problem core profiler

motoman · Post by **motoman** » Sun Aug 16, 2015 11:25 am

Hello,
I have faced pretty big trouble with core profiling with the help of router.
I will start from the very beginning.
By the example from "how to" we have created wooden core profiler.
Rails were cut out on water-jet cnc machine so there could not be any errors.
First of all we tried to profile some trial wooden boards to be sure that everything is okay. One was thin and long and another was short. Long was profiled on longitudinal direction and short one on transverse direction.
At first glance, everything turned out well, but today we tried to profile our first poplar board.
The problem is next.
When we put board on profile table it is possible to see some small gaps between base and board. It means that board is not absolutely flat.

Here we can see how boards are cut.

Here we can see the result. It is seen that board profile has some curvature.

In the result it is not possible to get desired result since when you go router the gap between base and board becomes bigger and bigger. As a result router takes more wood layers in the place of gaps since the surface is not flat.

The only thing comes to my mind is to use double sided tape or place nails all around the board.

We even tried to put some load in the places of gaps.
Have anybody such kind of problem?

motoman · Post by **motoman** » Sun Aug 16, 2015 11:36 am

we use 20 mm cutters.

Here are their tracks.

chrismp · Post by **chrismp** » Mon Aug 17, 2015 12:06 am

What you need to build is a vacuum table like this: https://www.youtube.com/watch?v=fOrkvPF0pro

Nothing else holds cores down as well as a vacuum table. We have a big CNC that will rip any core into pieces if not held down properly and we found that a proper vacuum table with two vacuum cleaner motors hooked up directly to the table works best. Even with this setup I would recommend sealing the edges of the core with tape or hot glue to get good seal against the table.

mammuth · Post by **mammuth** » Mon Aug 17, 2015 8:41 am

And use the correct routing bit. There are some which like to pull up the material, these make it worse

motoman · Post by **motoman** » Mon Aug 17, 2015 12:06 pm

Dear chrismp,
I have red one post where you recommended to use vacuum to hold the board and I really think about it.
Today I solved my problem but it took to much time to profile the board.
I used two loads on the left and on the right part of router and worked the board by small sections (parts). Loads helped to keep small sections almost flat.
Tomorrow I will show the picture of this strange work.

May be the reason is in quality of cutting or some temperature conditions that effect the boards bending...

chrismp · Post by **chrismp** » Mon Aug 17, 2015 11:24 pm

Of course wood tends to warp under certain conditions, but a slight warp will easily be pulled down by the vacuum as long as the surface of the board is flat and even.

Like mammuth said, downcut router bits help too. They can be a bit hard to come by in larger sizes though.

MadRussian · Post by **MadRussian** » Tue Aug 18, 2015 5:37 am

I tried a number of techniques to hold core to the table. Vacuum is most reliable. 2 shop vacs enough and work great. make sure motor has separate cooling. I don't think any other method can substitute for well build a vacuum table

Another issue you might/will encounter is a router bridge. it have to be very strong or you will have same results even with a vacuum table.

end-mill cutters for metal 3 or 4 flutes is another option carbide or HSS. They also spiral but different compare to 2 flutes woodworking kind.

There is number of discussions on all three subjects with people having IDENTICAL problems and suggestions how to solve them

don't try to reinvent the bicycle. It time-consuming, expensive and him very very frustrating

mammuth · Post by **mammuth** » Tue Aug 18, 2015 7:16 am

btw. chrismp, what shop vaacs did u use? Need to upgrade to a dual setup as well, my little kärcher is not strong enough for thick raw core

sammer · Post by **sammer** » Tue Aug 18, 2015 7:33 am

Hot glue!!!
Clamp your board down flat to your table and hot glue the perimeter.
Don't have to have a solid bead, glue a couple inches leave a couple inches, like stitches.
Leave a spot to check thickness of board at the middle and end of your profile length.

Just gotta be careful when removing it, razor knife or chisel under the glued edge pops right off my laminate (counter top) table.

One day I'll get around to building a vacuum hold down table, in the mean time hot glue has been working fine. Any core profiling issues have been my own errors/odiocy.

sam

chrismp · Post by **chrismp** » Tue Aug 18, 2015 8:09 am

@mammuth: I just bought bare vacuum cleaner motors on ebay and glued wood boards to the front to be able to attach a hose. Make sure you get motors with a fan in the back to keep them cool. This way you get better suction, but need to build a housing.

mammuth · Post by **mammuth** » Tue Aug 18, 2015 9:39 am

Cool, thanks. Duty cycle with this setup is 100%?

Something like this i assume:

http://www.ebay.de/itm/Staubsaugermotor ... 1439189011

or this one, easy mounting with the flange:

http://www.hevo-shop.com/Staubsaugermot ... hr-TP.html

Dont know if theres a difference between 2 stage and 3 stage turbines, in theory the 3 stage should make more vacuum

motoman · Post by **motoman** » Tue Aug 18, 2015 11:29 am

Dear sammer,
hot glue is a good variant. Probably, I will use this way before I build vac table.
Generally, when I found out about the vacuum table I was enlightened and soothed. Very clever solution.

chrismp · Post by **chrismp** » Tue Aug 18, 2015 1:18 pm

@mammuth: that's exactly what I'm using. Looked for the cheapest model with a fan and bought it. They've been running for several hundred hours now and have not failed so far even when it got to around 40°C ambient temp the last couple weeks. I recently made some skateboard molds which took about 3h to finish with the motors running full time. Profiling a core should take a lot less time. Don't know about the models with the mounting flange nor about the difference between 2 and 3 stage, just went with the cheapest ones

As for the hot glue: I used to do it like sammer described, but still had problems with wide snowboard cores getting sucked into the router bit when the ends got thinner. These problems are history with the vacuum table.

Hannes · Post by **Hannes** » Wed Aug 19, 2015 10:19 am

I am using my coreprofiler only once in a while since I build only two or three pairs of ski a year. A few of you guys will say this is botch but I have good results with double faced adhesive tape.
So it looks like this:
Core
parceltape
double sided adhesive
parceltape
coreprofiler

Since the double sided adhesive is rather strong I use the parceltape in between because it is easier to remove.
Actually I wanted to build a vacuumtable this year but I was too lazy and decided to do it the fast and dirty way once again.

motoman · Post by **motoman** » Tue Sep 01, 2015 11:59 am

I made vacuum table!!!
Results are impressionable!!
Thank you guys for good advice!
And for all advice in general.

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problem core profiler

problem core profiler