Blade Prototyping

More in-depth discussion on our inaugural product, the Drengr Folding Knife. Design goals, challenges, insight into what goes into making it.
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Aett Armorers-Chris
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Blade Prototyping

Post by Aett Armorers-Chris » Wed Feb 06, 2019 3:17 pm

This is a peek into our prototyping process.

First, when we prototype, everything is being done for first time and we don’t want to invest heavily in special workholding fixtures on a design that might not work or change substantially. Things go slower because of this.

Squaring Stock (blank material):
  • This is to get accurate edges so that you can tell the CNC machine exactly where the part is repeatably.
  • I was doing this manually before, one blade at a time. Took forever. If a part is machined wrong or doesn’t fit right later, I would have to come off an operation and go remake another blank.
  • I do 4 pieces at a time now using 2 programmed operations to square my stock.
Cutting Prototypes:
  • I print out the setup worksheet and go line-by line through it after the run.
  • Is my work point of origin 100% accurate, repeatable from last run result(s)?
  • Cut widths and depths correct or need to be adjusted?
  • If there are matching cuts on both sides, do they accurately match?
  • Cutter speeds and feeds optimal or need to be tuned?
  • Does the part properly fit with corresponding parts?
  • I make adjustments based on notes from everything above then cut the next part then run through the same steps above to check it.
  • Once everything is good, I lock the CAM set up from editing so no accidental changes get made to it.
Another day I will post what it looks like going from design (CAD) to programming cuts (CAM). Just because you have the design how you want doesn't mean it's simple to actually machine it to match. You have to chose right cutting tools, right type of cutting operation, stock to leave to get your tolerances right, check your speeds and feeds are appropriate for that particular operation and a few other important details.


Challenges this week:
  • Challenging week, broke 3 bits and put premature wear on a specialty $200 bit.
  • Doing prototypes in a vise without workholding fixtures takes way more time. Hard to balance spending the time designing and making a work fixture on parts where you may change the part itself or how it is machined substantially.
  • Broke a bit doing an odd operation which I’ve never done before. Was related to machining the pivot pin while it was installed in the knife frame.
  • Getting the blade taper to end right before the fuller (blood groove) and match exactly from side to side is very difficult. If I am off just a little bit in my setup or don't have tool length exact, the taper bit shows those errors in multiples it seems. For now, I am moving on even though I don't have it perfected because I have to get a full knife assembled to check function. Once I know it functions correctly I will come back and perfect the cosmetics.
General stuff:
  • Mounted a camera in machine enclosure to get some vids of machining. It’s working well but was messing with camera focus/direction settings when the machine crashed. Not just once, but twice. So, I’d rather get my machining right before messing with vids, third or 4th time I run setup and am comfortable with it I will video.
  • Saturdays are supposed to be my day to compile pics/vids/comments for social media but most Saturdays I have been machining instead. Catching up, so I’m getting to it more.
  • Getting a workflow established which is helping every day to speed things up.
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