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Speaking of Precision Blog 
Dear Miles,
I hope you are doing well, I read your articles they are very impressive. maybe you can help me on this, I have a tunnel oven in my bakery the size 20’L X 7’W While we were in production making bread we had a power outage, the whole block, all my machines stopped, no electric power for a good 3-3/12 hours, this oven is a direct heat ovens, roof brick arched, the bread is bakes at a high temperature 1100-1300% baking time 15-35 seconds, after electric came back the slates size 48″X 4″ 1/4 tick, now they are not turning smooth there is scratchings very dip on the baking plates, and some are warped, I made a claim to my insurance, I have two experts evaluations that was a sudden heat exposure, and the oven is four years old they said that since every day the steel was exposed to heat, the steel grains are changed since not properly cooled off result to warped, but my insurance is denying my claim, saying that is not caused from heat exposure,
after I turn the oven off we leave the ovens blower fan for about two hours to cool the oven evenly, but that day I was not able to do so,
is there any advise you could give me,
Best regards,
George Nazarian
Sorry to learn of your problem. I am not surprised to learn that the Insurance company is in denial. That seems to be a requirement for hiring in that industry.
From your description of the events, it seems to me that the plates that warped are all in a single section- the section that was stuck in the furnace at peak temperature when the power went off. That is yet another piece of evidence that contradicts whatever reason the insurance company gave for denying the claim.
From a technical point of view, once you have determined that the plates are warped, and it is not the bearings and carriage mechanism in the furnace that is misaligned and causing the scratching, then perhaps you have a couple of options.
Replacing the warped parts of course is the best solution.
Perhaps a less expensive one is to remove the warped plates and then interleave them between good plates so that the “problem” is not as severe and localized. But if in your judgement, that would just ruin more plates, then that is not what you should do.
Based on the expense of this repair and cost of loss of use of this oven, I would hire an electrician to propose and install a permanent corrective action:
1) Wire the fans and carry plates/ slates to a separate circuit.
2) Install a back up generator to keep power running to the fans and keep the plates moving until the oven cools in the event of a power outage.
3) Give your insurance policies and your reports of the damage (take pictures before you do any repairs) to your attorney to review.
Denial is an easy response that requires no critical thinking. As a customer, you deserve more respect than that.
Good luck! Keep us posted on your progress.
Hello,
I am a manufacturing engineering in one of the medical device company. We have problem with maintaining staight barstock due to shipping and handling probelms. I was wondering if there are any industry standards for shipping the barstock in certain type of package to maintain straightness of the barstock and also handling. It is very cruical for our process that the barstock is straight.
Deepthi, ASTM A 700 is the standard practice for Packaging Marking and Loding Methods for Seel Products hre in North America. For the high precision, critical straightness cold finished bars that you require for your equipment, see sections 7 in this standard, and also look at figure 10 (wooden box).
In my experience the problem isn’t that suppliers don’t know how to package the bars for maintaining straightness, it’s that purchasing agents don’t want to pay the additional fee for protective packaging. For swiss machines, straightness is the critical factor, and boxed material is mandatory.
Here is a link where you can purchase this standard:
http://www.astm.org/Standards/A700.htm
Miles
Thank you Miles. This definitly helps.
Regards,
Deepthi Anga
Thanks for connecting!
Iinadvertanlty came upon Miles blog, and came away deeply impressed with the quality and accuracy of his comments. To add to what he has to say and to support his desire to help others, I am forwarding a link that contains a broader array of FAQ’s about powered industrial trucks. Go to Appendix A of the document. Easy search, first press the “control” then “F” buttons, and a seach box will appear on your screen. Type in what you are searching for in the document.
Miles, thank, you for your work.
Noah James West
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=2277
Miles.
Good morning.
You always have interesting valuable articles for our PMPA members. If you ever promote interesting products, check out OASIS optical measuring system for small turned parts.
The folks at George Products: http://www.georgeproducts.com/ have done a great job packaging this technology to help PMPA member’s measure their small turned parts.
For more information on Oasis I can be reached at (517) 414-3445, or call the factory direct at (302) 449-0199 and ask for Jeff Palmer.
Best Regards,
Dirk Dietsch
Dirk, I sent out a note to all PMPA Tech members regarding the fact that I am seeking CASE studies to share with our community.
HI,
I have read a number of your articles and have found them quite informative. I now have a question for your consideration.
I am trying to turn armatures (2.20 diameter) from 2.50 diameter, 12L14 stock. They turn well, surface finish OK but we lost 39 of 50 due to small cracks that we found after they were finished. Is speed /feed causing this?
If its a nitrogen issue, how do we know what the nitrogen content of incoming material might be as it is not part of the chemical composition?
Thanks for your assistance,
John
John, Are you certain that they are cracks? or are they just linear longitudinally oriented dark indications? If so they could be either A) Lead stringers or B) Manganese sulfides.
The recommended stock removal for all Resulfurized steels is 0.001″ per 16th of an inch of bar diameter per side! presuming 2.50 is 2-1/2 inches stock removal should be 16+16+8= 40 sixteenths X 0.001 or 0.040″ PER SIDE. that would be 0.080″off diameter, or 2.500 – 0.080″ = 2.420. So you are taking sufficient stock removal.
Nitrogen will help make a crisper chip and brighter as machined finish, but will not cause “small cracks” until the part is cold worked after machining. And then they will produce usually a large crack or cracks as the part fails due to lack of ductility. The threshold for nitrogen induced cracking is at or above 0.010 wt %.
My guess is you are seeing manganese sulfides if these are small (ie short in length and less than a 0.5mm pencil lead in thickness.
Hope that this helps. Sorry for the slow reply I have been out of country the last ten days.