[asciutto]

Hi there,

I'm continuing to research more into the 2006 R2 CNC build, but have a question. Is it possible to make the CNC entirely out of HDPE? Rather, is it recommended? I thought I read somewhere that it could cause extra back lashing/binding if I made it entirely out of HDPE.

If I only make parts of it our of HDPE, which parts are MDF? I assume most of the torsion boxes, but the gantry's and carriage are entirely HDPE, correct?

Thanks for reading!
Anthony

[ger21]

Look at the bottom picture here. Kits & Plans
The majority is MDF.
I think the biggest problem with using all HDPE, is that you can't glue it together.

[asciutto]

Thanks for the quick reply!

[gumppy]

Look at the bottom picture here.
The majority is MDF.
I think the biggest problem with using all HDPE, is that you can't glue it together.

Perhaps there is a solution for an all-HDPE Joes 2006.

Check out the TAP video on PolyWeld at YouTube

[cpy911]

Hi all,
Is there a list of which parts are MDF and which are HDPE somewhere?

Thanks!

[jckstrthmghty]

Perhaps there is a solution for an all-HDPE Joes 2006.

Check out the TAP video on PolyWeld at YouTube

you could do it but wouldn't make any sense. MDF is used for it's economy factor. That much hdpe would not be cost effective considering the 80/20aluminum builds. Imagine how much that much plastic would weigh?

cpy911, motor mounts, z-axis, router mount, and gantry bearing adjustment block are hdpe. Joes site has the plans where you can examine all the parts.

[LaughingJaguar]

Look at the bottom picture here. Kits & Plans
The majority is MDF.
I think the biggest problem with using all HDPE, is that you can't glue it together.

My biggest concerns using MDF are:

1. It's very dense and needlessly heavy for such a poor structural material, compared to Baltic Birch plywood.

2. The effect of changes in geomery caused by variations in humidity. Sealing it to prevent warping and to get a good finish is difficult: it soaks up paint like a sponge!

Joe's web site is a bit contradictory and confuses matters. It shows several photos of 2006 machines made almost entirely of HDPE but the photo of the kit shows mostly MDF.

I would love to identify the faced plywood Norm Abrams uses for cabinates on "This Old House". It's covered with what appears to be a plastic laminate. Anyone know what it is called?

My shop is short on space. I like the footprint of the 2006 but prefer the mechanical structure of the 4 x 4 hybrid.

Not that it matters: I spent an hour trying to find the 2006 "Free plans" here at CNCZone and couldn't.

Thanks

L.J.

[joecnc2006]

The pictures you see are the MDF painted white so it may look like HDPE at a first glance.
The Hybrid 5x5 machine is scalable. people have built it from a 2x4 up to a 5x10..

[abqjohn]

I spent an hour trying to find the 2006 "Free plans" here at CNCZone and couldn't.

Joes CNC Model 2006 R-1 - CNCzone.com-The Largest Machinist Community on the net!

But you need to read down pretty far in the thread to find the R2 plans, versus the R1 plans. The R2 have the files in more formats, and are easier for some people to use.

more helpful info:
http://www.cnczone.com/forums/joes_c...s_2006_r1.html

http://www.cnczone.com/forums/joes_c...2006_mods.html

[harryn]

HDPE often contains stress, so finding some that is stress relieved is part of the challenge with that material. Sometimes you can find stress relieved pvc or poly "wet sinks" used in the semiconductor industry that have been scrapped out. Just make sure to test the material with pH paper to be sure any acids are completely neutralized.

MDF - while it is commonly used, I won't use the stuff for anything, not even to clean my shoes on. I think people either love it or hate it.

If it were me, I would build using some decent plywood, and then rebuild it with Al when / if you really think your machine meets your needs. Hardly anyone builds just one of these cnc routers without wanting to change something.

[LaughingJaguar]

To all who responded to my request. . . . thanks!

MDF is, in my opinion, not really wood. It's used because it's cheap. Its density, compared to real wood, is heavy making things made from MDF needlessly heavy without imparting any structural benefit.

Working MDF without benefit of a mask is looking for trouble as it's formulation contains known carcinogens.

Painting any cut surfaces is difficult if not impossible without first applying several coats of sealant. It absorbs paint like a sponge thus making an already heavy material even more so.

I looked up specs on HDPE and shopped around. Average price for a .5" x 4 x 8 sheet is close to $200. I can get a 4 x 8 sheet of Apple plywood for about $130. Apple Plywood is the domestic 9 ply equivalent to Baltic Birch which I love. I can glue Apple with most any good glue, you can't do that with HDPE.

The only thing I can see that is needed is to adjust the widths of the half notches in the table ribs which are currently sized for the full half thickness of MDF. Apply plywood is 15/32nds.

One thing does puzzle me: does anyone know why Joe chose to make his longitudinal ribs two pieces instead of one?

I know I can create a table with a sealed inner chamber as I've done so in my shop when bagging composites. I'm toying with the idea of using pegboard for the top table skin and apply a vacuum as a method for holding material down.

Please note: the Mass Properties image reflects the estimated weight of the table when made with MDF and with top and bottom skins of quarter inch tempered Masonite.

Thanks to all who answered my questions.

L.J.

[louieatienza]

To all who responded to my request. . . . thanks!

MDF is, in my opinion, not really wood. It's used because it's cheap. Its density, compared to real wood, is heavy making things made from MDF needlessly heavy without imparting any structural benefit.

Working MDF without benefit of a mask is looking for trouble as it's formulation contains known carcinogens.

Painting any cut surfaces is difficult if not impossible without first applying several coats of sealant. It absorbs paint like a sponge thus making an already heavy material even more so.

I looked up specs on HDPE and shopped around. Average price for a .5" x 4 x 8 sheet is close to $200. I can get a 4 x 8 sheet of Apple plywood for about $130. Apple Plywood is the domestic 9 ply equivalent to Baltic Birch which I love. I can glue Apple with most any good glue, you can't do that with HDPE.

The only thing I can see that is needed is to adjust the widths of the half notches in the table ribs which are currently sized for the full half thickness of MDF. Apply plywood is 15/32nds.

One thing does puzzle me: does anyone know why Joe chose to make his longitudinal ribs two pieces instead of one?

I know I can create a table with a sealed inner chamber as I've done so in my shop when bagging composites. I'm toying with the idea of using pegboard for the top table skin and apply a vacuum as a method for holding material down.

Please note: the Mass Properties image reflects the estimated weight of the table when made with MDF and with top and bottom skins of quarter inch tempered Masonite.

Thanks to all who answered my questions.

L.J.

You should be able to get appleply in 3/4" nominal thickness (13 ply).

[LaughingJaguar]

Louie wrote: ""You should be able to get appleply in 3/4" nominal thickness (13 ply)"

I am sure I can Lou but why would I want to?

Half inch Apply Ply, while lighter than half inch MDF is much stronger.

I am not familiar with the history of this design though I understand that there are 100 in use. Are you suggesting that the table design lacks rigidity?

Thanks

L.J.

[abqjohn]

MDF is, in my opinion, not really wood. It's used because it's cheap. Its density, compared to real wood, is heavy making things made from MDF needlessly heavy without imparting any structural benefit.

One thing does puzzle me: does anyone know why Joe chose to make his longitudinal ribs two pieces instead of one?

MDF *IS* a wood product, and is at least slightly more stable than plywood, is it not?

My understanding on the ribs is that they are two pieces so you you can cut them on a jgro machine; if you have the ability to create them as one piece, rock on.

[louieatienza]

Louie wrote: ""You should be able to get appleply in 3/4" nominal thickness (13 ply)"

I am sure I can Lou but why would I want to?

Half inch Apply Ply, while lighter than half inch MDF is much stronger.

I am not familiar with the history of this design though I understand that there are 100 in use. Are you suggesting that the table design lacks rigidity?

Thanks

L.J.

For some reason, I thought the entire machine was made of 3/4" MDF not 1/2" though admittedly, I hadn't looked at the plans in a while. There are probably thousands in use.

As to weight, I thonk you'll find weight can be your friend, and buildning something lighter doesn't necessarily mean it will be better...

[LaughingJaguar]

As to weight, I thonk you'll find weight can be your friend, and buildning something lighter doesn't necessarily mean it will be better...

After 35 years of doing machine design I've learned that people who are unfamiliar with material properties are inclined to add mass. In their uncertainty, they think that by doing so, they are adding strength. Not so; often they weaken the part. And, if it's a design that must carry a payload, it looses money it shouldn't.

If something, like the table, doesn't move and never will, the only burden is money thrown away in materials and extra fabrication costs that yield no benefit.

In the gantry however, extra mass burdens the steppers, the power supply and all the fixturing that must be made oversize to compensate.

The inertial loads increase exponentially. Double the mass and the forces increases four times and stress everything accordingly!

Starting, stopping and changing directions must be done more slowly.

I am trying to think of a situation where ". . . .weight can be your friend. . . " and frankly I can't. Perhaps you can help me.

Thanks for the tip on the bed size. I'm lengthening mine to accommodate 8 foot material.

L.J.

[harryn]

The main place that weight can be your friend is in vibration dampening. There are of course other methods, mass is one method and can be useful.

Is there any chance you can change fonts ? That one is hard on my eyes.

Thanks

Harry

[LaughingJaguar]

Hello Harry

Over the last 35 years I've built many parts from advanced composites including landing gear struts for aircraft.

Vibration dampening is a natural with these materials and a critical factor in the design of landing gear which must be designed to dampen any stored energy.

Failure to do so will bounce the aircraft back into the air and reduce the ability to apply brakes. You can't add weight to dampen vibrations or reduce the natural frequency.

Same thing applies to telescope mounts. Optical systems that magnify images 500X and higher, also magnify vibrations. You can't add mass to correct this, not if you intend to make the system portable. The trick is to make certain that there is sufficient hysteresis's in the system to dampen any vibration within 2 cycles.

All this is rather moot at this point as I have abandoned the 2006 router in favor of the 4 x 4 design. I found myself spending too much time and energy trying to accumulate a BOM and adjust the design for my needs. I still don't know what steppers it uses. I also figure that Joe has learned a lot since he designed the 2006 and that his latest creations contain improved design elements not found in the 2006

I'll buy the plans set and start by substituting Appleply for the MDF. I may even buy his kit if I can convince him to substitute ApplyPly for the MDF.

I'm curious to know why the rack and pinion model is more popular than the screwfeed.

Any idea?

Thanks

L.J.

[louieatienza]

Hello Harry

Over the last 35 years I've built many parts from advanced composites including landing gear struts for aircraft.

Vibration dampening is a natural with these materials and a critical factor in the design of landing gear which must be designed to dampen any stored energy.

Failure to do so will bounce the aircraft back into the air and reduce the ability to apply brakes. You can't add weight to dampen vibrations or reduce the natural frequency.

Same thing applies to telescope mounts. Optical systems that magnify images 500X and higher, also magnify vibrations. You can't add mass to correct this, not if you intend to make the system portable. The trick is to make certain that there is sufficient hysteresis's in the system to dampen any vibration within 2 cycles.

All this is rather moot at this point as I have abandoned the 2006 router in favor of the 4 x 4 design. I found myself spending too much time and energy trying to accumulate a BOM and adjust the design for my needs. I still don't know what steppers it uses. I also figure that Joe has learned a lot since he designed the 2006 and that his latest creations contain improved design elements not found in the 2006

I'll buy the plans set and start by substituting Appleply for the MDF. I may even buy his kit if I can convince him to substitute ApplyPly for the MDF.

I'm curious to know why the rack and pinion model is more popular than the screwfeed.

Any idea?

Thanks

L.J.

I never said that adding mass arbitrarily would lead to more ridgidity. I also don't belive in making a part unnecessarily heavy as much as making it unnecessarily light. I also think many people underestimate the power that these steppers can produce, as a relatively small stepper can move a relatively large load. My previous machine had one 425in-oz stepper (with only 48V psu) driving a timing belt turning two 8-start leadscrews moving a gantry weighing over 90lbs, at over 500ipm rapids and 30in/s/s accel. At cutting speeds I couldn't stall the steppers by leaning on the gantry. I used phenolic as a frame material; though heavier than plywood, it is a lot harder and denser and stiffer, moisture resistant, and holds threads really well. If mass was not an issue, then machining centers (or most commercial stationary power tools for that matter) wouldn't have to weigh in the hundreds or thousands of pounds. Just the A-C head alone on a 5-axis router can weigh over 400lbs, yet those machines can move them ovver 4000ipm. The same inertia that makes it harder to move a heavier gantry also makes it harder for it to move under a spike in force, as with an abrupt change of direction during a cut, or moving from cut to open space, cutting into a corner, etc...

The rack and pinion is probably more popular because it is easier to achieve higher speeds, well over 1000ipm rapids. To do this with leadscrews would be difficult because at those lengths they'll tend to sag and whip, and the steppers normally used would probably not have enough torque at that speed to move the gantry. A way larger screw can be used but then the stepper must also fight the inertia of the larger screw, and they are expensive. Ballscrews are even more expensive and to achieve the speeds of the R&P probably would require servos. The spring tensioner on the pinion assembly probably also makes it more tolerant of misalignment than leadscrew or ballscrew....

A great alternative to appleply would be PSF plywood, which is a baltic-birch style plywood with a phenolic surface film on both sides. It is incredibly strong, in fact it's used to make concrete forms. It also looks pretty cool, at least I think so... I think a Joe's hybrid made with phenolic would be another great alternative, too.

As the the 2006, I don't think lengthening to 8 feet would be a good idea for the above mentioned problem with longer leadscrews, unless you decide to make the long axis R&P.