Vacuum pump question

[CRB]

The company I work for has just bought a simple CNC router. Naturally too short for the longest common job we do, too narrow to use the most common sheet we use, and with only one cutting head so not enough to do any of the jobs we do every week. Basically crap. Even the 'engineer' who came to set it up was crap, and the machine was not skimmed prior to us getting it, crap etc etc.

All that is beside the point though. In conversation regarding the thickness of the sacrificial bed, MDF, I asked whether we could use a thicker material instead of the 6mm supplied, and also whether a mat specifically for Pacer routers could be used. I do not know enough about this particular material but will on Monday.

We were told that the pump, Busch Mink MM 1252AV, could not handle either suggestion.

Now this seems a bit suspect.

Please correct me if I am wrong, I probably am. The vacuum pump removes air from the void under the CNC bed. It will do so no matter what material is between it and the seals, be they the material to be cut or the packing tape around the sides. Therefore any thickness MDF or sacrificial mat will be suitable.

Before the jumping around starts, I am wanting to ditch MDF altogether, and use PVC or this clever mat stuff.

 

[500e]

CRB
I can understand the idea of getting rid if the MDF (Dust not good for you) but why thicker ?
Are you looking at Texon Fein or Trend style mat

 

[AndyStobbs]

Yep vacuum is vacuum, and unless its upside down or off horizontal the thicker material will help it stay in position as it'll be heavier in itself. Assuming like for like density etc.

 

[CRB]

I will find out more about the mat on Monday, but it was used on the previous 900x700 machine and they bought a bigger panel, 2100x1400, for the new machine before asking whether it could be used. Our best sheet size is 3000x1500, so you can see how crap the sizing of the new machine is.

Initially I would go with thicker MDF since I would tend towards not cutting through and always leaving a skin to preserve the integrity of the vacuum. It also meant that any skimming to gain the surface back would still leave a heavy board meaning less flex and more skims before chucking it.

@500e I have searched for 'Texon Fein or Trend style mat' but neither give a decent result. I know Trend and Fein, and now Texon but cannot find a reference to either. ?Links?

@AndyStobbs Just as I thought. I do understand that the application will vary the specification of the pump.

 

[MCKDAVID]

It might be more a case of the problem is not necessarily the vacuum, more the volume of air you need to remove to achieve that. If the system is sized for a certain surface area, and hence volume of air beneath it (the void). Obviously it wll take a specific time to achieve the level of vacuum that's sufficient to hold the sheet in place. Now, also logically if you increase that size of sheet (by a factor of three if I understand correctly), you also increase the volume of air necessary underneath (the void) to achieve the same vacuum. If you're looking to do it in the same time scale, then logically it would require a larger pump.
I would say, that it's not necessarily that the vac pump won't be able to cope with maintaining the vacuum as before, just more the time it will take to remove that larger volume of air. Basically you might not get the same performance that you had before. At least I would assume that's what the manufacturer is referring to. Might make little or no difference in your application, but you get nothing for nothing, larger volume of air to be removed, small pump, if everything else remains equal equals longer time.

but then again, I could have missed the point completely....

 

[wheresmejumper]

A bush mink vacuum pump?
Check ann summers

 

[CRB]

It might be more a case of the problem is not necessarily the vacuum, more the volume of air you need to remove to achieve that. If the system is sized for a certain surface area, and hence volume of air beneath it (the void). Obviously it wll take a specific time to achieve the level of vacuum that's sufficient to hold the sheet in place. Now, also logically if you increase that size of sheet (by a factor of three if I understand correctly), you also increase the volume of air necessary underneath (the void) to achieve the same vacuum. If you're looking to do it in the same time scale, then logically it would require a larger pump.
I would say, that it's not necessarily that the vac pump won't be able to cope with maintaining the vacuum as before, just more the time it will take to remove that larger volume of air. Basically you might not get the same performance that you had before. At least I would assume that's what the manufacturer is referring to. Might make little or no difference in your application, but you get nothing for nothing, larger volume of air to be removed, small pump, if everything else remains equal equals longer time.

but then again, I could have missed the point completely....

Time is not a problem, and the increase in area, at present would be nil. If the bed gets increased, at most 50% increase, time will still not be an issue.

At the moment the operator insists on holding parts down rather than using my method, only gained over eight years of running a two drill two router 8x4, of packing tape on everything that is not going to move. That is edges of the sacrificial board too. Ye gods.