BuildLog CNC Router?

[gene]

For holding down parts we always use custom vacuum forms made from wood with the sticky vacuum roll tape on top ( a hole drilled in it somewhere that hits one of the wooden channels below). These wooden forms are then put over the channeled vaccuum router top and stiff rubber is fitted around it to form a vaccuum lock. These work really well for all kind of parts even the tiny stuff. The top of the 4x4ft cnc looked like this

[bdring]

I have some question for you...

Do you have a source for a decent priced vacuum pump?
How loud is the pump?
What size pump would be needed for the this sized router?
Does saw dust and chips run through the pump or is there a filter before it?

[gene]

I have some question for you...

Do you have a source for a decent priced vacuum pump? Nope we have two big ones and one came with the cnc machine when we bought it early mid 90s. It's controlled through switches on the panels. I'll check the pumps and the specs when I'm there next. We have a smaller one that pulls 2CFM that we use for spot duty for custom stuff as well. Havn't needed to replace but i'll see what I can find out on them. I believe we picked the one up in the used market for pennies on the dollar and it's HUGE about the size of a 5hp air compressor


How loud is the pump? the large ones we have are pretty quiet. The little one is old and small and is centrifugal so it's loud.

What size pump would be needed for the this sized router? We have used a really small one for indivdual forms before at about 2 CFM. If you don't have leaks anywhere you don't need a whole lot. The larger the cfm the pump has, the faster the air is sucked out so you can cycle the parts quicker. You'll need much higher cfm if you plan to run it and will have any air leaks or if you want to create a vaccuum with something that is air permeable (example is MDF). You don't need a whole lot of area vacuumed on the part due to the pressure created so sometimes you can get away with just a few strategic inches of part vacuumed. Usually we design the forms we make to not allow areas that are cut through to be in the vacuum chain so the holes don't break suction and very little dust gets in the vacuum filters.

Does saw dust and chips run through the pump or is there a filter before it? There are filters that fit into the suction hole from the top of the table that keep the dust out. Occasionally you have to blow it out. Also the vacuum pump has it's own filter further up the chain.

In the future, I'd like to try out making a vacuum table and see how that works on a cnc. Basically think of air hockey type small openings in a top material with a vacuum instead of a fan and that's what I'm talking about. You'd have to have a good filter between the vacuum and the openings but I think it would work pretty well.

[thechoochman528]

I ran across this site with videos, yesterday.

It shows the difference between two Harbor Freight dust collectors and building a nifty MDF vacuum hold down system for a blackfoot 4x8' cnc router.

http://wn.com/clicclic99

[bdring]

I would think that only works because of the size of the sheet of material. That dust collector might be able to do 10 inH20 which is about 0.36 psi. That is not going to hold a little 2 square inch part from flying around. A standard shop vac can do over 50 inH2O which is 1.8 psi. That might work. An expensive Festool dust collector can do about 95 inH2O. That is about 3.4 psi. A vacuum pump can do 10-14 psi. Now we are talking.

[macona]

Most places use a regenerative or a roots blower. Both have the vacuum and the cfm to get the system down. A dust collector might work for sheet things like you say. For small parts it hard to beat double sided carpet tape on a router. You can even get away with it on a cnc mill every now and then as long as the coolant is off.

[bdring]

There is a relatively new class of vacs called dust extractors. Festool, Fein and Dewalt have a few models. These are usually quiet, clean (HEPA), and adjustable suction to levels nearing 100 inH2O. They usually have tool power outlets that activate the vac when the tool is turned on. You could have some cheap PVC ball valves on the back of the enclosure to direct the flow. You could have a spindle mounted fitting, a hose to suck out the corners and a hose to a vac hold down.

It would be interesting to test one of these. There is a Woodcraft store near me. I might take a look.

[macona]

Main thing you need to find out is if the motor cooling is separate from the moved air. Most shop vac and standard vacuum cleaner designs have the air that has passed through the filter flow though the motor. If you use them at low flow/high vacuum for any extended amount (minutes) of time they will burn up.

[nickgoodenough]

Any updates on the router?

I’ll be building a 4'x4' router soon, and Joe’s Hybrid CNC is the only quality & affordable build I’ve found. Wouldn’t a makerslide 4'x4' router have higher quality and affordability–and an open source!

How difficult would it be to design a 4'x4' makerslide router?

Do you think it would be on par or above Joe’s Hybrid CNC in quality and affordability?

Joe’s Hybrid CNC
http://www.joescnc.com/themachines-hybrid.php

Thanks!

[bdring]

Any updates on the router?

I am still working on it.

Right now I am doing some work on a new spindle design. I want it quiet, but I think the Chinese VFD spindles are too expensive for this project. They realistically cost close to $500 after shipping, etc. at qty 1.

I have a design I am working on that uses an ER11 collet powered by an RC car motor. I seen have similar designs around the web, but I want mine to be a little more robust that what I have seen so far. I plan to use (2) angular contact bearings on the ends of the spindle shaft. This will give the motor long life and no axial play. The RC motor gives a lot of options. There are brushed and brushless versions. Some brushed motors can run straight off a 12V power supply. These motors can pull a lot of current, so a high current PC supply would be a nice, inexpensive option. At the other end are the brushless motors. These can run as high as several horse power. They require a special speed controller. The car motors usually have some sort of cooling method built in. There are some water cooled boat versions, but that might be more complicated than necessary.

I want the design to allow the spindle to be mounted as close to the z mounting plate as possible. Too much overhang on the Z looses stiffness and can allow vibration.

I have a ER11 shank and a motor. I have a second shank on order with a slightly better design for the mounting of the bearings.