Fuji　Engineering
Machining technology by vacuum chuck

huckVacuum chuck is atechnology that was used for a long time, but when using vacuum chuck with machining, there are few technical materials in fact.
This may be for the reason that the technology could not be used univerally. But it could be very useful depending on how it' used.
In this section, we'd like to explain how to use vacuum chuck, which was established through our experiences. We hope it could be of service to your company.
The important point for machining with a vacuum chuck is the type/shape of table on which you set a workpiece.
In our vacuum chuck method, we consider that the leak from the vacuum chuck is as small as prossible, so we keep the displacement of the vacuum pump unit used to the minimum necessary.
【Method used in vaccum chuck】
The following schemes are typically used in our vacuum chuck.

1）Method, using O ring (this method can be used on the condition that the material of plate is stainless).
・Process O ring grooves into a shape that matches the contour of the workpiece.
・Process grid-like O-ring groove.
2）Method not using O-rings (Used for work with good flatness)
① The system that has a leak groove.
 ・Process the leak groorove into the shape matching the contour of the workpiece.
②The system that has a continuos exhaust port.
・Process the leak groove into the shape matching the contoure of the workpiece.
③The system that has an exhaust port in the grid.
 ・Processing method of the drainage port which was relatively small diameter.
④The system that has a prorous exhaust port.
 ・Use pumice-like material (effective for thin materials which cause adsorption strains).
The above methods are commonly used.
【Parts use in machining】
Vacuum pump unit.
1）Hose for vacuum line.
2）Joint
3）Vacuum chuck
4）O ring
5）Vacuum unit.　
1） Hose for vacuum line.
①It is used for lathes and other machining tools, so take into consideration the oil resistance, elasticity, waring resistance, and price.
②If the thickness is φ6 or more on the inner diameter, there is no problem except for special cases.
③Do not use it longer than necessary.
④Use transparent Parts if possible, which enable detecting flaws of cutting oil.
⑤Our company uses Toyoron hose φ9mm, soft nylon tube (inner diameter φ6), or coiling tube for air tool piping, depending on situations.
【Joint】
①It is convenient to use a joint used in air piping as a substitute.
②Hose joint φ9 PT 1/4 (Connect to Toyoron hose and attach to vacuum chuck with PT 1/4 screw)
【The parts often used for cuum chuck jig】
It is convenient to arrange one-touch joints. It is useful for taking out a vacuum line from the back of a jig or arranging multiple jigs.

jigs.Neoprene sponge round cord. Hose joint.fitting.soft nylon tube.
【Vacuum chuck】
Here we describe the method using the O ring.
①O-ring groove
②Leak groove
③Material of vacuum chuck
④O ring
⑤Stopper
⑥Vacuum unit
【O-ring groove】
1）Make an endless groove in the jig for insertion of the O-ring. Make the inner area wise to increase the adsorption force.
2）The grove dimensions should be such that the compression ratio of the O-ring is 10% to 25% (If the workpiiece flatness and surface accuracy are good, the compression ratil could be made small. Also, if the flatness and surface preclsion are poor, the compression ratio must be increased)
3）If the finished surface accuracy of the O ring groove is Rmax 25s or more, there is no problem, if you do get expected result by machining, finish it using grinding paper, etc.
4）When hand finishing is difficult, lacquer paint, manicure, etc may be painted.
【Leak groove】
1）Make a groove through which air flows between the exhaust port of the vacuum chuck and the O ring.
2）Depending on the size of the vacuum chuck, if it is a jig having a size of about 500mm A cross-sectional shape with a cross section of around 2㎟ wil do.
3）Plane shape should be made inside of the O-ring (about 2mm from the surface), and insert several grooves connecting to the exhaust hole.
★Be sure to make the leak groove, the purposes of which are aire ventilation. And provention and drainage of cutting oil leakage.
Material of jig
【Material of jig】
You should choose the materials of the materials of the vacuum chuck which are easy to handle, unles they are costly or cause accuracy problems.
Bakelite. Acrylic. Alminum.copper.SS〜S55C etc etc, It is good to consider from familiar things..
【O-ring】
It is used to separate the atmosphere from the vacuum.　
1）Since it is used in machining, it is only necessary to have a cord-like shape with oil resistance, elasticity and low hardness.
2）We recommend using a neoprence Sponge round cord φ3, when starting the first jig. Although there is a shortcoming in life span, it is flexible and easy to handle.
3）When you want durabillty, use Viton silicone rubber cord.
【Stopper】
　For that purpose, we often use a thread pilot hole, through hole, and counter bored hole as a finishing positioning stopper, which is finished by H7 tolerance.(we also use a free vice and other bolts)

Vacuum chuck.. Right side work (cut out from Aluminum plate)
Black line on the left side is O-ring upper and lower circle is prositioning stopper pin.
・Center hole on the left side, exhaust port and leak groobe.
・Size of the work Vertical 205, horizontal 95, Thickness 3mm.Material-aluminum( 5052). Adsorption power-110Kg.
【Porous chuck】
Test using porous table(prouct name Air Pad)released from Naveya company.


【Work assumption】
Cut out a workpiece from a resin/thin metal, using a lathe/milling machine,
 Although double-sided tape and adhesive can be usek, pretreatment and post-treatment are unnecessary when using the vacuum chuck, so workability will be improved.
In such a case, it is advisable to set a paper (copy paper etc.) between the table and the work for adsorption.
Because paper has breathability, it can be adsorbed without problems.
※Cutting should be the final process of machining in order to reduce the cutting load .Cut the workpiece 0.05mm deep from the back of the work and cut the workpiece.
※ Since the thickness of copy paper is about 0.08mm, there will be no scratches on t table
.※ Use a cutter blade that is as thin as prossible.
※When there is a lot of leakage from the cut surface. set the vacuum of the unit to L mode
※ cutting oil can not be used because the paper breathability disppears.

【Processing data】
Vacuum chuck shows more ability than expecred depending onn how it's used. but if you mistakenly use it, it will not be able to demonstrate its real value.

Vacuum chuck shows more ability than cxpected depending on hou it's used, but if you mistakenly use it, it will not be able to demonstrate its real value.
we recommend recording the processing data as precisely as possible.
There isn't much vacuum chuck machining data. The data that your company gathered will be important for your processing know -how.

【Rotary joint and Lathe Attachment】
When using it on a lache, it is necessary to connect a vacuum line to the rotring part, so attach the rotary joint to the attachiment as shown below.

Rotary joint exampler

【Work with Uneven seal surface】
Until now. we have mainly explained a workpiece whose surface to be sealed has a planar sha;e, but in the case of a workpiece with unevenness on the seal face, there are cases in which it is not prossible to use conventional methods.
the same is true in cases where the vacuum chuck is three-dimensional, but in this section. we will explain the case of work with uneven seal surfaces.

To solve this problem, use sealed silicone rubber to seal.
The workpiece in this case has a ring shape with an inner diameter of φ130 and an outer diameter φ of 200, fo it was shaped as shown in the photofraph below.
(the picture is a part of the packing. There is a bulge on the seal face part because there is a through hole in part of the seal face).
The sectional shape of the vacuum chuck and packing is asa shown in Fig.

In Fig 1, the packing is not fixed (positioning is done) because the backside of the packing is vacuumed..
　Figure 2 shows the case where tha packing height was increased to raise the elasticity of the rubber, the lateral rigidity of the packing was insufficient, and the middle plate was placed in order to provent the packing from falling inward(cross-sectioal view A part of the exhaust port of omission is omitted).
Advantages
1) Even if the seal surface has unevenness, it can be adsorbed without an problem.
2) Since the vertical direction of the packing can be freely set, it can take a large crushing margin, and the flexibility of the rubber increase, and also, the adhesion increases.
3) The airtightess of rubber is higher than that of neoprene sponge string.
Disadvantages
1) specified mold for marking packing is required.
Compatibility with products.
1) Mass production parts.
2) In case of small quantity products, products with high added value.

【Advanced usage】
So far, the line of the vacuum unit and the vacuum chuck has benn used in the connected state, but when you want to use the line, separeting the vacuum chuck and the unit, such as when using the NC lathe/ pallet changer without a through hole in the machine, take the following measures:
After using the vacuum unit, close the valve on the vacuum chuck side after clamping, and detach the line connected by coupler etc. After that, it is necessary to make the change of degree of vacuum as much as possible, until the processing is completed, so that there is no leak from the line.
【O ring】
Using O-rings made of rubber cord with oil resistance is desirable, rather than those made of neoprene sponge round cord. when it is difficult to obtain the O-ring with proper dimensions, you can change the size by cutting, or connecting it. The soft rubber(hardness 30th) increases adhesion.(common O-ring has hardness 70th)

【O-ring groove】
・Conform the wicth of O-ring groobe to the specification of the O-ring to be used.
· Set the depth of the groove so that the collapse allowance of O-ring is 10% to 30%
・ Finish the surface of the groove by the surface roughness of 25s or less (It can be finished with manicure lacquer paint).
【Others】
・ It is convenient to attach a vacuum gauge, or the one that can check the degree of vacuum on the vacuum chuck side.
・ It is also prossible to check the degree of vacuum with a touch sensor.
・ It is effective to apply grease to the surface, on which the O-ring hits, to prevent leakage.

【Tesut 1】
・ We've tried putting the O ring of viton, which we've made endless, to a jig, using a neoprene soponge cord.
・ The data from the work day, and from 4 days later.
・ It rose by about -0.0075 MPa in 4 days.(It is unknown whether leak is from line or betwnn work and vacuum chuk)
・ We stop the hose with a panty.
On adsorption 4 days later
OThis time, it is not a vacuum chuck made on the premise of detachment, it is changing the
O ring.

【Test 2】
This is the date collected for every 10minutes using neoprene soponge cord.
There is no problem if it is used with the vacuum unit connected.

It has reached atmospheric pressure in about 50 minutes.
Leakage can be reduced in the case that cutting oil is used.

【Test 3】
This picture shows the state in which the neoprene sponge cord was removed.
・ There is no problem if it's dry cutting.

data.1
data.2

data.3

・ Picture of data 1 Activating only the unit in the state that the line is removed.
・ Picture of date2   During work suction (only main pump operating)
  ・Picture of date3  　8seconds after the leak test started.

・ The vacuum chuck used this time is ajig, predicated on the use of neoprene sponge cord.The surface roughness of work.. vacuum chuck is finished to R max25s〜30s in wetype,
cutting oil flows in, but there is no problem if it's dry type.
It's possible to process resin etc. without using neoprene sponge cord.

Vacuum chuck unit ・ air filter.t・ Toyoron hose ・ A jig ・ A work
Technical consultationt　Fuji　Engineering
cell phone number　090-1530-2928
TEL　0554-43-4839
FAX　0554-43-4851
e-mail：fuji-e3@nifty.com

　

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