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Mold Plate Guide drilling

kaemd

Plastic
Joined
Oct 27, 2016
hello ,

I am trying to make my first plastic injection mould, As there is no mold base supplier in my area, I need to make it myself, I just ended facing and squaring the edge of the plate, I am heading to drill guide holes in A and B plate.

the guide bushing/Pin are 25mm, so the holes need to be 25H7 , my concern is how to drill this four holes in an accurate way so it will match.

I am planning to spot drill with 6mm short lenght carbide drill ( I already have is in ATC , and no spot drill in the market ) , than drill 24mm using Morse taper HSS drill , follow by a 24.5 HSS drill, chamfer the edges, go throw with a 25H7 Reamer. Do you think this is a good way to do it ?

and with this approach would the holes match in both plates A and B. or should I drill the two plate together at the same time.

My machine is a leadwell V32i with a 14.7HP spindle.

thank you all
 
The best way to do it to ensure that they line up is to leave stock for boring. If you have no boring capabilities, then Place the A and B plate together and drill and ream thru both of them in the same setup. You only have about .0015 clearance between pins and bushings. Too much can go wrong just drilling and reaming alone.
 
I am planning to spot drill with 6mm short lenght carbide drill ( I already have is in ATC , and no spot drill in the market ) , than drill 24mm using Morse taper HSS drill , follow by a 24.5 HSS drill, chamfer the edges, go throw with a 25H7 Reamer. Do you think this is a good way to do it ?

hy / you may forget the spot drill; that o24 can handle things on its own

carefull, because both o24 and o24.5 may deliver a hole with at least 0.5 bigger

i would suggest roughing how you like, and final operation to be a helix or an excentric knife

... that o25 reamer may throw you out, thus may deliver +0.05 / depends :)


what is the depth of the 25H7 ?
 
thank you,

as no boring capabilities for now, need to place the two plate together.

the two plate are 50mm thick , and the Reamer has 65mm flute.
 
go gentle with the drills, dont go directly full depth :)

before the reamer, you may measure each hole with a micrometer, and even if micrometer shows same values, the reamer may not deliver H7

thus, even if you use a reamer before the last reamer, you may still not be certain of what the last reamer will output

if you manage to get all holes at 25-0.3, or even at 25-0.1, a boring tool will save the day :)

that cnc of yours seems pretty ok / why dont you helix it ?
 
go gentle with the drills, dont go directly full depth :)

before the reamer, you may measure each hole with a micrometer, and even if micrometer shows same values, the reamer may not deliver H7

thus, even if you use a reamer before the last reamer, you may still not be certain of what the last reamer will output

if you manage to get all holes at 25-0.3, or even at 25-0.1, a boring tool will save the day :)

that cnc of yours seems pretty ok / why dont you helix it ?

I don't really understand what do you mean by helix it and what tool should I use for that ?

Also I am thinking about getting a boring tool, I guess this one will be ok MD-KMB - Modular Boring | Hole Making Tools | Cutwel Ltd but pricey adding tool holder for BTMAS gonna be around 900$ , but still need to find a way for now situation, as I will not get the tool in less than a month if I order today.
 
Oh thank you , I already know how to do it, just didn't recognize the name of it as I use another language :) , but the problem is , It always get noisy when I do so , and finish by breaking the edge of the endmill, another problem is the plates are 50mm thick , but the best choice I have is a gurhing diver 16mm endmill with 38mm flutes, and If I use a taller tool , than with this diameter there will be a huge deflection to avoid, means a too slow feedrate.

some told me that flute length is not a problem ??? , also I can use the endmill as a boring bar but still not enough flute length, also do you think using this technique in different plates separately will get you a good line up ?
 
far as i know, 25 H7 is +21um

i would craft holes in both plates toward maximum, thus towards +20um

maybe i would use a o16 end mill, with a groove after it flutes, with a gentle feed and hope to work

if a lot of vibrations would occur right from the start, i would try something else, like an excentric knife, or simply pass the plates to a coordinates grinder, or maybe i would grind it inside the mill :)

also, i would craft the arbor 25h7x100 towards minimum :)
 
Hi kaemd:
There are a bunch of things you should consider when you make your own mold base.
First, if you are going to cut big insert pockets in, you need to rough out those pockets before you finish the leader pin bores.
Otherwise the plate may bow when you cut the pocket, and the bores will no longer be orthogonal to the parting plane.
Second, you have to be comfortable that your mill is accurate enough to jig bore the bores.
It needs to be better than 0.01 mm for position over the whole travel you'll need to get all the bores in.
If it is, you can drill bore then ream them.

If it is not, you need to mill the pockets finished, bore and ream the bushing bores, leave the leader pin bores just drilled, line up the A plate and the B plate and ream through the bushings.
This is the old-fashioned way of getting excellent alignment between the A plate and the B plate.
Some people will match grind the outsides of the plates and mill the pockets finished by referencing the outside edges, others will mill both pockets finished and then drop in a plug to align the pockets before reaming the leader pin bores; the main thing is that you end up with pins and bushings that line up very well.
Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com
 
hi,

it an old post but I think sharing my experience will help others.

I did try drill with 24mm hss drill first than finish with a 25mm reamer. but it doesn't work, the holes come slightly misaligned, when I put the bushing and pins the plate get together by force, hummer work :D , too hard to separate plate after.

so I tried with other two plate and as my machine have a 0.003mm accuracy, I drill with 24mm hss drill, than I used a 12mm carbide mill as a boring bar. doesn't matter cut it at full depth or use helical interpolation when its too deep to avoid chatter. it work just fine. I made 4 mold till now and always get perfect aligned holes everytime. it took me 8 month to finish the first successful mold :D . but guess it's a good start for a beginner in machining and mold manufacturing world.(after 18month I still consider my self as a beginner as everyday I learn full of new things and ways to do work)

thanks lot everyone for your help.
 








 
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