-2012, 09:33 PM
Tenson,
hopefully this pic will give you a better idea of how it works. This is 25mm thick plate its clamping. At the moment I have a wooden bed so Im using a wood screw but once my ali bed is in place I can use a 6mm bolt.




5784


Ian

Jonathan
15-04-2012, 12:23 AM
you don't need a lot of force to hold down the board, which means less warp upwards in the middle of the board.

Hence I just use double sided tape for PCBs. No distortion as well, no force really...
You could drill a 4mm hole somewhere convenient in or near the spindle mount and put a 4mm 'banana plug' on the wire. Annoyingly that method doesn't work for me since. presumably, the oil in the spindle bearings is electrically insulating the tool so I have to clip directly to the tool.

Tenson
15-04-2012, 12:38 AM
Tenson,
hopefully this pic will give you a better idea of how it works. This is 25mm thick plate its clamping. At the moment I have a wooden bed so Im using a wood screw but once my ali bed is in place I can use a 6mm bolt.

Ian

Thanks for the picture, I imagined it the other way around with the flat part pushing down on the material. I might just copy some of these :)

Web Goblin
15-04-2012, 12:45 AM
The dxfs are here, hopefully.

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