[limbo]

After playing around with my current router for over a year I think I've gathered enough excuses to start building a new (3rd) one. This one should have:
-larger travel: 24" by 48" to fully access standard plywood panels.
-vacuum hold down for those bendy balsa sheets that follow your bit wherever it goes.
-rack & pinion on X and Y
-supported rails on X to finally be done with the sagging.
-a nicer color (hey, I do need excuses)
Although it will probably not be the fastest build, I thought it would be nice to start a build log. All comments en suggestions welcome!

Here's a pic of the frame being assembled and result:

greetings,
John

[jimini]

I see by the picture that you're starting at a good, young age. lol

[limbo]

I see by the picture that you're starting at a good, young age. lol

Yes, but my daddy is helping me a little.
Here's a bit more progress and a sketch of the gantry. The steel tubes that serve as X-guides are bolted down every 20 cm's. After having screwed together the frame Ynneb's saying "more bolts than the Sydney harbour bridge" popped in my mind a few times. I can imagine his complete machine must have a factor more...

John

[lurch]

A very nice start!! Simple, and clean, a good design. One question what keeps the x axis trucks from lifting under a downward load?

[limbo]

The only thing that keeps the gantry down is gravity. The gantry on my current machine weighs around 30kg, so I'm expecting this one to be around 50kg. I'm sure my router will not be able to lift that. (In fact, I hope those cheapo skate bearings will hold up.) The bearings are spaced far apart (28cm) while the gantry is as low as I could get it. The centre of gravity is mid betweed bearings and only some 12cm above the rails, so that a sudden stop after a rapid move will not cause the gantry to fall over.

John

[Hobbiest]

. (In fact, I hope those cheapo skate bearings will hold up.)
John

unless you got the cheapest bearings money can buy (which they don't look like) they should be fine. A skateboard uses 8 bearings, and I have known skaters who weigh 300 to 400 pounds!

[limbo]

They are labeled ABEC5-608something. I dont think they are very good quality though. Brand new out of the box they have some play in them. Not side to side, but I can vary the angle of the inner ring w.r.t. the outer ring a bit by taking the bearing in one hand and holding the inner ring between thumb and finger of the other hand. Is that normal? They don't seem to have any play in axial or radial direction.

John

[cnc2k]

Anyone know best why to drill linear holes a steel rod?

[Ferenczyg]

They are labeled ABEC5-608something. I dont think they are very good quality though. Brand new out of the box they have some play in them. Not side to side, but I can vary the angle of the inner ring w.r.t. the outer ring a bit by taking the bearing in one hand and holding the inner ring between thumb and finger of the other hand. Is that normal? They don't seem to have any play in axial or radial direction.

John

IF I am not in a mistake skate bearings are from abec-1 to abec-7 in uneven numbers, being better for higher number so yours are at least on the good side

/F

[limbo]

Hmm, I found a few old abec3 bearings in my scrap box and they have no play at all. Now I know why these abec5's were so cheap.. Oh well, I'll look at it from the positive side and say that some play is necessary to cope with misalignment in the bearing trucks.

Its too cold in the garage to start longer projects like routing the gantry side panels, so I did a few quick jobs. I made some U shaped extensions that will increase the Z-axis stroke, and a quick test to see if I could make the gear pulleys myself. I'm amazed at how well they came out. The part is accurate within 0.2mm! :banana: The material is Trespa. Very strong and weather proof but easyer to route than aluminium.

John

[Mike F]

John,

What is Trespa? I have not heard of this material but it sounds interesting. Is this a trade name in the Netherlands?

What size are the pulleys and what belts are you using with them?

Sorry for all the questions but this is one of the great things about this forum - the fact that you can glean so much information so quickly and pose many questions easily.

Good looking machine by the way.

Mike

[limbo]

Trespa is the trade name. In the Netherlands it is commonly used in house building, to finish the sides of the roof and as panels below windows and so on. It doesn't need to be painted and will last forever, even in our climate. I've heard that it consists of layers of paper, drenched in resin, pressed together under high force at high temp. It looks a little like the old brown PCB boards, but I think Trespa is more dense and heavyer. Great stuff.

The pulleys are for 1/5" pitch toothed belts (5.08mm pitch), 9.5mm wide. There is 40T on the pulley which is 64.6mm (~2.5") dia. The stepper has a 10T pulley giving 1:4 reduction for the pinion drive.

John

[Mike F]

Any idea of what kind of resin is used? The old type PCBs used a phenolic resin but that is usually a very dark brown and has a very rancid, bitter smell when cut. Your pulleys seem to be quite a light colour. It sounds a very useful material indeed and I would like to try and trace a supplier here in the UK.

What diameter tool did you use? Was it selected to be the same diameter as the profile of the teeth?

Mike

[limbo]

The smell when cutting trespa is different from the brown PCBs. Now you've mentioned it I remember that they had a very specific odor indeed. The color is almost the same however. Trespa has the top and bottom finished in different colors (I used light grey) but the inside is dark brown. The dust makes it look a little brighter in the pics. BTW, this dust also smells strange (unhealthy?) and clogs the vacuumcleaner filter bag in no time.

The part in the pic had 2.5mm holes and was made with 2mm bit. Turbocnc played tricks with me and drilled about 5 of the holes directly (so without widening them up to 2.5mm). If you look very close at pic 2 you'll see I marked them. I'm certain my G-code was correct. Rather than spending hours on finding out what went wrong I changed the bit for a 2.4mm one and drilled all holes directly. Dont have a pic of that one but it looks identical.

John

[joecnc2006]

can this material be used to build your router?

[limbo]

Yes, actually there is one guy in the Netherlands doing just that: http://www.2004all.com/paket.jpg
I'll just make some parts of it. The gantry side panels are 72mm thick. Routing them from Trespa at 2mm per pass would take forever.

Mike, it seems you were right about the phenolic resin. Have a look at:
http://www.woodweb.com/cgi-bin/forum...pl?read=331889

Here's another little part: The mounting plate for the Y pinion drive. The stepper motor is suspended from 4 "springs" that will allow some up and down movement but are stiff in left-right direction. This way the pinion can be springloaded into the rack.

John

[limbo]

Ok, the Z-axis is finished. Its one half of a small XY table. The other half sits happily on my current router . For this one I made a few trespa panels to extend the stroke to 3.5". Also I got fancy and plagiarised some "anti cage creep" patent I found on the web. I soldered thin copper plate to the ball cages and connected them to a small pinion in the middle. This pinion rolls between two nylon racks, one mounted on the moving part and one to the base. This should keep the ball/cage assy in place even during strong vibrations. So far it works fine, lets see how it holds up in real life..

John

[limbo]

Finally got around to route the gantry side panels. I'm pleased with the fit, the shafts can be slid through the stacked panels with some force and will stay put. I'll probably need to strengthen the holes with thin CA glue for durability.

I'm not so happy with the gearbox. The belt is 9.5mm wide and there is 10.5mm room between the two plates. When turning the belt it sometimes moves a bit upwards or downwards on the large pulley, causing it to slide against one of the plates. This was planned to keep the belt in place but I didn't expect it to cause so much friction. Its like sliding rubber over glass, sticks like crazy. Have to re-think this one.

John

[limbo]

Problem solved. I simply routed a groove in both panels to give the belt more clearance. Luckily the rims on the small pulley keep the belt in place on the large pulley.

I have a crazy linear drive idea I want to run past you guys here. What is wrong with using plain allthread as a rack? It is fairly accurate, I have two pieces of 1.5 metre that interlock over the whole lenght when held together. A modulo 0.5 (~48pitch) pinion rolls beautifully on M10 allthread. If I use nylon pinions, would the allthread wear faster than the pinion?

All suggestions welcome,
John

[JavaDog]

Really nice build you have going on here! :cheers:

That gearbox looks really nice. You have a unique design to all of your parts, looks and functionality!