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Posted by Den on May 2, 2008, 2:36 am
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I'm sure this has been done to death before. I've checked the archives and
found some information, most of it quite old.
Any opinions on using a ShopBot to machine connector openings in small
polycarbonate / ABS / PVC enclosures?
In particular I'm looking at the Buddy:
http://www.shopbottools.com/shopbot_buddy.htm Yeah the picture detracts
from the product and I can't find much practical or specs info on the
website either. I'm awaiting reply to a request for info email I have sent
to them.
While I wouldn't expect this level of machine to be anything near as robust
as a cast iron machine its price is significantly lower. I'd imagine it
might need a little coaxing and a few swarf shields etc added.
I've seen the results that others have achieved in timber and most owners
seem satisfied, but I cannot find any info on anyone machining polycarbonate
/ ABS etc. Would it handle low volume work of this nature? Anyone?
TIA.
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Posted by Polymer Man on May 3, 2008, 6:53 am
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> I've seen the results that others have achieved in timber and most owners
> seem satisfied, but I cannot find any info on anyone machining polycarbona=
te
> / ABS etc. Would it handle low volume work of this nature? Anyone?
>
> TIA.
I take heavy cuts in polyethylene (1/2"DOC) with a 1" three flute
cutter turning 13,000 RPM and feeding at 600 IPM without coolant on a
router. I also take 1/2" cuts at 18,000 RPM with a 4 flute 3/8" cutter
feeding at 1,800 IPM without coolant. (Feeding at 1800 IPM folks, yup)
I was surprised when I started using a router on plastics that chip
welding is not a problem.
Part of the reason is the cutters are designed for plastic with lots
of relief and aggressive cutting angles, which generate less heat. You
can get production router bits for plastic from Vortex tool, Onsrud,
and many others. I have mine made specifically for my application by
Data Flute, great folks.
The other reason you don't get a lot of chip welding is feed rate. I
try to maintain pretty healthy chip loads. Anywhere from .010 to .040
per tooth.
Anyway, that little shopbot looks to me like it could handle light
duty production in ABS ect. I know a rotational molder who uses a
shopbot (a bit bigger) to trim out parts in production.
You might want to get a dust collector to go with it to suck up your
chips. Recutting chips is a no-no.
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Posted by Den on May 3, 2008, 10:41 am
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> I've seen the results that others have achieved in timber and most owners
> seem satisfied, but I cannot find any info on anyone machining
> polycarbonate
> / ABS etc. Would it handle low volume work of this nature? Anyone?
>
> TIA.
I take heavy cuts in polyethylene (1/2"DOC) with a 1" three flute
cutter turning 13,000 RPM and feeding at 600 IPM without coolant on a
router. I also take 1/2" cuts at 18,000 RPM with a 4 flute 3/8" cutter
feeding at 1,800 IPM without coolant. (Feeding at 1800 IPM folks, yup)
I was surprised when I started using a router on plastics that chip
welding is not a problem.
Part of the reason is the cutters are designed for plastic with lots
of relief and aggressive cutting angles, which generate less heat. You
can get production router bits for plastic from Vortex tool, Onsrud,
and many others. I have mine made specifically for my application by
Data Flute, great folks.
The other reason you don't get a lot of chip welding is feed rate. I
try to maintain pretty healthy chip loads. Anywhere from .010 to .040
per tooth.
Anyway, that little shopbot looks to me like it could handle light
duty production in ABS ect. I know a rotational molder who uses a
shopbot (a bit bigger) to trim out parts in production.
You might want to get a dust collector to go with it to suck up your
chips. Recutting chips is a no-no.
Thanks PM. From what I gather there is quite a bit for me to learn about
cutter selection, speed & feeds. I take it that you yourself have a machine
other than a shopbot?
Its good to hear about your colleague with the shopbot cutting plastic. Most
of the shopbot info I've found so far involves wood.
The more I look the broader the field gets. K2CNC is another low cost entry
level option that looks interesting. I'm still waiting on a reply from
shopbot - not a good start!
Thanks for the reply.
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Posted by Polymer Man on May 3, 2008, 11:17 am
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>
> Thanks PM. From what I gather there is quite a bit for me to learn about
> cutter selection, speed & feeds. I take it that you yourself have a machin=
e
> other than a shopbot?
>
> Its good to hear about your colleague with the shopbot cutting plastic. Mo=
st
> of the shopbot info I've found so far involves wood.
>
I have CNC machines, but the router I'm talking about isn't my
property, I set it up and program it, that's all. It certainly isn't
entry level either. Weighs close to 20,000 lbs and cost in the six
figures. Not a shopbot, but the same principals apply.
I don't think you'll have too much to learn. The cutter selection is
pretty straight forward, the catalogs describe what they're for, and a
little bit of trial and error and you're ready to go.
Machining strategies are a different story. I like to program the
cutter to make major changes in direction outside of the material,
that reduces dwelling in the cut. I also connect cuts with curves so
the machine doesn't have to change direction suddenly, this prevents
unnecessary acceleration forces which speeds cycle times, reduces
dwell, improves finish and reduces wear on the machine. Did I mention
this thing is feeding at 1800 IPM? That's really fast, much faster
than the RAPID on my fastest mill. Sudden stops and changes in
direction is best avoided. It processes 25,000 pounds of plastic sheet
a week in a repetitive program, so little tweaks like that improve the
machine life.
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> seem satisfied, but I cannot find any info on anyone machining polycarbona=