Adventure in assembly a Book Scanner Kit v0.9.10

[Fab52]

Hi,

I just start today to do the assembly of my scanner kit. I got my kit cut from the plan given here on this site. The custom CNC cutter who do it, he's used to cut kitchens cabinets and newels posts where precision of +/- 0.015" (+/- 1/64") seems to be the standard. This is something I don't know at the time.

Like I already mention in thread overhere (http://www.diybookscanner.org/forum/viewtopic.php?f=14&t=1192&start=280)there is some programming error in the cutting and some infos that was not clear for the CNC owner from me because I'm a newbie and know nothing about CNC router. I could'nt say where's the head or the tail on that machine....

So I hope this thread will help you get a perfect kit the first time by knowing where are the pitfalls.

The first pitfall seem to be the feedrate vs cut depth and router rpm, for cutting this kit Cnc owners have to work with a 1/4" bit.

Daniel show us in an other thread (using G-Wizard) that the maximum this bit could take is 0.250" (1/4") deep cut and a feedrate of +/- 287 ipm(inch per minute) at 12000 rpm. (http://www.diybookscanner.org/forum/viewtopic.php?f=14&t=2467&start=40

Here's a photo of the work of a bit with to much feedrate and to much depth of cut:

This is a full depth cut (I think ???) at a speed the bit could not take it ...





Here's an other photo of a cut at a better speed and depth:





The guy who custom cut my kit, break six bits, I saw the place where he break it. Take a look at the cut depth.

Here's a photo:


It look like at he end he do not have 1/4" router bit anymore so he cut my craddle angle with two differents bits size . I do not notice that fact at first, but today when I get to the assembly of the book craddle, I do not like how everything fit together. So I start looking closely at the parts.

Here's my find, my 4 craddle angles was cut with much bigger router bits then 1/4" , look like 5/8" and 3/8" router bits so using those router bits throw all the measure off and scrap my 4 craddle angles....

Take a look at the round corner this will tell you the size of the bits:



Any of you guy could PM me a 1:1 template of the craddle angle so I could cut it and can continue assembly my scanner ????

To be continue.....

Fab
English is a second language for me, you can laugh at me or help me improved.

[rob]

Here are the files. Note that there are two "conformations", A and B. You need two of each.

[Fab52]

Hi Rob,

Thanks for the 1:1 template, here's a photo of the template and the parts I got from the cutting....



Rob do you have a link to all the pdf parts in 1:1 ????

See you

FAb

[daniel_reetz]

FAb, it's also possible that some part of the mistake is from the bit cutting INSIDE the line instead of OUTSIDE the line...

Your CNC operator was definitely being too aggressive with the bits... that is a shame.

[rob]

Fab -- that is a good idea to provide PDF files. Here they are. I can't put each part on a separate piece of paper, but at least you will be able to print every part.

[Fab52]

Hi guys,

I cut my craddle angle this afternoon from the 1:1 template Rob post in this thread. I cut the template with an exacto over a gypsum board to make sure I will be more in control of the exacto .

I used the template with the exacto to mark the piece of plywood to be cut. I used the exacto instead of a pencil because it is more a precison tool....

I make the craddle angle from 3/4" standard spruce plywood, the tools I use was simple, my trying square, table saw do do the roughing cut, a small band saw to do the more complex contour, and a hand held small router to do the 0.500" X 0.220" groove to fit into the craddle platform.

Doing this groove was the challenging part of the work. There is probably 1000 ways of doing it with but I pick the first one it come to my mind.

Those pieces are to small to be handle in the table router, dangerous, so here's some pick of how I do it:




First I lay down the pieces on a long board and stapple it with my finishing nailer and I use my small hand held router with the guide and a 1/8" bit. So every pass I'll do the 4 pieces at the same time, this ensure the deep and the with will be the same at the end.

Here's the photo at the end:



Here's the book craddle with the new cut craddle angle:



See you

Fab
English is a second language for me, you can laugh at me or help me improved.

[rob]

Nice job, Fab! I'm glad to know that you're able to make new parts to replace the bad ones.

[Fab52]

Hi,

FAb, it's also possible that some part of the mistake is from the bit cutting INSIDE the line instead of OUTSIDE the line....

G'wiz Daniel you win, look at this photo done with the 1:1 template Rob send me:



The next photo show you why I have wide radius in the corner:



I learn every days with you guys !!!!

See You

Fab
English is a second language for me, you can laugh at me or help me improved.

[Fab52]

Hi guys,

I still working on the test assembly of my kit for the book scanner, now the craddle angle is ok. How about the the bearing pocket in the levers arms ?

Since I have only bearings pockets on one side of the levers arms I have to take a decision.... My bearing pockets are far from a press fit don't even think about a thumb fit bearings, they have 0.014" free play, epoxy or lock tite ? I think it won't work in this case....

I take the decision to keep the original design of two bearings heres how I do it:

First a I use Fostner bit to tackle this job on an old Poitras (1960) mortising press drill, this press drill have a kind of milling table with an X , Y and Z axis... I could used my Bridgeport to do it but I hate doing woodwork on my machinist tools, they are not done to do that and the speed are to slow...

I first use a 11/16 fostner bit to center my work since the levers arm was already have this hole in it and this is the one I have to take as a reference from.

Here's a photo:



After this I used a 7/8" fostner bit for the bearings pockets.... I Know, I know, 22mm is 0.866 but my bearings pockets are already off by 0.014". Hey !!! this levers arm are not made to be used to land anything on the moon.

But I make sure I don't do any error in the centering, with the 7/8" bit, i first turning it by hand to make sure I'm well centered.

Here's a photo:



I do all my pockets bearing this way and it is working in a design of two bearing per arm...

I know Rob you wanna go with one bearing per arm, I'm 100% behind you with this idea, much more easy for the custom cutter and it will work as fine as two bearing for sure. We or you just have to make it clear in the instruction for the customs cutters that the pockets bearings have a strict measure of 0.0863 or any other press fit you choose.

Can you adjust the design with one bearing so we can use the bearing spacer that come in a kit like this one, instead of of a pile of washers or a nut??

The bearing kit I buy come with 8 spacers (0.415 + 0.275 for the bearing =0.680)like this one:



Oh by the way I'm not using 5/16" washer, they are to big, I'm using a 1/4" washer here's a photo, they fit perfectly on the bearing and on the 5/16" bolts:



To be continue....

See you!!!

Fab

[rob]

If your 5/16" washers are too big, then you got the wrong type of washer The two types have different outer diameters. The "normal" or USS standard 5/16" washer has outer diameter 14/16", while the SAE standard 5/16" washer has outer diameter 11/16". We specify the SAE washer.

What you got is a USS standard 1/4" washer, which has inner diameter 5/16" and outer diameter 12/16". So it is a reasonably good approximation to the SAE 5/16" washer, it's just that the inside is a little tighter and the outside is slightly bigger. But this is a good point -- if the USS washers are easier to find, then maybe we should also specify USS 1/4" as a substitute if you can't find SAE 5/16".

As for the spacers... I have to think about it. If the spacers are too expensive, there's no point -- just throw together some nuts and washers.