Cracks in finished polyester resin...

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WildcatHollow

WildcatHollow

Member
Joined
Nov 4, 2009
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Location
Boyce, Virginia, USA
The image below is from the near the top of a Majestic Series I finished a couple of days ago using an Golden Dawn PR from Exotic Blanks. I was using it to practice my photography, when I noticed what I thought was a blemish in the finish.

Turned out it was several cracks near the end of the pen. I went back to the photos I shot a couple of days ago, and they don't appear in any of those.

All of them are within 3/4 of inch of the end of the tube. They're all curved, and the curve is pointing towards the top. Some of them are under the surface of the acrylic, while two of them have broken through the surface (E and F).

EDIT: I just noticed there are additional, subtle cracks further to the right of F. The cracks are all on one side of the pen. No other cracks anyplace else.

Any idea what I might have done to cause this effect?

Thank you.

t.

1_DSC_0006-2.jpg
 
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Unless I'm mistaken, the blank is polyester resin, not acrylic. PR is relatively more brittle than acrylic and will crack if not handled with care. My guess is that you either applied too much tool pressure, got the blank too hot during sanding, or pressed too hard during assembly of the pen components. It is also possible that some glue or other material was left inside the tube and caused binding during pen assembly.
 
I had the same problem recently. I had a Golden Dawn PR blank that I used for a Cigar twist pen. After turning the pen to size I noticed a pin hole on the lower blank. No problem easy fix. After finishing and assembling the pen I noticed what looked like two white hairs that turned out to be cracks on the lower blank near the center band running parallel with the blank. One's about 3/8 and the other is 1/2 inch long. I've had really great luck with exotic blanks and this is the first time one has done this. Not sure if I did something wrong or what. I just figured I'd keep this one for my personal use because even though it has two cracks I really like the pen.
 
go talk to Dawn..if she believes she had a "bad pour" she will talk with you..if she believes you left glue uin the tube and forced in a component, she'll tell you...go to the source first then here to the forum..she's a good gal and will help
 
I think it may be the nature of PR. Most of the pr I have turned is more brittle then other "plastics". Since you said the cracks appeared after the pen was finished and photoed, then I am really unsure. Most of mine occur when working on the blank and occasionally when assembling. If a customer were to bring me one back with cracks I would assume that maybe they dropped it or rough handled it.
 
I work with a lot of PR and the location and all I am going to say to much pressure putting the pen together. its great stuff just have to be careful working with it. the results are amazing though.
 
I am not the OP but I did have a question. I believe that the OP said that the cracks appeared after he had finished and photoed the pen and posted it. If the cracks came from assembling the pen then wouldn't show up right away and not later on down the road?
 
I am think stress fraction from a bit too much pressure these might not show right away. too much pressure putting parts in will also keep that same tight pressure. I have even craked up wood after a day or few hrs thinking that extra pound of pressure was a good thing.

rjwolfe3 said:
I am not the OP but I did have a question. I believe that the OP said that the cracks appeared after he had finished and photoed the pen and posted it. If the cracks came from assembling the pen then wouldn't show up right away and not later on down the road?
Click to expand...
 
Well I'm pretty positive that it isn't from heat as I've heated loads of PR with a heat gun to form it into shape. I've had it so hot that you really can't touch it.
Couple of things...Is it only on one part of the pen ?( cap or body ) Is the other end fine?
Are you positive that the inside of the tube was clean?

I did a pair of Majestics recently where the fittings were so tight that I had to stop pressing half way and pull them out and skim them down on my metal lathe. I had to skim the plastic cap thread sleeve too so perhaps it is the tubes on Majestics that are just made a bit too small:confused:
 
Inside of Tubes...

Skip...

Having read an earlier post where one of the members had trouble with his majestic, I made sure the inside of each tube was spotless, and that there were no burrs on the ends.

I also gave the plastic a bit of beeswax before I pressed it. Expecting the worst, and a lot of friction based on the reading of earlier posts, I was surprised at how easy all the components pressed together - smooth and quick with very little pressure.

The cracks are in the pen body near the cap end rather than the writing end.

A couple more of the cracks have appeared since my last post, so whatever is happening is continuing. And, I've handled this pen a like a baby. It's been wrapped in a piece of suede since I finished it.

Thank you all for the help. Please let me know if you have any other questions.

By the way, I am far less likely to blame it on a bad blank than I am on something that I did.

Would it have been better for me to use Gorilla Glue for the tubes rather than CA?

Regards,

t.
 
I don't "think" that it is what I am about to suggest but there are the possibilities:

Storage in widely varying temp ranges over a 24 hour period causes ebonies and snakewood to crack. Tubes expand and contract at a different rate that wood or PR/acrylic. IMO that this does not affect each other unless too tightly fit. (Temp range dramatic, too tight a fit to allow for expansion / contraction.)

There was no direct sunlight on the pen, or pouch (with pen inside) coming through a window for an hour or so, was there? That will do it.
 
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Toby, I am very interested in this. The cracks that you show seem to be radial, not longitudinal? All on one side, and continuing to progress?:confused:

I would like to get as much information as possible to help find cause. If it is the resin, I need to know so that I can make it right!! If anyone else is experiencing the same problem, please PM me or post here.
 
I have never seen cracks like those and the fact they are continuing is odd.
I have done every scenerio mentioned. I have left pens and blanks both in the sun for hours at a time, I have used extreme pressure to get parts fit together, I have done as Skippy and heated blanks for various reasons, I've purposely created heat with sanding/cutting (which only caused the adhesion between the tube and blank to let go, nothing more), I've dropped pens and blanks purposely, I've left pens in my shop and in vehicles in varying temperature changes, and any other things people post they have problems with and I've never had a blank crack in any way.

I would like to see how this plays out.
 
I think the blank is a micro amount too long maybe? If that is the case, when you press the parts, the part would sit against the PR instead of the end of the tube. If you use a tiny bit too much pressure, you crack the blank. It takes a while for the cracks to show up because the subtle changes in temp cause the PR to expand and contract ever so slightly, pushing the parts out a micro amount and exposing cracks.

Explains how they got there, Explains the direction, and nature of the cracks, Explains why they took so long to show, and explains why they keep showing up. Just my thoughts, but it could be tested i guess.


It will be interesting to follow and see the final conclusion! I am intrigued for sure.
 
RAdams said:
I think the blank is a micro amount too long maybe? If that is the case, when you press the parts, the part would sit against the PR instead of the end of the tube. If you use a tiny bit too much pressure, you crack the blank. It takes a while for the cracks to show up because the subtle changes in temp cause the PR to expand and contract ever so slightly, pushing the parts out a micro amount and exposing cracks.

Explains how they got there, Explains the direction, and nature of the cracks, Explains why they took so long to show, and explains why they keep showing up. Just my thoughts, but it could be tested i guess.


It will be interesting to follow and see the final conclusion! I am intrigued for sure.
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Just adding a thought here not trying to contradict you. I would buy into a bit more if it were a crack or two. The first crack or two would relieve the stress from the pevious scenario, I would not think there would still be enough stress to continue the cracking on down the blank that many times. Again, just another thought. If anyone has any more of those particular blanks to put through some testing might be the only way to get any answers, and then maybe not.
 
hunter-27 said:
<snip> If anyone has any more of those particular blanks to put through some testing might be the only way to get any answers, and then maybe not.
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Just to add more data...

I have 2 of the Golden Dawn blanks (purchased separately in July and August), turned a JGII out of one in mid-November and no cracks to date. I've made 30+ pens using Dawn's PR blanks and the only problems I've had with cracking were me drilling too fast (but I knew it right away :redface: -- never had a crack develop after completing the pen).
 
PR_Princess said:
Toby, I am very interested in this. The cracks that you show seem to be radial, not longitudinal? All on one side, and continuing to progress?:confused:

I would like to get as much information as possible to help find cause. If it is the resin, I need to know so that I can make it right!! If anyone else is experiencing the same problem, please PM me or post here.
Click to expand...

Hi, Dawn...they are indeed radial, rather than longitudinal. They are only on one side, and on one of the two halves of the pen I turned. I am not of the opinion that it's a failure of your product, but I probably don't have enough experience in these matters to be credible.

I'm going to try disassembling the pen this weekend. If you like I can send them to you for additional analysis.

Regards,

t.
 
Cracking Stopped...pen disassembled.

The cracking stopped progressing.

I used my PSI pen-disassembly kit to salvage most of the parts. I wasn't able to reduce the middle section with the center band and delrin without damaging it, so I left it alone. I called PSI and ordered a replacement for that part, which they had in stock.

Dawn, although I don't think this is the fault of the blank, I'd be happy to send you the pieces if you'd like to analyze them further.

Thanks for the input, guys, I really appreciate it.

Regards,

t.
 
Toby, I don't know if I will be able to tell anything from the pieces. But I am curious, and wouldn't mind taking a look at them.

Meanwhile, I have some replacements on the way to you!!:cool::biggrin:
 
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