HDPE question

[Gary-Wiant]

I'm hoping this is the right location to post this question.

I recently built my CNC Router Parts 4896 Pro and I made my dust shoe that is on their website.

Universal CNC Dust Shoe | CNCRouterParts

The top piece of material started out as a 1" piece of HDPE and after being machined it is about 3/8" thick. After I finished mine looks great except for the fact that the top section bows up so the bottom piece wont snap into place.

My question is can I use some heat to straighten / flatten the HDPE or do I need to start over?

Thanks
Gary

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[cyclestart]

I bend 1/4" HDPE with a heat gun all the time.
3/8 " just needs more heat or patience ?? Test on scrap.

EDIT/ OOPS. Went into the shop to check and the HDPE I've bent is 1/8". My mill enclosure among other things.
The problem with this stuff as it gets thicker is the outside can be heated to melting without warming the core.
More of my rubbish advice unfortunately.

[routalot]

I have had UHMW polyethylene curl up when removing a large proportion of the thickness,Delrin too.It seems likely to me that the material is rolled to thickness while still a bit pliable,at the factory,and the stresses induced are balanced until you remove some material and unbalance the forces.It comes as a real shock when you have held the stock flat with a vacuum hold down and then it curls up when the vacuum is switched off.The only solution I found was to rough machine to a slightly oversize shape and then a much lighter finishing cut.

[Gary-Wiant]

Cyclestart - thank you, I still think I'm going to try to heat it because if it works I'm good if not I'll need to start over anyhow so it's worth a shot, right?

Routalot - I'm not real familiar with plastics, how close is UHMW to HDPE? I would think that CNCRP Would design in a way to negate the bow if it happens often. What would be a better material to use so this doesn't happen? If I'm going to have to remake it anyhow I'd like it to be see through if possible.

Thank you
Gary

[Jim Dawson]

UHMW and HDPE are both polyethylene. The UHMW has a higher density, but other than that no substantial difference for most applications. If I wanted a ''see through'' something for an application requiring strength and resilience, polycarbonate (Lexan, Tuffak) would be my choice.

Warping is common when machining some plastics (and some metals), but if you take off about the same amount of material from each side you can minimize this. In your case, heating the material and trying to straighten it might work, or it may get worse. Just depends on the stresses in the material.

[cyclestart]

If I wanted a ''see through'' something for an application requiring strength and resilience, polycarbonate (Lexan, Tuffak) would be my choice..

I bought a clear cast acrylic dust shoe from kentcnc. There are 3 LED lights on the bottom of the router. The ability to watch the cutter while the brush is in contact with the table is something I'll never do without. The shoe wouldn't be hard to replicate if you have a good source for brushes.

The HDPE used used by Cnc Router Parts may have less internal stress. It's also possible your tool/speeds/feeds introduced additional stresses. I was tempted to suggest stress relief in an oven at low temperature but there might be toxic fumes ? If the canary dies it's time to evacuate.

[hfjbuis]

he HDPE used used by Cnc Router Parts may have less internal stress. It's also possible your tool/speeds/feeds introduced additional stresses. I was tempted to suggest stress relief in an oven at low temperature but there might be toxic fumes ? If the canary dies it's time to evacuate.

If you want to stress relieve HDPE, PP or LDPE, boil it in water in a large tub for one hour, put the lid on and let it cool down by itself, the slower the better!

[Gary-Wiant]

Hfjbuis - I'll try the boiling water prior to starting over. Would it be best to remove the metal nuts & bolts to keep it from heating that area more than the other areas?

Cyclestart - I'll check into that dust shoe. I have a good source for brushes. I purchased mine at mastercarr. Where does the power for the LED's come from?

Jim - thanks for the reply I'd need to get a piece 2" thick to remove the same from both sides. Plus I'm learning one sided cnc I'm not ready to attempt 2 sided yet.

Thanks
Gary

[Jim Dawson]

.............

Jim - thanks for the reply I'd need to get a piece 2" thick to remove the same from both sides. Plus I'm learning one sided cnc I'm not ready to attempt 2 sided yet.

Thanks
Gary

Not sure why you would need a piece 2'' thick. Let's look at the math here. Let's say you start out with a piece 1 inch thick (1.000) but you need to make it 0.375 thick, so 1.000 - 0.375 = 0.625, therefore you would take half of the difference off of each side or 0.625 / 2 = 0.312 So if you were to take 0.312 off of each side then you would have removed the same amount from each side, and the final part thickness would be the target of 0.375 thick (ok, yes I know the math works out to 0.376, but trying to keep things simple here).

2 sided is simple if the part is symmetrical, just flip it over. If not symmetrical, then you need to do a mirror part in CAD, as far as I know all CAD programs will do this.

[cyclestart]

Cyclestart - I'll check into that dust shoe. I have a good source for brushes. I purchased mine at mastercarr. Where does the power for the LED's come from?

My router happens to have them built-in. There's also angel eyes or halo rings available that run on 12V so use a wall wart or tap into a power supply.

[Gary-Wiant]

Jim - I'd need a 2" piece because I start with a 1" piece & in the end part of the finished piece is 1" so if I need to take even amounts from both sides I'd need a 2" piece.

Cyclestart - ok thank you

[Jim Dawson]

Jim - I'd need a 2" piece because I start with a 1" piece & in the end part of the finished piece is 1" so if I need to take even amounts from both sides I'd need a 2" piece.

Cyclestart - ok thank you

The top piece of material started out as a 1" piece of HDPE and after being machined it is about 3/8" thick.

OK, I guess I am confused, according to your first post, the part finished at 3/8''

[Gary-Wiant]

Did you look at the dust shoe I shared the link to?

[Jim Dawson]

Did you look at the dust shoe I shared the link to?

No, but I just looked at it. I see the problem. That being the case, about the only solution is to try to stress relieve it, maybe before machining. I have had some UHMW and HDPE try to turn into a pretzel when machining.

[hfjbuis]

Hfjbuis - I'll try the boiling water prior to starting over. Would it be best to remove the metal nuts & bolts to keep it from heating that area more than the other areas?

Just make sure everything is submerged in water, then is will be ok.

[Gary-Wiant]

I'm planning on boiling the top section of the dust shoe today but even if it does work I'm considering making the top piece out of clear acrylic and attaching an led to is so I can see what the router is doing. My question is. Once I route out the 1" piece of acrylic like I did the HDPE the acrylic will be milky white & not see through. If i flame polish the routed area will it actually be clear enough to see through? I looked at the Kentcnc dust shoes and I'd have done that if I hadn't already spent the money to make my own & I see that his are not routed and he uses a black plastic piece that mounts to the dust collection hose and his spindle pushes into the top section then righted with a screw, so his isn't routed near as much as the CNCRP dust collector. How can I go about doing this?

Also does anyone have a link to a 90mm led that is AC powered? I've found plenty of a DC powered but the adapters power wire isnt near long enough to reach my control panel & I don't know if the small adaptors would be able to have that much wiring added without causing power issues.

Thank you
Gary

[ger21]

You'll probably need to do some sanding before flame polishing. The finer the grit used, the clearer it will be.

[hfjbuis]

the acrylic will be milky white & not see through

You can get the acrylic absolutely clear by sanding and polishing using a soft cloth and copper polish liquid. You can do it using a dremel or power drill.

I've found plenty of a DC powered but the adapters power wire isn't near long enough to reach my control panel & I don't know if the small adapters would be able to have that much wiring added without causing power issues.

You don't see any difference even if the power lines are very long. Just give it a try.

[routalot]

Wouldn't it be a whole lot easier to use a piece of 1/4" clear acrylic and then attach a boundary piece to it?

[Gary-Wiant]

Gerry - thank you

Routalot - thank you I know it wouldn't matter with AC power but I wasn't sure about DC since the inverter is right at the outlet.