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atemylunch
09-13-2004, 03:59 AM
What do you guys use to hold down your workpieces(t-slots, vacuum, bubblegum)?

Ken_Shea
09-13-2004, 08:50 AM
t-slots Yes
vacuum Yes
bubblegum No :)

Vise (get a good one), clamps, screws, double sided tape, contact cement, fixtures, and everything in between except holding it with your fingers, I ask my friends to do that :D

My stuff is straight forward enough that holding presents little problem, but it is getting more complicated as the parts get more complicated. I have seen fixtures what appear to be more complex then the part being machined.

Rekd
09-13-2004, 09:13 AM
t-slots Yes
vacuum Yes
bubblegum No :)

...I have seen fixtures what appear to be more complex then the part being machined.

Been there, done that, got an ulcer.

You're only limited by imagination. I've used everything. (Yes, including my own as well as other's fingers; "Ok, Ngyun, you don't move that hand, and I'm gonna run this fly-cutter right next to it..") :rolleyes:

tjstraz
09-13-2004, 11:33 AM
On my router I use carpet tape to hold down sheet material as well as foam. Works really well.

Jim Stein
09-15-2004, 02:08 PM
Magnets

Brian V.
09-15-2004, 03:14 PM
I have a drawer full of aluminum magnets and wood magnets, unfortunately they all arived in a nonworking state from the distributor. Nicely the guy I bought them from said it sometimes happens durring shipping so he sell me replacement ones for 1/2 off.
:cheers:

Kookaburra
09-17-2004, 05:04 PM
A combination of (Vacuum or Tape) + side clamps is what I have found works for me. The side clamps don't need to be anything special, a slotted clamp and a bolt is all you need to simply press the clamp against the side of the material and lock it down with the bolt on two sides to force the material against your stops or if you are not using stops use two clamps on all four sides. This way you are assured the material will not move sideways during a cut. I find it also handy to produce your toolpath in such a way that it leaves the job attached to the main material. You then simply knock it out after completion.

Hope this helps :cheers:

Cold Fusion
09-17-2004, 08:37 PM
I use a blind hole grid and bolt down the material on 4 edges with long M5 screws and locknuts.

tpworks
09-18-2004, 09:12 PM
I use an old kirby vacuum to power my vac-hold-down table using a 2" iron pipe base plate attached to the vac and the large shopvac hose. I made a grid to route out the MDF using turbocad (dxf) and created the toolpath using deskam and then drilled 3/16 holes in a sacrificial piece of particle board. The idea is from shopbot where you can download files for a full 4' x 8' but I only made mine 12" x 48".

Tom

sixpence
09-24-2004, 12:55 AM
I spoke to a guy running a big Multicam system with no vacuum. I don't know what material you are cutting but when he cuts small pieces from a sheet of 3mm mdf he does not cut all the way through. He leaves a paper thin layer which holds the sheet together and then runs it through a drumsander and all the pieces drop out the other side. Perfect no trimming necessary!
Just need to bulid myself a drum sander now! It never stops does it!

Graham S
09-24-2004, 06:52 AM
Has anyone tried ice?

I have seen things called ice chucks, they have peltier coolers I think and are used to clamp really thin things and also very hard to clamp things. I bet for occasional jobs you could stick things to a lump of steel in the freezer. Obviously not something to do in the middle of summer on a long 3D job but I bet there are a few things it could come in handy for.

Graham

ger21
09-24-2004, 09:22 AM
I saw a website somewhere that did CNC ice carvings. The ice was frozen to the table I believe.

Vac-Clamp
11-21-2004, 11:14 PM
I hope that this does not sound too much like an ad.
We have vacuum clamps which are powered by compressed air (venturi) which might solve a number of the issues raised.
Website http://www.vac-clamp.com
Regards,
Errol

Vac-Clamp
01-05-2005, 06:46 PM
A previous respondant mentioned wood magnet and an aluminium magnet, this is probably the best way to describe Vac-Clamps. The only difference is that these work well.

Click here for the review.
http://www.cnczone.com/forums/showthread.php?p=59052#post59052


Errol
http://www.vac-clamp.com

Chamm128
04-10-2005, 10:03 PM
Anybody know of a good material to use as a sacrificial top for a vacuum table? the top of my table is going to be alluminum, but I want something to go on top of that that is sacrificial, but I don't want to constantly be drilling holes when I need to replace it that match up to my table top. I was thinking of using pegboard, that way I would only have to drill half as many holes. Any ideas??? Thanks, Chuck.

miljnor
04-10-2005, 11:03 PM
Ice seems abit risky to me (read scary). Gives a whole new meaning to "breaking the ice!". Seems to me a low melt wax (which I've used to good effect) would do the same thing.

sp00k1e
04-12-2005, 04:44 PM
Our machine at work uses sheets of some porus fibreboard about 2 mm thick. it is almost like stiff felt, the vacuum works through this.
Paul

Chamm128
04-12-2005, 05:48 PM
I may just end up going with pegboard and drilling more holes in it.

Chombie
04-13-2005, 11:28 AM
MDF makes a good spoil board, if you use 1/2" or 3/4" you can rout slots into the board not all the way thru, drill holes in the slots this way you get vacuum rite where you want it.

whiteriver
04-13-2005, 12:00 PM
If you can get it LDF workes way better. Hart to find. Seal the edges.

Donny

www.whiterivermfg.com (http://www.whiterivermfg.com)

2muchstuff
04-13-2005, 12:23 PM
Use your router to do the hole drilling for you.

Chamm128
04-13-2005, 01:20 PM
What exactly is LDF?

ger21
04-13-2005, 01:23 PM
LOW density fiberboard

Chombie
04-13-2005, 04:00 PM
If you have problems loosing vacuum when using mdf or ldf thru the edge, edge band it or put tape over the edge.

CNCRob
04-13-2005, 04:30 PM
We use LDF alot for forms at my job. We seal the edges with duck tape and skim just a hair of the coating off for better suction.

Chamm128
04-13-2005, 05:48 PM
How much CFM does it take to get enough suction to hold something down?

2muchstuff
04-14-2005, 12:35 AM
It's not the CFM that holds things down, it's the "strength" or amount of pull. It is generally measured in inches of water, inches of mercury or mm of mercury. You can have a perfect seal on something with no CFM and still hold it in place if you have enough pull. CFM is used to size the pump, how fast a vacuum can be pulled down or maintained. CFM will also allow you to have leaks in the system (open holes in the table) and be able to hold a set vacuum level holding your parts in place.

It is always a good idea to get a pump at least twice the size that you need. Installing a vacuum regulator on the suction side of the pump will allow you maintain the level you want and allow for a level of reserve vacuum. Also with a vacuum regulator your pump won't work as hard and last longer by keeping a constant flow of air thru it keeping things inside cooler.

xairflyer
04-21-2005, 06:56 AM
So is a shop vac any good or do you need a pump.

Bloy2004
04-21-2005, 08:34 AM
My experience with shop vacs was....
when there is not enough air flow through the motor , the motor would race faster from less loading of air through the cooling fan and thus the motor would have no cooling and heat up melting the brush holders causing them to stick and a resulting arcing with soon motor burnout.
shopvacs need constant good air flow (lots of it) to function well under long use.
If you've ever placed your hand over the intake of a shopvac (or it got plugged, you notice right away the increase in rpms. Running it for an extended time like this will result in eventual burnout.
I used one with an extra bag inside to filter out finer particles having the motor reduced in air flow and although it worked great for a while, after a lengthy operation the motor gave out.

Bloy

P.S contributing factors also incuded a probable "cheap" shopvac.