Rippling effect of stencils

What Snap-Off are you running ?

I've seen this happen when a large negative Snap-Off is used. If you "contact" print (I.E. Zero Snap-Off) this tends to minimize the stencil coining. We use a mix of MPM & Transition Automation blades. I have noticed that the stencils that we run the Transition Blades with do tend to have a different wear pattern than the Stencils used with the regular MPM blades. I'm going to look into this a little closer to see if ours are wearing faster as well.

Hope this Helps, Dave G

reply »

What about reducing your force and slow the blades down slightly

reply »

I have printed 1000's of boards with dozens of stencils with TA permalex blades and have not had the issue you speak of.

Sorry I was not much help.

Cal

reply »

Silly question, but, are TR blades 'exactly' the same size as MPM's and seat themselves in the holders just like MPM's? Also, different types of steel are harder (less flexable) than others. Are TR's the same? If harder (due to steel strength or coating), they will deflect less under same downstop setting, and a different strain on the stencil will result. We were thinking of going Permalex for our MPM's; would like to see what everyone here comes-up with.

reply »

O.K. Try this one on for size. I can't remember if I mailed this to someone privately or said it in the forum. I refuse to pay the exorbitant prices people are asking for squeegee blades.

You people are robbers and flim flam men.

I get my stencil manufacturer to make them. 0.010" thick s/steel with the bottom edge that contacts the stencil etched to 0.003" > 0.005" for a distance of 0.120". I supply the cad file - they supply the blades - SIX PER SHIM - $300.

Try it, you'll like it!

Take yer set of overpriced, dooverlacky, hoity toity, rickerpoodley and a fandoogally, titanium, teflon, whacko the diddle-o, whatever-o, "premium" blades to your stencil man and say, "duplicate that as closely as you can".

If it fails you've lost the price of a shim.

If it works you've got squeegee blades for 10% of the price these bozos are askin'.

You can do ten experiments, together, with different thicknesses, grades, cutaways etc. for the cost of ONE set of overpriced, dooverlacky, hoity toity, rickerpoodley and a fandoogally, titanium, teflon, whacko the diddle-o, whatever-o, "premium" blades.

I was gonna write a paper on this, but stuff it, let 'er rip.

reply »

Hi. I am familiar with the Transition blades. Normally, when there is metal to metal contact, as in the squeegee-stencil situation, there will be scratches, or a "brush pattern". Sometimes it takes the pattern of the high profile surface elements under the stencil (like pc traces etc).

The Transition blades produce a "marble" pattern, after a few hundred strokes. If the board is very flat, and support is good, the pattern will spread out around the whole print surface. If the support isn't so good, the pattern may stay restricted to the areas of good support.

The Transition blades coating has a hard porous coating with Teflon trapped in it. At the begining, high points of metal contact the stencil and scratch. After the inintial "wear-in", there is essentially teflon contacting the stencil.

The marble pattern is actually the grain of the stencil metal showing after the polishing action of the squeegee.

I don't think your stencils are wearing out. I think they are exhibiting the polish pattern. TO BE SURE, YOU CAN CHECK THE STENCIL THICKNESS -OLD VERSUS NEW.

Finally, it is very important to know the vintage of your TR blades. If they are old and have a nicked edge, that will cause wearout.

Normally the TR blades will last 12 months of rigourous production. They are expensive. But who wants to be changing squeegee blades on a printer every three months?

Take care,

reply »