Verifying Clamp Tonnage

[joeprocess]

Is there an instrument that can be used to verify that what a machine says you are getting for tonnage is actually true?

Also, does anyone have a quick reference guide or instructions on how to check platen parallelism. I haven't done it in so long that I don't want to do it incorrectly.

[MTUHusky]

I have used something called "Fuji Paper", I have also heard it called "pressure paper". There are different grades of it that will turn a bright red color when it reaches a certain pressure. I use it to check my shut off all the way around the parting line as "bluing" off a mold doesn't really give you an idea of home much pressure there is at shut off. Using different grades could get you close to what the actual pressure is but its a guessing game. I would bet there are digital sensors you could buy to back check your tonnage sensor on the machine but those will not be cheap.

I am not sure if platen parallelism is the same as leveling the tie bars but we will periodically have to level the tie bars for certain machines. We check them by placing 1 machinist level across the tie bars near the stationary mold face. Then one machinist level across the tie bars behind the moving half. Finally one more machinist level at the back across the tie bars. Then if you have to adjust you loosen the bolts, get everything level and tighten them all back down with a 50 ft*lb torque wrench.

Hope this helps,

Husky

[chrisprocess]

Some machines have a pressure gauge or a lynx-type pressure sensor tied directly in to the machine cylinder or clamping unit for electric. This is a great way to compare controller readings vs actual readings but you'd need third-party equipment to read the lynx sensor, such as eDart system though I bet there are many.
I've seen machine manufactures include these sensors in their machines, or offer it as an additional add-on package. However I imagine the capabilities to install them yourself are still there in the machine components.

Never used Fuji Paper but sounds very interesting, might need to give it a shot.

One way to measure platen parallelism that's worked for me in the past is using a magnetic base with stand and a plunger dial indicator.
Move the platen to desired position (within reasonable length of magnetic base/stand), attach the magnetic base in platen corner while holding the plunger in a 'pushed' position, then slowly releasing the plunger until it shuts off on the other platen, record that number, repeat at all platen corners without moving the platen, comparing the deltas all 4 numbers will give you an idea of how the platens are sitting.

Or if you want to check parallelism during high pressure clamp, just clamp your mold (or moldset both halves together), set the magnet/stand to correct height that allows the plunger to be pushed in very slightly, then just clamp the mold up with the the indicator in each corner of the platen and comparing the 4 numbers.
Using both methods will give you a great deal of information, if the machine platens aren't parallel or if the mold stack is messed up..

I've also heard of laser systems to check platens but I've never used

[Suhas]

I am going to ask Arburg and see what they say.
Will post.
Suhas

[rickbatey]

All,
While verifying actual clamp is important don’t forget that mold design and surface area are the final piece of actual clamp force exerted on the tool!! Until you take that into consideration you’re still just using “Kentucky Windage “.
Rick.

[RobertPHale]

Gefran has an instrument called Sensormate. It's a set of strain gauges that attach to your Tie-Bars using magnets. These sensors will measure the stretch of your tie-bars and based on the diameter, will tell you what force is being applied to each one very accurately with a digital readout in tonnage.

Here is a link to their site. I have used these in the past after maintenance jobs when tie-bars were replaced to verify that the strain on all tie-bars are equal.

https://www.gefran.com/en/products/428-qe1008-magnet-mount-strain-sensor

They are not cheap however, a full set of 8 sensors is around $18K, but worth it if you have a lot of machines and have had tie-bar issues in the past.

[Joel JS]

Hi,

You can also do a cheaper solution with a dial indicator, or 4 indicators is best, to measure tie bar stretch, which correlates to tonnage.

Here is a link of a good write up of such, with a formula to measure tonnage.

http://www.woodrell.com/stretch.html

Joel

[joeprocess]

Thanks everyone. I will give these dial indicators a try.