Bed Plates

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GlennW
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Bed Plates

Post by GlennW » Mon Sep 03, 2012 4:55 pm

Not much happening on here, so I figured I'd post something.

I'm a fan of the "screw the stack down and then machine it" method when possible, so I carved out a decent sized (12" x 24" x 1 1/2") bed plate for my mill.

Set the plate up on parallels, clamped it down, and cut some hold down slots.
P9020041.JPG
Re-clamped it using the slots and zipped around the perimeter with an end mill and then chamfered the edges with a chamfer mill. It'll get skimmed with a face mill when I am ready to put it to work.
P9030046.JPG
Made a smaller one that will fit on either of my milling machines or my rotary table. I can use the plate and a vise on the mill tables and still have plenty of room.
P9020043.JPG
For the smaller stuff, I just grab a piece of aluminum flat in the vise and skim it with a face mill and screw the stock to that.

Any parts made on the plate will have the fixture offset in the part program relative to the plate X0, Y0, Z0 it was originally made on, so repeats will be easy.

Not rocket science, just a Holiday weekend, and I haven't played with the CNC machines all year...
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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rmac
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Re: Bed Plates

Post by rmac » Mon Sep 03, 2012 7:38 pm

For us rookies, can you explain what you do with these plates now that you have them?

-- Russ

JackF
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Re: Bed Plates

Post by JackF » Tue Sep 04, 2012 7:23 am

Glenn,

I hope this isn't one of those stupid questions but will these at all be used as a sacrificial plate at times?



Jack.

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GlennW
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Re: Bed Plates

Post by GlennW » Tue Sep 04, 2012 7:27 am

Here is a simple example of a smaller plate that would be held in a vise.
P9030047.JPG
Just tap a few holes in the plate that correspond to existing holes in the part. Band saw a blank out and screw it to the plate, press the green button and watch the machine profile the part and interpolate the holes in it.
P9030050.JPG
Cuts out a nice part without having to remove tabs or file off hiccups.
P9030049.JPG
Parts can also be stacked for cutting multiples at once depending on flute length of the cutter.

I also need to make parts from thin Phenolic sheet, so the sheet can be stuck to the plate using double sided tape and small parts profiled from the sheet.

Keep in mind that this CNC stuff is pretty net to me, so other methods exist as well.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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rmac
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Re: Bed Plates

Post by rmac » Tue Sep 04, 2012 8:34 am

Thanks, Glen. So over time I guess the plate winds up with a bunch of holes in it and then you make a new one. This idea looks like it might be useful sometimes even on a manual (not CNC) machine.

-- Russ

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GlennW
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Re: Bed Plates

Post by GlennW » Tue Sep 04, 2012 9:25 am

Yes, they are basically sacrificial plates.

Having the thickness that they do, I can skim them with a face mill and clean them up after they start getting too many cutter tracks on them. I try not to cut more than a few thousandths into the plate when profiling parts.

Another advantage is that when you skim the plate with a face mill prior to use, if the head is square, you will be working on a surface that it parallel to the X,Y axis movement. If screwed down to the plate, even parts made on a worn out knee mill will stand a chance of being uniform in thickness.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

kapullen
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Re: Bed Plates

Post by kapullen » Sun Sep 30, 2012 6:19 pm

These plates are commonly used in industry.

A known pattern of threaded holes is drilled in the top face
for the tool engineer to design special tooling around.

Many shops, and machinists love them.

My personal view is they take up too much head room (z axis travel).

Mount a vice on the plate, and that job you could barely do height wise,
is not possible without removing the vise, and plate.

Remove the plate, and your table is a corroded mess!

The plates are also a pain to clean off because of the tapped holes
in the surface collect those little blue chips.

I have a small plate with shoulders milled to fit the Kurt vise jaws, and tapped
out for 1/4-20 for that little flat job that needs face clamping.

Many ways to skin a cat.

Kap
Fadal Turn, Fadal Vmc 15, Prototrak 16 x 30 Cnc Lathe, Pratt and Whitney 16 x 54 lathe, Pratt and Whitney Vertical Shaper, G & E 16" Shaper, B & O Electric turret lathe, 36" Doall band saw,
Enco B.P. Clone, Bridgeport CNC Mill, Delta 12" Surface Grinder.

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GlennW
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Re: Bed Plates

Post by GlennW » Sun Sep 30, 2012 6:33 pm

These plates are not intended to reside on the table and have a vise mounted on them.

They are to be used only when needed when a vise will not work.

The smaller plate was used a week or so ago for a specific job profiling sheet metal parts, and the larger plate is for a specific job where I need to machine a 13 1/2" x 23" aluminum sheet that is 1/8" thick that has a number of clearance holes in it for 6-32 screws, as well as many other machined features.

I guess it all depends on what type of work one does. :)

I had a guy in my shop one time that told me my bed turret was a useless piece of equipment and I'd probably never use it.

Dunno what type of work he did, but my turret gets used 90% of the time and I wouldn't be without it! (which is why I bought it)
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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Rick
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Re: Bed Plates

Post by Rick » Mon Oct 01, 2012 7:53 am

We machine composite sheet here at work in our cnc's. We have aluminum bed plates with a composite face in all of the machines we do composite work in. The plates stay in the machines all the time. The reasoning is that do to the speeds we run the cutters thru the composite(typically 10k rpm), the cutters fail instantly if they touch alum or steel. This way we can cut thru the composite sheet into the facing without cutter damage. We resurface the facing every now and then with a cup grinding wheel mounted in the spindle. The composite material grinds better than it machines, its wierd stuff. We also put in a couple of tapped holes to be able to mount a vise if needed. Another benefit to a bed plate is when you crash (and with a cnc we all will at some time) the table is protected.
Just another way of doing things.
Rick

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Sandiapaul
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Re: Bed Plates

Post by Sandiapaul » Fri Mar 15, 2013 9:17 am

I am continually surprised that the use of these is not more common. Yes they are "sacrificial" , but they will last a long time. While the example of the OP is one that bolts to the bed, I have a few that you just clamp in a vise. I make mine by taking a large chunk of alum(approx 3"x3"x 6"long) and bolting a thick piece(1/2" min) of alum tooling plate to it. Countersink the heads down well below the surface of the plate so you don't hit them with a cutter. Thats why a thick piece is good, most of mine are 1". Make the top plate any size you want, but for use on a reg. knee mill something about 8"x10" is about right.

You should cut the block you clamp in the vise all over so the side are parallel and square before you bolt it up to the plate.

Now clamp the thing up in your vise and flycut the top surface just enough to clean it up. Then cut all sides so the top is square to your X and Y.

I see lots of guys drill and tap a lot of holes in it, but I never do, I just do that as the need arises. In time there will be plenty of holes to clamp up odd shape stuff. I use Kantwist clamps a lot on the plate to clamp stuff down too. When the top surface gets too pock marked, take another flycut across it and you have a (mainly) renewed surface. When it gets really bad flip it over and bolt it up again to the block and you have a "brand new" surface.

I use these as much or more than my vise. I have even made some using MDF for the top surface for doing work on large plates, though that is mainly for plastic parts.

I do mainly prototype work and this methods works well for me as the parts are usually all different and odd shaped.

Paul

Harvey M Richards
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Re: Bed Plates

Post by Harvey M Richards » Tue Mar 19, 2013 10:12 am

I have one bed plate that I've been using regularly for 8 years. It also has another set of hole patterns in the other side. I try to keep a drawing of it updated in AutoCAD, so I can add other holes if they will fit.

Image

I also made a large plate that simply straddles the vise and is held in alignment by the vise. It's very handy for quick work, usually on plastic parts.

http://www.homemadetools.net/forum/vise ... atform-194

Another vise platform I use often is an aluminum V block for machineing flats and drilling holes in small diameter shafts.

http://www.homemadetools.net/forum/v-bl ... 90#post501

chief
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Re: Bed Plates

Post by chief » Tue Mar 19, 2013 9:43 pm

Harvey,

Great addition to this thread! I've been making plates following Glenn's lead for a while, but I really like you bridge plate. Sometimes there is just one small step the plates make easier, but you hate to move the vise, then have to re-zero it. Especially as I get older, that darn vise gets heavier. :)

Terry

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