Avoiding Machine Gotchya's

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Re: Avoiding Machine Gotchya's

Postby GeneMpls » Sun Jul 12, 2015 6:38 pm

Need more tools- Pictures and part numbers please. Thanks Gene
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Re: Avoiding Machine Gotchya's

Postby Adrian » Sun Jul 12, 2015 6:45 pm

What happens if you lose air pressure though?
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Re: Avoiding Machine Gotchya's

Postby LittleGreyMan » Sun Jul 12, 2015 7:04 pm

Hello,

Need More Tools wrote:I have been reading about people using double sided tape. That to me just sounds a bit dangerous.


Double sided tape is actually a very handy and reliable solution. But it is not universal and requires some caution.

We use it to machine industrial parts, with very few glitches. These glitches have a minor cost, compared to the ease of use.

You need to use extra strong hold tape, and carefully test it. Not all tapes give a good result, and not on all materials.

Heat is your enemy. When temperature is high, adhesive melts, and your part is no more correctly held. It means you generally cannot use it for aluminum, as cutting it produces heat.

We use it for a majority of our PU board machining on melamine spoil board. For large parts, we also use vacuum on a large machine, and in particular cases, mechanical hold.

The trick is to put a heavy load for a few minutes on your raw material in order to compress the tape and increase adherence.

HTH
Best regards

Didier

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Re: Avoiding Machine Gotchya's

Postby Leo » Sun Jul 12, 2015 8:43 pm

We use double sided tape to hold aluminum parts down on large industrial grinders.

I have used it many times in my shop to hold down wood parts.

It does have its place.
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Re: Avoiding Machine Gotchya's

Postby scottp55 » Sun Jul 12, 2015 9:18 pm

Fairly essential daily use here(boy will I be glad to lose it for a vacuum jig sometime soon though:)
Discovered yesterday though how much even 15F 30%humidity increase affects the residue sticking to wood fibers.
Solution was to coat the black wood with 3 coats GF Woodturners Finish(water based PU....have been using lacquer which was better than shellac), good clean release.
Solution for .19" stock was to sand backside of wood to 600G instead of 320G like at 50-70F...still plenty of hold down, but residue came off clean:)
Ace Hardware 1.88"(NOT 2" stuff which is HORRIBLE to get paper off!!) heavy-duty indoor-outdoor Fiberglass reinforced is the best out of 6 I tried.
Yep, J roller,removing dust from wood, and whacking stock with a deadblow/spacer is pretty ESSENTIAL!
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Re: Avoiding Machine Gotchya's

Postby LittleGreyMan » Mon Jul 13, 2015 12:21 pm

Leo wrote:We use double sided tape to hold aluminum parts down on large industrial grinders.


Sorry if there's a double post, I don't see my answer.

You're right Leo. 3M manufactures a high end product, with a very precise thickness, which can be used for mechanical use, especially grinding.

Maybe it's cheaper in the USA, but even for our professional use, we don't use it here as it is way too expensive, and we do not require such thickness precision.
Best regards

Didier

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Re:

Postby skieva » Thu May 02, 2019 2:22 am

Bagzzz wrote:I agree, I slow my cuts down alittle and the cnc does as you say "hum" along with no errors. I too used to watch the machine incase of screw ups.
I now know I can walk away and be more productive doing something else while the cnc routs alittle slower than full boar.



At my stage I am mesmerized by the action and can't stop watching!!!! I guess I will over this stage....
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Re: Avoiding Machine Gotchya's

Postby CharliesWoodStuff » Mon May 27, 2019 11:41 am

I set my speed to 80IPM for the most part. I do worry about the speed being too slow and the chip load being wrong. I just can’t get me head wrapped around chip load and I’m probably dulling my bits before their time...
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Re: Avoiding Machine Gotchya's

Postby scottp55 » Tue May 28, 2019 1:37 am

Charlie,
Nothing wrong with your feed IF getting the cut quality you need AND the bit is room temp(or Slightly warmer) at the end of the cut.
BUT ignoring the Chip Charts, and starting slow and shallow, and watching cut quality and bit temp and getting even Small chips(look CLOSE and make sure it's not saw dust)
is where you want to start. Chip Charts aren't really as important for 80% of our machines, as they're just not rigid enough.

FEEL the machine when it's cutting at different feeds and RPM's doing Air Cuts(or even just driving it around)! IF you have vibration at certain speeds and RPM's ...avoid them.
Vibration DOES transfer to the cut.

THEN try cutting materials...It REALLY doesn't take long to find a low feed/low rpm cut with shallow passes and inspecting cut quality to get a FEEL for the Sweet Spot for YOUR machine!
THEN you can increase feed/speed proportionally Together, to find the bit and materials Sweet Spot. I like using Sugar Maple for testing as it's mid range for my work for hardness.

Depth of pass can usually be done with a Fluting test cut and inspecting cut....maybe start all cuts at 1/2Diameter of the bit passes? Pretty much won't break a bit and then increase.
When cut quality gets worse..you know you've gone to far trying to max everything out....Back off about 10%, and you'll be close to Sweet Spot.

DON'T forget that almost ALL cut quality for finished product, WILL be improved by a very small Finish pass so toolpath accordingly.

If you're doing cabinet sheets or foam...I apologize for my Hardwood thoughts :oops:
For Sugar Maple test cuts with a never used bit, I find (IPS) 1-1.5(XYFeed), .5(Plunge rate), and about 15-16K at 1/2 Diameter of bit is a good starting point...THEN move up or down.
HOT/SCREAMING bits increase feed/lower RPM.....LOUSY edge quality and tear out....reduse feed or increase RPM.

Can't stress enough how important it is to find the Smooth Spots on your machine cutting Nothing! IF it's a vibration air cut...really doesn't get better if going for top quality cuts.

THIS is not as good as it once was for Newbies...BUT found it VERY useful!!
https://www.precisebits.com/tutorials/calibrating_feeds_n_speeds.htm
I Tweak All my bits before I use on an actual one-of project in Maple....then go at it conservatively.

Every body, every machine, every bit, every material is different.
Find your Sweet Spot:)

HOPE I didn't confuse the Heck out of you.
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Re: Avoiding Machine Gotchya's

Postby armbrusterco » Wed May 29, 2019 5:25 pm

Great post, Scott. Great advice. I could not agree more.

When I was starting, it took me a while to learn that what you describe is the best way to get great results on our machines.

Thanks
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